-------
The 0.32 cm (0.13 in) calcite column system proved to be the most
effective for removing P of all the systems tested (Table A-13^). However,
this system also lost considerable P removing ability near the end of the 6
month experiment. This series removed 99% of the P entering the columns in
the first month, but P removal decreased to 12.% in the sixth month of operation.
Phosphorus removal was 6k% for the first k months of the study and 52% for
the entire 6 month period. The column series with the 0.6k cm (0.25 in) cal-
cite chips was less effective than the columns using 0.32 cm (0.13 in) calcite
chips but more effective than either of the dolomite series. Phosphorus
removal was S>7% for the first month, but decreased to 5% for the sixth month.
The percent removal for the first k months was 5k% while for the entire 6 month
operation k2% was removed.
Using 0.6k cm (0.25 in) calcite chips, a decrease in temperature from 20
to 6°C resulted in less P sorbing capacity in both the sand and the calcite.
The percent removal was 63% for the first month, 2k% for the second month, and
only 11% for the fourth month. The total percent removal for the k month
study was 2J% as compared to 5k% for a similar system at 20°C.
Several conclusions can be gleaned from these results. First, increasing
the residence time from 1 to 3 days removes more P from septic tank effluent
(Figure A-65). Also, calcitic limestone is superior to dolomitic limestone
in P removing ability. However, the ability of either limestones to remove P
from septic tank effluent for several months is limited. Over several months
of operation the P sorption capacity decreases markedly. This decrease in P
removal appears to be due to organic anions in the effluent competing with P
for sorption sites plus microbial growth physically blocking sites.
Organic anions such as glutamate and acetate compete with P for sorption
sites, decreasing the P removal ability of the limestones (Struther and Sieling,
1950). In a separate study calcite columns were dosed daily with an NaCl
solution containing P equaling the ionic strength and P concentration of
septic tank effluent. The average cumulative P removal of 80% for a 6 month
study was obtained (Bent, 1975). At the termination of the U.W. experiment,
the columns were disassembled and considerable slime growth was noted. This
was especially true for the second column in each series where the majority
of the denitrification occurred. However, the data did not indicate excessive
inhibition of P removal in the second column versus the others. Therefore,
it appears the slime growth and/or organics hamper the P removing ability of
the limestones. Unless some means could be developed to inhibit slime growth
or remove organics in the effluent, the success of P removal using limestones
would only be temporary.
Another conclusion is that the smaller size limestone is more effective
for P removal, undoubtedly due to the fact that smaller chips offer a greater
total surface area. Smith, et al., (l97l)> however, found that clogging
increased with smaller sized bed materials. In this light, a conflict develops.
If a system is to function for both N and P removal, the surface area of
limestones must be sufficient for effective P removal and denitrification with-
out excessive clogging. Although methods are available to remove the clogged
portions and gas build-up, the frequency of treatment would be less if larger-
sized chips were employed.
-------
Field denitrification phosphorus removal study—In an effort to demon-
strate the effectiveness of a limestone filter bed system for phosphorus and
nitrogen removal a field unit was installed at site J (Figure A-62). Details
of this system were presented in the nitrogen section. As indicated, phos-
phorus removals were poor due to the development of biological growths on the
limestone and possibly due to competitive reactions at the sorption sites by
organic anions.
DISINFECTION OF WASTEWATER
The investigations on sand filters and other on-site treatment systems
have demonstrated that effluents of relatively high quality can be produced
on site. There are, however, still questions as to the safety of discharging
this treated effluent to surface waters or on the land. Some discharges may
require the use of disinfection processes to further reduce the risks of in-
fectious disease. The following review of disinfection looks at some of the
most promosing disinfectants for on-site use and discusses some of the factors
which affect their usefulness.
Factors Affecting Disinfection
Disinfection is a physical-chemical process conducted on biological
systems and as such is governed by the laws of chemistry and physics but is
complicated by the large number of biological systems and possible biochemical
reactions. Early in the study of disinfection it was shown that the destruc-
tion of cells by chemical agents occurs at some finite rate (Chick, 1908).
What controls this rate has been the subject of a considerable amount of
research. Also important is the level of disinfection because, generally, at
some point in time the rate becomes zero. Some of the most important factors
are: 1) nature and chemistry (or physics) of the disinfectant, 2) concen-
tration (or intensity) of the disinfectant, 3) the nature of the microorganisms
being disinfected, k) number of microorganisms, 5) presence of interferences
in the wastewater, 6) time of contact between disinfectant and microorganism
and 7) the temperature of the system (Fair, et al., 1968). This list alone
shows the complexity of the process; however, the first simplifying assunrotion
is that tnese will be discussed in terms of their relationship to small waste-
water flows.
Nature of the Disinfectant—
A list of potential disinfectants (Table A-135) shows a considerable vari-
ation in the types that could be used for small waste flows. The ideal dis-
infectant should meet the following criteria: l) effective against infective
organisms at reasonable concentrations, 2) relatively unreactive with other
constituent in wastewater, 3) safe to handle in concentrated forms, H) easy to
administer reliably, 5) economical, and 6) not a pollutant in itself (ASCE,
1970). Some of the disinfectants in Table A-135 can be immediately ruled out
by these criteria. Quaternary ammonium (cost), dyes (effectiveness), detergents
(effectiveness), hydrogen peroxide (effectiveness), X-Rays (safety and cost),
ultrafiltration (hard to administer), freezing (effective, cost, hard to
administer) and ultrasonics (cost, effectiveness) are not presently practical
alternatives for disinfection of small wastewater flows.
A-2UU
-------
TABLE A-135. POTENTIAL DISINFECTANTS FOR SMALL WASTE FLOWS
Chemical
1. iodine
2. chlorine & compounds
3. bromine & compounds
k. ozone
5• heavy metals
6. dyes
T. soaps & synthetic
detergents
8. quaternary ammonium compounds
9. hydrogen peroxide
10. alkalies and acids
11. formaldehyde
Physical and Mechanical
1. heat
2. ultra filtration
3. freezing
Radiation
1. U.V. light
2. X-rays
3. Ultrasonics
Possible Mode of Action
oxidation
oxidation, enzyme inactivation
oxidation
oxidation
enzyme inactivation
protein denaturation
destruction of cell membrane
destruction of cell membrane
oxidation
protein denaturation
protein denaturation
protein denaturation
removal from liquid medium
osmotic pressure
DNA damage
molecular action
cell disruption
Where the other disinfectants rate in relation to the above criteria has
been the subject of considerable debate. As of yet, no disinfectant is known
to adequately meet all criteria under all conditions. The alternative then
is to outline the proper conditions for application of a particular disin-
fectant .
Probably the most important disinfectants for small flows are: chlorine,
ozone, ultraviolet light and iodine, in that, more is known about these methods
and equipment exists for their application to small flows. Chlorine is the
most popular disinfectant because it has been demonstrated to be quite
effective, and it is relatively cheap. However, it is sensitive to pH changes
in the normal range of 6-8 and has been shown to be toxic to aquatic life in
low concentrations (when combined with wastewater). Iodine undergoes many of
the same reactions as chlorine but at different rates and at different pH values
and iodine is unreactive with ammonia. Some studies have indicated that iodine
is superior to chlorine as a wastewater disinfectant but the cost is considerably
greater.. Little is known about the toxic effects of iodine and related compounds.
Use of ozone has created new interest, and many studies have alluded to its
superiority over chlorine. However, ozone is more sensitive to oxidant demanding
materials in wastewater and presently its application is much more expensive
than chlorine (Budde, et al., 1977)- Ultraviolet light has also been shown
to be an extremely effective disinfectant, giving not only a rapid rate of
-------
kill but also providing a high level of disinfection (Huff, 1965). However,
the required equipment is expensive and its effectiveness is inhibited by
turbidity and other potential interfering wastewater constituents.
Concentration of the Disinfectant—
As the concentration (or intensity) of a disinfectant increases both the
rate and level of microbial kill increase. The goal of disinfection is to
obtain a desired level of kill in a reasonable length of time with the least
amount of disinfectant. Because of the many interferences in wastewater, it
is very difficult to control the level of active disinfectant. The term "con-
centration of disinfectant" should not be confused with "dosage of disin-
fectant," as a great percentage of the dosed disinfectant may be immediately
converted to ineffective forms. A disinfectant "residual" should be maintained
throughout the contact period.
Nature of the Microorganisms—
There is an extreme variation in the rates at which various groups of
microbes are inactivated by a given disinfectant at constant conditions or in
the required concentration of active disinfectant to achieve a given level of
reduction in a given time.
The organisms of primary interest in wastewater disinfection are bacteria,
virus and amoebic cysts. Bacterial spores are generally the hardest to inacti-
vate while young, growing bacteria are the easiest. Somewhere in between are
viruses and cysts. Of particular concern is the use of bacterial indicators
to evaluate the efficiency of disinfection, as an effluent made devoid of
coliforms may still harbor large numbers of viruses or cysts. There is,
presently, no good indicator of adequate disinfection.
Number of Microorganisms—
Because disinfection is a rate process, the larger the number of organisms,
the longer the time to reach a desired level in the effluent. Appendix C
reports on the numbers of selected bacteria normally found in typical small
wastewater flows.
Interferences in the Wastewater—
Wastewater is known to contain many materials which may interfere with
the process of disinfection. Materials which react with the disinfectant
before it has a chanae to act on microorganisms obviously affect the disin-
fection process.
A primary example of interference is the reaction of chlorine with ammonia
to form chloramines. Although chloramines have been shown to have disin-
fecting properties, they react at a much slower rate than chlorine. The
presence of suspended solids interfere with the penetration of ultraviolet
light and may also shield the microorganisms against chemical attack. An
increase in organic material more severely affects the demand for ozone than
that for chlorine. The pH of a wastewater has a dramatic effect on the action
of free chlorine which is much more effective at pH less than 7 than at pH
greater than 8.
A-2U6
-------
Comparisons of the average characteristics of various small wastewater
flows show that sand filtered effluent would be the easiest to disinfect
because it contains the lowest level of interferences. It should also be noted
that there can be large variations in effluent quality for a particular type
of effluent. This increases the difficulty of controlling disinfection.
Contact Time—
Since disinfection is a rate process, the longer the contact time between
disinfectant and microorganisms, the greater the percentage of kill. It does
not necessarily follow that holding a mixture of disinfectant and wastewater
for long periods of time will lead to high levels of disinfection. Many of
the factors listed above may act to decrease the rate of disinfection to zero
after a relatively short time. In general, the amount of contact time
required to achieve wastewater disinfection using ultraviolet light is in the
order of magnitude of seconds. Ozone requires longer periods although less
than chlorine and iodine.
For small flows, it is fairly easy to construct contact tanks giving
extended contact times up to 2k hours. The primary cost of such installations
is that for labor.
Temperature of the Wastewater—
Chemical disinfection proceeds at a slower rate at lower temperatures.
Contact times should be increased to account for cold weather flows. It is
not clear how cold temperatures affect ultraviolet light disinfection.
Summary—
All the above factors can be controlled to some extent thus improving the
chances for successful disinfection. It is important to know how a particular
disinfectant reacts in the particular wastewater being treated, what the
potential variability of the wastewater is and what potential health hazards
exist for each particular waste. One conclusion which can be reached from the
above discussion is that sand filter effluent should be the easiest to disin-
fect not only because many of the interferences have been removed, but also
because the number of microorganisms is less. The following discussion will
consider several disinfectants and how they might react in sand filtered
effluent.
Disinfectants for Small Flows
As can be seen in Table A-135 there are many possible disinfectants which
could be applied to small flows; however, only a few are presently practical
for use. Although this section discusses only the most promising, it is not
implied that these are the only choices. The disinfectants chosen for dis-
cussion were done so on the basis of the disinfectant presently being available
at reasonable costs and the availability of reliable feeding equipment.
Chlorine—
Chlorine remains a disinfectant of choice because it is readily available
and it is the least expensive. More is known about chlorine as a disin-
fectant than any other. The primary disadvantages of its use are its reactivity
with wastewater interferences, and the toxic effects of its residual to other
aquatic life forms.
A-2kj
-------
Chlorine can be fed as a gas (012), a liquid WaOCl and Ca (OC^) or a
solid (Ca (001)2). Because of the potential safety hazard of feeding chlorine
gas, the use of hypochlorites is a. "better choice for small flow use. Hypochlo-
rites are easier to transport and to store and use in remote locations. How-
ever, they are more expensive than elemental chlorine. The most common type
of chlorine feeder for small wastewater flows is the solid feeder. Flow past
chlorine tablets dissolves them at a slow rate. Dosage can be controlled either
by flow-control weirs or by diverting only a controllable portion of the flow
through the unit.
A portion of the chlorine, when added, is rapidly utilized as a "chlorine
demand." These are the side reactions with interferences. It is generally
felt that disinfection by chlorination is most effective when a residual of
free chlorine is present after the designed contact time. In larger scale
installations continuous monitors have been used to closely control the residual
levels after disinfection to limit the amount being discharged into receiving
waters. These, however, would be much too expensive for small scale use. The
only alternative to 'assessing the effectiveness of a chlorination system is to
take occasional grab samples and measure the free chlorine level. The dilemma
is to have a residual to demonstrate the efficacy of the process but not to
have a high level of residual which might prove toxic to other forms of aquatic
life.
A dry feed chlorinator was tested at two of the field sites (E and H) des-
cribed previously. Sand filter effluent flowed through the chlorinator and
then into a 0.57 m^ (150 gal) contact chamber at site E and a 0.^3 m3 (115 gal)
chamber at site H. These volumes provided detention times of from 3 to 21
hours. The flow was directed past one stack of 7 cm (3 in) diameter calcium
hypochlorite tablets. Dosage was found to be a function of flow as is shown
in Figure A-66. It ranged from 7 mg/L to UO mg/L at site E and average 18 mg/L
at site H.
The effect of sand filtration and chlorination on the reduction of indi-
cator bacteria in the treatment unit effluents is shown in Table A-136 and
A-137. As would be expected, the higher dosage (lower flow) at site E
resulted in slightly higher kills, yet, with the exception of total bacteria,
these kills were not significantly higher at the 95% confidence level. Of the
indicators, fecal and total coliforms appeared to be more sensitive to des-
truction by chlorination (the highest percentage reduction), while total bacterial
counts were least affected. A substantial portion of the reduction of bac-
teria can be attributed to removal of sand filtration. No tests were run to
determine the impact of these chlorinators on the level of viruses in effluents.
The major maintenance problem experiences during the use of these chlori-
nators was the failure of the tablets to move downward as the bottom tablets
dissolved. This was caused by a disintegration of the upper tablets due to
high humidity in the chlorinator. At other times, this disintegration caused
parts of the tablet to slake off and thus produce excessive dosages of chlorine
(the highest measured residual was over 20 mg/L).
The chlorine tablets utilized in the chlorinator cost about $U.20 per
kilogram ($1.98/lb). If one considers an average dose of about 20 mg/L, then
-------
1.8
o
o»
UJ
1.5
1.2
UJ
0.9
UJ
t 0.6
CE
3
o
2 0.3
-40mg/l
-30mg/l
-20mg/l *
HYPOCHLORITE UPTAKE DURING
DRY FED CH LOR I NATION
NOTE: TABLET = 4.5oz.
FIELD SITE E
FIELD SITE J
HOmg/l
I
I
100 200 300 400 500 600
FLOW RATE (GPD)
700
800
Figure A-66. Hypochlorite uptake during dry feed chlorination.
it vould cost about $23 per year to treat an average flow of 0.76 cubic meters
per day (200 gpd).
Iodine—
It has been suggested that iodine is a better wastewater disinfectant
than chlorine because it is less reactive to interferences, nonspecific
reactions are slower, and it remains in the elemental state at normal pH values
and it is unreactive with ammonia (ASCE, 1970). Like hypochlorite, it is
relatively easy to transport, store and use. Some of the disadvantages are
that little is known about the required doses for sand filter effluent or about
its toxic effects.
Iodine is normally fed as a solution (See Figure A-67 for a configuration
of a typical iodine saturator), but since it is sparingly soluble in water,
large amounts of solution may be required to achieve proper dosage in the
effluent. The solubility is affected by both pH and temperature.
Although the cost of iodine ($6,00/kg) makes it too expensive for large
scale treatment, the advantages of transport and storage may outweigh chemical
-------
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OVERFLOW
WATER INLET
IODINE CRYSTALS
GLASS BEADS
IODINE SOLUTION OUTLET
Figure A-6T. Iodine saturator*
costs for small installations.. If one were to assume that a dosage of 5-10
mg/L would adequately reduce the levels of bacteria in sand filter effluent
(Budde, et al., 1977) and an average household flow of 0.76 cubic meters per day,
then the yearly chemical cost of iodine would be about $8 to $17 per year.
Ozone—
Like chlorine and iodine, ozone acts to oxidize cell components, thus
activating them. It is such a powerful oxidant that it is also effective
at reducing organic compounds and taste and odor problems. Because it is
an unstable compound, ozone must be produced at the point of application. The
primary disadvantage for its use is the expense of reliable equipment needed
for its production.
Some of the advantages of ozone are: l) it is not sensitive to pH, 2) it
does not produce a toxic residual, and 3) it is effective at low concentrations.
A disadvantage of ozone is that it is fairly sensitive to changes in effluent
quality. A sand filtered effluent should be fairly easy to disinfect since
much organic material is removed in the process. Ozonation is also quite
sensitive to temperature changes.
A-252
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Utraviolet Light—
The germicidal effectiveness of ultraviolet light has long been known.
Only recently has its use been applied to wastewater disinfection. UV is
germicidal in the wavelength range of 230 to 300 nm with the optimum effi-
ciency at wavelength 25^ nm. Mercury vapor lamps emit a. major percentage of
their energy at this wavelength, making them the most efficient for use.
Ultraviolet irradiation has been demonstrated to be effective against
many types of microorganisms. The primary mode of action is the denaturation
of nucleic acids, which makes it very effective against viruses. The primary
interferences with UV are turbidity and dissolved substances which absorb UV
light. Some of the advantages of UV are: l) no toxic residuals are formed,
2) destructive action is rapid, 3) no chemical handling required, and h) auto-
mation is easily accomplished. The primary disadvantage of ultraviolet is that
the equipment for its application is expensive; however, power costs for small
units have been shown to be very low. Because it contains little turbidity,
sand filter effluent should be easily disinfected by ultraviolet radiation.
A commercially available ultraviolet water purifier was installed at
Laboratory site N where it was used to disinfect aerobic unit effluent and later
at site J where it was used to disinfect sand filter effluent. The unit, which
is designed for water supply disinfection, consisted of a 75 cm (30 in), low
pressure mercury vapor lamp enclosed in a 2.4 cm o.d. quartz jacket and centered
in a 7-3 cm i.d. stainless steel tube. The flow rate through the unit varied
from 7-5 to 15 liters per minute (2 to k gpm) giving a detention time ranging
from 11 to 22 seconds. Finally, the ultraviolet energy being emitted by the
lamp was 15 W according to the manufacturer's specifications.
A summary of the laboratory data is presented in Table A-138 and a plot
of this data is shown in Figure A-68. It is interesting to note that all
the bacterial indicators monitored at site N were reduced by about the same
order of magnitude (lO~3-3) or about 99-96%. Separate runs were made at
site N to relate flow to bacterial kill (Figure A-69). It was expected that
the level of kill would be inversely proportioned to flow (i.e. as flow
increased the level of kill should decrease) since the exposure is inversely
related to flow. Figure A-69, however, does not indicate such a relationship.
An attempt to relate kill to the concentration of suspended solids also indi-
cated no such relationship existed (Figure A-70).
At field site J, the unit was first used to disinfect aerobic unit-
sand filter effluent and then septic tank-sand filtered effluent. The flow
rate was set at 15 liters per minute (h gpm). The results of this field test
are presented in Table A-139- The reductions of indicator bacteria by the
septic tank-sand filter irradiation system were very high about (99-999$) for
all the monitored organisms. The reductions were not as high for the aerobic
unit-sand filter-irradiation system but it must be noted that the influent
organism counts were substantially lower and that the numbers coming out of
the ultraviolet unit were usually below the bacterial detection limit (about 1
per 100 ml).
To test the effectiveness of the ultraviolet unit against virus, a 15
liter batch of septic tank-sand filter effluent was inoculated with poliovirus-1
A-253
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TABLE A-138. BACTERIA REDUCTIONS BY ULTRAVIOLET
IRRADIATION - LABORATORY
Site
Parameter
Lab Site N
January-July, 1975
Submerged
Media
Effluent ,
log N
o
UV Water
Purifier
Effluent
log N
Ratio of
Survivors ,
N
N
o
H.93 - 8.07 2.13 - H.
Total Bacteria, log #/L
Mean (# of Samples) 9-85(12) 6.58(12) 3.27(12)
Coeff. of Variation O.oU 0.15 0.25
95% Conf. Int.
Range 9.37 -
Fecal Coliforms, log #/L
Mean (# of Samples) 5.85(28) 2.^5(28) 3.^0(28)
Coeff. of Variation O.lH 0.60 0.29
95% Conf. Int.
Range k.52. - 7.0 .57 - 3-78 2.l6 - 6.1
Fecal Strep, log #/L
Mean (# of Samples) 5.01(12) 1.70(12) 3.31(12)
Coeff. of Variation O.lU 1.U2 0.38
95% Conf. Int.
Range U.
- 6.33 0.30 - 3.90 1.67 - U.
Ps. aeruginosa, log #/L
Mean (# of Samples) 5.26(lM
Coeff. of Variation 0.21
95% Conf. Int.
Range U.ll - 7.U
3.32(11*)
0.90 O.UO
1.30 - 3.73 0.57 - 6.08
and passed through the unit. The inoculated sample had U x 10^ PFU/mL, "but no
virus (< 1 PFU/mL), was detected in the irradiated effluent.
The UV unit had an automatic cleaning device to prevent "build-up of
residues on the quartz jacket. However, the cleaner was deliberately 'dis-
connected in order to determine the consequences of inadequate maintenance.
Several months later, another pass of inoculated septic tank-sand filter efflu-
ent (> 10" PFU of poliovirus-1 per milliter) was put through the unit. No
reduction of virus titer was observed. A substantial build-up of opaque material
was noted on the quartz jacket. Given proper maintenance, ultraviolet irradi-
ation appears to be capable of achieving good disinfection both for virus and
bacteria.
A-256
-------
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LAB SITE N
JAN. 1975 - JULY 1975
0?
O-FECAL COLIFORM
D-TOTAL BACTERIA
A- FECAL STREP
X-
X?
1 1 1
10 20 30 40 50 60 70
SUSPENDED SOLIDS, mg/,£
Figure A-TO.
The effect of influent solids on bacterial
reduction by ultraviolet light.
Operation and maintenance of this unit involved periodic cleaning of the
quartz enclosure and the provision of power to the UV lamp. Even when the
automatic wiping device was operational, the quartz had to be cleaned at least
once every 6 months. During the last cleaning, the enclosure was broken and
had to be replaced. The lamp, which was operated for over a year, never needed
replacement. Although the unit was equipped with an intensity meter, it was
not sensitive enough to determine if the lamp was decreasing its output of energy.
The ultraviolet lamp utilized power at a rate of 1.5 kwhr per day when oper-
ated continuously. When operated intermittently (about 70 minutes per day) the
unit only used 2.2 kwhr per month.
Summary—
Although only four disinfectants have been discussed in this section, it
is not implied that these are the only practical disinfectants for small flows.
Much work has been done demonstrating the effectiveness of bromine as a disin-
fectant; however, its use is not widespread. Its advantages and disadvantages
very much parallel those of chlorine.
A-257
-------
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Silver, mercury and copper have "been shown to be effective disinfectants
in low concentrations but concern over toxic effects has limited their use.
Recent studies have concentrated on the use of a combination of disin-
fectants, one disinfectant covering the disadvantages of the other. Halogen
mixtures and the combined use of ozone and chlorine are two possibilities
for future use.
At the present time, it appears that the use of hypochlorite, iodine and
ultraviolet light are the most promising disinfectants for small flow use.
More work is needed to adapt these processes to small flows.
DISINFECTION OF SEPTAGE OR SEPTIC SLUDGE
The agents commonly used for disinfection of water and wastewater include
the halogens, ozone and ultraviolet irradiation, but all have serious limita-
tions when applied to concentrated wastes. In fact, disinfection of heavy
organic and particulate wastes has long been an unsolved problem.
Concentrated wastes require drastic treatment to provide disinfection and
comparatively little work has been done with septage, septic tank sludge or
municipal sludge. Those concepts that have been suggested and tested will be
mentioned. Although data for the effectiveness of the first groups of disin-
fection processes are inadequate, the literature should at least be recognized
here.
Hess and Breer (1975) reported that pasteurization of municipal sludge
at 70° C for 30 min resulted in less than 10 enterobacteriacae/g in 98 to
100% of the samples. Noack and Burger (197*0 patented a process where fresh
sludge was pasteurized at 70° C for 20 min, followed by mesophilic digestion
for 12 days. Pasteurization is, of course, an energy consuming process, so
the Noack and Burger patent is attractive for treating municipal sludge from
the standpoint that the heated sludge is then subjected to a mesophilic or
thermophilic digestion so the heat from pasteurization can be conserved and
provide further benefit.
Gamma irradiation has been tested as another approach to sludge sterili-
zation (Suess, 197^; Herruhut and Bosshard, 197^; Hess and Breer, 1975)•
Hess and Breer (1975) indicated that 300 Krad resulted in less than 10 entero-
bacteriacae/g in 97.2% of the samples.
Pasteurization and irradiation are processes that require specialized
equipment and technical personnel. The complexity and cost of the processes
may account for infrequent use.
There are a number of simpler methods for disinfecting concentrated wastes,
Feige, et al., (1975) studied lime stabilization of septage followed by sand-
bed dewatering. They found that liming sludge to a pH of 11.5 produced fecal
coliform (FC) reduction within the first day to levels below 1 x 1Q3/100 ml
(at least 3 logs of reduction). The fecal streptococci (FS) were not killed
A-259
-------
as readily, their counts being lowered no more than 1 log within the first
day of pH 11.5 treatment, but numbers dropped about 3 logs after 5 days.
Similiar results were found in lime stabilization of municipal sludge (Farrell,
197^i Doyle, 1967). Salmonellae were initially present in the municipal
sludge and testing for them after lime treatment revealed the pH of 11.5 to 12
was lethal to them.
Sobsey, et al., (197*0 examined a variety of chemicals for the disinfection
of holding tank sewage. Included were calcium hypochlorite, zinc sulfate,
phenol, formaldehyde, methylene blue, benzalkonium chloride and cetylpyridinium
chloride. They found that formaldehyde, methylene blue, benzalkonium chloride
and cetylpyridinium chloride were effective bactericides and virucides at pH
10.5, but not at lower pH values. Calcium hypochlorite, zinc sulfate and
phenol were ineffective when used on holding tank sewage.
The Feige, et, al., (1975) and Sobsey, et al., (197*0 findings provide at
least a basis for considering disinfectants for septage. Lime stabilization
appears capable of killing both fecal indicators and pathogens, but long con-
tact times (days) and the high pH of the resulting sludge would be two disad-
vantages of the process. The agents which were successful in killing bacteria
and inactivating viruses in the Sobsey study with holding tank sewage deserve
further consideration for septage since the two wastes are both high in organic
matter and solids.
Also noteworthy is the approach which combines alkalinity with a disin-
fectant to improve performance. This approach may also improve disinfection
of other agents.
Materials and Methods
A number of disinfectants were tested on septic tank sludge and the course
of these experiments (Deininger, 1977). The method of analysis for gluteral-
dehyde was based upon the reactive index of gluteraldehyde which J. H. Luft (1976)
(University of Washington, personal communication) reported rises above that of
water (Np20 1.3330) by 0.0168 for each 10/S of gluteraldehyde content. No
analytical method was found for measuring gluteraldehyde rendered in sludges.
Bacterial analyses were performed in accordance with methods described
in Appendix C.
Septic tank sludges that were tested included those from site N, and a
farm home occupied by two adults (LD). The septage from site N had a total
solids concentration of approximately 3^,000 mg/L (after sieving to remove
gross solids)whereas the farm home septage solids were about 70,000 mg/L.
Testing of Five Selected Disinfectants on Sludge
A variety of agents was selected for testing of their ability to kill
fecal coliforms (FC) in sludge. Elemental iodine, like chlorine has been
used to disinfect drinking water and wastewater. It was expected that sludge
organic matter would lower its effectiveness, but it was included in the study
for comparative purposes. lodophor compounds are commonly used for surgical
A-260
-------
scrubbing and cleaning dairy equipment. The iodine is coupled to carrier
molecules which allows iodine to be released slowly, thereby reactive iodine
remains in solution for longer periods of time. Benzalkonium chloride
(benzalkonium-Cl) belongs to the class of cationic detergents which are widely
used to clean and disinfect surfaces, particularly in hospitals and laboratories,
Formaldehyde has been found to be an effective disinfecting agent for both
bacteria and viruses, if acting at pH 10.5- Glutaraldehyde was included in
the study because of its chemical similarity to formaldehyde, its successful
use as a sterilizer of surgical equipment (Stonehill, et al., 1963), and its
well known properties as a biological fixative (Hayat, 1970).
These agents were tested on site N septage over a range of concentrations
considered reasonable from literature findings. The pH values at which the
agents were tested were based on recommendations from the literature. Ben-
zalkonium-Cl and formaldehyde were reported most effective at pH 10.5 in
treating holding tank sewage. It was the experience of this study that FC kills
were very different at pH 10 and 11, and that pH 10.5 was near to the pH where
bacterial death took place with no additional disinfecting agent. For this
reason pH values of 9 and 10 were chosen as maximum test levels to avoid any
masking effect of pH being the dominant factor in FC kills, and also to mini-
mize caustic handling problems. Contact times of 1, 2 and h hrs were allowed
for all of the agents to facilitate comparisons.
Results of the experiment are found in Table A-1^0. The data are ex-
pressed as percent survivors to simplify comparisons between agents tested.
An asterisk beside a survivor percentage indicates at what percentage survivors
the FC counts were less than 200/100 mL.
Elemental iodine and iodophor were most effective at initial dosages of
500 mg/L iodine. Iodine was only tested at pH 7.3 since that is near the
optimum pH for iodine disinfection (Chang, 1958). Also, this is within the
normal pH range for most septages.
Benzalkonium-Cl was bactericidal at concentrations of 500 mg/L and some-
what at 300 mg/L. The bactericidal activity does appear to be enhanced by
increasing the pH from 9 to 10.
Formaldehyde treatment at pH 10 and glutaraldehyde treatment at pH 9 and
10 gave the best performance of all of the agents tested in this experiment.
A concentration of 200 mg/L of formaldehyde reduced FC below 200/100 mL within
h hrs of contact. There seemed to be no advantage in combining benzalkonium-Cl
and formaldehyde for sludge treatment. Glutaraldehyde produced FC kills to
levels below 200/100 mL even at the 100 mg/L dosage. The kill was rapid with
the majority of deaths taking place during the first hr of contact. On the
basis of these preliminary experiments, formaldehyde and glutaraldehyde seem
to warrant further study.
Formaldehyde Studies
Further detailed work was performed with formaldehyde to better character-
ize its effectiveness on septic tank sludges. Results of experiments conducted
A-261
-------
TABLE A-lUO.
TESTS OF VARIOUS DISINFECTING AGENTS AGAINST
FC IN SITE N SEPTAGE*(Deininger , 1977)
Percent FC survivors
after
contact time (hr) of:
Disinfectant
KI + I2
PH 7.3
lodophor
pH 7.3
Benzalkonium-Cl
pH 9.0
Benzalkonium-Cl
pH 10.0
Formaldehyde
pH 9.0
Formaldehyde
pH 10.0
Formaldehyde/
benzalkonium-Cl
pH 9-0
Formaldehyde/
benzalkonium-Cl
pH 10.0
Glutar aldehyde
pH 9.0
Glutar aldehyde
pH 10.0
mg/L
100
300
500
100
300
500
100
300
500
100
300
500
50
100
200
50
100
200
50/100t
100/200
200/300
50/100
100/200
200/300
100
200
300
100
200
300
(FC/100 mL)
U.3 x 106
U.3 x 10JJ
U.7 x 106
9-3 x 10*2
9.3 x 10°
U.3 x 106"
9.3 x 106
2.3 x 10°
U.3 x 106
U.3 x 106"
9-3 x 10°
7-5 x 10°
1.5 x 10 J
7.5 x 106
1.5 x 10T
9.3 x 10^
U.3 x 10°
7-5 x 106
U.3 x 106
1.5 x 10?
1.5 x 10^
U.3 x 10*2
3.9 x 10°
9.3 x 10b
U.3 x 106
1.5 x 10 J
9-3 x 10°
U.3 x 106
U.3 x 10°
2.3 x 10°
1
100
100
0.0020
26
100
0.10
U6
100
1.0
100
U.6
0.0057
2.9
10
29
81
10
0.31
53
29
15
5.3
59
2.5
< 0.070
< 0.020
0.0032
< 0.0070
< 0.0070
0.013
2
100
100
0.00050
100
0.025
0.17
U60
Uoo
< 0.00070**
100
0.081
0.00053**
5.0
10
0.62
2.5
0.053
0.0053**
100
2.9
2.9
100
38
o.ooU6
0.0070
0.0020
< 0.00032**
< 0.00070**
< 0.00070**
< 0.0013**
U
100
100
0.0050
U6
O.U2
0.053
U6o
100
0.00093**
53
0.0025
0.0031
29
5.7
2.9
0.25
0.053
0.00067**
56
2.9
6.2
10
3.8
< 0.00032**
-------
with the farm home (LD) septage (TS = 70,000 mg/L) appear in Table A-lUl. Of
the groups tested, FC and P_. aeruginosa were most reactive to formaldehyde
at pH 10.0. It is apparent from the control data that formaldehyde, not pH
alone accounted for the bacterial kill measured.
The effect of sludge concentration on required formaldehyde dose is shown
in Table A-lU^, again employing (ID) septage. A more rapid rate of killing
is apparent at the lower sludge concentrations. At 12 hours of contact, how-
ever, approximately the same reduction of FC was achieved. In additional
experiments, it was shown that allowing sufficient contact time (6 to 12 hrs)
was more important in providing adequate bacterial kills than was vigorous
mixing.
Gluteraldehyde Studies
Bacterial Disinfection—
Further testing was also performed with gluteraldehyde. Results of ex-
periments conducted with the (LD) septage using gluteraldehyde at pH 7-1
appear in Table A-1U3. The FC and P. aeruginosa bacterial groups were the
most sensitive tested, and a dose of 750 mg/L or greater reduced FC to unde-
tectable levels (7 log drop) within 3 hours. The total bacterial counts (TBC)
were little effected by even the highest doses of gluteraldehyde. Further
analyses suggested that spores accounted for the resistance to this disin-
fectant.
The effect of sludge concentration on gluteraldehyde disinfection at pH
7.1 appears in Table A-l^. As with formaldehyde, it was apparent that the
same dose of disinfectant was more effective at lower solids concentrations.
Since the binding capacity of glutaraldehyde to target chemical groups
increases with increased alkalinity (Hayat, 1970), it would be expected that
this disinfectant would be most useful at pH values in excess of 7-0. The
effect of septage pH on disinfection is shown in Table A-145. It is apparent
that gluteraldehyde treatment at pH 7 or lower results in greater FC and FS
reduction than treatment in the weakly alkaline range. This is likely due to
the non-specific binding of aldehyde to inert protein within the sludge. At
lower pH, more effective penetration is achieved, even though the rate of
binding is decreased.
Studies in the temperature range of 6 to 20° C indicate that within this
range there is little effect on glutaraldehyde disinfection at pH 7.1.
Virus Inactivation—
The procedure by which the model septage suspensions were inoculated with
virus was as follows:
1. Septage (LD sludge, TS = 70,000 mg/L) was sieved through 1 cm
(3/8 in) hardware cloth and blended at "high" speed with a
Waring blender. The sludge thus prepared characteristically
has a TS concentration of 66,000 mg/L.
A-263
-------
TABLE A-lUl. FORMALDEHYDE TREATMENT OF LD SEPTAGE AT 20C
AND pH 10.0* (Deininger, 1977)
Formaldehyde
Concentration
Control
pH 7
Control
pH 10
500 mg/L
750 mg/L
1,000 mg/L
1,250 mg/L
Bacterial
group**
FC/100 mL
FS/100 mL
PA/100 mL
TBC/mL
FC/100 mL
FS/100 mL
PA/100 mL
TBC/mL
FC/100 mL
FS/100 mL
PS/100 mL
TBC/mL
FC/100 mL
FS/100 mL
PA/ 100 mL
TBC/mL
FC/100 mL
FS/100 mL
PA/100 mL
TBC/mL
FC/100 mL
FS/100 mL
PA/100 mL
TBC/mL
Bacterial
1 hr
1.7 x 108
6.6 x 106
No data
3.2 x 106
1.7 x 108
6. It x 106
No data
2. U x 106
1.7 x 10T
5.8 x 106
5.0 x 101
1.1 x 106
3.5 x 106
7.6 x 106
<2.0 x 101
7.2 x 105
1.3 x 106
5.9 x 106
<2.0 x 101
1.7 x 105
7.0 x 101*
5.0 x 106
<2.0 x 101
1.8 x 105
survivors after contact of:
6 hr
8
1.7 x 10
5.0 x 106
2.3 x 1011
8.U x 106
7.0 x 10T
9.0 x 10^
7.0 x 101*
It.U x 106
3.5 x 101*
3.5 x 106
<2.0 x 101
1.3 x 105
U.9 x 102
9.1 x 105
<2.0 x 101
1.7 x 105
2.2 x 102
6.9 x 10 5
<2.0 x 101
1.5 x 105
2.0 x 101
7.0 x ID1*
<2.0 x 101
1.2 x 105
12 hr
1.6 x 109
5.5 x lO^
2.3 x 10^
1.5 x 10T
9.2 x 108
7.U x 106
1.3 x 103
1.1 x 10 7
<2.0 x 101
2.3 x 106
<2.0 x 101
1.7 x 105
<2.0 x 101
3.2 x 105
<2.0 x 101
1.2 x 105
<2.0 x 101
5.0 x 102
<2.0 x 101
1.1 x 105
<2:0 x 101
<1.0 x 103
<2.0 x 101
1.5 x 105
* LD Sludge, TS - 70,000 mg/L
** Initial numbers
FC/100 mL = 2. it x 10
FS/100 mL = 8.1 x 10
PA/100 mL = 3.5 x 10
TBC/mL = 6.8 x 10°
°
A.-26k
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-------
TABLE A-lUi GLUTARALDEHYDE TREATMENT OF LD SEPTAGE* (Deininger, 1977)
Glutaraldehyde Bacterial Bacterial survivors after contact of:
concentration group**" 1 hr 3 hr 6 hr 12 hr
500 mg/L FC/100 mL <2.0 x 103 8.0 x 101 2.0 x 101 2.2 x 103
FS/100 mL 2.0 x 105 1.0 x 10^ k.Q x 103 1.5 x 10°
PA/100 mL <2.0 x 10 <2.0 x 101 <2.0 x 101 <2.0 x 101
TBC/mL 2.9 x 105 1.7 x 105 1.7 x 105 2.0 x 105
750 mg/L FC/100 mL 5.0 x 102 <2.0 x 101 <2.0 x 101 <2.0 x 101
FS/100 mL 1.0 x IQ^ <1.0 x 102 <1.0 x 102 <1.0 x 102
PA/100 mL <2.0 x 101 <2.0 x 101 <2.0 x 101 <2.0 x 101
TBC/mL 2.8 x 105 1.2 x 105 lA x 105 1.5 x 105
1,000 mg/L FC/100 mL 2.0 x 101 <2.0 x 101 <2.0 x 101 <2.0 x 101
FS/100 mL 5.0 x 10 3 <1.0 x 102 <1.0 x 102 <1.0 x 102
PA/100 mL <2.0 x 101 <2.0 x 101 <2.0 x 101 <2.0 x 101
TBC/mL 3.2 x 105 1.7 x 105 1.2 x 105 i.U x 105
1,250 mg/L FC/100 mL 1.7 x 103 <2.0 x 101 <2.0 x 101 <2.0 x 101
FS/100 m.L 2.0 x 103 <1.0 x 102 <1.0 x 102 <1.0 x 102
PA/100 mL <2.0 x 101 <2.0 x 101 <2.0 x 101 <2.0 x 101
TBC/mL 3.0 x 105 l.H x 105 1.3 x 105 lA x 105
* LD sludge, TS = 70,000 mg/L; pH = 7-1; T = 20° C
** Initial numbers
FC/100 mL = 1.3 x 108
FS/100 mL = 1.8 x
PA/100 m.L = 2.2 x 103
TBC/mL = 2.9 x 106
A-266
-------
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A-267
-------
TABLE A-lUj. INFLUENCE OF SLUDGE pH ON GLUTARALDEHYDE DISINFECTION OF
BACTERIA* (Deininger, 1977)
Percent survivors** after
contact of:
PH
Initial/Final
8.5/8.3
7.1/7-1
6.0/5.9
5-U/5.8
Glutaraldehyde
dose (mg/L)
Control
500
1,000
Control
500
1,000
Control
500
1,000
Control
500
1,000
Bacterial
group
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
FC
FS
Initial
counts 1 hr
9.2 x 108
7.2 x 107
O.OU9
0.91
0.071
O.lU
1.7 x 10T
2.U x 107
0.0053
O.OU2
0.038
0.021
9.0 x 107
U.O x 107
0.017
O.UU
O.OlU
O.OUU
9.0 x 107
U.O x 10 7
0.0022
0.96
<0.27
0.0020
3 hr
0.013
0.015
0.12
_
-
0.015
O.lU
0.0038
0.0083
_
-
0.019
O.OOUO
0.0013
0.012
_
-
O.OlU
0.026
0.000l6t
0.066
6 hr
59
110
O.OU8
1.0
0.0026
0.15
U2
96
0.0076
0.058
O.OlU
-------
2. A measured volume of septage sufficient for an experiment (usually
between 200 to 1*00 mL) was stirred in a sterile 500 mL erlenmeyer
flask with a magnetic stirring bar.
3. The poliovirus stock at 3-0 x 10? PFU was added at the rate of 0.5
mL per 100 mL septage with constant stirring for 30 min. Final
virus concentration = 1.5 x 10? FPU/mL.
h. Virus-inoculated septage was then refrigerated at h° C overnight to
allow adsorption of virus to sludge particles.
5. The next day the inoculated septage was again stirred for 15 min
to mix and resuspend particles. The virus-inoculated septage was
then ready for use in experiments.
It was found during the bacterial studies that glutaraldehyde treatment of
neutral or slightly acidic septage resulted in greater bacterial kills than
in alkaline sludge. Consequently, it was necessary to examine whether pH
would play a role in virus inactivation when septage containing virus was
treated with glutaraldehyde.
Following the above procedure, the stirred virus-inoculated septage
was mixed for 15 min with a magnetic stirring bar after which the material
was divided into sterile flasks of 100 mL each. The contents of the flasks
were adjusted to pH 5.0, 6.0, T.I and 8.0, respectively, with 10% KOH or 10$
HC1. Thirty milliliter quantities of septage, two each for each pH point,
were added to sterile 25 x 200 mm test tubes and equilibrated to 20° C. Each
tube was treated with 500 mg/L glutaraldehyde and allowed 3 hrs of contact
before it was assayed for virus. A control was run at pH 7 without glutaral-
dehyde treatment to determine the initial level of PFU in the septage. The
recovery procedure described earlier was followed for all samples and included
FCS addition, adjustment to pH 9 and sonication. The plaque assay was per-
formed on HeLa cells according to the usual procedure.
Table A-lk6 shows that pH from 5.0 to 8.5 had little effect on the number
of PFU found in the virus-septage preparation after treatment with glutaral-
dehyde. Despite the small differences in virus inactivation with glutaral-
dehyde at the four pH values, slightly greater inactivation was found in the
acidic range. The close agreement of the duplicate tests at each pH suggest
that although the improvement in inactivation under acid conditions was small,
it was probably significant rather than due to imprecision of the analyses.
This is compatible with the results from bacterial experiments in which
glutaraldehyde treatment of septage in the acidic range favored bacterial kill,
but it appears that the pH is of only minor importance to viral inactivation.
Since the 500 mg/L glutaraldehyde level applied in this experiment
reduced the PFU only 0.8 to 1.5 logs, it would be desirable to provide a higher
degree of inactivation. The bacterial work with glutaraldehyde also showed
a 500 mg/L dose to be marginally effective in destroying fecal coliform and
fecal streptococcal bacteria in septage, but a 1,000 mg/L treatment was more
effective. An experiment comparing viral inactivation in septage at pH 7-1
with glutaraldehyde at dose levels of 500 to 1,000 mg/L was then performed.
A-269
-------
TABLE A-1U6. INFLUENCE OF pH ON POLIOVIRUS INACTIVATION IN
SEPTAGE WITH 500 MG/L GLUTARALDEHYDE
pH
Initial/Final
5. 0/1*. 6
6.0/6.1*
7.1/7-3
8.5/7.8
Percent
after
Average
6.6t
U.5
11
15
virus survivors
3 hr contact
Range
6.1* to 6.9
3.6 to 5.3
0
ll* to 16
tlnitial number of poliovirus = 5-8 x 10°/mL
*LD sludge, sieved, blended, TS = 66,000 mg/L
Temperature = 20° C
Sieved, blended septage (LD sludge, TS = 66,000 mg/L) was inoculated with
poliovirus to a level of 1.5 x 10? PFU/mL, as described before. After over-
night adsorption of l*°c, 30 mL quantities of virus-inoculated septaee were dis-
pensed into sterile 25 x 200 mm test tubes and equilibrated to 20° C for about
1.5 hrs. Glutaraldehyde was then added to the tubes of septage to concentra-
tions of 500 to 1,000 mg/L. At selected time periods, duplicate tubes of the
two dose rates were treated for 1 min with 1,260 mg/L NapSO_. Next, fetal
calf serum (FCS) was added to each septage sample, and the septage FCS mixture
was adjusted to pH 9. This mixture was then stirred with a stirring bar for
15 min. The remainder of the recovery procedure and plague assays were per-
formed as usual. Control samples received no glutaraldehyde but were other-
wise processed as above.
The 500 mg/L glutaraldehyde level caused 1.1* log-j_g of reduction of polio-
virus titer, The virus inactivation occurred mostly during the first hour
of treatment with little change during the 1 to 3 hour span of contact. The
dose rate of 1,000 mg/L produced 2.7 logj_o of poliovirus inactivation. In-
activation was most rapid during the first 1.5 hours of contact, but nearly
0.5 log of inactivation took place between 1.5 and 3 hours.
Poliovirus appears to be more resistant to glutaraldehyde treatment than
the fecal indicator bacteria. A glutaraldehyde dose of 500 mg/L produced
approximately 3 and 1* Iog10 of reduction, respectively, of fecal streptococci
and fecal coliforms compared to 1.1* log]_g of reduction of poliovirus. A
1,000 mg/L glutaraldehyde dose produced about 1* log^g reduction of fecal
streptococcus and k to 7 log]_Q of fecal coliform reduction while poliovirus
was reduced approximately 3 log]_g. Just as a 500 mg/L glutaraldehyde treatment
was considered marginal for bacteria, it also appears to be marginal for virus.
A 1,000 mg/L concentration of glutaraldehyde is therefore recommended.
A-270
-------
The treatment procedure of septage with glutaraldehyde could be performed
in the tank of the pumper truck. After estimating the volume of septage to
be pumped, the required amount of glutaraldehyde could then be added and be
mixed with the septage in one of two ways. First, the glutaraldehyde could
be added to the empty truck tank and mixed by pumping the septage into it.
A gradient of glutaraldehyde would form as the septage entered and would be
diluted to the proper concentration when the contents of the septic tank filled
the truck tank. Alternately, the glutaraldehyde could be metered into the
septage as it is pumped into the tank of the truck. In either procedure, ad-
ditional mixing would occur due to sloshing back and forth of the liquid as
the truck moved.
As mentioned, 1 to 3 hrs of contact is needed before bacterial kill and
viral inactivation is nearly complete (some additional bacterial kill may
take place for up to 6 hrs). This could not be feasible if it would have to
be held in the truck tank for an entire contact period before discharge.
However, if the truck empties its tank contents into a holding tank at the
disposal site, additional disinfection would likely occur in that vessel.
GREY WATER TREATMENT
Typically, when segregated systems are suggested with the toilet wastes
handled through use of a non-conventional toilet system (e.g., composting,
incinerating, recycle, low-volume flush/holding tank) grey water treatment
and disposal involves a conventional septic tank-soil absorption system
(possibly of reduced size). Although this is an obvious method of treatment
and disposal, the characteristics of grey water appear to be such that simple
alternative methods might exist which could be more desirable in certain appli-
cations. Some treatment methods might even facilitate surface disposal or
outside reuse of the grey water. To enhance the near non-existent data base
regarding the on-site treatment of household grey water, this preliminary
study was conducted. The major objectives established were to:
1. Identify the comparative performance of septic tank treatment of
grey water versus that of combined black and grey water,
2. Identify the comparative performance of septic tank treatment of
grey water utilizing a 2.0 nP (500 gal) septic tank versus a U.O
m3 (1000 gal) septic tank,
3. Investigate the comparative performance of intermittent sand fil-
tration of septic tank effluent as generated by grey water versus
combined black and grey water, and
h. Identify areas for further research.
To provide a controlled environment for this preliminary study and facili-
tate the above types of comparisons, this effort was conducted at laboratory
site N. This grey water treatment study was initiated at this facility in
April, 1976 with active data collection beginning in July, 1976. The results
presented and discussed herein involve a one-year period from April, 1976 to
April, 1977-
A-271
-------
Data Generation Methods
To summarize briefly, at laboratory site N the waste-water generated by
typical household events was simulated utilizing conventional appliances as
well as specially designed equipment and consumer materials/waste products
(more detail is provided elsewhere in this Appendix). Utilizing a sophisti-
cated electronic control system, the simulated household events were made to
occur intermittently during the day, yielding a loading pattern representative
of that generated by a family of four. By staggering the schedule of events,
the same event sequence and daily loading could be applied to each of several
treatment units.
The general flow sheet for this study is presented in Figure A-71.
As shown, the individual events were simulated and the resulting grey waters
were directed to each of two, septic tanks of 2.0 m^ (500 gal) and
U.O m.3 (1000 gal) size. A third septic tank of H.O my size, received the
same grey waters, as well as toilet flush wastewaters. The effluent from
each septic tank flowed into its own 0.2 m3 (55 gal) sump from which it was
intermittently pumped. The effluent from the 2.0 m3 grey water tank sump was
.WASTEWATER SIMULATION
GREY WATER GREY WATER GREY a BLACK WATER
BATH-SHOWER
DISH RINSING
DISH WASH
LAUNDRY
OTHER
BATH-SHOWER
DISH RINSING
DISHWASH
LAUNDRY
OTHER
BATH-SHOWER
DISH RINSING
DISHWASH
LAUNDRY
OTHER
TOILET
0.2m3
SUMP
SAND FILTERS!
0.9m2 x0.6m
DEEP
CITY SEWER
Figure A-71. Grey water treatment study - flow sheet.
A-272
-------
discharged directly to the city sewerage system, as was a majority of the
effluent from each of the k.O m^ tank sumps. A portion of the effluent from
each of the U.O m3 septic tanks was applied to a series of sand filters (8).
Each filter had a surface area of approximately 0.09 m2 (l.O ft2) and a depth
of 0.6 m (2.0 ft).
Simulated Raw Wastewater—
Each of the three septic tanks received the same grey waters and one of
the units also received toilet flush wastewaters. The day-to-day loading was
constant for all events with the exception of the laundry which varied from
none to three occurrences per day. A summary of the make-up of the simulated
event wastes is shown in Table A-1^7 with the daily loading pattern to each
unit depicted in Figure A-72.
The average characteristics of the simulated wastewaters were identified
through periodic analyses of the individual material constituents, the results
of which were composited mathematically. Several actual influent composites
were also taken and analyzed. Based on these results, the characteristics
of each of the two simulated influents were, on an average daily basis, as
shown in Table A-lW. Variations from the values shown in Table A-1^8 occurred
as a result of the day-to-day laundry variation. Further, infrequent pro-
grammer malfunctions and maintenance requirements also resulted in variations
from the values shown in Table A-1^7, as well as Table A-1U8 and Figure A-72
during the course of the study.
TABLE A-lVT. SIMULATED WASTEWATER EVENT CHARACTERISTICS
Event
Simulated
Bath
Shower
Dish Rinse
Dish Wash
Laundry
Miscellaneous
Toilet
L .
Event
79
102
11
53
180
19
19
Number
Day
1
1
3
1
3
2
0
3
12
L
Day
79
102
33
53
5^0
360
0
57
228
Material
Event
Liquid Soap
Liquid Soap
Food Slurry
Detergent
Detergent
Detergent
-
-
Urine Solution
Hog Manure
Paper
Quantity
Day
25 mL
25 mL
780 mL
80 gms
375 gms
250 gms
-
-
3.8U L
ihOO gms
19 gms
A-273
-------
50
O
-1189
T -TOILET
OR- DISHRINSE
L -LAUNDRY
0 -OTHER
30 -
25-
20
15
10
5h
NOTE: FOR DAYS WITH 3L,
L, , L, , a L, OCCUR JFOR 2 L,
DW-DISHWASH £
- B -BATH
S -SHOWER
NOTE: FOR THE GREY
WATER UN ITS, NO
• TOILET EVENTS
OCCUR, v
C
i »
X
) T
_i — i — i — i —
»
TTTC
)
i'
•
i
T
L, a L2 OCCUR; FOR 0 L ,
NONE OCCUR.
'
1
: i
FT 1
I,
D'
'T
#
'
E
•
i
J
-
TO T "
MN
9 NOON 3
TIME OF DAY
-100
-75
50
25
0
MN
O
O
Figure A-72. Approximate daily loading pattern.
TABLE A-ll*8. SIMULATED RAW ¥ASTE¥ATER CHARACTERISTICS - DAILY AVERAGES*
Parameter
Flow
BOD
COD
**
TS
TSS
TN
TP
Grey Water
Mass /Day
U8U Liters
108 Grams
203
396
52
5-6
21.5
mg/L
-
220 mg/L
U20
820
110
12
UU
Combined Wastewater
Mass /Day
711 Liters
186 Grams
519
87^
295
57
U0.2
mg/L
260 mg/L
730
1230
UlO
80
57
* Does not take into account infrequent down-days, programmer malfunctions, etc,
** Includes 300 mg/L total solids contribution from the tap water
-------
Septic Tank Operation—
All three of the septic tanks utilized in this study had been used during
the previous research effort at laboratory site N. All three tanks had re-
ceived simulated combined wastewater for approximately 15 months prior to the
start of this study. The 4.0 m3 tanks were left as is, while the 2.0 m3 tank
was pumped down and cleaned out except for a few cm of residual material. For
three months prior to the start of this evaluation, the three septic tanks
were fed their respective new raw wastewaters, grey or combined, to stabilize
their performance.
During the course of this study, daily flow composited samples of each
septic tank effluent were collected weekly. These samples were obtained, as
desired, by directing a fraction of the wastewater pumped from each septic
tank effluent sump to refrigerated containers through a 0.6 cm diameter sample
line. The samples collected were analyzed for various chemical/physical
parameters. In addition to these composite samples, several grab samples were
obtained from each septic tank effluent for bacteriological analysis.
Sand Filter Operation—
Eight sand filters were established specifically for this study. Each
filter had a surface area of 0.09 m^, 30 cm of freeboard, 60 cm of sand under-
lain by 13 cm of pea gravel and 18 cm of coarse stone. All eight filters were
housed in a single lysimeter constructed of plywood supported by an angle-iron
frame, as shown in Figure A-73.
Portions of effluents from the ^4.0 m^ septic tanks were applied to the sand
filters in several intermittent doses with a special distribution system. As
shown in Figure A-73, the system was attached to the top of the sand filters
and consisted of two identical chambers, one receiving grey water septic tank
effluent and one receiving combined wastewater septic tank effluent. The
operation of each chamber was essentially the same, and therefore, the follow-
ing description will deal only with that for the grey water.
Each time the sump receiving the effluent from the grey water septic
tank received about 28 L of effluent, a pump was activated with most of the
wastewater discharged to the city sewer. However, a portion (adjustable)
of the effluent was directed to the grey water distribution chamber through
a 2.0 cm diameter section of plastic pipe connected to the sump discharge
line. After three, 6 L fractions were so directed to the grey water chamber
(four, U.5 L portions for the combined wastewater) a high-level float switch
was triggered, activating a relay which opened a 3.0 cm drain valve attached
to the chamber bottom and also recorded the event. The effluent from the
chamber flowed through the valve and into a fitting which divided the flow
into 8, equal fractions. Each fraction was carried away from the fitting in
a section of 0.6 cm diameter tygon tubing to drains or to an operating sand
filter. In the latter case, the end of the tubing was held in place above the
filter by insertion through a hole in a wood dowel attached to the top of the
filter. The size of the dose and the daily hydraulic loading to a filter
could be varied with this system by directing more than one section of tubing
to it. The effluent flowing through each section of tubing was directed onto
a splash plate on the sand surface. After this distribution chamber emptied,
A-275
-------
Figure A-73. Sand filter system.
a low-level float switch was triggered, deactivating the relay, closing the
drain valve, and resetting the system.
The majority of the effluent applied to a filter drained througli a 3.0
cm diameter line attached to its "bottom, to a sump from which it was discharged
to the city sewerage system. A fraction of the wastewater moving through a
filter was collected near the filter bottom in four, reducer fittings (3.0 cm
x 1.25 cm) whose upper lips were 5 cm above the filter bottom. The 1.25 cm
end of each fitting projected through the filter bottom and a short section of
1.0 cm diameter tubing was attached to each. These four, sample collection
tubes from each filter were directed to a collection tray for disposal or, as
desired, to a sample bottle for a flow composited sample.
A summary of the experimental design used in the sand filter research
is presented in Table A-
A-276
-------
TABLE A-ll*9. SATO FILTER EXPERIMENTAL DESIGN
Filter
Number
1
2
3
k
5
6
7
8
Effluent
Applied
Grey Water
11
ii
a
Combined
Wastewater
11
it
ii
Application
Rate
(cm/ day)
30
30
15
15
15
15
30
30
Media Size
Effective
Size
(mm)
.28
.30
.30
.28
.28
.30
.30
.28
Uniformity
Coefficient
3.2
2.9
2.9
3.2
3.2
2.9
2.9
3.2
During the first two months of operation, the appropriate septic tank efflu-
ent was applied to each sand filter at the prescribed loading. In total,
approximately 850 and 1700 L were applied, respectively. Then the loading was
discontinued, the top 15 cm of sand were replaced, and the filters were rested
for nine days prior to the start of actual data collection.
During the course of this study, daily sand filter loadings were recorded.
Visual observations of the sand surfaces were routinely made and depth of any
ponding above the sand surface was noted. Flow composited samples of the filter
effluents were collected bi-monthly and analyzed for various chemical/physical
parameters.
Results and Discussion
Septic Tank Performance—
The results of selected chemical/physical analyses on daily flow composited
samples of each septic tank effluent are presented in Table A-150. The efflu-
ent from the 2.0 nP septic tank treating grey water was significantly higher in
BOD,- and COD than the k.O ra? septic tank also treating grey water. For the
other measured parameters, there was virtually no difference between the concen-
trations in the two, septic tank effluents. The increased residence time in
the larger tank (about eight days versus four days) would seem to have been
responsible for the greater BOD,- and COD reductions, but of little additional
value in terms of suspended solids removal or nutrient conversion. It is also
possible that the physical characteristics of the smaller, circular tank could
A-277
-------
TABLE A-150. SEPTIC TANK EFFLUENT COMPARISON, MG/L
Parameter
BOD5*
COD
TSS
VSS
Total-N
WH3-N
Total-P
Ortho-P
Grey Water
2 m3
101(U)**
88-llU
236(142 )f
220-252
U7(Ul)t
^2-53
37(^0 )t
32-Hl
6.5(22)
6.1-7.0
1.M25)
0.9-1.8
UU(28)
1*1-1*7
3M27)
29-38
Grey Water
1* m3
62(57)t
56-68
17l(55)t
159-183
U6(56)t
Ul-51
3M55)t
32-37
7.7(22)
7.0-8.1*
2.1(39)
1.7-2.5
UO(30)
37-^2
3M26)
31-37
Combined Wastewater
1* m3
55(60 )t
50-61
l69(58)t
155-185
l*6(58)t
1*1-52
33(58)t
30-37
79(22)
75-81*
5MU3)
^9-59
^3(27)
1*0-1*5
36(27)
33-39
Based on 10 sample analyses, soluble BOD,- to total B01X equal to 0.8 for
all units.
Each data block includes: Mean (samples); 95% confidence interval.
t Log-normalized data.
have resulted in the tank effluent being more influenced by surge loadings than
the larger cylindrical tank.
Although the concentrations of BOD^, COD and suspended solids were con-
siderably higher in the raw combined wastewater as compared to the raw grey
water (Table A-150) the measured characteristics of the effluents from the
two, 1*.0 m3 septic tanks were essentially the same. The grey water tank
provided an average retention time of eight days while the combined wastewater
tank provided five days. Visual inspection of the two septic tank effluents
during the course of the study revealed that the grey water tank consistently
produced an effluent which was grey-black in overall color with substantial
A-278
-------
quantities of fine, black solids. The combined wastewater tank produced an
effluent which had a lighter color vith significantly less fine, black solids.
The black coloration and fine, black solids was believed to be due to the
reduction of sulfates (approximate tap water concentration, 80 mg/L as SOJ7) to
sulfides under anaerobic conditions, with resultant precipitation as metal
sulfides. A sulfide odor was noted in both septic tank effluents, but the odor
was considerably stronger in the effluent from the grey water tank. The pH of
both effluents was about 7-3.
The results of bacteriological analyses on several grab samples of each
septic tank effluent are presented in Table A-15L The results for the septic
tanks receiving grey water were not anticipated. After April, 1976, no material
of fecal origin was added to either grey water tank. It was anticipated that
initially, indicator bacteria would be present in the septic tank effluents as
a result of pre-sampling operations during which both tanks received combined
wastewaters. At the start of this study, the grey water tank was not pumped
or cleaned, while the smaller grey water tank was washed down and cleaned out,
except for a few cm of residual material. With time and the dilution effected
by the influent grey waters, it was expected that the concentration of indi-
cator bacteria in the septic tank effluents would decrease to low levels. As
shown in the table, this did not happen. Even after seven and thirteen months
of operation, very high levels of indicator bacteria were found in the grey
water tank effluents. It would seem that the indicator bacteria were actively
reproducing in these tanks. If the traditional indicator bacteria do, in fact,
actively reproduce in a grey water septic tank environment, one must question
the value of using the effluent concentrations of these organisms to assess
the potential for pathogenic contamination of the raw grey waters.
Sand Filter Performance—
Each of the eight sand filters was operated until its hydraulic con-
ductivity decreased to the point where it no longer accepted the wastewater
applied and ponding above the sand surface reached a height of about 25 cm.
When this occurred, loading to the filter was discontinued and it was allowed
to drain. Since only the four high-rate filters (l, 2, 7» 8) failed during
the course of this study, the following discussion will be restricted to
these four filters. A summary of the operational data for each filter and its
filter run is presented in Table A-152.
As presented in the table, the filters receiving grey water septic tank
effluent yielded filter run lengths over twice those of the filters receiving
combined wastewater septic tank effluent. As the hydraulic loading rates
were approximately equal, the grey water filters (l, 2) accepted about twice
as much wastewater on a total volume basis. Utilizing the mean characteristics
of each applied wastewater (grey water and combined wastewater septic tank
effluents), the quantities of BOD^ and suspended solids per square metre of
surface area were calculated. The grey water filters received about ikO per-
cent more BOd- and 60 percent more suspended solids than did the combined
wastewater filters (Table A-152}. Since the effluents from the four filters
were of very similar quality, the grey water filters effectively removed
approximately 1^0$ more BOD,- and 60% more suspended solids than the combined
wastewater filters.
A-279
-------
TABLE A-151.
BACTERIOLOGICAL CHARACTERISTICS OF
SEPTIC TANK EFFLUENTS, NO./100 ML
Organism
Total
Coliform
Fecal
Coliform
Fecal
Streptococci
Total
Bacteria
Sample
Date
1-16
11-76
5-77
7-76
11-76
5-77
7-76
11-76
5-77
7-76
11-76
5-77
Grey Water
2 m3
15 x 10^
31* x 103
<100
hO x 106
Grey Water
h m3
33 x 101*
12 x 10^
5^ x 10 5
33 x 10^
U9 x 103
36 x 10 5
18 x 103
23 x 102
31 x 10?
Ul x 105
33 x 10T
Combined Wastewater
U m3
U9 x 105
12 x 1011
50 x 10 5
U9 x 105
31 x 103
lU x 105
U8 x 102
3^ x 10^
11 x 10^
16 x 106
16 x 109
TABLE A-1J2. HIGH-RATE FILTER OPERATION
Filter
1
2
7
8
Effluent
Applied
Grey
Grey
Combined
Combined
Daily
Application
Doses
Day
5
5
6
6
cm /day
29
29
31
31
Run Days to-
Ponding
226
260
10^
108
Failure
26U
285
12l4
12U
Total Application
m^
L
6610
7110
3330
3310
Grams
UUlO
U7^0
19^0
19^0
Grams
3230
3550
20UO
20UO
During the operation of the filters prior to failure, a distinct visual
difference was noted between the surfaces of the grey water and combined
wastewater filters. The surfaces of both high-rate grey water filters ex-
hibited significantly less solids accumulation and surface impeding layers than
did the high-rate combined wastewater filters. After a filter failed and was
allowed to drain, visual inspection of the sand surface was made. Subse-
quently, the filter was carefully excavated from the surface down to allow
observation of any subsurface impeding layers and the filter profile with depth.
A-280
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The combined waste-water filters had a thin mat of solids covering a majority
of the filter surface. Upon digging into each filter, a black colored zone
was found to extend to a depth of several cm followed by a gradation through
grey to visually clean sand. In contrast, the grey water filters had only a
sparse accumulation of solids on their surfaces. Upon excavation, a black
colored zone was found to exist to a depth of about 25 cm before gradation to
visually clean sand.
The black colored zones within these filters are most likely due to
reduction of sulfates under anaerobic conditions during ponding with the
resultant precipitation and accumulation of metal sulfides on the sand particles.
The deeper penetration of the black zones in the grey water filters may have
been due to the more reduced state of the wastewater initially, as well as the
greater ponding times (38 to 25 days for 1 and 2 versus 20 and 16 days for 7 and
8).
The results of analyses for selected chemical/physical parameters on daily
flow composited samples of the effluents from each of the eight sand filters
is presented in Table A-153. As shown, filtration through 60 cm of medium
sand at an application rate of 15 to 30 cm/day provides a high quality efflu-
ent with regard to BODcj and volatile suspended solids, with values consistently
less than 5 mg/L and 10 mg/L, respectively.
TABLE A-153. SAND FILTER EFFLUENT CHARACTERISTICS
Parameter
Loading
cm/ day
BOD *
COD
SS*
VSS
1
30
1(17)**
1-3
26(6)
13-39
12(19)
9-16
8(19)
6-9
Grey
2
30
1(18)
1-3
17(7)
7-27
1M19)
10-19
7(19)
5-9
Water
3
15
1(17)
1-3
21(7)
7-35
11(16)
7-16
7(16)
5-9
k
15
1(18)
1-2
16(7)
12-20
8(20)
6-10
5(20)
U-6
5
15
2(19)
1-3
16(9)
10-23
8(20)
5-12
5(20)
3-6
Combined
6
15
1(13)
1-3
18(9)
10-25
15(13)
9-23
6(13)
h-9
Waste
7
30
M15)
2-7
25(6)
9-^0
18(1U)
11-31
10(15)
6-lk
8
30
M20)
2-6
57(9)
29-86
17(20)
12-25
8(20)
5-10
* Log-normalized data
** Each data block includes:
Mean (samples);
confidence interval
Further, the nitrogen in the septic tank effluents, largely as ammonia,
was almost completely nitrified, while there was no significant effect on the
phosphorus concentrations as a result of the sand filtration.
A-281
-------
Summary
The results of this study may be summarized as follows:
1. The reduction in BODi- and COD are considerably greater in grey water
when treated with a 4.0 m^ septic tank as compared to a 2.0 m-^
septic tank. However, with regard to other chemical/physical para-
meters such as suspended solids, nitrogen and phosphorus, there is
no appreciable difference.
2. Bacteria used as indicators of fecal contamination were seen to
maintain high concentrations in the effluents from septic tanks
receiving just grey water after as much as thirteen months of oper-
ation without a fecal input. Residual material in the septic tanks
from a previous study during which they received combined wastewater,
would seem to have provided the seed from which the bacteria repro-
duced to maintain the high levels.
3. Sand filters receiving grey water septic tank effluent yielded filter
run lengths over twice as long, and removed over 140% more BODc and
6Q% more suspended solids than did similar filters receiving com-
bined wastewater septic tank effluent (dosed 4 to 5 times daily with
a total loading of about 30 cm/day).
4. A distinct difference was noted, both on the surface and with depth,
between sand filters loaded with grey water septic tank effluent
as compared to combined wastewater septic tank effluent.
5. Intermittent sand filtration of both grey water septic tank effluent
through 60 cm of medium sand at application rates of about 15 and
30 cm per day, produced effluents low in BODr and suspended solids,
almost completely nitrified, with the phosphorus largely unchanged.
As indicated by the results of this preliminary laboratory study, further
research is necesssary regarding grey water treatment and disposal. Research
which would l) further identify the characteristics of grey water septic tank
effluents, 2) identify the efficiency of sand filtration of grey water with
regard to chemical/physical and microbiological parameters, 3) delineate the
most appropriate filter operating conditions and maintenance techniques, and
4) investigate the development of clogging and occurrence of failure in sands
and other soils receiving grey water septic tank effluent as compared to
combined wastewater septic tank effluent.
PROCESS COSTS
The evaluation of on-site waste treatment and disposal alternatives
includes an analysis of technological effectiveness, institutional arrangements
and owner acceptance and cost effectiveness. The first of these general areas
of evaluation have been discussed at length in the preceding sections; the
second will be discussed in detail in Appendix D. Information on cost
A-282
-------
evaluation of potential on-site treatment and disposal alternatives is meager
at the present time owing to the small data base. The information presented
herein is based, primarily upon the experiences of this research effort. Costs
will be subdivided into capital investment plus installation, operation and
maintenance costs. Range of costs will be presented in most instances to
reflect a variety in labor, power and material costs. Costs will be based on
1977 dollars.
In-House Alteration Devices
The research studies reported herein did not include an in-depth cost
analysis of the extensive array of devices and systems which provide for waste
flow reduction and/or waste segregation are commercially available. Cost
information regarding their processes may be found elsewhere (Wallman and
Cohen, 197^; Milne, 1976; Nelson, 1976; Reid, 1976).
In general, the costs for these types of in-house devices vary dramatically
from virtually zero capital and operating costs for the simple flow control
faucet inserts, to as much as $5000 in capital and $125 per year in operating
costs for the sophisticated closed-loop recycle toilets. In identifying
costs for these types of in-house devices, caution must be exercised as the
unit costs for a given type of device can vary significantly depending on
many factors, including l) the commercial manufacturer, 2) the location of
the nearest distributor, 3) the method of installation (self-installed vs. hired
labor), and h) the costs for utility service (e.g., power and water).
Treatment Processes
Septic Tanks—
Costs of septic tanks vary with the materials used and the site conditions.
The delivered cost of precast concrete septic tanks in Wisconsin (1977) can
be calculated by the approximate formula,
C = $200 + 0.20(V-750)
in which C is the delivered cost and V is the capacity in gallons (x 3.75 liters),
This formula is good up to 6975 L (l800 gal) tanks. Above that, cast-in-place
tanks are used. Similar costs are found for steel tanks.
Installation costs including building sewer from the home are approximately
$100-$200. Although no maintenance costs were incurred in this study, it may
be assumed that pumping would be required every 3 years. In Wisconsin, pump-
ing costs for a 3.75 HH (1000 gal) tank would range from $*iO-$60. Based on
these figures, the range of unit costs for a 3.75 m.3 (1000 gal) septic tank
would be as follows:
3.75 m3 tank, installed $350 - $*+50
Operation 0
Maintenance $12-$20/yr.
A-283
-------
Aerobic Units—
The cost for aerobic units is high due tc a generally low demand for
these units. Costs could reduce with increased market penetration. Presently,
costs range from approximately $1200 to $2200 for a home-sized package
aeration unit, depending upon propietary device and location. Installation
costs are normally higher than for septic tanks owing to the greater complexity
of the unit and the necessary electrical work. These costs may range from
$200-$300. Power consumption for these units also vary, ranging from 2A to
1.h kwh/day. Other costs include costs for pumping, which should be performed
at least yearly and preventative maintenance services performed approximately
4 to 6 times per year. For pumping costs, a range of from $UO-$6o is assumed
and additional maintenance costs may range from $25-$50/yr.
Based on these figures, the range of unit costs expected for a package
aerobic unit for the average home would be as follows:
Package aerobic unit, installed $1500-$2500
Operation (Power: 2.k to 7.U kwh/d @ 1^/kwh) $35-4108
Maintenance (l pumping per year plus service
calls $65-$110
Chemical Precipitation/Coagulation—
Little information is available on actual capital costs for household
chemical treatment units. A hydraulically driven unit could be purchased for
approximately $700-$800 which includes a settling chamber, but not the treat-
ment unit preceding it. Operating costs would be dependent upon chemical costs,
For alum, approximately 200 mg/L would be used which would amount to about
0.15 kg/day for a household of U. Iron salts for coagulation and phosphorus
removal would require similar dosage. Detailed chemical cost analysis is
beyond the scope of this report but crude estimates based on the figures above
and the costs given in Table A-15^ would indicate a range of from $12 to
$60/yr. Sludge pumping would likely be required at least once per year.
Maintenance calls would likely be required at least U times/yr. Based on
these crude estimates, chemical coagulation unit costs would be estimated as
follows:
Mechanical unit, installed $800-$1000
Operation Costs (Chemicals) $12-$60
Maintenance (includes 1
pumping/yr plus h main-
tenance calls) $65-$HO
Sand Filters—
Based on Wisconsin experience, construction costs including a precast
concrete filter shell (septic tank), plumbing, media, insulated cover and
installation could range from $15 to $20/ft2 of filter area. Additional costs
for dosing sump and pump are not included (see below). Maintenance costs
-------
TABLE A-15U. CHEMICAL COSTS (19T7)
Chemieal Cost (FOB)-$
Alum (dry,bulk) 6.60-7-70/100 kg
FeCl3 (liquid, bulk as FeCl3) 8.80-11.00/kg
Lime (dry pebble, bulk as CaO) 2.20-2.75/100 kg
FeSO^ • 7 H20 (dry, bulk, 21% Fe#) 2.20-2.65/100 kg
Calcium hypochlorite (70$ HTH) 170/100 kg
Calcium hypochlorite tablets (70$ HTH) U20/100 kg
Iodine (elemental) 600/100 kg
lodophor (1.75$) 1.65/liter
Gluteraldehyde (50$ solu) 121/100 kg
Formaldehyde (31% solu) 35/100 kg
KOH (1*5* dry, bulk) 16.50/100 kg
WaOH (50$ dry, bulk) 15-WlOO kg
would vary depending upon pretreatment unit and techniques but can be estimated
at $.75 to $1.25/ft*/yr.
Based on these figures, the unit cost range for household intermittent
sand filters will be as follows:
Equipment and installation - $15-$20/ft2
Maintenance costs - $0.75-$1.25/yr
Pump Chamber and Sump Pump—
Costs for pumping chambers required to precede sand filters, or other
unit processes are based on Wisconsin experience. Installed cost for a 1.5 m
(5 ft) section of 1.2 m (ii8 in) diameter concrete pipe with poured bottom slab
and plumbing appurtenances would be approximately $200-$500. A 0.37 kw (1/2
hp) submersible pump with controls is estimated at $300-$500. Power demand
is estimated at 0.1 kwhr/day.
Based on these figures, the cost for a dosing chamber would be approxi-
mated as follows:
A-285
-------
Pump Chamber, installed $200-$250
Sump Pump with controls $300-$350
Operation - (0.1 kwh/d @ $O.OU/kwh) $1.50/yr.
Maintenance Costs (l hour/yr) $6-$10/yr.
Chlorination and Contact Chamber—
Chlorination of wastewater prior to surface discharge may be accomplished
through the use of simple tablet feed devices. Based upon field studies at
several locations in Wisconsin, it is estimated that approximately .015 kg/day
of tablet should be used at a cost of $lu20/kg for a household of k. In
addition to the basic tablet feed Chlorination system, which may cost from
$150-$175 a contact tank (1.2 m dia. concrete pipe at 2.75 m length plus
slab and appurtenances at $300) is required. Sometimes a 1/3 hp sump pump
to discharge the wastewater from the contact tank to the surface recipient
($100-$150) may also be required.
The estimated cost for a Chlorination system is as follows:
Chlorine contact tank plus installation $HOO-$500
including plumbing and excavation
1/3 hp pump and controls $100-$150
Chlorinator - tablet feed $150-$175
Maintenance Costs (l hour/yr) $6-$10/yr.
Operation Costs
Electrical power - (o.l kwh/d x $Q.OH) $1.50
Hypochlorite tablets (0.015 kg/d @ $^.20/kg) $26/yr.
Ultraviolet Disinfection—
The ultraviolet system basically consists of a staging tank for pumping
effluent to the unit, a sump pump and a UV sterilizer. The staging tank can
be a 0.9 m dia. concrete pipe 2.75 m in length with poured slab. There are a
number of propietary UV disinfection units on the market today with costs
ranging from $750-$900. Little experience has yet been gained with maintenance
costs but unit cleaning is paramount to effective disinfection of wastewater.
System costs estimated below are based on disinfection of sand filtered
effluent for a flow of approximately 750 L/day.
A-286
-------
Staging tank plus installation $300-$1*50
1/3 hp submersible pump and control $100-$150
UV sterilizer unit $750-$900
Maintenance ( 10 hours per year) $^0-$6o/yr.
Operation -
Pover (1.5 kwh/d % Wkwhr) $20/yr.
Septage Disinfection—
Based upon laboratorty experiments with septage reported in this study
(Deininger, 1977) an estimate of cost of septage disinfection was forecasted.
These costs are based upon chemical costs given in Table A- . This esti-
mate does not include ultimate disposal costs which are estimated from $^0-$60
every three years. Costs for three disinfection alternatives for 3750 L
(1000 gal) of septage are shown in Table A-15^.
TABLE A-155. SEPTAGE DISINFECTION COSTS
Disinfectant
Glutar aldehyde
(no pH adjustment)
Formaldehyde
(sludge adjusted to pH 10)
Chlorine
(no pH adjustment)
Dose Level
mg/L
500
1,000
500
1,000
2,000 **
Cost to Treat 3750 L
(1000 gal) of Septage
$9-17
$6.28*
$18.72
* Including pH adjustment estimate with KOH (Cost = $2.79)
** The highest chlorine dose tested; provided marginal treatment of
40,000 mg/L TS sludge.
Soil Disposal Costs—
Soil absorption fields—Based on Wisconsin experience, soil absorption
field construction costs currently range from $1 to $1.25/ft^ of bottom area
depending upon soil type and location. Wo maintenance costs have been identi-
fied for these systems.
Mounds - There is now a substantial body of data available on cost of
mound construction in Wisconsin. Installed costs including septic tank, sump
and pump, mound construction, plumbing and landscaping range from $3000 to
$1*500. Maintenance costs include those associated with septic tank pumping
and occasional maintenance of the sump pump. Estimates for maintenance are in
the range' of $l8-$25/year. Power consumption costs for pumping to the mound
are based on approximately 0.25 kwh/day consumption.
A-287
-------
Estimated mound unit costs range would be as follows:
Installation and equipment costs $3000-$**500
Maintenance $l8-$25/yr.
Power - 0.1 kwh/d § O.OU/kwh $1.50/yr.
A-288
-------
ATTACHMENTS TO APPENDIX A
Attachment A - Individual Home Water Use Patterns
Attachment B - Statistical Analysis Results for Each Event, mg/cap/day
Attachment C - Literature Revieved and Contacts Made
Attachment D - Description of Laboratory Site N and the Influent Waste-water
A-289
-------
ATTACHMENT A - INDIVIDUAL HOME WATER USE PATTERNS
Daily Flow Patterns
30
ZOh
T TOILET
0 DISH WASH
WS WATER SOFTENER
MOON
TIME OF DAY
Figure A-71*. Family A daily flow
pattern (L/cap/day =
30
25
20
K>h
8.
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
9 NOON
TIME OF DAY
Figure A-75. Family B daily flow
pattern (L/cap/day =
96).
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
NOON 3 ~6~
TIME OF DAY
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
TIME OF DAY
Figure A-76. Family C daily flow Figure A-77- Family D daily flow
pattern (L/cap/day = pattern (L/cap/day =
155).
A-290
-------
30-
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
30-
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
TIME OF DAY
NOON ~3~
TIME OF DAY
Figure A-78. Family E daily flov
pattern (L/cap/day
157).
Figure A-79- Family F daily flov
pattern (L/cap/day =
125).
25
20
^L.
1-15
10-
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
30
25
20
£
|
10
a.
o
"MN 3 6 9 NOON 3 6 9 MN
TIME OF DAY
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
MN 3 6 9 NOON 3
TIME OF DAY
9 MN
Figure A-80. Family G daily flow
pattern (L/cap/day =
111).
Figure A-8l. Family H daily flow
pattern (L/cap/day =
188).
A-291
-------
30
25
20
r
10
30-
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
3 6 9 NOON 369
TIME OF DAY
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
0L
'MN 3
9 NOON 3 6 9 MN
TIME OF DAY
Figure A-82. Family I daily flow
pattern (L/cap/day =
158).
Figure A-83. Family J daily flow
pattern (L/cap/day =
170).
30
25
20
I
15-
10-
T TOILET
L LAUNDRY
B BATH or SHOWER
D DISH WASH
0 OTHER
WS WATER SOFTENER
0L 0
MN 3 6 9 NOON 3 6 9 MN
TIME OF DAY
Figure A-8^. Family K daily flow
pattern (L/cap/day =
215).
A-292
-------
Weekly Flow Patterns
125
153 261 229 196 2|2 221 221
35L (404) (691) (60.6) (518) (587) (586) (586)
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
« TOTAL
M T W T F
DAY OF THE WEEK
125
100
75
o
•se
141 182 203 183 168 183
351. (37 4) (483) (536) (485) (443) |29 (48.4)
(34.1)
• TOILET
30h ° LAUNDRY
° BATH or SHOWER
° DISH WASH
2SL • WATER SOFTENER
r • OTHER
o TOTAL
-|4
| IB
10
5
M T W
DAY OF THE WEEK
Figure A-85• Family A weekly flow
pattern (L/cap/day =
21k).
Figure A-86. Family B weekly flow
pattern (L/cap/day =
96).
243
125
100
25
I4>6
(388)
166
(439)
M T W T
DAY OF THE WEEK
'3
'I3
(326)
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
TOTAL
151 143 172 148 139
35
125
100
f"
a
•4!
-1 50
25
0
30
25
^
-§20
Q.
J3
•4; 15
- "5
r Ol
10
5
0
(4QO) (379) (454) (391) (368)
122
(322) * TOILET
LAUNDRY
° BATH or SHOWER
° DISH WASH
• WATER SOFTENER
• OTHER
o TOTAL
0 /
_^°"~ " ^~^»— ~- ~~ /
_ >Z[7~~~° /
— ^^ * ' • — —*^r^
^~—~~.^^~ ^^fS^f^l~— -~_ /
* *'*~*^ \ ,_(„ | -L
S M T W T F
*y
(559)
JL
/r
1
^
~-~^
s
DAY OF THE WEEK
Figure A-Sj.
Family C weekly flow Figure A-J
pattern (L/cap/day =
Family D weekly flow
pattern (L/cap/day =
155).
A-293
-------
125
100
75
-I
S
o
50
25
0L
35
30
25
20-
15
10
241 157 201
(638) (416) (S31)
. TOILET
• LAUNDRY
» BATH or SHOWER
° DISH WASH
WATER SOFTENER
OTHER
TOTAL
266
(704)
T W T F
DAY OF THE WEEK
125
100
o
I
50
25
35
30
25
- g"20
1
15
10
(518)
122
(322)
'? 'I9
(315) (315)
'I9
(368)
97
(256)
(266)
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
TOTAL
S M T W T
DAY OF THE WEEK
Figure A-89. Family E weekly flow
pattern (L/cap/day =
15T).
Figure A-90. Family F weekly flow
pattern (L/cap/day =
125).
125
K>0
75
50-
25
35
30
25
I" 20
15
10-
125
(332)
(284)
ISO
(344)
90
8* (239)
(222)
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
TOTAL
102
(269)
M T W T
DAY OF THE WEEK
139
(367)
125
100
>»
I™
L
25
201 148 188 162 175 Ifl 26,2
351 (532) (391) (498) (429) (462) (505) (692)
30
25
20
R
I5h
10
TOILET •
LAUNDRY •
DISH WASH °
BATH or SHOWER
WATER SOFTENER
OTHER
TOTAL
M T W T
DAY OF THE WEEK
Figure A-91. Family G weekly flow
pattern (L/cap/day =
111).
Figure A-92. Family H weekly flow
pattern (L/cap/day =
188).
-------
125-
100
5-75
50
35
30
25
ex
o
S.
15
10
203 280 165
(536) <60°8> <43°7)
137 138
(36°2) (364)
163
(432)
9^4
(248)
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
TOTAL
S M T W T
DAY OF THE WEEK
125
100-
' 75
I so
25
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
TOTAL
(25.7)
156
(41.3)
121
(32.0)
M T W T
DAY OF THE WEEK
Figure A-93. Family I weekly flow
pattern (L/cap/day =
158).
Figure A-91*. Family J weekly flow
pattern (L/cap/day =
170).
125
100
' 75
1
50
25
173 304 203 212 205 180 225
35, (458) (805) (538) (56°0) (543) (477) (594)
TOILET
LAUNDRY
BATH or SHOWER
DISH WASH
WATER SOFTENER
OTHER
TOTAL
S M T W T
DAY OF THE WEEK
Figure A-95. Family K weekly flow
pattern (L/cap/day =
215).
A-295
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A-299
-------
ATTACHMENT G - LITERATURE REVIEWED AND CONTACTS MADE
TABLE A-16U. JOURNALS, ABSTRACTS AND INDEXES REVIEWED
Literature
Date Covered
Pollution Abstracts
Selected Water Resources Abstracts
Applied Science and Technology Index
Chemical Abstracts
NTIS Reports
EPA Reports Quarterly
Journal, Water Pollution Control Federation
ASCE Environmental -Engineering Division Journal
Public Works
Water and Sewage Works
American Water Works Association
Water and Wastes Engineering
Water and Pollution Control
Water Resources Research
Water Research
Water Resources Bulletin
1970 - December, 1976
1968 - December, 1976
1965 - December, 1976
1962 - December, 1976
196k - April, 1975
1972 - September, 1976
1928 - October, 1976
1965 - December, 1976
1965 - June, 1976
1967 - June, 1976
1971 - June, 1976
196k - November, 1976
I960 - December, 1975
1965 - October, 1976
1967 - November, 1976
1970 - October, 1976
TABLE A-165. TEXTS AND MANUALS REVIEWED
Text
Author
Date
Sewage
Water and Wastewater Engineering
Sewerage and Sewage Treatment
Biological Waste Treatment
Municipal & Rural Sanitation
Industrial Water Pollution Control
Water Supply Engineering
Sewer Design & Construction
Disposal of Sewage & Other Water
Borne Wastes
Water Quality & Treatment
Water Supply & Pollution Control
Wastewater Engineering
Environmental Engineering & Sanitation
Manual of Individual Water Supply Systems
Manual of Septic Tank Practice
Environmental Protection
Wastewater Treatment Systems for Rural
Communities
Rideal 1900
Fair, Geyer & Okun 1958
Babbitt & Baumann 1958
Eckenfelder & O'Connor 196l
Ehlers & Steel 1965
Eckenfelder 1966
Babbitt, Doland & Cleasby 1967
WPCF MOP #9 1970
Imhoff, et al. 1971
AWWA 1971
Clark, Viesmann & Hammer 1972
Metcalf & Eddy 1972
Salvatto 1972
EPA 1973
PHS 1967
Chanlett 1973
Goldstein & Moberg 1973
A-300
-------
TABLE A-166. INDIVIDUALS AND ORGANIZATIONS FROM
WHOM INFORMATION WAS REQUESTED
Individual/Organ!zation
Description
No. of
Responses*
Federal/Regional
Government Agencies
State Environmental
Agencies
Universities
Establishment
Associations
Magazine Editors
Miscellaneous
Government agencies, including 6l
NASA, USEPA, U.S. Coast Guard,
U.S. Navy, U.S. Army, Park Service.
The principal state environmental k6
offices in each of the 50 states.
The professor in charge of the 26
Sanitary Engineering program at
each of k3 colleges and universities.
Fourteen of the more veil known
experiment stations.
Associations dealing with the type 13
of establishments being investi-
gated.
The editors of 12 magazines and l6
journals dealing with waste treatment
and pollution abatement.
The editors of magazines dealing with
the types of establishments under
investigation.
Attendants of various recent ^2
conferences who might have informa-
tion.
Equipment manufacturers and firms
dealing with package treatment units
and water saving devices.
* Responses were received to approximately 50$ of the inquiries made,
A-301
-------
ATTACHMENT D - DESCRIPTION OF LABORATORY SITE N AND THE INFLUENT WASTEWATER
PROGRAMMER CONTROL
Programmer Operations
The automation of the laboratory was accomplished by using a specially
designed control system. The heart of the system was a series of 20 switch cam
programmers as shown in Figure A-96. These programmers stepped forward one
position when provided with an electronic signal. Operation is such that when
one programmer reaches the resting position no. 20, the next programmer in the
series steps to position no. 1. Since there were 5 programmers with 19 avail-
able positions (no switches can be ON at the resting position), 95 distinct
steps are available. Thus, the day was divided into 96 equal 15 minute seg-
ments with all programmers going into a 15 minute rest at the end of the day.
The programmer switches could easily be programmed by sliding a portion of
the adjustable cam to the ON or OFF position, providing for a great amount of
flexibility in the simulation program. These switches were wired in parallel
with toggle switches, which override them if a manual mode was desired.
The problem of stepping the programmers in the proper sequence and pro-
viding a resting step were handled by using a solid state counter, followed by
digital logic. The logic sorted the counter signals and stepped the proper
programmer corresponding to a particular number.
Table A-167 presents the switch assignments for the 20 programmer switches.
Each switch initiated one of the subroutines. The timing of these subroutines
are described below.
Program Matrix
The program matrix was an assignment of an ON or OFF position to the
various switches versus a time scale (step number). Figure A-97 shows a blank
matrix. The matrix was developed by choosing a desired loading schedule
(Figure A-98) and staggering the starting times such that major events (all
except toilet) to the various units did not overlap in a given 15 minute
interval. These events were then converted to switch assignments, and the
matrix was completed. A completed matrix is shown in Figure A-99 which is the
matrix used during the first stages of testing.
Simulator Control
The simulator operations were controlled by a special electronic counter
similar to that used for programmer stepping. This counter counted every 7-5
seconds and is reset at the end of the 15 minute step. The timing of the
opening and closing of the various valves, activation of motors and control
of solenoids was accomplished by using signals from the counter. Solid state
A-302
-------
1. Heavy-duty drive, high-torque AC pulse-motor
rated for continuous duty.
2. Drive gear, standard, permits addition of tap
switches later . . . indicator strip shows step num-
ber and which tap switch circuit is made.
3. Segment indicator strip... identifies cam segments
with camshaft in or out of the 1800 . . . for accurate
programming and re-programming.
4. Control cam operates control circuit to keep motor
from driving through more than one step from
sustained STEP command signal
5. Camshaft holddowns at both ends of the camshaft
hold firmly, lift out and up, to release the camshaft
assembly ... no tools needed
6. Sliding segment cams —white segments in the white
do not actuate the switches . . . white segments slid
over into the black do actuate the load switches
20 segments per cam. one for each step
7. Camshaft assembly is easily removed, providing
storable memory of a complete program . . . keyed
coupling insures proper installation.
8. Heavy duty load switches . . 10 amp SPDT Form
C precision switches, independently replaceable.
9. Fully accessible terminals accept .250" push-on
connectors.
Figure A-96. Cam programmer.
A-30 3
-------
TABLE A-167. PROGRAMMER SWITCH ASSIGNMENTS
Switch No. Function
1
2
3
U
5
6
7
8
9
10
11
12
13
lit
15
16
17
18
19
20
Unit #1 Toilet
Unit #2 Toilet
Unit #3 Toilet
Unit #U Toilet
Unit #5 Toilet
Blank
Shower
Bath
Dishwasher
Clothes Washer
Dish Rinse
Garbage Grinding
Blank
Blank
Monitor
Monitor
Monitor
Manifold Control
Manifold Control
Manifold Control
digital logic took these signals, along with signals from the programmer
switches, and, at the proper count, performed the required function.
Distributor
Once a wastewater event was simulated, it required routing to the desired
treatment unit. This was accomplished by using a specially designed distri-
butor which is shown in Figure A-100. It consisted of a rotating pipe arm
driven by a 1* rpm gear motor. The arm stopped above one of six ports when
the proper sensor was triggered (a micro-switch was tripped by the end of the
arm). If no event was occurring during a 15-minute interval, the arm returned
to a drain port in the event of any equipment malfunction which could add
unwanted water.
The arm could be positioned via an automatic or a manual mode. The
automatic mode (switches set on AUTO) took signals from switches 18, 19 and 20
of the programmer, sorted them out through digital logic, and activated the
motor until the proper sensor was tripped. The proper combination of switches
to be set to ON are presented in Table A-168.
A-304
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A-3 07
-------
TABLE A-168. SWITCH SETTINGS
Treatment Unit
Rotating Disks
Septic Tank
Batch Aeration
Extended Aeration
Submerged Filter
18
Off
Off
Off
On
On
Switch No.
19
Off
On
On
Off
Off
20
On
Off
On
Off
On
SIMULATOR OPERATION
Laundry
The laundry was simulated by running a Maytag commercial clothes washer
through its normal cycle. Switch 10 on the programmer activated this cycle.
Detergent was added by the feeder shown in Figure A-lOl. The sequence of events
was as follows:
1. Switch 10 of programmer switched ON.
2. A relay was activated to provide power to the machine timer through
the machine's ticket mechanism. (Power was provided for at least
30 seconds).
3. The same relay provided power to a 2 second, time delay relay which
in turn provided power to the feeder motor.
k. The feeder advanced to dump the contents of one feed container.
5. The feeder motor shut off when micro-switch was opened.
6. Power was removed from activation circuitry (Switch 10 to OFF).
T. Washing machine completed normal cycle.
The normal cycle was set at COLORS but could have been switched to any
other desired setting. The machine was modified such that opening the cover
did not stop the cycle. The detergent feed container held up to H50 ml of
material.
In order to increase flow from the clothes washer, the cycle could be
changed to PERMANENT PRESS, increasing the flow from 150 to 190 L (Uo to 50
gallons).
Dishwasher
Dishwashing was simulated by running a Sears Kenmore dishwasher through
its normal cycle (NORMAL WASH). Switch 9 on the programmer activates this
A-308
-------
Figure A-100. Flow distribution manifold.
Figure A-101. Laundry detergent feeder.
A-309
-------
cycle. Detergent was added to the washing machine by the feeder shown in
Figure A-102.
The sequence of events for this simulator were as follows:
1. Switch 9 on programmer switched ON.
2. Relay provided power to the machine timer (power provided for a
minimum of 60 seconds).
3. This same relay provided power to the feeder motor.
U. The feeder rotated to dump contents of detergent container (container
held 1/U cup of detergent).
J>. The feeder automatically stopped when micro-switch was opened.
6. Power was removed from activation circuit (Switch 9 is OFF), and
detergent feeder would reset for next cycle.
7. Machine completed normal cycle.
The machine was modified such that power was removed from the heating coil
for the last half of the machine cycle by using the power which normally was
used by the blower.
Dish Rinsing
The dish rinse was simulated by a specially designed apparatus shown in
Figure A-103. The electronics were activated by switch 11 of the programmer.
A blended slurry of assorted food materials was automatically added along with
a metered amount of hot water in the following sequence:
1. Switch 11 of programmer switched ON.
2. Electronic control turned mixing motor on.
3. Air cylinder retracted allowing measuring chamber to fill with slurry.
k. Air cylinder extended, isolating measuring chamber from slurry
reservoir. Measuring chamber empties.
5. Mixing motor turned off.
6. Electronic control opened solenoid valve to wash slurry into distri-
butor. Time was variable from 0 to 180 seconds and controlled by a
time delay relay.
7. Valve closed.
8. Switch 11 of programmer switched OFF.
A-310
-------
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The feed slurry reservoir held up to 11 liters of slurry which was "blended
manually in a commercial size Waring blender. The measuring chamber was about
200 mL in size.
Bath
The bath was simulated by a specially designed simulator shown in Figure
A-10U. Liquid hand soap was added automatically with a piston feeder pump.
The sequence of events were as follows:
1. Switch 8 of the programmer switched ON.
2. The electric controlled ball valve opened.
3. Power was provided to soap feeder pump for 1 minute to pump a variable
volume of soap (0-100 mL).
U. Power was removed from soap feeder pump.
5. Electric controlled ball valve closed after tank has emptied.
6. The solenoid fill valve opened to fill barrel.
T. Solenoid fill valve closed when water level reaches PVC float.
8. Switch 8 of programmer switched OFF.
The rate at which the barrel emptied was controlled by opening or closing
a gate valve following the ball valve. The total volume was controlled by
adjusting the level of the PVC float.
Shower
The shower was simulated by a timer controlled solenoid valve. Liquid
soap was added automatically with a piston feed pump. The system is shown in
Figure A-105. The sequence of events were as follows:
1. Switch 7 of programmer switched ON.
2. Timer solenoid valve opened allowing a flow rate of 11.3 L/m (3 gpm).
3. Power was provided to soap feeder pump for 1 minute to pump a variable
volume of soap (0-100 mL).
k. Power was removed from soap feeder pump.
5. Timer closed solenoid valve after selected time (adjustable from 0
to 15 minutes).
6. Switch 7 of programmer switched OFF.
A-312
-------
Figure A-lOk. Bath event simulator
Figure A-105. Bath and shower soap feeder
A-313
-------
Toilet
The toilet was simulated by a specially designed system shown
which could be broken down into 3 distinct functions: urine addi-
tion, feces addition, and water flush. The urine solution was a specially mixed
solution of salts, metered to each unit via a constant volume measuring chamber.
Provisions were made to add feces manually. The flushing water comes from a
standard toilet tank which was automatically flushed. A water cut-off valve was
installed in the water line in the event that the toilet ball could not seat
properly. Each treatment unit was equipped with its own simulator (5 total).
The sequence of events were as follows:
1. Switch 1, 2, 3, ^, or 5 of programmer switched ON.
2. Upper solenoid valve on urine measuring chamber opened allowing chamber
to fill.
3. Upper solenoid valve closed.
U. Bottom solenoid valve and water cut-off valve opened simultaneously.
5. Solenoid was activated to flush toilet tank.
6. Solenoid was deactivated.
7- Bottom solenoid valve and water cut-off valve closed (after 2 minutes
to allow tank to fill).
8. Switch 1, 2, 3, U, or 5 of programmer switched OFF.
With the manual addition of feces (hog manure) a certain amount of toilet
paper was added once per day.
INFLUENT WASTEWATER CHARACTERISTICS
The laboratory units were fed wastewater that was generated by the equip-
ment described previously. The purpose of this discussion .is to outline the
characteristics of this simulated wastewater and to summarize (by months) their
average values.
Toilet Simulation (Urine, Feces and Paper)
Urine—
Urine is simulated by addition of a salt solution containing the following:
Urea = 2.6? kg KC1 = 1.02 kg
Na3POl+ = 0.93 kg NH^Cl = O.UU kg
Na2SO^ = 0.83 kg HC1 = 0.50 L
NaCl = 0.5U kg Water to make 150 liters
-------
This solution had the following characteristics in grams per liter:
BOD_5 COD OB TSS TN_ ^L.
g/L .055 4.7 29 .038 8.0 1.3
and the following monthly utilization:
Jan 75
Feb
Mar
Apr
May
June
July
Aug
3.86
1.46
3.47
3.48
3.88
4.01
3.99
4.21
Sept 75
Oct
Nov
Dec
Jan 76
Feb
Mar
4.52
3.82
4.23
4.20
4.00
3.99
4.15
Feces—
Hog manure is added manually to each of the units daily. Several
analyses of the manure yielded the following average characteristics:
BQDg COD TS TSS_ TN TP
g~g °f .057 .21 .20 .16 .015 .0098
reces
The average daily addition was :
Jan 75
Feb
Mar
Apr
May
June
July
Aug
432
411
453
453
453
453
402
402
Sept 75
Oct
Nov
Dec
Jan 76
Feb
Mar
680 g/unit/day
680
566
680
549
680
636
Paper —
Nineteen grams of toilet paper were added manually to each unit every day
of the test period. This quantity of paper had the following characteristics:
BOD5 COD TS TSS TN T_P
g/unit/day 4.7 18 19 19 0 0
Laundry
Detergent was added to each laundry event. There was one event per day.
Tide detergent had the following characteristics :
g/8 of
detergent
BOD,-
?
.21
COD
.44
TS
.86
TSS
.21
TN
.004
TP__
.086
A-315
-------
and the following daily utilization:
Jan 75
Feb
Mar
Apr
May
June
July
Aug
11+7
90
90
129
118
li+2
ll+lt
150
Sept 75
Oct
Nov
Dec
Jan 76
Feb
Mar
150
ll+5
111
ll+8
150
83
129
150 g/unit/day
Bath/Shower
Liquid hand soap added to each of the 3 daily bath/shower events had the
following characteristics:
BQDc COD TS TSS
g/mL of soap .75 1.25 .33 .1+6
The following are the average daily utilization:
TN
.01
TP
.008
Jan 75
Feb
Mar
Apr
May
June
July
Aug
106
53
50
73
63
62
51
59
Sept 75
Oct
Nov
Dec
Jan 76
Feb
Mar
1+5
1+1+
1+7
50
63
90
17
U5 mL/unit/day
Kitchen
Dish Rinse—
A specially blended slurry containing the following ingredients was fed
into the units after March 16, 1975:
2 cans beef stew (5 Ib),
6 cans chicken noodle soup (1+ Ib),
6 cans vegetable beef soup (1+ Ib),
200 mL cooking oil,
200 mL soap, and
Water to make 9.5 liters of slurry.
Before this date a somewhat weaker slurry was added.
these slurries are:
g/mL of
slurry
BOD,-
.01+ It
.060
COD
.085
.113
TS
.062
.105
TSS
.036
.056
TN
.0021+
.0057
The characteristics of
TP
.001 to 3/16/75
.001 after 3/16/75
The following amounts were added to each unit on an average basis:
A-316
-------
Jan 75 606 Sept 75 660 mL/unit/day
Feb 65^ Oct 57!*
Mar 590 Nov U6
Apr 5^0 Dec 599
May 580 Jan 76 621
June 58l Feb 517
July 625 Mar 686
Aug 600
Dishwashing—
Detergent is added to each wastewater event and has the following
characteristics:
TSS
.22
51 g/unit/day
51
60
58
61*
86
73
g/g of
detergent
The average daily
Jan
Feb
Mar
Apr
May
June
July
Aug
BOD,. COD
?
.OVf
use by month was :
75 55
55
70
27
27
38
20
51
TS
.73
Sept
Oct
Nov
Dec
Jan
Feb
Mar
75
76
Influent Wastewater Summary
Table A-169 was prepared by combining each event waste characteristics and
relative flow rate. These values are summed to get total grams of character-
istic per unit per day (e.g. g BODc/unit/day) . The total mass of the various
parameters are also calculated in order to determine the average values for
the test period.
Grease
Grease determinations were made on several samples. The grease content
of the influent waste was about 120 mg/L of which 50$ was contributed by the
feces and the dish rinse slurry.
A-317
-------
TABLE A-169.
TEST PERIOD INFLUENT WASTE CHARACTERIZATION
(1/1/75 - 3/31/76)
Month
Jan 75
Feb
Mar
15th
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Jan 76
Feb
Mar
Totals
Flow*
820
7l*0
7^0
7l*0
7l*0
71*0
7l*0
71*0
7l*0
7^0
71*0
61*0
71*0
7l*0
71*0
716
3l*0
m^
BOD_5
167
116
113
135
1^5
138
ll*2
13U
lUo
1U9
lU2
123
1U8
152
160
122
63-9
kg
COD
378
275
285
328
322
329
339
320
332
381
365
300
378
369
391
330
156
kg
TS
^56
318
392
U69
1*23
U26
U57
1*37
U69
536
503
1*57
525
505
1*89
508
211
kg
TSS
202
16U
170
19l*
188
181*
191
177
187
228
222
193
228
215
235
210
91.4
kg
TN
1*1
20
37
39
39
1*2
52
U3
1*8
51
1+5
1*6
1*8
U5
1*6
1*8
19.9
kg
TP
31
22
27
32
25
2l*
28
25
30
3l*
32
30
3U
33
32
33
li*.0
kg
* All entries in g/unit/day, except flow in L/d.
A-318
-------
APPENDIX B
SOIL ABSORPTION OF WASTEWATER EFFLUENTS
PART 1
SITE CHARACTERIZATION FOR WASTEWATER ABSORPTION
A successful wastewater treatment system produces an effluent which is
compatible with the environment to which it is discharged. The environment,
of course, is part of the system providing the final treatment necessary
before the water is of sufficient quality for reuse. If the pollutant load
received by the environment is too great, the environment will not break down
and recycle the pollutants rapidly enough. The result is that the pollutants
will accumulate, leading to failure of the system.
The maximum permissible limits of pollutants that can be discharged to
the environment vary with the type of pollutant and the local environment into
which they are discharged. To properly design a treatment system, therefore,
it is necessary to evaluate the physical characteristics of the local environ-
ment where discharge of the partially treated wastewater is to be made. Each
site has its own characteristics that limit its potential as a treatment
medium.
Proper evaluation of the receiving environment becomes particularly
critical where onsite wastewater treatment systems are necessary. Onsite
systems lack the advantage of institutional control of central sewerage where
wastes can be collected and conveyed to a treatment plant located at a site
which is selected for its suitability to receive the pretreated wastes. In-
stead, they must be located near the point of waste generation and local
environmental conditions are often less than optimal.
Traditionally, the septic tank-soil absorption system has been used to
provide onsite treatment and disposal of liquid wastes. Soils are very
effective biological and physical filters which break down organic and other
chemical substances as well as remove pathogenic organisms and viruses.
However, not all soils and the site characteristics with which they are
associated, are equally effective in providing absorption and purification over
a reasonable lifetime. Therefore, site and soil characterization is necessary
to select a suitable system design.
The factors that influence the design and operation of onsite absorption
systems include the hydraulic conductivity, depth of soil over zones of
saturation or bedrock, the slope and topographic position, and the site's
management history. Proper site selection requires a knowledge of how these
factors influence system operation and the methods of successfully determining
them.
B-l
-------
FACTORS INFLUENCING SITE SUITABILITY FOR LIQUID WASTE DISPOSAL
Soil Hydraulic Conductivity
The rate of acceptance of liquid by a soil absorption system will be
limited by the hydraulic conductivity of the soil and the resistance of any
impeding layer at the infiltrative surface. If the soil cannot accept the
water at the rate it is applied because the soil is too slowly permeable
and/or the clogging mat is too resistant, failure will occur.
Direct measurement of the hydraulic conductivity at the moisture
potential expected for the system design gives a loading rate for sizing.
Different methods of measuring or estimating the hydraulic properties of
soils have been used. Some of these are based on the known physical charac-
ter of liquid in soil materials while others are empirical.
Physical Characterization of Liquid in Soil Materials—
Soil wetness refers solely to the total amount of liquid in a soil sample,
Soil wetness can be expressed in two ways:
100 • M
Percentage by weight: 6 =
W M
S
Where, M = mass of water (g)
M = oven dry weight of soil (g) and
S
100 • V
W
Percentage by volume : 6 = =——— —
saw
3
where, V = volume of water (cm )
w
3
V = volume of soil solids (cm ) and
s
3
V = volume of soil air (cm )
3.
These two characteristics are interrelated as follows:
9 • B.D.(dry)
w
v p
w
3
Where, PW = density of water (g/cm )
B.D. = the bulk density (g/cm3)
Soil volume is a relevant factor in several soil characteristics. This
volume may change when dry soil is wetted. Most soil materials containing
clay will expand upon wetting, which is mainly due to the mineralogical and
B-2
-------
chemical nature of the clay minerals and to chemical characteristics of the
wetting liquid. Thus, it follows that bulk density and 6y values will be
affected. In addition, it is important to ascertain the distribution of water
in the soil at different moisture contents and to understand the natural laws
that govern it. As the moisture content of a soil sample decreases, water
leaves the larger soil pores but remains in the finer ones. This can be
explained by considering the basic phenomena of liquid surface tension and
capillarity. Surface tension occurs at the interface of a liquid
and a gas. Molecules in the liquid attract each other from all sides. At
the surface areas the molecules are attracted into the denser liquid phase
by a force greater than the force attracting them into the gaseous phase .
The resulting force draws the surface molecules inward, which results in a
tendency for liquid to contract. Surface tension has the dimension of
dynes/cm. Increased salt concentrations tend to increase the surface tension
of water, whereas organic solubles like detergents tend to decrease it.
Capillarity refers to the well-known phenomenon of the rise of water into a
capillary tube inserted in water, due to its surface tension (Figure B-l).
The finer the tube, the higher the capillary rise and the greater the neg-
ative pressures below the water meniscus in the tube. This negative pressure
(p) is a result of the curvature of the meniscus, which increases as tubes
become smaller, and can be calculated (in dynes/cm ) as follows (assuming
that the contact angle between water and tube is zero):
26
P = —
Where, <5 = surface tension of the water (dynes/cm)
r = radius of the capillary (cm)
The height of capillary rise (cm) is
26
Where, g = gravitational constant (cm/sec )
Pictured as a continuous graph in Figure B-l capillary radius is related to
corresponding pressures. This negative pressure below the meniscus in the
water can thus be expressed in terms of the height of the column of water (cm)
that can be "pulled" from a cup of water by the capillary tube. For example,
a cylindrical pore diameter of 100 microns corresponds with a relatively low
capillary rise of 28 cm water (pressure below meniscus = -28 cm water) , while
a diameter of 30 microns corresponds with a relatively high rise of 103 cm
(pressure -103 cm water). These figures imply that it takes a greater force
(more energy) to remove water from a small pore than from a large one.
To represent the porosity of a certain soil material as a bundle of
capillaries with a characteristic size range is, of course, a simplified
model since real pores in the soil have a much more complex configuration,
with varying sizes and discontinuities. This representation can nevertheless
be helpful to visualize the energy condition of water in soil and flow
B-3
-------
cr
CD 120-
3
z
0100-
co
UJ
*~ 80-
UJ
(£.
3
co 60-
^40-
CO
20-
1
1
\
\
\<
,
\L_
^
V
V
^.
\
"\
$
\
n
^
IM
^
«««*
'^|
1
'
0 50 100 150 200
DIAMETER OF TUBULAR PORE (MICRONS)
Figure B-l. Graphical expression of the relationship between tubular pore
size and corresponding soil moisture tension (Bouma et al., 1972).
phenomena, particularly when soil moisture contents are relatively close to
saturation.
Soil moisture potential — Water moves from points where it has a higher
potential energy status to points where it has a lower potential status. The
energy status is referred to as the "water potentia," a central concept in soil
physics. A thorough and clear discussion of this concept has been given by
Rose (1966) and only a brief summary will be presented here. The total poten-
tial or energy per unit quantity of water (i)^) is defined as the mechanical
work required to transfer a unit quantity (e.g. unit mass weight or volume) of
water from a standard reference state (i|> = 0) to one where the potential has
the defined value. The total potential (i|»t) of water (which in the following
will be expressed in terms of energy per unit of weight because this results
in the simplest expression) is composed of several components, which will' be
discussed separately.
Pressure potential (4y,) — Water in unsaturated soil occurs only in the
finer pores because the total amount of available water is insufficient to fill
all the pores and the smallest pores can "pull" strongest. The pressure in the
water is then less than that of the local atmosphere. As the available amount
-------
of water decreases, the moisture pressure becomes more negative. It is con-
venient, but not necessary, to refer to a negative (less than atmospheric)
pressure as a "tension" or "suction." A tension or suction of, for example,
30 cm water represents a soil water pressure of -30 cm water. Also, low
"tensions" or "suctions" are equivalent to relatively low "pressures."
The pressure potential in unsaturated soil is referred to as the metric
or capillary potential (^m). The matric potential is used extensively in the
following sections on hydraulic conductivity. Expressed per unit weight, the
dimension of the matric potential becomes
-2 -2
g • cm • t -cm
* ~3 12 = Cm>
^ g • cm • cm • t
This notation is more convenient than others expressing the potential per
unit mass or volume.
The matric potential, which can be measured by tensiometry is the most
important component of the pressure potential in most cases because soils
above the water table are usually unsaturated. The soil water is at a
pressure higher than one atmosphere if submerged beneath a free water sur-
face. The potential associated with this has been called the submergence
potential (S) by Rose (1966). The submergence and matric potentials are
mutually exclusive possibilities; if either of them is nonzero, the other
must be zero.
Gravitational potential ( ijQ—The gravitational potential is due to the
attraction of every body on the earth's surface toward the center of the
earth by a gravitational force equal to the weight of the body. To raise
this body against this attraction, work must be done, and this work is stored
by the raised body in the form of gravitational potential energy (Z), which
is determined at each point by the elevation of the point relative to some
arbitrary reference level. Therefore
ipg = mgZ
Where ij> = the gravitational potential energy of a mass m of water
at a height Z above a reference and
g = acceleration of gravity
This potential, expressed per unit weight, becomes i|>~ = Z (in cm).
o
Osmotic Qo; and overburden potential (^)— The osmotic potential des-
cribes the effect of solutes on the total potential of soil water and is
important for the study of water movement into and through plant roots and
for studies of evaporation and vapor movement. The overburden potential is
important when soils are free to move and its weight becomes involved as a
B-5
-------
force acting on the water. The osmotic potential and overburden potentials
will not be discussed further here, since they do not significantly affect the
mass movement of water through soil between tensions of 0 and 100 cm under the
conditions of most interest in the context of this review.
Total potential (^-t-) — The total potential of soil water at any place in
the soil is thus equal to the sum of the major component -potentials ifo, \j» ,
^0, and 'J'jj. Theory of water flow uses the hydraulic potential (cm) (5r head),
which is the sum of pressure and gravitational potentials previously defined.
It is common to refer to the hydraulic potential in terms of the "hydraulic
head" (H) (cm). Therefore:
or *m) + *g
Of major concern here is
Moisture retention in soil — At zero tension all pores in the soil are
filled with water (assuming that isolated air pockets do not exist). With
increasing soil moisture tension, progressively smaller pores will empty as the
capillary force they can exercise becomes insufficient to retain water against
the tension applied. The rate of decrease of water content in a soil sample
upon increasing tension is a function of the pore-size distribution for each
soil material. This simplified discussion assumes that the soil matrix is
rigid and that water extraction does not result in soil shrinkage, thereby
releasing water without creating empty voids. This is, however, an important
process in clayey soils.
Techniques are available to experimentally determine the so-called soil
moisture retention curve, which gives the water content of the soil at any ;
given tension (see Fig. B-2). The simple apparatus in Figure B-3 can be
used to establish the moisture retention curve. The saturated soil sample is
placed on a porous disk inside the Buchner-type cup. A tension is applied by
adjusting the point of water outflow at a specific level below the plate.
A detailed discussion of this and another important method can be found in
the literature (Bouma et al., 1974a).
Figure B-2 shows moisture retention curves for a sand (C horizon of
Plainfield loamy sand), a sandy loam (IIC of Batavia silt loam), a silt loam
(B2 of Batavia silt loam), and a clay (B2 of Ribbing loam), demonstrating
the effect of their different pore types. The sand has many relatively
large pores that drain at relatively low tensions or pressures, whereas the
more clayey soils release only a small volume of water because most of it
is strongly retained in fine pores. The sandy loam has more coarse pores
than the clay soil.
Moisture contents in a soil sample are different at corresponding
tensions, depending on whether the moisture content was reached by removing
B-6
-------
60
40
830
UJ
-------
water from an initially wetter sample (desorption) or by adding water to
an initially drier sample (adsorption). This phenomenon is referred to as
hysteresis and is illustrated using Figure B-H. The water-filled void (top)
will drain (desorption) if the applied tension exceeds the relatively large
capillary force corresponding with the smallest pore diameter (2r) in the
system. An air-filled void (bottom) will fill with water (adsorption) as
soon as the relatively small capillary force, corresponding with the largest
pore diameter (2R), is sufficiently strong to pull the water in. This com-
parison shows that the water content of a soil at a given soil moisture tension
will be greater following desorption than following adsorption. It takes more
energy to get water out of the soil once it is in, than to get it back in.
SUCTION TT
(a) DESORPTION
SUCTION TR
(b) ADSORPTION
Figure B-4.
Cross section through an idealized void illustrating the
hysteresis phenomenon (Bouma et al., 1974-a).
_Water movement in soil—The amount of flow through a soil sample is pro-
portionate to the drop of the hydraulic head per unit distance (hydraulic
gradient = AH/L) in the direction of flow. This, basically is Darcy's law
as stated for a one-dimensional, steady-state condition of flow:
V= K • M
Li
where K is the hydraulic conductivity and V is the flux.
B-8
-------
The flux (V) is measured across unit cross-sectional area. Part of
that area (at least 40%) is occupied by the solid phase, which implies
that the real velocity of flow in the soil pores is larger than V. If
the soil were composed of simple capillary tubes of specific sizes,
calculations of the real flow velocity in those pores would be easy.
However, pores vary in shape, width, and direction, and the actual flow
velocity in the soil pores is variable. At best, therefore, one can
refer to some "average" velocity (v1) that can be calculated on the basis
of the water-filled porosity at each tension.
v' =1-
w
where ew is the water-filled porosity, as derived from the moisture retention
curve. At unit hydraulic gradient (AH/L = 1), we find
i K
v1 = —
w
Using these relationships, travel times at different moisture contents during
steady-state flow can be estimated for different soil horizons if a K curve is
available. According to the above equation, flow rates in a given soil mater-
ial at a certain moisture content can vary considerably with varying hydraulic
gradient. The hydraulic conductivity (K), however, is defined as the flux at
unit gradient, and can, therefore, be considered a characteristic value for the
soil. K curves of different .soil materials vary widely due to different pore
size distributions in the soils.
Physical equations have been developed to express flow rates based on pore
size at a given hydraulic gradient (Childs, 1969). The equations shown in
Figure B-5 express the flow rate Q/t (cm / cm^/sec) as a function of the
density of water p (gr/cm^), gravitational constant g (cm/sec^), viscosity n
(dyne/cm), hydraulic gradient symbolized by grad $ (cm/cm) and the pore
radius r (cm) or width D (cm). These equations are graphically expressed in
Figure B-6, demonstrating the significant effect of pore size on flow rates.
The dominant effect of pore sizes on permeability is evident when comparing
K values of a soil material measured at different degrees of saturation. Unsat-
urated soil below an infiltrating surface may occur because of a physical
barrier to flow at the infiltrative surface or an application rate of liquid
which is lower than the saturated hydraulic conductivity of the soil. We may
assume three different soil materials, with pore size distributions schematically
represented in Figure B-7. The uppermost "soil" is coarse porous material (like
a sand) and the lowest one is fine porous material (like a clay). Without a
physical barrier ("crust") at the soil surface and with a sufficient supply
of water, all pores are water-filled and each will conduct water downward as
a result of the potential gradient of 1 cm/cm due to gravity. The larger
pores will conduct much more water than the smaller ones. If a weak crust
forms over the tops of the tubes, pores will fill with water only if the
capillary force they can exercise is strong enough to "pull" the water through
the crust. The larger the pore, the smaller the capillary force that can be
B-9
-------
PLANAR VOID MODEL
TUBULAR VOID MODEL
GRAD<£
RADIUS r I
K=Q FOR GRAD£«ICM/CM
FLOW AREA-ICM2
Q _irq/>r4
r
Figure B-5. Relationships between sizes of tubular and planar voids and flow
rates at defined hydraulic gradients (Bouma et al., 1972).
10
- io6
7 io5
•J-icf
I io3
! io2
M io
tr
1
10"
io2
io5
PLANE SLITS
(UNIT LENGTH)/
TUBULAR PORES
I
10 100 1000 tOOOO
PORE DIAMETER OR WIDTH (MICRONS)
Figure B-6. Graphical expression of flow rates through tubular or planar
voids as a function of pore size at a hydraulic gradient of
1 cm/cm (Bouma et al., 1972).
B-10
-------
exercised. Therefore, larger pores will empty first at increasing crust
resistance, creating unsaturated soil and soil moisture tensions which, in
turn, leads to a strong reduction in the hydraulic conductivity of the soil.
High
or
Absent
Rate of application
of liquid
Degree of "crusting'
I
I'
SAND
LOAMY SAND
SANDY LOAM
SILT LOAM
(Liquid
CLAY
Crust
Figure B-7. Schematic diagram showing the effect of increasing the degree of
crusting or decreasing the rate of application of liquid on the
rate of percolation through three "soil materials" (Bouma et al.,
•1972).
With no crusts present, unsaturated soil conditions can occur when the rate
of application of water to the capillary system is reduced. With abundant
supply, all pores are filled. As this supply (which is supposed to be divided
evenly over the infiltrating pore system) is decreased, there is not enough
water to keep all pores filled during the downward movement of the water.
Assuming that the pores are horizontally interconnected, larger pores will
empty fir-st, as they conduct most liquid, while at the same time they exer-
cise only relatively small capillary forces. In this system a certain size of
pore can be filled with water only if smaller pores have an insufficient capa-
city to conduct away the applied water.
B-ll
-------
The rate of reduction in K upon desaturation and increasing soil moisture
tension is characteristic for the pore size distribution of the soil material.
Coarse porous soils have a relatively high saturated hydraulic conductivity
(Kga-f-), but K drops rapidly with increasing tension. Fine porous soils have
a relatively low Ksa^-, but K decreases more slowly upon increasing tension.
Experimental curves, determined with the crust test show such patterns for
natural soil. Figure B-8 shows curves for the sand C horizon of the Plainfield
loamy sand, the sandy loam IIC horizon and the silt loam B2 horizon of the
Hibbing loam. Moisture retention curves for the same soil horizons were
presented in Figure B-2. The curves for the pedal silt loam and clay hori-
zons demonstrate the physical effect of the occurrence of relatively large
cracks and root and worm channels. Soil structure inside the peds is very
fine porous and these fine pores contribute little to flow. The large pores
between peds and root and worm channels give relatively high K values (14-0
cm/day for the silt loam), but these pores are not filled with water at low
tensions and K values drop very strongly between saturation and 20 cm tension
(1.5 cm/day for the silt loam).
Flow into crusted soil—A special case of the two-layer flow system
occurs when very thin layers with different hydraulic properties occur in a
flow system. An example will be discussed concerning thin barriers (crusts)
on top of infiltrative surfaces (Hillel, 1971).
Assuming steady infiltration the flux through the crust (a ) should be
equal to the flux in the subcrust soil (q ).
s
— V ( \ _ w" ( \
b s D dZ b s dZ s
where Kb and Ks are hydraulic conductivities of .the barrier and the underlying
soil with dH/dZ the hydraulic head gradient in each material. The hydraulic
head gradient will be approximately unity in the soil at steady infiltration
(Baver et al., 1972). Assuming flow in the soil to result only from gravi-
tational forces:
H + ilj + Z,
., _ v- . o m D^
s(ib ) D Z
m b
K
s(^ ) K, -,
m D 1
H + ij) + Z, Z,
o m b b
where K-^ ) is the unsaturated K value of the soil at a moisture tension
of ^m cm, ^ is the positive hydraulic head on top of the barrier exerted by
the depth of ponded liquid, Z is the thickness of the barrier, and R =
B-12
-------
1000-:
> 10-5
3
O
8
I '.
-------
derived from the above equation assuming different RJ-, and H0 values, and a value
of 2 cm for Z^. The curves are composed of all points where the relationship
between Ks(^, ) and fym is valid for the assumptions made. Curves were drawn in
Figure B-9 for Rb = 5, R, = 100 and R, = 1,000 days, combined with HQ = 5,
H0 = 30 and HQ = 60 cm (for R, = 1,000 only H = 5). Points where both types of
curves cross represent the only hydraulic conditions, in terms of tensions below
barriers and flow rates , that can be expected at the specified HQ , Z, and R,
values. Some conclusions of practical interest can be drawn from Figure B-9:
1) Infiltration rates decrease and tensions below the barrier
increase as the resistance of the barrier increases. The
effects are a function of the capillary properties of the
underlying soil, as expressed by the K curve. For example,
a barrier of R^ = 5 days (Ho = 5) induces tensions of 35 cm
(sandy loam), 28 cm (sand), 13 cm (silt loam) and 3 cm (clay)
with corresponding flow rates of 8 cm/day; 7 cm/day; 4- cm/day
and 1.8 cm/day, respectively. A barrier of Rv, = 1,000 days
(HQ = 5 cm) induces tensions of 108 cm (sandy loam), 105 cm
(silt loam), 94 cm (clay), and 56 cm (sand) with flow rates
of 0.14- cm/day, 0.14- cm/day, 0.10 cm/ day and 0.05 cm/day,
respectively. For R^ = 1,000 days and HQ = 5 cm, a clay is
more permeable than a sand.
2) Identical barriers induce different moisture tensions in differ-
ent soils because their hydraulic effect is not only dependent on
their own resistance but also on the capillary properties of the
underlying porous medium. For example, a crust with R^ = 100
days and HQ = 5 cm induces tensions of 80 cm (sandy loam),
45 cm (silt loam), 40 cm (sand), and 20 cm (clay).
3) Increasing the hydraulic head on top of a barrier with fixed
R]-, increases the flow rate and reduces the tensions in the
soil, but effects are generally minor. For example, a
barrier induces flow rates of 0.5 cm/day (HQ = 5), 0.7 cm/day
(H0 =30) and 1 cm/day (HQ = 60) in sand. Corresponding
tensions are 42, 40 and 38 cm, respectively. The effect
of increasing the head is a function of the capillary pro-
perties of the porous medium and thus , the shape of the K
curve .
4) Barriers with a small resistance (Rv, = 5 days) will not affect
the clay soil (except for HQ = 5 where a tension of 3 cm and
a flow rate of 1.8 cm/ day is induced). In fact, the Rv, and HQ
curves reflect hydraulic conditions imposed by the crust and
the K curves reflect those allowed by the soils. The most
limiting of the two (the K curve in the example discussed)
determines conditions if the curves do not cross .
In summary, the higher the "crust" resistance or the lower the steady
rate of application of water, the higher the soil moisture tension in the
underlying soil and the lower the water content and the relevant hydraulic
B-14
-------
1000-
100-
(0
•O
^
o
O 10-
Q
z
o
o
o
cr
O
I
01 -j
Rb'5 H0 = 60
Rb-5 H0-30
Rb-5 H0. 5
Rb-100 H0-60
Rb-100 H0-30
Rb- 100 HO-5
1000 H0
\
20 40 60 80 100
SOIL MOISTURE TENSION (cm water)
SOIL MOISTURE POTENTIAL (-cm water)
Figure B-9. Hydraulic conductivity curves for four major types of soil and
curves expressing the hydraulic effects of impeding barriers
of different resistances (see text) (Bouma, 1975).
conductivity (K). These characteristics apply to steady-state conditions in
a one-dimensional system, where, at a hydraulic gradient of 1 cm/cm, flow rates
are equal to the hydraulic conductivity. More complex flow systems, for
example, those where the moisture content is changing with time, need more
complex mathematical expressions which are beyond the scope of this discussion.
Flow dispersion—The longer a volume of liquid waste is kept in contact
with soil particles, the greater the chance of good purification. If flow is
such that all of the liquid present at equilibrium (one pore volume) will be
"pushed out" before the applied liquid passes, then simple flow procedures
can be used to explain the system. If some of the applied liquid passes
through the soil before all of the liquid initially present leaves, then
hydrodynamic dispersion has occurred. Physically, this can happen if channels
B-15
-------
or pores allow water to move through the soil so fast that the water does not
have time to enter the smaller pores. Dispersion or short circuiting has
been used to explain poor bacteria removal from effluent passing through soil
columns at high loading rates. Dispersion coefficients (D) and breakthrough
curves have been defined for soils of different structures and loading
(Anderson and Bouma, 1977a,b).
For columns initially saturated with water and dosed with an unlimited
amount of water, breakthrough occurred before 0.5 pore volumes had passed in
subangular blocky structured soils. In soil columns with prismatic structure,
breakthrough occurred after that in subangular blocky soils. If the struc-
tured soils were initially drained and an unlimited dose was applied, break-
through was very rapid. Reducing the dosing rate to 1 cm/day delayed the
breakthrough considerably; however, dispersion was still prominent. Addition
of an artificial crust at the infiltrative surface to simulate a clogging
layer of a soil absorption system further delayed breakthrough and reduced
dispersion.
The high dispersion found using an unlimited dose in previously drained
soil may be controlled in on-site soil absorption systems by controlling the
loading rate or allowing limited clogging to occur. Differences in dispersion
are related to soil structure and possibly predicted from soil descriptions.
Methods of Hydraulic Conductivity Measurement —
In this section, five permeability measurement methods are discussed.
These include: 1) the field percolation test; 2) the use of small soil cores;
3) the instantaneous profile method; 4) the double-tube method; and 5) the
crust test. Detailed experimental procedures are given for each method, except
for the percolation test, which has been widely used. The advantages and
shortcomings of the methods are discussed in some detail along with the method
description.
The field percolation test — Henry Ryon is generally credited as the
originator of the field percolation test in 1926 (Federick, 1948). He used it
as a rough empirical measure of the ability of the soil to accept septic tank
effluent over a long period of time. Since that time it has been widely used to
evaluate site suitability for soil absorption field construction because it
is simple and easy to use. However, the test has been criticized because it
is generally an ineffective predictor of absorption field performance.
— There are many variations on the percolation test. The follow-
ing description summarizes the technique used by the Wisconsin State Division
of Health (1967).
A hole is augered to the soil horizon in which a proposed drainage field
is to be constructed. A cylindrical hole with a diameter ranging from 10 cm
(4 inches) to 25 cm (10 inches) and often larger is used. The bottom and
sides of this hole are carefully scratched to ensure an unsmeared surface
and 5 cm of gravel or coarse sand is placed in the hole. Water is carefully
poured into the hole so that the soil is not disturbed by violent water flow.
B-16
-------
Usually water is introduced to a depth of 30 cm. If the 30 cm of water flows
away rapidly (less than 10 min), indicating high permeability the test can
proceed at once. If more than 10 minutes are required for seepage of the
water, then water must be maintained at 30 cm depth for 4 hours and a period
of 16 to 30 hours must be allowed for swelling of the soil before measure-
ments can be made.
Measurements are made of the amount of head change that occurs in thirty
minutes. The water depth is 15 cm at the beginning of each experiment. When
these measurements remain nearly constant, the percolation rate is calculated
and expressed in minutes per inch or inches per hour.
»
Comments—Many papers have addressed problems that are associated with
the percolation test (Winneberger and McGauhey, 1965; Hill, 1966; Bouma, 1971;
Luce, 1973; Chan, 1976). The test itself has several weaknesses. The
flow of water from a hole can be used as a rough means of ranking the soils
ability to conduct water. But to extrapolate the rate of flow under these con-
ditions to the design of a subsurface drainfield very often leads to inadequate.
sizing of the system. The reasons for this failure are easily recognized. The
percolation test measures flow from a hole out in all directions. The flow rate
or "perc rate" measured is based only on the dimensions of that hole and cannot
readily be used to calculite the effective flow rate of a given seepage field
trench. The percolation rate is a combination of the vertical and horizontal
component of soil hydraulic conductivity.
The diameter of the hole used for the test does not appear to influence
the resulting measurements in practice (Chan, 1976). Logically, a change in
rate would be expected, but any differences seem to be cloaked by the large
general variation within the technique. These variations may also be due in
part to soil and climatic conditions.
The depth to which water stands in the hole does make a notable difference
in measured percolation rate. Increasing the height of water in the test hole
can more than double the percolation rate (Chan, 1976). There is less varia-
tion when a constant head of 12 cm is maintained than when a falling head is
used as described here. For a series of falling head measurements, Bouma
(1971) found the coefficient of variation to be 54 percent, as opposed to
35 percent with the constant head procedure in the same soil.
Several other factors affect the test. The initial moisture condition
of the soil can lead to errors. Percolation rates are often higher in summer
because a longer wetting time is required in dry soils, particularly those
with fine texture. Slaking of the bottom and sidewalls of the hole can occur,
restricting flow. Entrapment of air in soil pores can prevent reproducible
saturated conditions from occurring. There is not space to discuss these
further, but a good discussion of the percolation test is presented by
Chan (1976).
The great failing of the percolation test, as with all saturated permeability
tests, is that it cannot predict the rate of flow from a drainage field after
a clogging layer has been formed. To do this, the unsaturated hydraulic con-
ductivity and the soil moisture potential under the drain field must be known.
B-17
-------
The use of small soil cores for laboratory measurement of hydraulic
conductivity — The measurement of saturated hydraulic conductivity through
packed sand and soil columns has been a useful tool for hydrologists since
the early experiments of Darcy (1856). Since that time the method has been
applied to measurement of saturated flow in undisturbed soil cores which main-
tain much of the natural soil structure. Richards (1949) extended this method
further to measure hydraulic conductivity of soil for unsaturated conditions.
Measurements of K from soil cores and columns generally require the estab-
lishment of a steady state flow of water through the soil. Although many
variations on this method have been used, the basic procedure remains the
same . i
The use of soil cores has several logistical advantages. Cores can be
collected rather easily and quickly in the field. The cores can be run in
the laboratory under controlled conditions. Although the test conditions
are reproducible, the results may be highly variable. This method yields
information on saturated and unsaturated hydraulic conductivity.
Experimental apparatus — Special laboratory apparatus is required for the
measurement of unsaturated K by this method. Figure B-10 (Richards, 1949),
represents an arrangement that allows the use of 7.5 cm diameter soil cores
of up to 10 cm height. The exact construction of this chamber can have several
forms depending on the size and shape of samples used. Seals can be made by
the use of "0" rings to fit the cylindrical soil core (Klute, 1965). The
sample core is enclosed in a chamber and two tensiometers T and T are
inserted into the soil from the side. These will be used to calculate
the potential gradient across the sample. Porous plates are placed into firm
contact with the soil samples upper and lower surface and sealed to the outer
wall of the chamber. Flow into the chamber (Qj) is measured in a burette
that has a constant head device (M), a Mariotte tube inserted. Outflow (O^)
is via a drip point connecting to the chamber below the second porous plate,
This liquid is collected in a graduated container. The distance that the drip
point is below the soil sample controls the applied moisture potential by
adjusting the heights of the inflow water container and the drip point. The
applied hydraulic gradient can be varied. This arrangement is accurate in the
soil moisture potential range of 0 to -200 cm water, and cannot be used for
potentials less than -750 cm, because of the vaporization of water.
Saturated hydraulic conductivity (Kgat) can be measured by a simpler
technique requiring only the constant application of water to the sample's
upper surface under a minimum hydraulic head. Water flows out of the core
and this flux is taken as K at saturation. This technique is very dependent
on the size of the soil sample used. Anderson and Bouma (1973) have shown
that the value and the amount of variation of the measured K is inversely
proportional to the length of the soil core used. This suggests that the
values for K recorded may be arbitrary numbers of limited use. Standardized
core sizes must be used for this purpose.
— The hydraulic conductivity of the soil sample at a given
moisture potential ^m is
B-18
-------
CONSTANT
WATER
SUPPLY
SYSTEMS
"sL
"T
h4
t
b
_ _
--
T A!
^B
•-
-^T-,i !
"^f ll=
«2
DRIP;
POINT
T
IT
SOIL
iK
-|
•:t
<
-BUBBLE
TUBE
i i
ajD»—- _
3 ^-^
9?
*?
m
\
^•""Ir!
-T
*>
6
S
H,
If-
TO CONSTANT
GAS PRESSURE
SOURCE
Figure B-10.
DRAULIC HEAD REFERENCE
Diagram of apparatus for steady-state method of measurement of
conductivity of unsaturated soil. The meaning of the symbols
is explained in the text (Klute, 1965).
'
for downward vertical flow, where
o
Q = net flow rate (cm /day),
f-\
A = surface area of the soil sample (cm ),
) = hydraulic conductivity for moisture potential ^ (cm/day),
AH = the difference in hydraulic head (cm),
L = the length of the core (cm).
For the special case of gravity drainage, the last term (L/AH) is nearly equal
to one and can be dropped from the equation.
The procedure is carried out by securing the sample in the chamber with
porous plates positioned and tensiometers inserted. Water is applied to the
upper plate until steady state flow is achieved and constant potentials are
B-19
-------
recorded by the tensiometers. This flow rate, Q, and the potentials are
recorded. The average potential is ty for that K value as found in the above
equation. For saturated K, only the flux, Q, is measured.
Comments — This method yields both saturated and unsaturated hydraulic con-
duct ivrty^SatTa for small samples. Variation in measured K of undisturbed soil
samples is large. Mason et al. (1957) reported a coefficient of variation
of 70 percent within sites at saturation. A large portion of the variation is
dependent on the size of the sample taken. For a structured soil, a 7.5 cm
diameter ring may contain only a few soil peds and correspondingly few struc-
tural pores. Another sample taken at the same site can be a little different,
having perhaps one additional pore, but compared to the effects of the other
few pores, this may have a large effect on water flow through that sample.
Also, a change in length of the core or column can have a similar effect
on the measured flow rate. The longer the column, the lower the probability
that a given chain of pores will connect all the way through the sample.
Anderson and Bouma (1973) showed that variation in saturated Kgat decreased
markedly for 7 . 5 cm diameter cores that are greater than 15 cm in length. At
this length K values approached those measured by the double tube test for a
soil with subangular blocky structure.
Soil cores have the advantage that entrapped air can be purged from
the pores more readily than in other methods. This is accomplished by the
use of reversed hydraulic gradient. Also, the reduced field time, fewer
weather problems, and the ability to measure saturated and unsaturated K
are advantages. The inherent disadvantages are that significant laboratory
time is required, variation in results is large, and relatively large cores
or large numbers of cores are required to reduce this variation.
The instantaneous profile method for measuring hydraulic conductivity
of unsaturated soil in situ — In the instantaneous-profile method, a~ fallow
plot of soil is artificially wetted to saturation. The plot is then covered
to prevent evapotranspiration, and internal drainage occurs. By the use of
tensiometers, placed at depths corresponding to the lower part of major
horizons, soil moisture potentials are measured. Moisture contents at these
depths are also determined simultaneously. These two characteristics are
measured frequently, starting at saturation, which represents time zero.
From these data, the hydraulic gradient (9H/9Z) and the change in mois-
ture content over time (98 /9t) can be obtained and subsequently the hydraulic
conductivity can be calculated.
Theory — Taking the general equation of vertical hydraulic flow in a soil
profile
where 0 = volumetric moisture content,
H = hydraulic head (H = ty + Z),
B-20
-------
K(9) = hydraulic conductivity at moisture content 6,
Z = depth (positive downward),
t = time.
By integration and rearrangement, we find
||
or
In a multilayered profile the factor (96/91:) • Z becomes the sum of
-------
The hydraulic gradient (9H/9Z) of an internally draining, initially
wetted profile is often unity. The exact value is the slope of the line
created by plotting hydraulic head (H = ty + Z) versus the depth A to the
tensiometer cup where the head is measured (Fig. B-12). This slope varies
with time, and must therefore be determined for each time of observation at
which K is calculated. This will be discussed in greater detail in a specific
example later.
Site selection and preparation—A nearly level site is selected for the
experiment so that water may be ponded more or less uniformly over the entire
area. To retain the water, a simple earthen dike can be constructed surrounding
the plot. A water depth of about 2 or 3 cm over all portions of the pond is
desired, but may be difficult to achieve. On slopes of low grade, uniform
distribution of water is not a problem, but on steeper slopes, uneven infil-
tration and subsurface flow can occur. Figure B-13(A) illustrates the desired
flow pattern in the experimental plot. Water infiltrating over the entire
area of the plot moves generally downward under the influence of gravity.
Because the soil surrounding the plot is drier than the soil directly under
the pond, lateral movement of water is expected to occur. This drier surround-
ing soil exerts a tension on the water inside the experimental volume, pulling
it away from the center of the plot. This effect is greatest at the boundaries
of the area and decreases toward the center. As the flow lines indicate, flow
is nearly vertical below the center of the plot. Here, approximate one-
dimensional flow is achieved. All the details of plot preparation are designed
to maintain vertical drainage at this point, isolating this zone from the
effects of lateral flow and from changes of soil moisture content due to
external factors such as evapotranspiration and precipitation.
Figure B-13(B) illustrates the effect of slope on water movement for a
plot where uniform infiltration occurs. Vertical flow is seen to be shifted
somewhat from the center of the plot and lateral flow is seen to be greatest
on the downslope side of the plot and least on the upslope side. In such a
case, knowing where vertical flow occurs may become a problem. The location
and orientation of instruments is dependent on this knowledge. On gentle
slopes (< 3%) this problem is very small, assuming uniform infiltration over
the entire area.
One of the largest problems on slopes is achieving uniform infiltration.
Often the surface is such that water will be a few inches deeper on the
lower portion of the plot than on the upslope portion of the area. Figure
B-13(C) indicates this situation. There is not only a problem with distri-
buting the water over the surface but also the difference in hydraulic head
will cause flow rates to vary from upper to lower sections. The length of the
flow lines in the figure represents the relative magnitude of flow rates.
Notice that vertical flow is found downslope from the center of the experimental
area.
It can be seen from these examples that the ideal case will rarely
be encountered in the field experiment. A sloping site will cause
nonvertical flow under the center of the plot and uniform distribution of
water will become diffi cult to achieve.
B-22
-------
50
H HYDRAULIC HEAD (cm)
100 150
200
50
UJ
o
100
150
Figure B-12. Total potential as a function of depth and time during drainage
of an initially saturated profile.
I-
Figure B-13.
Diagrams illustrating possible flow patterns occurring when
saturating soil for the instantaneous-profile method.
B-23
-------
Other problems may arise due to flow of external moisture from upslope
through the soil of the plot. Figure B-13(D) depicts this situation. This
directional flow is most significant at saturation when downslope movement
due to gravity is the dominant force involved. Saturation may occur in the
form of a real water table or of a "perched" water table where water is tempor-
arily ponded above slowly permeable horizons or strata. Water contained in
this manner by a less conductive horizon below, may well cause saturation in
the horizon above the less pervious layer, and downslope rather than vertical
flow may occur. If this occurs upslope from the experimental plot, external
water may be introduced at one or more levels in the pedon, setting up a
complex drainage pattern which may change the gradients drastically. Data
obtained under these conditions can be extremely difficult to interpret.
A related situation is encountered when the site of the experiment is
located in a depression, where not only surface water but also subsurface
moisture flow is concentrated due to downslope gravity movement.
In homogeneous media, such as some sands, a nearly uniform gradient is
found during drainage. In multilayered soils where horizons have different
hydraulic conductivities, a nonuniform gradient develops. Impeding horizons
and other features will prevent free drainage from occurring within the
experimental volume of soil. Soil moisture potentials above such an impeding
layer may approach or reach zero (saturation) while the potential beneath the
layer can be higher (lower moisture content). Such a layer can then behave
as an impeding crust, preventing saturation from occurring in horizons below
itself. Therefore, a part of a given multilayered soil may not reach satura-
tion, and K values close to saturation for the unsaturated horizons cannot be
determined by a free-drainage method such as this. Examples of some soil
features that can act as impeding layers are a plow sole, an argillic horizon,
and pans.
Once a site has been selected, the area must be prepared for the experiment.
These efforts are designed to isolate the plot from its surrounding environ-
ment and to ensure that the plot is a closed system.
The size of the plot used may depend on the moisture condition of the
surrounding soil. For example, when a very dry soil surrounds the plot,
lateral movement from the plot to the surrounding environment can be great.
This may lead to exaggerated drainage rates, as recorded by the instruments
located at the center of the plot. Because the latter movement of moisture
is not uniform over the depth of the profile and is usually greatest for the
uppermost horizon, the head gradient (9H/9Z) can be exaggerated. If the plot
is surrounded by very moist soil, drainage will take place very slowly. Mois-
ture may enter the system from the surrounding soil, and the length of time
required to achieve a certain tension in the plot may be very long. This may
be because there is no place for the moisture to drain, a moisture regime that
rarely achieves a low enough tension or a high water table which interferes
with the head gradient because of its capillary fringe.
A circular plot of a diameter of 3 meters has been used successfully
(Davidson et al., 1971), but under extreme conditions of drying in the sur-
rounding soil, this may be an inadequate volume to allow undisturbed internal
B-24
-------
drainage at the center of the site (Vepraskas et al., 1974). In such a case,
the diameter of the plot may be expanded to ensure unaffected drainage at the
center. On the other hand, in some environments a smaller plot may be suffi-
cient to eliminate boundary effects over a low-tension range.
The site is selected and the necessary area is estimated. Vegetation is
either entirely or partially removed. Cutting vegetation off at ground level
is more effective than pulling or hoeing it, as this will not disturb the
infiltration surface. Plant removal is relatively simple in open fields but
on wooded sites where shrub and tree roots permeate the soil, little can be
done without destroying these plants. The root systems of trees on a hot
summer day can noticeably affect the moisture content of a profile, thus
interfering with the experiment. Selection of a site at a location farther
from trees may bias the experiment somewhat, but the results will be more
representative of the actual conductivities of the soil at that point. Also,
if the roots of the plants remain, revegetation is faster and the soil is
less subject to erosion.
Walking on the plot should be held to a minimum when the plot is dry
and should be eliminated entirely if the soil is moist or wet. This pre-
caution is necessary to prevent puddling of the soil surface. Placing a
sheet of plywood on the plot or extending planks across it supported with
blocks at the boundary are two simple methods to keep traffic off the soil.
An earthen dike about 7 cm high can be constructed easily with sod from
outside the boundaries. The purpose of this dike is to allow ponding of water
over the area of the plot. It also prevents any surface runoff from upslope
from flowing over the plot, rewetting it, and interfering with the experiment.
Figure B-14- shows a prepared plot with the earthen dike in place.
After the profile has been wetted, it must be isolated from such factors as
precipitation and evapotranspiration. These can be controlled with two layers
of plastic sheeting large enough to cover the plot. One should be sufficiently
broad to allow it to be supported at the center with the sides sloping out
beyond the boundary of the plot. The smaller of the sheets should be spread
over the freshly wetted area. Cut a hole about one foot in diameter in the
center of it so that the instruments can protrude for convenient maintenance
and recording. The earth between the instruments can then be covered over with
aluminum foil or small plastic sheets. If the plastic sheet is nontransparent
preferably black, sunlight will not easily penetrate to the soil surface and
plant growth will be severely retarded. With a transparent sheet, plants
will grow quickly allowing transpiration to occur with removal of moisture from
the soil. The sheets are held down at the edges with weights or stakes. The
larger plastic sheet is used as a tent to shed precipitation. It is supported
at the center of the plot by a post about 1-meter high, on the top of which is
a circular wooden disk about 25 cm in diameter. The disk should not have rough
edges that would tear the plastic. The circular design distributes the weight
of the plastic uniformly and prevents punctures. Figure B-15 shows a prepared
plot with the second plastic sheet in position.
3-25
-------
Figure B-14.
Picture of prepared plot for the instantaneous-profile method
with the first plastic sheet in position (Bouma et al., 1974a),
Figure B-15.
Picture of prepared plots with the second plastic sheet (b)
in position (Bouma et al. , 1974-a).
B-26
-------
Alternate forms of plot preparation are possible. One involves the digging
of a ringlike trench around a 1-meter diameter undisturbed column of soil
(Anderson and Bouma, 1973). The trench is made to a depth somewhat below the
deepest horizon for which the conductivity is to be determined. Following this,
a detailed profile description can be made on the wall of the column, providing
accurate horizon boundaries for location of the tensiometers. The sides of the
column must be covered with plastic sheeting or aluminum foil to prevent
evaporation. The surface is prepared as described previously, and a ring or
dike is constructed to retain the ponded water on the top for wetting. Figure
B-16 shows a prepared column arrangement.
Figure B-16. Large excavated column for running the instantaneous-profile
method on sites where the regular procedure cannot be applied.
p = metal pipe for neutron probe; c = soil column; t = tensio-
meters and s = tensiometer boards with calibrated scales for
reading moisture tensions (Bouma et al., 1974a).
This arrangement has the distinct advantage that tensiometers can be im-
planted from the sides and the problems of vertical placement can be eliminated.
For this application, small 0.6-cm diameter tensiometers, as described for the
crust test method, can be used. The neutron moisture probe is a convenient
tool for moisture-content measurement here.
B-27
-------
One of the main advantages of the column method is that one-dimensional
flow is maintained. There is no lateral interference with drainage or down-
slope moisture flow. Internal drainage proceeds uninterrupted. Effects of
neighboring vegetation are eliminated and problems associated with slope are
greatly reduced. However, the procedure is elaborate and costly.
Instvumentat'Lon—Accurate soil-moisture-tension and soil-moisture-content
measurements are necessary for the implementation of this technique. The care-
ful placement of tensiometers in specific horizons of the profile and the sealing
of these tensiometers in place will be discussed here, followed by a discussion
of methods of moisture-content determination. Before this, it is important
to point out that an accurate profile description of the soil at or adjacent
to the site is essential for the determination of depths of placement of
tensiometers and for the useful interpretation of results. This technique
can be applied very well to major horizons, but may not be specific enough
for smaller soil features, such as some subhorizons.
Normally, the depth of tensiometer placement is meant to coincide with the
lower boundary of the horizon to be studied. Placement a few centimeters
above this boundary is perhaps more realistic since the tensiometer does
not read pinpoint tensions, but measures the tension of the small volume
surrounding the cup. It is the difference in tension across the layer which
is needed to find the conductivity of that layer. This is the head gradient.
So if only one horizon is to be studied, a tensiometer is needed at both the
top and bottom of that particular horizon to define that gradient (see Fig.
B-17).
Tensiometry—Tensiometers with porous cup measuring 1.9-cm OD and 5-cm
long, attached to clear plastic tubing of 2.0-cm OD, and cut to various lengths
have been used. These were placed in the soil by the following methods.
Using a screw auger, a hole is bored of slightly larger diameter than the
tensiometer itself. This hole is made 5 cm less than the depth of desired
tension measurement. A push auger of a smaller diameter than that of the
tensiometer may be used to extend the depth of the hole, or if the soil is
moist enough, the tensiometer may be pushed into final position. This last
technique will disrupt some structure and may cause rather severe puddling
surrounding the cup.
A cavity along the side of the tensiometer may conduct water to the vicinity
of the cup leading to tension measurements not representative of that horizon.
For this reason, the space surrounding the tensiometer must be filled or sealed.
To seal the auger hole around the tensiometer, a liquid slurry is poured
into the empty hole in such a way as not to trap air at some point along the
cavity. This is accomplished by pouring the slurry just to one side of the
hole so that it will flow as a stream down one wall of the hole thus not pre-
venting the escape of air from below. Once the hole is filled, the tensio-
meter is pushed into the slurry forcing it out at the surface to form a cap
over the hole (see Fig. B-18). If some air has been trapped, it will also
rise to the surface. The displacement causes the slurry to be forced into
B-28
-------
- MANOMETER
BOARD
-MERCURY CUP
POROUS CUP
2
Figure B-17.
Schematic diagram showing appropriate locations of tensio-
meters in a soil profile with three horizons (Bouma et al.,
Figure B-18.
Installed vertical tensiometer with slurry forced out at the
surface to form a cap over the hole (Bouma et al., 1974a).
B-29
-------
holes and cracks along the walls of the auger hole, reducing the possibility
of lateral water movement. In a dry soil with well-developed structure, slurry
may be forced back along interpedal voids or into biopores for a distance of a
few centimeters from the tensiometer. If this were to happen to any great
extent, the natural moisture flow associated with these voids would be
affected. Where the cup of the tensiometer reaches the bottom of the hole, it
must be forced into place to provide good contact between the cup and the
soil. Some smearing along the sides of the cup are inevitable, but smearing
should be held to a minimum. Figure B-19 illustrates the good contact between
the cup and soil and the sealing along the length of the tensiometer.
The slurry is prepared from soil of a texture equal to or slightly heavier
than the texture of horizons being studied. For instance, a silty clay loam
is used for profiles which are largely of silt loam texture. This material
is placed in a shallow basin and small aliquots of water are added, with mix-
ing, until a viscous liquid results. Time must be allowed for the swelling of
clays. The material must be mixed thoroughly and any aggregates or clods
should be broken down. An electric hand mixer of the type used for mixing
cake batter in the home may effectively be used for this purpose. The slurry
should be a viscous liquid and must flow evenly when poured.
Another method of tensiometer placement requires making a hole to the
required depth with a push auger of slightly smaller diameter than that of the
tensiometer itself. The tensiometer is then forced into place, assuring good
contact with the soil.
Either of these techniques provide good contact between the porcelain cup
and the soil. However, the first method assumes that there is a cavity
along the tensiometer and procedures are defined to fill it, while the second
method relies on the tensiometer being forced in for the length of the hole
to a close fit. It is important that there be no unnatural vertical cavities
in the profile, since at saturation such a cavity will act as a shortcircuit
and conduct water rapidly downward, creating an unnatural moisture distribution.
Small holes are bored in the walls of the plastic tube for insertion of a
0.3-cm flexible tube that connects the plastic tensiometer tube to the mercury
cup via a manometer board as shown in Figure B-20. The scales for the boards
are graduated to read cm of water and can be purchased individually. An
adequately large mercury reservoir is selected so that the surface of the
mercury in the reservoir does not fluctuate greatly as tensions vary. A top
for the mercury reservoir is recommended with holes drilled in the cap to
accommodate the 0.3-cm tubes. The reservoir should be taped or otherwise
anchored to the manometer board to avoid spillage.
The tensiometers are filled with de-aired water by pouring the water down
the inside of one wall of the plastic tube of the tensiometer until the shaft
is completely full. The water is poured gently to avoid dissolving too much
air in the water. Next, a 50 or 60 ml plastic syringe with a single-hole
rubber stopper (No. 1) fixed on the tip is inserted into the plastic hole
(Fig. B-21) with the stopper fitting tightly in the plastic tube. By pushing
the plunger of the syringe forward, water is forced into the system and fills
B-30
-------
Figure B-19.
ExcaVated tensiometer cup showing good contact between soil
and porous cup and complete filling of the hole above the
cup with slurry (Bouma et al., 1974a).
Figure B-20.
Tensiometer assemblage, showing the connection of the plastic
tube (T) with the manometer board (B) and mercury cup (M) through
0.3 cm flexible tubing (t). The black box with a lock serves as
a deterrant to vandalism. The access tube (A) for the neutron
probe is next to the tensiometers (Bouma et al., 1974a).
B-31
-------
the 0.3-cm plastic tubing. When water flows out of the top of the mercury
reservoir the syringe is removed, the tube filled to overflowing and a solid
rubber stopper (No. 1) is inserted to close the system. With the tensiometers
shaft-oriented vertically, any air in the water tends to rise to the top of the
shaft under the rubber stopper. Even though de-aired water is used, some air
may appear here, particularly at higher tensions. Whenever air accumulates
under the stopper it should be removed'by filling the tube with more water. Gas
in the system can lead to erroneous tension measurement, due to expansion and
contraction with temperature variations. If a lot of air is present or if the
condition persists for several days, this may indicate a leak in the system,
usually a pinhole or crack in the 0.3-cm tubing or a bad seal of the fine
tubing to the tensiometer shaft.
PLASTIC
SYRINGE
POROUS
CUP
MERCURY
CUP
Figure B-21.
Filling of the 0.3 cm flexible tubing, using a plastic syringe
which connects the water-filled plastic tube and porous cup
and the mercury cup (Bouma et al., 197Ha).
B-32
-------
Soil moisture content—Two methods can be used here: 1) indirect values
derived from moisture retention curves and 2) direct values derived from in
situ neutron probe measurements.
Soil moisture content can be determined by the use of moisture retention
(desorption) data for the given horizons (Davidson et al., 1971). Soil cores
(7.5 cm diameter, 5 cm high) are taken adjacent to the plot at the depths to
which tensiometers are to be placed. The plot is wetted and drainage occurs.
In this case, only matric tension is recorded as the experiment progresses.
The moisture content of a specific horizon is determined from the moisture
retention curve by finding 6 for the core at the tension recorded in the
horizon at that time. The moisture content data are indirectly gained but can
be used in the calculation of K. The limitation of this technique is that the
soil core may not represent the horizon as a whole. Several cores may be
needed for a good average of values. Double tensiometry may also be needed to
ensure accuracy.
The neutron probe may also be used for this purpose. The neutron moisture
probe consists of a fast neutron source and slow neutron detector. Fast
neutrons travel radially into the surrounding soil where, if they strike the
hydrogen atom of a water molecule, they are slowed considerably. The main
source of hydrogen in the soil is water, and so, aside from the small back-
ground noise of the soil material itself, the number of slow neutrons detected
is roughly proportional to the amount of water in the soil (Cannell and Asbell,
1974). A counter attached to the probe converts this information into digital
form. With calibration, counts/minute can be translated toperosnt water by volume.
An access tube, 4.1 cm OD thin-walled metal conduit, is placed in a hole
augered several inches deeper than the deepest horizon at which measurement is
desired. The pipe should fit the hole tightly and may need to be driven into
place. The hole should not be filled in around the pipe as this may lead to
unrepresentative moisture contents. The probe can then be lowered in the
access tube to the depth where measurements are required, measured from the
soil surface to the neutron source. Note that the size of the roughly
spherical volume of soil for which the moisture content is being determined
varies with the moisture content of the soil. When the soil is very wet, a
small volume is required to slow the neutrons and, when the soil is very dry, a
larger volume may be needed to slow the neutrons. This means that in drier
soils, a larger sample volume is needed and the moisture probe becomes less
specific for a single thin subhorizon. So the neutron probe cannot yield the
specific information in a dry soil that it can in a wetter soil. If a measure-
ment is taken near a horizon boundary, the resulting moisture content may be
somewhere between that of each horizon.
Gravimetric determinations of the soil moisture content can be used. A
limitation of the technique is that a large number of samples would need to
be taken during the course of the experiment, and variability across the plot
may lead to slight variations of the data. The change in water content over
time will be recognized as 36/3t.
B-33
-------
Experimental procedure—Now that the plot has been prepared and the
instruments are in place, the plot can be wetted. Often it will be necessary
to wet the plot a day or two before the start of the actual measurements.
This allows time for the swelling of clays and adsorption of water by the
peds. Wetting can be accomplished by running a hose from a nearby house or
by the use of trailer-mounted, large-capacity water tanks. Impact of the
water on the plot surface should be dissipated to avoid disturbing the surface
and suspending soil material which in turn may cause clogging of some pores.
Water is ponded on the surface to assure uniform infiltration. Application of
water continues until instrument readings remain constant. At this point the
wetting process ends, and as soon as water is no longer visible on the surface,
the first measurements are taken (time = zero). The plot is then covered with
plastic sheeting as previously described. Subsequent measurements are taken
every hour or two for the first several hours. The time intervals may be
extended as the rates of change decrease, until at about a week's time,
measurements are taken every second day. The frequency of measurement depends
on the rate of change of the gradients.
In some cases, a tensiometer may show positive tensions. If these are of
low magnitude they may be due to temporary ponding of water on a less permeable
feature or horizon. In such a case, a detailed soil profile description can be
useful in determining the cause for this behavior. Another possible cause( of.
positive tensions is a large cavity adjacent to the cup of the tensiometer.
This may be due either to some large natural void, i.e., worm burrow or root
channel, near the cup or an inadequate seal. Use of duplicate tensiometers
decreases the probability of such an occurrence.
If a tensiometer does yield sizable positive matric tensions that do not
decrease rapidly during the first few hours, the wetting procedure may need to
be repeated (after resealing that tensiometer). If the questionable tensiometer
shows a decreasing tension approaching the expected value, then in many cases
the tensions of the first few hours can be approximated by extrapolation back
to time zero (but not necessarily to zero tension). This procedure, although
less reliable, can save time and eliminate the need to repeat the whole pro-
cess .
Example oaloulat'Lon—After data have been collected over a period of time,
covering the range of soil moisture tensions desired, hydraulic conductivities
can be calculated. An example calculation is carried out here based on data
gathered for a Batavia silt loam (Mollic Hapludalf) (Bouma et al. , 1974-a).
Tensiometers were placed at depths of 30 cm, 55 cm, 81 cm, and 100 cm corres-
ponding to the Ap, Bl, B22, and B3 horizons, respectively.
Table 1 presents the matric tensions recorded at each depth for severa.1
times. At time 0 all tensiometers show positive tensions, indicating ponding
of water above the tensiometer cups. Within 0.15 days these heads had been
eliminated, except in the very heavy textured horizons.
Table 1 also presents soil moisture content (8) data for the same horizon
depths determined at the times that tensions were recorded. These numbers
were obtained by conversion of neutron probe counts by use of a standard
curve for the probe. These moisture contents (expressed as %vol. are plotted
B-34
-------
TABLE B-l. SOIL MOISTURE PROBE DATA
Time
(days)
0.0
0.15
3.0
6.75
10.0
12.0
17.0
18.0
ij> (matric tension, cm) 6 (Vol %)
m
Horizon Ap Bl B22 B3 IIB3 Ap Bl B22 B3
depth(cm) 30 55 81 110 160 30 55 81 110
+36 +29 +25 +11 29 30 31 30
- 9 - 7 0 +15 +2
-36 -25 -11 +15 +6 29 28 27 29
-44 -31 -19 -15 - 3 28 29 28 28
26 26 25 26
-50 -33 -18 -15 - 7 28 27 26 28
28 26 26 28
-57 -38 -21 -18 - 6
IIB3
160
28
29
30
28
28
28
B-35
-------
as a function of time of measurement in Figure B-ll. A curve is plotted in this
way for each of the horizons studied. From this graph the slope of each
curve at the times of measurement are derived. These slopes are the gradient
36/3t (cm3/cm3/t) and appear in Table 2.
Hydraulic head is the recorded matric tension at a particular depth and
time , plus the gravity head affecting that depth. The gravity head is
the depth to the middle of the tensiometer cup down from the ground surface.
Figure B-12 is the result of plotting hydraulic head (H) versus the depth
(Z). For any given time the set of readings will form an approximate line
or series of lines whose slope varies as drainage proceeds. This slope repre-
sents the desired gradient 3H/8Z. The gradient can be found for specific times
after the beginning of the experiment and is recorded in Table 3 'for the res-
pective times for each depth. For the cases where a single line is not accur-
ate, two or three slopes may need to be taken, each one specific for the hori-
zon at which it occurs.
Following the example of Hillel et al. (1972), incremental flux is calcu-
lated for each horizon and time (Table 3) by multiplying the moisture content
variation by the thickness (dZ) of the horizon affected. The sum of these
increments is the flux q for the depth Z of the deepest horizon. K is calcu-
lated by dividing q by 9H/3Z (Table 3) for each time. Also listed in this
table are the corresponding moisture content 6 (%) and matric tension
(cm) for each time and depth.
Figure B-22 presents these K values for each horizon plotted against the
matric tension. A logarithmic scale is used on the vertical axis to contain
the wide range of values achieved over the small range of tensions.
1000
t
100-
10-
Ap - 30cm
B, - 55cm
8
.J2
B,
81cm
110cm
IIB3 160cm
10 20 40 60 80
SOIL MOISTURE TENSION (mbar)
Figure B-22.
Hydraulic conductivity values determined with the instantaneous-
profile method (Bouma et al., 1974-a).
B-36
-------
TABLE B-2. CALCULATION OF SOIL MOISTURE FLUX
Time
( days )
0.0
0.15
3.0
6.8
12.0
18.0
Z
(cm)
30
55
81
110
160
30
55
81
110
160
30
55
81
110
160
30
55
81
110
160
30
55
81
110
160
30
55
81
110
160
3 6
3t
( days )
1.70
1.75
1.70
1.15
0.42
1.50
1.70
1.65
1.10
0.40
0.10
0.30
0.18
0.18
0.12
0.04
0.08
0.05
0.04
0.14
0.04
0.02
0.04
0.04
0.08
0.04
0.02
0.03
0.04
0.06
-
(cm/ day)
51.0
43.8
44.2
33.4
21.0
45.0
42.5
42.9
31.9
20.0
3.00
7.50
4.68
5.22
6.00
1.20
2.00
1.30
1.16
7.00
1.20
0.50
1.04
1.16
4.00
1.20
0.50
0.78
1.16
3.00
q - Z(ff)dZ
(cm/ day)
51.0
94.8
139.0
132.4
193.4
45.0
87.5
130.4
162.3
182.3
3.00
10.50
15.18
20.40
26.40
1.20
3.20
4.50
5.66
12.66
1.20
1.70
2.74
3.90
7.90
1.20
1.70
2.48
3.64
6.64
B-3T
-------
TABLE B-3. CALCULATION OF HYDRAULIC CONDUCTIVITY
z
(cm)
30
55
81
110
160
q
(cm/ day)
51.0
45.0
3.00
1.20
1.20
1.20
94. 8
87.5
10.5
3.20
1.70
1.70
139.0
130.4
15.2
4.50
2.74
2.48
172.4
162.3
20.4
5.66
3.90
3.64
193.4
182.3
26.4
12.66
7.90
6.64
8H
9Z
(cm/cm)
1.00
0.86
0.65
0.63
0.53
0.63
1.00
0.86
0.65
0.63
0.53
0.63
1.00
0.86
0.65
0.63
0.53
0.63
1.00
0.86
0.65
0.63
0.53
0.63
1.00
0.86
0.65
0.63
0.67
0.81
K
(cm/ day)
51.0
52.3
4.62
1.90
2.26
1.90
94.8
101.7
16.15
5.08
3.21
2.69
139.0
151.6
23.4
7.14
5.17
3.94
172.4
188.7
31.4
8.98
7.36
5.78
193.4
212.0
40.6
20.10
11.79
8.19
6
(%)
31.7
31.5
30.1
29.7
29.4
29.1
39.4
39.0
28.6
27.7
27.3
26.9
34.0
33.7
29.5
28.9
28.5
28.4
33.7
33.4
30.3
29.8
29.7
29.7
30.0
—
31.4
—
30.5
30.2
*m
(cm water)
- 9
-36
-44
-50
-57
+26
- 7
-25
-31
-33
-38
+29
0
-11
-19
-18
-21
+25
+15
+ 5
-15
-16
-18
+11
+ 2
+ 9
- 3
- 7
- 6
B-38
-------
Double tube method for in situ saturated hydraulic conductivity—The
double tube method can measure saturated hydraulic conductivity for horizons
within a soil profile. It is similar to a well test under special conditions.
The method is not quick or simple, and it requires specialized equipment.
The saturated hydraulic conductivity measured is not in the vertical direc-
tion. It is the resultant of all directional components, thereby reducing
the application of the data to many real world situations. It is a useful
method for ranking K. among soils.
Pin.no'lples and procedures—For this method, an auger hole is dug to the
soil horizon where permeability is to be measured. The diameter of the hole
must be larger than that of the outer tube as shown in Figure B-23. The
bottom of the hole is made level, cleared of loose debris, and covered with
2 cm of coarse sand. The two concentric tubes are installed so that their lower
edges cut into the soil to a depth of 2 to 4 cm. The cover plate with standpipes
is attached to complete the apparatus. The diameter of the outer tube must be
at least twice that of the inner tube (Bouwer, 1962).
INSIDE TUBE
STAND PIPE
OUTSIDE TUBE
STAND PIPE-
INSIDE TUBE
COARSE SAND
UNDISTURBED
SOIL SURFACE -
Figure B-23.
Schematic diagram of equipment for the double -tube method
in place (Boersma, 1965).
Water is applied, maintaining equal head in both tubes. When valve B
is open, the two concentric systems are interconnected; when the valve is
closed, they are isolated from each other. Water is applied for considerable
B-39
-------
time to saturate the surrounding soil. When this has been achieved the test
can begin.
Two measurements are made, and from these results, the hydraulic conducti-
vity is calculated. First, the water is forced into both systems until the
two standpipes overflow. The water supply is cut off and valve B is closed.
The water levels in the standpipes will begin to fall. By manipulating valve
C in Figure B-23, the outside level can be made to fall at the same rate as
the level in the inner tube. The time required for the water level to drop
past calibration marks on the inner tube are recorded on a series of stop-
watches . In the second experiment the water level is maintained at the
top of the outer tube standpipe while the level in the inner pipe drops at
its own rate. Again time intervals are measured. A second person with stop-
watches is required for these recordings.
The hydraulic conductivity can be calculated from (Bouwer and Rice, 1961)
K _ Rs AH
sat FR /Hdt
where R = radius of the inner -tube standpipe
Ry = radius of the inner tube
F = a dimensionless factor encompassing the geometry of the apparatus
The F for a particular apparatus can be found from standardized curves
(Bouwer, 1962).
The results of the two tests are plotted, as shown in Figure B-24-. These
curves generally approximate straight lines where applying the following
expression (Bouwer, 1964b)
2 At
eq.lev.
Here AH is the difference in its head for the two measurements at a given
time and yHdt is the magnitude of the head loss until that time, t equal
levels. The right hand quantity can be calculated easily from the time inter-
val data and the result substituted into previous equations for K
•Comments — The double-tube method yields a value for hydraulic conductivity
only under saturated conditions. However, this conductivity is poorly defined
being some resultant of the vertical and horizontal conductivities of the soil
at the sample point. Because of this fact the numbers obtained by this method
cannot be used directly for calculation of infiltration rates or drainage field
size. This relegates the technique to the role of simply ranking the saturated
permeabilities of soils.
B-t+0
-------
AH
t
RUN I
RUN 2
0.5 1.0 1.5 2.0
TIME, MINI.
Figure B-24.
Graph showing the results of the observations necessary to
calculate the hydraulic conductivity obtained by the double-
tube method (Boersma, 1965).
The double-tube test was developed for use on sandy soils, where isotropic
conditions were assumed. The dimensions of the apparatus (Bouwer, 1962) were
experimentally adjusted for these soils and may be inadequate for use on soils
with well-developed soil structure, where horizontal and vertical components
of hydraulic conductivity may differ greatly.
K values obtained with the double-tube method are conservative estimates
when compared to the results of other methods. For example, the mean K
of the Piano silt loam, B22t horizon is 138 cm/day when measured with the
double-tube method (Bouma, 1971). The crust test method yields a mean value
of 610 cm/day.
In summary, the test is complex and requires special equipment. The
data obtained can be used to rank soil permeability but not for direct esti-
mation of drainage field size.
B-Ul
-------
The crust test method for in situ measurement of saturated and unsatur-
ated hydraulic conductivity—In the crust test method (Hillel et al., 1970;
Bouma and Denning, 1972; Baker and Bouma, 1976b) both saturated and unsaturated
vertical hydraulic conductivity are measured. A free-standing, in situ pedes-
tal is carved with its upper horizontal surface at the depth where K is to
be determined. A ring infiltrometer is affixed to the top of the column and
tensiometers are installed from the side, just below the upper soil surface.
An artificial barrier to flow—a "crust"—is placed on the soil surface to
restrict movement of water into the soil. The infiltrometer is closed and
attached to a constant head reservoir where the volume of water entering the
soil can be measured. Water is introduced to the system on the top of the
barrier and moves down, wetting the soil. An equilibrium flow rate, q, is
reached that is determined by the resistance (rj-,) of the crust and the pore
size distribution of the underlying soil. The soil moisture potential is then
read from the tensiometer and the flow rate is measured directly as volume
change at the reservoir. This flow rate change
at that soil moisture potential. By varying the resistance of the barrier,
other conductivities at corresponding tensions can be found. If no barrier
is used, unrestricted or "saturated" hydraulic conductivity can be deter-
mined. The corresponding tension under these conditions is approximately
zero. In this way, several points (tension-conductivity pairs) on the K
curve for that soil are obtained.
Principles involved—An artificial "crust" or barrier to water flow
located at the horizontal surface of the soil pedestal acts to restrict
entry of water into the soil. The fewer, finer pores of the crust cannot
conduct liquid to the underlying soil as rapidly as when the water is able to
flow downward through the natural soil. This results in a water-saturated
crust with water standing on its upper surface. The soil is not saturated
if the saturated conductivity of.the soil is greater than that of the barrier.
This is true as long as a water table or another restrictive layer do not inter-
fere by their presence, causing the hydraulic gradient to differ greatly from
unity.
Under steady state flow,
b soil
and
b dZ soil dZ
where q, and qso;ji are the flow rates or fluxes through the barrier and soil,
respectively, and (dH/dZ) is the hydraulic gradient in each case.
The gradient in the soil during steady state flow approximates unity,
with gravity as the major force. For the crust test then,
B-42
-------
q = K ..(*)= K. (
soil soil m b dZ
By measuring cUo^-i and the corresponding soil moisture potential (ijim), a
potential-conductivity pair is defined for each barrier used.
Installation of equipment — The crust test measures the vertical hydraulic
conductivity of a volume of soil from a horizontal plane downward. For this
purpose, a free-standing pedestal of soil is carved out in situ, its undis-
turbed base continuous with underlying soil horizons. Water entering the
upper surface of the soil is restricted to essentially downward flow by the
sidewalls of the pedestal. Because the pedestal is still attached to under-
lying horizons, pore-continuity is assumed to be maintained and water movement
representative of natural soil conditions.
A small pit is dug at the site where K measurements are to be made and a
ledge is formed on one side at the horizon of interest. Care must be exer-
cised to avoid compacting this horizontal surface for this is where infiltra-
tion occurs during measurements. This level can be approached by the use of
a shovel. Final preparation of the infiltrative surface is done with a knife
or spatula by either scraping or lifting out portions of the soil. It is best
to cut downward about 1 cm with the blade of the knife and then lift and move
it to one side at the same time. This will loosen a fragment of the surface.
By taking only small bits (2 to 3 cm wide) at a time and by holding the
loosened soil against the blade as it is raised, a suitable surface is
created. Practice is required before this becomes efficient, but it does
leave a fresh horizontal soil surface with no smearing. In sandy soils, this
method of surface preparation may not be necessary.
Infiltrometers are 24— cm inside diameter (see Figure B-25). Thus,
the area enclosed is about 490 cm^ , and in structured soils , includes
many soil peds, channels, and pores. It is sufficiently large to
accomodate several networks of pores and not truncate meandering flow path-
ways that involve some lateral movement. This is especially important for
conductivities at or approaching saturated conditions. The minimum diameter
that will yield relatively accurate data is about five times the width of
the peds in the soil. In sandy soils, small areas could be used but this
practice may not include the influence of biopores at or near saturation. For
these reasons, a minimum infiltrometer diameter of 15 to 20 cm is advised.
Diameters greater than 40 cm are difficult to work with but may be necessary
for special conditions. A comparison of 24 cm and 48 cm diameter rings
indicates no measurable difference in mean unsaturated hydraulic conductivities
for medium, subangular blocky silt loams and for sandy soils, but the varia-
bility of results on the larger samples is somewhat lower (Baker, 1976d).
However, for K measurement at or near saturation (^m -> 0), a significant
difference was measured for pedestal diameters of less than 24 cm.
Next, a free-standing soil pedestal is carved down several centimeters
to facilitate placement of the ring infiltrometer on the pedestal. At
first, the pedestal is made four or five centimeters larger in diameter than
B-43
-------
MANOMETER
CRUST
'--V TENSIOMETER
RING
INFILTROMETER
Figure B-25. Schematic diagram of the crust-test procedure.
the ring. A strong-bladed hunting knife works well for this purpose. The
infiltrometer is placed on top of the pedestal and then carefully pushed into
the soil. By grasping the ring with both hands and gradually applying weight,
the sharp edge of the ring will part the soil allowing a good fit. Excess
soil around the outside of the ring can be cut away with the knife. The
ring is pushed down until only about 1.5 centimeters of sidewall remains
above the soil. This space is required later in the procedure for the
barrier and water. A small gap may appear between the soil and the side of
the ring but is no cause for concern. Under unsaturated conditions, water
will not flow along this void and as the soil becomes wetter it will expand
to seal the gap. Therefore, at saturation, no peripheral void will exist.
-------
The soil pedestal must be carved to a height of at least one ring dia-
meter. For a 24 cm diameter ring, a height of 30 cm is recommended.
Experiments have shown that differences in saturated hydraulic conductivity
due to the height of the soil pedestal can be large for low pedestal heights
(Baker, 1976d). K , values measured for a pedestal 15 cm high were 20 percent
higher than those measured at 30 cm height. If, however, heights of 30 or
greater are used, no significant difference in K values is detected. This was
found to be true for both structured (silt loam) and nonstructured (sandy) soils.
Carving is best carried out again with the knife or a hand trowel. Use
of a shovel in close quarters may easily result in the cracking or breaking
of the soil pedestal. The pedestal should be of uniform diameter (+ 1 cm) over
its entire length. When complete, it is wrapped in aluminum foil to reduce
evaporation from sidewalls. This covering remains in place for all unsaturated
measurements and is replaced by a quick-setting plaster coating for saturated
K measurements.
Tensiometry—Small diameter (4-. 5 mm) porcelain tensiometers are used to
measure soil moisture potential within the soil pedestal. These instruments
have a tee configuration (see Figure B-26). The porcelain cup can have pore
sizes of about 0.25 to 1.00 . Pore sizes greatly outside this range will
affect the response time and air entry value of the tensiometer. The porcelain
cup is attached to 3-mm (1/8 inch) flexible plastic tubing which runs to one
arm of a brass tee fitting. The tubing on the other arm of the tee is fitted
with a brass screw cap assembly. Fine nylon tubing then runs inside from the
cap, through the tee to the very tip of the cup. This is used for filling the
tensiometer to purge the cup of entrapped air. A third plastic tube extends
from the base of the tee to the manometer board where the free ane d is submerged
in the mercury reservoir.
Before placement of the tensiometer cup in the soil column, a hole is
augered horizontally into the soil pedestal from the side to a point just
beneath the center of the soil surface. The diameter of the augered hole is
slightly less than that of the porous cup so that a snug fit assures good
contact with the soil. After the cup is in place, the hole should be sealed
with mud or glue to prevent evaporation. Tensiometers should be placed at a
depth of 2 to 5 centimeters under the infiltrative surface. Holes can be
made in the sidewall of the infiltrometer to facilitate this. Earlier in the
development of the crust test, two tensiometers were placed in series, one
2 cm below the other so that the hydraulic gradient could be measured
(Hillel et al., 1970). This practice is not always practical. Two indepen-
dent tensiometers can be used to yield the average potential of the soil.
This is useful because a tensiometer generally registers the tension of only
the soil in its immediate vacinity. Sometimes this can be misleading.
In setting up the apparatus tensiometers are arranged as shown in
Figure B-27 where the free end of the tensiometer runs through a manometer
board to a mercury reservoir. A graduated scale is used to read potential as
centimeters of water when mercury rises on this scale. The difference in
elevation between the porous cup and the surface of the mercury in the
reservoir is referred to as the correction factor or CF. This is easily
B-45
-------
POROUS CUP
OUTER TUBING
UNION "T
CONNECTION
TUBING TO MANOMETER
Ik-SEALABLE
f CAP
Figure B-26.
Schematic diagram of tensiometer, showing major components of
the system.
coMtecrioN
FACTOR (CF)
Figure B-27.
Schematic diagram showing the components of potential (i/>m
^p.) and the measurement of correction factor (CF) on the
experimental apparatus .
B-46
and
-------
measured in the field with two meter sticks and a level. It is subtracted
from the total tension to yield matric soil tension.
Once installed properly, the tensiometer is filled with deaired water
using a 50-ml syringe with a 22-gauge needle. The needle is inserted in the
end of the fine inner tubing at the capped end and water is forced through
to the top of the porcelain cup. A wetting front will proceed along the space
between the inner and outer tubes from the cup through the tee and out the
capped end. If the outer tube is held tightly against the butt of the needle,
water can be forced up the third branch to the mercury reservoir. Continued
pressure will drive water out at the mercury cup, purging the system of all air.
The needle is withdrawn and the end is capped. Before inserting the tensiometer
cup firmly into the soil, the cup is wiped to remove excess water.
'Che flux measurement—Measurement of the rate of water flow through the
resistant barrier is accomplished by a burette system. A flexible plastic
tube connects the burette to a large port at the center of the plexiglass
cover plate where it is attached by a threaded brass fitting (see Figure B-25).
When the system is closed, i.e., when the cover plate is sealed onto the ring
infiltrometer, water can be introduced to the system via the burette. A large
hydraulic head is desired to maintain steady-state flow. This is easily
achieved by use of a Mariotte tube, consisting of a rubber stopper that fits
the burette with a small tube running through it. This inner tube extends to
the base of the burette and the vertical height that it is raised above the
crust surface is the effective hydraulic head in centimeters (Figure B-25).
Flux is measured as volume change in the burette. A correction must be made
for the amount of water displaced by the mariotte tube. Several burettes of
different sizes should be available as they may be needed for certain condi-
tions. The accuracy of any flow rate can be improved by using a more closely
graduated burette.
The resistant barviev or "cTUst"—A relatively quick-setting, dense
gypsum is used in the barrier or "crust." It is mixed with just enough water
to make a thick paste, which is then spread upon the infiltrative surface
to a thickness of 0.5 to 1.5 cm. This is easily done with the bare hand.
Care must be taken to tamp the paste near the edges to achieve good contact
with the metal ring. This contact is the site of most leaks through the
barrier.
The resistance of the barrier to water flow can be regulated by mixing
various proportions of sand and water into the gypsum before making a paste.
The presence of the sand in the crust causes larger pores to be formed thus
allowing more water to flow through. Higher sand content in the mixture
causes less resistance and allows higher rates of flow through the crust.
Proportions of sand and gypsum are measured by volume percent in a 1-liter
graduated cylinder. The proportion is expressed as the percentage of gypsum
in the crust. A 25 percent crust is one quarter gypsum by dry volume. The
dry sand and gypsum should be mixed thoroughly in a dishpan before water is
added.
-------
Generally, the first crust to be used is the most resistant one. Succeed-
ing crusts are progressively less resistant to flow. This allows the equili-
brium flow rate to be reached by wetting, yielding the wetting K curve. A
similar but slightly higher curve will be obtained if equilibrium is reached
by drying, due to hysteresis. For this reason, it is important to know the
soil moisture potential before introducing water to the system. If a crust
leaks or there is some other malfunction, the soil must be allowed to drain
before reinitiating the experiment.
Removal of the crust after its steady state flow has been reached is
sometimes a difficult task. A 100 percent gypsum crust is very tough, requiring
chiseling action by a .sharp implement such as a screw driver. The first one or
two pieces will shatter in the process, but following ones are more easily
removed. Excessive pounding may damage the soil pedestal. Crusts of less
than 75 percent gypsum are much easier to remove and can be handled with a knife
as used when preparing the fresh soil surface. This is the crudest technique
in the procedure and requires some practice.
Other types of barriers have been used with some success; noteably work
with synthetic foam sponges that rest on the soil (Baumer et al., 1976).
Few types of easily changed barriers achieve as good contact with the soil as
does a gypsum crust.
Measurement procedure—Once a site is instrumented, the crust is selected
so that its resistance to flow will yield the approximate soil tension that is
desired. This is based on a general knowledge of the soil's K curve (Figure
B-28). The tension induced by the crust must be somewhat lower than the start-
ing soil tension in order to achieve wetting of the soil. If the soil is quite
dry to begin with, a 100 percent crust is usually used first to yield tensions
in the 60 to 100 cm range. For higher tensions, silt loam or clay can be
smeared on the surface of a 100 percent crust.
After the crust has hardened, the gasket and cover plate of the ring
infiltrometer are bolted into place, so that the air escape port is at the
highest position (Figure B-25). The burette assembly is attached to the central
port and water is introduced. Care should be taken with low gypsum content
(light) crusts that a piece of aluminum foil or other material is placed dir-
ectly beneath the central port for water entry. This will prevent incoming water
from eroding a hole in the crust by impact. Water flows in under a hydraulic
head to speed filling of the space between the crust surface and the cover
plate. The air escape port is open until all air has been purged from the sys-
tem. At this point, the Mariotte tube and stopper are placed into the burette
to reduce the hydraulic head, and the air escape port is capped. The air
escape port is opened whenever the Mariotte device is unstoppered, otherwise
sudden changes in head and back-pressure from below the crust can cause leaks
to occur. When air bubbles begin to rise from the tip of the Mariotte tube,
the first volume measurement can begin.
Volume measurements are recorded periodically until equilibrium is reached.
Simultaneous tension measurements are also made. These values will change with
time as shown in Figure B-29. Equilibrium is reached as the values approach
B-U8
-------
I
u
O
O
_l
D
BATAVIA SILT LOAM. B22T
.0 40.0 80.0 120.0
104
-2 -• .1 .1.1. 1.1. i .1.1. i. i.l .1 .1
.0 40.0 80.0 120.0
SOIL MOISTURE TENSION (cm water)
Figure B-28.
Hydraulic conductivity curve measured at a site in
the B22t horizon of the Batavia soil series.
an asymptote. The conductivity at that tension is calculated from the measured
constant flow rate.
After equilibrium is reached for the first crust, it can be removed.
This is done by opening the air port, removing the plate and gasket and soaking
up any standing water with a sponge. The old crust is then taken off and re-
placed by a less resistant one. The procedure is repeated. Each succeeding
crust yields a point on the K curve. Figure B-28 exemplifies this for a
Batavia silt loam soil, showing the results of a series of crusts and the K
curve derived from these points. Each point represents the potential-
conductivity pair caused by a particular crust. The percentage indicated by
each point is the gypsum content of the crust that was used to obtain that
point.
-------
z
g
CO
LU
H
UU
cr
CO
O
steady state
is achieved
TIME
Figure B-29,
Generalized graph of the rate of decrease of matric
tension (^m) as equilibrium is approached by wetting
of the soil.
Saturated hydraulic conductivity is measured using the same apparatus with
one modification: the aluminum foil cover is replaced with a coating of quick-
setting dental-grade plaster. The dental plaster is mixed in a dishpan to be
very fluid and is poured or splattered against the sides of the soil pedestal
until the plaster is more than 3 mm thick. This seals the soil to prevent
water from flowing directly out the sides. Care is also taken that any extra
holes in the sides of the metal ring are sealed with plaster or glue. Leakage
of this sort is not a problem during unsaturated flow conditions when soil mois-
ture tension retains water in the soil pores.
For saturated flow measurements, no crust is used. If there is no barrier
to flow, all or nearly all pores will conduct liquid giving a reasonably accur-
ate measure of the maximum flow through the soil. The procedure is conducted
as for unsaturated conductivity measurements. Tensions are at or very near
B-50
-------
zero. Volume change is recorded until it is relatively stable to yield the
equilibrium flow rate. Water flow should not be maintained for more than 45
minutes or an hour. Appreciable changes in the soil pores will occur after
this time.
Trouble shooting—If problems occur that have no obvious cause, they can
be traced by examining the three basic subsystems of the test equipment. These
are the crust, the tensiometers and the water flow systems.
Probably the first thing to look for in a crust is a leak. This is a rela-
tively simple procedure. Push down firmly on the center of the plexiglass
cover plate of the infiltrometer and then release quickly. This decreases and
then increases the volume over the crust. To compensate for the volume change,
water must flow in via the burette, but this takes time. If there is a leak in
the crust, it is easier for air to bubble up from beneath the crust. There-
fore, if bubbles suddenly appear, a leaky crust has been demonstrated, and it
can be replaced. Data collected from a leaky crust should be discarded. It
is perhaps a good idea to conduct this test on all crusts soon after water is
applied.
Problems may occur in the flow measurement system. These may appear as a
lack of flow or as unbelievable flow rates. The first thing to look for is a
leak in the tubing or at the Mariotte stopper. Air bubbles of any size in the
system can also hinder flow, and they are prone to temperature effects, causing
inconsistent and inaccurate results. Also, fluctuations in the temperature of
the water in the system can lead to other inaccuracies. On sunny days or
partly cloudy summer days,-the direct heating of the sun's rays can be quite
dramatic, and the burette, tubing and cover plate must be covered with
aluminum foil to reflect most of the unwanted heat.
It is best to use two tensiometers so that if one should fail, the experi-
ment is not interrupted. All tensiometers should be tested and thoroughly
examined before they are taken to the field. This will save much time and frus-
tration on site. A good tensiometer can be used many times once it has proven
itself. The usual cause of problems is a leak allowing air to enter into the
system. Refilling the tensiometer with deaired water may be a temporary solu-
tion. If the cause is not apparent, it is best to replace the tensiometer
entirely with a spare. Periodically, tensiometers should be retested in the
laboratory.
Data analysis—When a final volume measurement of steady-state flow is
obtained, it can be used for calculation of the soil's hydraulic conductivity
at that tension. The volume of flow per minute is converted to centimeters per
day, by the following formula:
min x
kday' """ min' day fl , 2.
J J Area (cm )
B-51
-------
where the area is that of the infiltrative soil surface. For a 25 cm diameter
ring this area is 490 cm2. -Thus a flow rate of 30 ml in 30 minutes yields:
K = 30_ml t 1WO min -- 1 =
30 m,n day ^ ^2
at the equilibrium soil tension measured.
It is best to do the calculations before changing the crust. It is
possible to detect erroneous data and then by double-checking the subsystems
of the equipment, to eliminate the cause.
Advantages and disadvantages of the technique — The main advantage to the
use of the crust test is the direct and geometrically simple pattern of verti-
cal water movement that is measured. Also, this is accomplished in situ
without major disruption of natural soil pores. Most methods for hydraulic
conductivity measurement, especially at saturation, involve some component
of lateral if not radial flow. These involve more complex mathematics and
describe flow patterns that are not common to most real situations. The
pedestal in the crust test is also isolated so that external interference is
held to a minimum, unlike the instantaneous profile method. Another major
advantage of the use of crusts is that a range of unsaturated conductivities
can be obtained without as large a time commitment as some other methods .
Also, the amount of variation in the technique itself is much lower than that
of other methods .
Disadvantages of the method are that it is complicated, although not
nearly as complex as the double tube test is for a single conductivity. It
requires that work be carried out in the field and this means the work is
subject to weather limitations. The technique only measures vertical hydraulic
conductivities .
Comparison and discussion of methods — In choosing which permeability
measurement method to use, several factors must be considered. First, the
dimensions of soil permeability to be measured must be defined, and a proce-
dure must be selected that truly measures that permeability. Second, it must
be decided how accurate the measurements of permeability must be. The third
consideration is whether the procedure is efficient for the given purpose.
In most cases some compromise is made between these three aspects of the
problem. Each of these factors will be discussed with respect to the five
above-mentioned permeability measurement methods and their application to
liquid waste disposal.
Soil hydraulic conductivity (K) in the vertical direction (ICy) is required
for most wastewater applications . The importance of vertical movement is due
to the dominance of gravity flow in most waste disposal systems. Horizontal
conductivity (1%) may be more important for narrow subsurface trench designs
and in situations where downslope movement of effluent is anticipated. If the
expected steady state flow rate through a stable clogged soil layer is known,
then the required drainage field surface area can be calculated directly. The
steady-state flow rate is Kvss at ^mss> the soil moisture potential at steady-
B-52
-------
state conditions. This means that K must be known for particular unsaturated
conditions that will be dictated by the clogging layer. A useful method would
be one that estimates K
vss
Few of the procedures as described are capable of this measurement. The
percolation test measures a radial combination of vertical and horizontal con-
ductivities at saturation only. Neither K at saturation nor unsaturated K
can be determined. The test serves only as a rough ranking measure, simply
indexing soil permeability. Soil core methods can measure a vertical con-
ductivity, but these values are a function of core length (Anderson and Bouma,
1973) and exhibit high variation at small dimensions. The measured Kv may not
be applicable to field situations. The double-tube test measures only satur-
ated conductivity. Kvsa-t can be determined only by the use of a more compli-
cated procedure (Bouwer, 1964a) than the one described here. Both the instan-
taneous profile method and the crust test measure Kv for unsaturated condi-
tions. For determinations at a specified horizon, the crust test may be
simpler to use.
The accuracy and reproducibility of a few of these methods has not been
established. The coefficient of variation (Cv) of measured conductivities is
a convenient means of comparison of within test variation. For the percola-
tion test Bouma (1971) reported Cv - 54 percent for the falling head method
which is commonly used, and Cv = 35 percent for the constant head procedure.
Hill (1966) in Connecticut found similar values of Cv = 49 percent and Luce
(1973) reported Cv = 38 percent for soils in Iowa. Anderson and Bouma (1973)
found Cv = 66 percent for K measurements made on 10 cm long soil cores.
While comparing two field procedures for measurement of Kga^., Bouma (1971)
found that the double-tube test has Cv equal to 25 percent. Nielsen et al.
(1973) reported mean Cv of 86 percent at saturation, and average coefficient
of variation of 381 percent for soil at 60 percent saturation.
The method that is simplest and easiest to use, while still providing
useful information, usually finds the most successful field application. Of
the two techniques that can measure K for unsaturated soil, the crust test
is probably the least time-consuming. It requires little specialized or
expensive equipment, and only a few liters of water. The instantaneous
profile method requires expensive equipment and a much longer time period to
collect the data. A skilled technician is capable of carrying out either
procedure.
Selection of a method of conductivity measurement should be based pri-
marily on the suitability of the measured values for the particular applica-
tion. Then the feasibility of the procedure must be balanced against these
requirements. The percolation test is a good example of a test that is used
because of convenience, long after it was realized that it is not an acceptable
measure of soil permeability.
Variability of Hydraulic Conductivity in Soils—
Soil variability has been a topic of interest among soil scientists for
some time. This interest has been directed largely toward morphological
B-53
-------
(McCormack and Wilding, 1969) and chemical variations in the soil that led to
problems in classifying soils and also to nutrient variations (Beckett and
Webster, 1972) that influenced agronomic uses of the land. The variability
of physical properties has also been the subject of numerous investigations
(Mason et al., 1957) especially with respect to engineering and flood control
applications (Rogoswki, 1972). The variability of hydraulic conductivity is
of great importance for on-site liquid waste disposal (Bouma, 1973). Knowledge
of the expected range of conductivities or of the expected minimum conducti-
vity for a given site would facilitate the use of soil maps and soil series
identification, rather than the now almost exclusive reliance on the testing
of each and every site.
By defining the conductivity curve and its corresponding variation for
each of several soil series, it may be possible to compare and contrast these
series on the basis of their hydraulic conductivity characteristic. Series
with similar K characteristics, for all practical purposes, could be grouped
together into arbitrary hydraulic conductivity classes to facilitate use of
this information. This would result in a special use classification, designed
for application to waste disposal planning and design.
Recent work has focused on the variability of soil hydraulic conductivity
in the field (Mason et al., 1957; Nielsen et al., 1973-, Baker and Bouma, 1976b).
Current work by Baker (1976a) has dealt with variability of K in nine soil
series, the morphology of which range from single-grained structured sands
to heavy clay loam soils having well-developed structure. The results of
this study will be summarized briefly here.
Soils studied and site selection—The variability of K of nine soil
series in Wisconsin were studied. These soils were selected to span a wide
range of textural, structural and hydraulic properties. They were the Batavia
Boone, Hochheim, Magnor, Morley, Ontonogon, Piano, Plainfield and Withee series,
as described by the National Cooperative Soil Survey. Textural and structural
information for each series is summarized in Table B-4-. The soil horizons in
which conductivity was measured are also listed there. Generally, the hori-
zon with lowest permeability was selected for measurement since these layers
represent the limiting conditions for wastewater flow.
The genesis of these soils is of interest since the nature and subse-
quent environmental adaptations of the initial material strongly influence
some morphological properties of the soil (Boul et al., 1973). The sum of
these morphological properties is used to classify soils into groups and
series and some of the physical characteristics of soils are expressions of
these morphological properties. Detailed morphology of these soils can be
found in soil profile descriptions published by the National Cooperative Soil
Survey. The Plainfield series developed largely in glacial outwash in central
Wisconsin. Although it does not offer limitations to on-site waste disposal
due to permeability, it has been included in this study as a landmark soil.
The Boone series was formed in residual sand deposits eroded from Cambrian
sandstones in the hilly driftless area of Wisconsin. The Magnor and Hochheim
soils formed in loamy glacial till covered by a thin loess cap. Both soils
present waste disposal problems, especially the Hochheim which has weak struc-
tural integrity. The Batavia and Piano series developed in deep (1 to 2 meter
-------
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B-55
-------
thick) loess deposits overlying glacial till. The Batavia formed under forest
vegetation generally and the Piano under prairie. The Morley series formed in
loess and fine, calcareous glacial till in southeast Wisconsin. Long wet
periods during the spring and early summer limit wastewater disposal in this
soil. The Withee series chiefly developed from lacustrine sediments left by
glacial Lake Wisconsin. Finally, the Ontonogon was formed from lacustrine
deposits on the shore of Lake Superior. This last soil series is grouped as one
of the notorious "red clays" that have prevented development of large areas of
land in some northern counties of Wisconsin because of their low permeability.
Detailed soil maps in published soil survey reports (National Cooperative
Soil Survey), showing mapping units as small as 0.8 ha (2 acres) in area,
were used to select experimental sites in 13 counties of Wisconsin. Once a
mapping unit was selected, sites within that unit were determined by a random
number-grid scheme. This eliminated the natural bias to select sites away
from the unit boundaries. On a few occasions, it was necessary to work at
sites near, but not exactly at, the selected point to achieve landowner
cooperation.
A morphological inspection of the soil was made at each prospective site
to establish the accurate classification of the soil. If the morphological
characteristics were within the range of values assigned to that particular
soil series according to criteria of the Cooperative Soil Survey, the site
was accepted as an experimental location. In this way, variation within soil
series was measured, and not that within mapping units.
Methods used—The crust test method, as described in this Appendix was
used for field measurement of hydraulic conductivity. It was selected because
it can estimate K^ for saturated and unsaturated conditions, and it is accur-
ate over the range of ^m where most moisture flow occurs.
Weighted least-squares, non-linear regression aided in fitting curves to
the K data. Conductivity data were found to be generally log-normally distri-
buted, as has been reported by Nielsen et al. (1973) and Mason et al. (1957).
Therefore, log transformations were performed on the data. Following the
transformations, the mean log K(x^), standard deviations (SL) and coefficients
of variation of log K were calculated for intervals of log ^m. Variation was
presented graphically as one standard deviation taken about the regression
curve. It can also be expressed as the coefficient of variation with some
restrictions due to the log-transformations.
When transforming back to linear data, the antilog of x^ is the geometric
mean (G) of measured K (Snedecor and Cochran, 1967 ) . The antilog of standard
deviation of the logs (Antilog SL) then becomes a multiplier of G, such that
the 16th and 84-th percentiles of the log normal distribution of K correspond
to G/Antilog SL and GL Antilog SL, respectively.
Multivariate discriminant analysis (Discrim 1 program, Schlater and
Learn, 1975) was used to compare soil series on the basis of their distribu-
tions of \J>m and K about their center of mass. This helped determine which
data sets could be validly compared using this statistical technique. The
B-56
-------
results of the analysis as well as visual inspection of the curves were used
to arrange the soil series into groups of similar K characteristics. Eisenbeis
and Avery (1972) offer a thorough description of multivariate analysis and its
limitations.
Variation within soil series—The log of the hydraulic conductivity data
gathered for the Piano series is presented in Figure B-30. Each point repre-
sents a (log fym, log K) pair resulting from steady-state flow through an arti-
ficial crust.
PLANO SERIES
O
O
D
Q
O
O
3
X
Q
O
O
-1.0
-1.0 0.0 1.0 2.0
LOG SOIL MOISTURE TENSION
(cm water)
Figure B-30.
Hydraulic conductivity as a function of soil
moisture tension for the Piano series (Baker, 1976a).
To describe the relationship between K and moisture potential, it was
necessary to fit a line to the data set. Linear regression yielded a good fit
on log transformed data as shown in Figure B-30. The interval enclosed by one
standard deviation is also presented. The mathematical model that best des-
cribed this relationship was in the form of a power function.
B-57
-------
PI
) = c \ii
m m
where K = the hydraulic conductivity at potential ij; ,
c = a constant, such that log c = log K - p, ,
S3.TI -L
ty - an absolute value of soil moisture potential,
P-, = a power whose value is negative.
If the logs of both sides are taken the equation becomes log K(^m) = log c +
b]_ log ip or y = c1 + p^ x, where p]_ is the slope of the line and c' is the y
intercept of the line at log ^m = 0.0. Because the transformed data can be
described by a simple line many standard mathematical procedures can be applied
to the data, such as the construction of prediction intervals (Baker and Bouma,
1976b).
This function provides satisfactory fits for the data of four other soil
series: Hochheim, Magnor, Ontonogon and Withee (Figures B-31, B-32, B-33 and
B-34, respectively). The values of parameters c and p-j_ are indicated in the
figures. The variation about the regression line is not greatly different
among the series, as indicated. For these series variation was fairly large.
All five of these soils were well-aggregated except the Hochheim, which has a
weak blocky structure. The morphological properties of the soils can be compared
in Table B-4.
Other soil series could not be satisfactorily described by the above
power equation, because they were non-linear. Among these was the Boone sand,
the log- trans formed data of which is shown in Figure B-35. The indicated
curve can be described by adding an exponential term to the power equation.
= c 1
c v
A , p2
Antilog(i[i /T\> Y ^
where K(ijj ), c» ty and p are as described for the previous equation,
K = the mean saturated K of the soil,
sat
ty - a critical tension, being the potential at which
m Kty ) = 0.1 K .
rc sat
p = a power whose magnitude correlates roughly with the
homogeneity of pore sizes contributing to flow for
this range of moisture potentials (p > 1.0).
B-58
-------
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HOCHHEIM SERIES
-1.0 0.0 1.0 2.0
LOG SOIL MOISTURE TENSION
(cm water)
Figure B-31. Hydraulic conductivity as a function of soil moisture tension
for the Hochheim series (Baker, 1976a).
3.0
I
2.0
1.0
O 0.0
I
-1.0
-1.0
MAGNOR SERIES
0.0
1.0
LOG SOIL MOISTURE TENSION
(cm water)
Figure B-32.
Hydraulic conductivity as a function of soil moisture tension
for the Magnor series (Baker, 1976a).
B-59
-------
3.0
•o
E 2.0
O 1.0
o
o
o
O 0.0
3
cc
o
I -1.0
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o
ONTONOGON SERIES
Figure B-33.
-1.0 0.0 1.0 2.0
LOG SOIL MOISTURE TENSION
(cm water)
Hydraulic conductivity as a function of soil moisture tension
for the Ontonogon series (Baker, 1976a).
3.0
£ 2.0
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O
o
o
O 0.0
cr
o
-1.0
o
o
WITHEE SERIES
-1TT
0.0
1.0
2.0
Figure B-34.
LOG SOIL MOISTURE TENSION
(cm water)
Hydraulic conductivity as a function of soil moisture tension
for the Withee series (Baker, 1976a).
B-60
-------
3.0
E 2.0
o
O 1.0
3
O 0.0
D
>
* -1.0
BOONE SERIES
-1.0
0.0
1.0
LOG SOIL MOISTURE TENSION
(cm water)
Figure B-35.
Hydraulic conductivity as a function of soil moisture tension
of the Boone series (Baker, 1976a).
In the above equation, G^m ) is the tension which occurs when K equals
one tenth of the value of l^at 5 because this relationship is inherent in the
behavior of an exponential. It corresponds with x = 1.0 on the abscissa of a
unit exponential graph (see Figure B-30 to B-38). As such, ipm is simply a
scaling factor, which can be visually approximated from the untrans formed
data set. Good fits can be made using whole numbers for ^m .
Several expressions have been suggested (Raats and Gardner, 1971) which
almost fit the Boone data and similar series. These expressions generally
do not describe the data well for the potential range of 15 to 100 cm water,
except in coarse materials. For prediction of a soil's response to specific
wastewater management, K data must be accurately described in this range
(Bouma, 1975; Baker and Bouma, 1976a). The above equation has proven somewhat
more useful for this purpose.
Three other soil series (besides the Boone) which were well described by
the above equation were the Plainfield, Morley and Batavia. Their log-
transformed data sets and regressed curves are found in Figures B-36, B-37 and
B-38, respectively. In each figure the equation for the curve is given.
B-61
-------
3.0
2.0
1.0
0.0
-1.0
PLAINFIELD SERIES
-1.0 0.0 1.0 2.0
LOG SOIL MOISTURE TENSION
(cm witw)
Figure B-36.
Hydraulic conductivity as a function of soil moisture tension
of the Plainfield series (Baker, 1976a).
3.0
§,0
0
o
O
§ 0.0
tc.
a
-1.0
o
o
MORLEY SERIES
-1 0
0.0
1.0
2.0
LOQ SOIL MOISTURE TENSION
(cm water)
Figure B-37.
Hydraulic conductivity as a function of soil moisture tension
of the Morley series (Baker, 1976a).
B-62
-------
3.0
2.0
1.0
0.0
-1.0
BATAVIA SERIES
Figure B-38.
-1.0 0.0 1.0 235
LOG SOIL MOISTURE TENSION
(cm water)
Hydraulic conductivity as a function of soil moisture tension
of the Batavia series (Baker, 1976a).
The amount of variation of the data about the regression curve is large
in several of the soil series. The Plainfield series, for example, includes
some rather large deviations from the curve. Calculation of logarithmic means
(x), standard deviations (Si) and geometric means G and other statistics
(Rogowski, 1972) are presented in Table B-5.
Because variations within some soil series are rather large, accurate
prediction of expected conductivity values may not be feasible. Ninety-five
percent prediction intervals constructed for the Piano and Batavia series
(Baker and Bouma, 1976b) enclose K values that differ by nearly an order of
magnitude. However, knowledge of the variability of K for a given series does
permit, to a certain extent, estimation of the minimum expected value for a
particular moisture potential for a desired confidence level. Siting of a soil
absorption field is one use that would benefit by this information.
Not all soil series were as variable as the Plainfield series. The
Hochheim series exhibits considerably lower variation about the regression
curve. This would allow more accurate estimation of the range of values of K
for a given moisture potential.
Variation between soil series—Multivariate discriminant analysis was
used to help determine which of the soil series could be compared to one
B-63
-------
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B-65
-------
another. This was accomplished by simultaneous tests of the similarity of
distribution centers of mass and of the similarity of distribution variances
(dispersions) about that center. This would in theory indicate which series
can be placed together into groups of similar hydraulic conductivity properties.
However, in practice, these results must be considered only estimates, because
in real situations data sets rarely meet the statistical characteristics required
for the test to operate correctly (Pavlik and Hole, 1977; Eisenbeis and Avery,
1972).
The Morley, Batavia and Piano series exhibited very similar hydraulic
properties and could be grouped together. Figure B-39 illustrates their regres-
sion curves. Visually and statistically these series are very closely related.
A comparison of the general morphological information (i.e., textural and
structural data) for each of these series also show minor differences. These
series coalesce to form a common conductivity group, that will be temporarily
labeled here the "Batavia" group.
I
o
O
g
O
3.0
2.0
0.0
-1.0
I
I
I
-10 0.0 1.0 2.0
LOG SOIL MOISTURE POTENTIAL
(cm water)
Figure B-39.
Hydraulic conductivity as a function of soil moisture tension
for three soil series in a common conductivity group (Baker,
1976a).
B-66
-------
Another conductivity group is formed by the Magnor and Ontonogon series.
These regression curves are presented in Figure B-40 for visual inspection.
Morphological properties are similar. This conductivity group will be tempor-
arily named the "Magnor" group.
The data sets for the four remaining soil series, Plainfield, Boone,
Hochheim and Withee, were distinct and could not be placed together into
conductivity gmoups. Comparison of their regression curves in Figure B-41
supports this conclusion.
In Figure B-W., the regression curves for distinct conductivity data
sets are shown. Only one curve is shown for each of the two above discussed
conductivity groups, the Batavia and the Magnor, for their respective groups.
It can be seen that the various curves are easily distinguishable. As
saturated conditions are approached great disparities become apparent. In
this range of soil moisture potentials, soil macropores appear to dominate
moisture flow. These include structural cracks and biopores such as root and
worm channels. As the soil becomes drier, K decreases markedly, as the
effects of the larger pores decrease. This transition occurs gradually until
at a potential of about 30 cm, most of the curves flatten and appear to
approach some low K value asymptotically. In this region of the graph,
several of the curves are very similar, becoming indistinguishable from one
another. This suggests that exact classification of soil series for this
range of soil moisture conditions may not be necessary, since K values
differ little among series.
Effective planning and management for many land uses require the accur-
ate prediction of expected hydraulic conductivity values at a given site. One
way to provide this information is through the construction of prediction
intervals to include the expected value of K at any future site. Figure B-42
is such a prediction interval for the Piano series at the 95 percent confidence
level. The range of values enclosed in an interval of such high statistical
assurance is relatively large. However, planning and management of a soil
use such as liquid waste disposal requires prediction of the minimum expected
K at a site, not the range of expected values (Baker, 1976b). Therefore, the
lower prediction limit (line 2 in Figure B-42) can be used to project whether
the required conductivity can be expected for a given soil series and
value.
Summary and conclusions—Hydraulic conductivity data sets for nine soil
series exhibited relatively high variability. An empirical function was re-
gressed through each data set achieving good fits in all cases. Multivariate
discriminant analysis was used to help determine which soil series had similar
hydraulic properties and could therefore be grouped together. Five of the
soil series could be formed into two conductivity groups.
B-67
-------
3.0
f
2.0
1.0
u
u
0.0
(9
o'-I.O
i
l
-1.0 00 1.0 2.0
LOG SOIL MOISTURE POTENTIAL
(cm water )
Figure B-40.
Hydraulic conductivity as a function of soil moisture tension
for two series in a common conductivity group (Baker, 1976a).
3.0
2.0
1.0
0.0
-1.0
-1.0 0.0 1.0 2.0
LOG SOIL MOISTURE POTENTIAL
(cm water)
Figure B-41.
Hydraulic conductivity as a function of soil moisture tension
for soil series of dissimilar conductivity (Baker, 1976a).
B-68
-------
3.0
I
£ 2.0
u
O 1-0
Q
O
O
o o.o
>
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\
Figure B-42.
-1.0 OTOTO 2LO
LOG SOIL MOISTURE TENSION
(cm water)
Hydraulic conductivity as a function of soil moisture tension
with 95 percent prediction limits (Baker, 1976a).
Other Factors
Depth of Soil to the Water Table or Bedrock—
Adequate purification of effluent may take as much as three feet of
unsaturated soil. This distance has been shown to remove all constituents
except NO -N if loading rates are not too high and short circuiting is avoided
(see Appendix C). Not only does soil saturation limit the purification capa-
bility, it may also reduce the hydraulic potential difference. Also, under
these conditions a more intense clogging layer may form restricting flow even
more.
Bedrock may affect flow in two extreme ways. Non-porous bedrocks such as
granites or shales may stop flow, causing the water to either flow laterally
or back up. Creviced bedrock, such as that found in limestone formations may
allow wastewaters to pass very rapidly through the cracks to the groundwater
with little or no treatment. Septic tank soil absorption systems in Door
County Wisconsin, once believed to be working very well, have been found to be
B-69
-------
the cause of considerable groundwater contamination because of the shallow
creviced limestone (Water Resources Management Workshop, 1973).
Water table-—Whether the water table is real or perched, the zone of
saturation may be determined by direct measurement, or it can be estimated
based on soil morphology. Zones of saturation can be determined by direct
observation of wells, but the observations must be made during the wettest
period of a normal, or wetter than normal, year.
Holes prepared with an auger or drill mounted on a truck should be cased
with tubing. PVC tubing and electrical conduit have been used as casing.
Holes should be made in the casing so that water can move easily in and out but
other material cannot enter. The holes should only be located in the horizon
of interest. After placing the casing in the hole, gravel may be placed
around the casing to the height of the perforations to keep the soil on the
sides of the hole in place. Bentonite cement above the gravel will keep
surface water from running into the hole. When the zone saturates, water will
run into the hole to a height equal to the head pressure of the layer. Mea-
surements may be taken with a small rod or a weight on a string placed in the
hole.
Proper groundwater interpretation of a site requires that wells be placed
at various depths depending on the morphology of the soil. In a uniform
coarse textured soil the groundwater of concern would be continuous from the
top of the zone of saturation downward. A well placed within the zone of
saturation would reflect the height of the groundwater. If a horizon of slow
permeability exists, a zone of saturation may occur above it but not neces-
sarily below it. To detect this "perched" water table, a well should be
placed only as deep as the top of the less permeable horizon. If the well
is placed below the horizon, water may not enter the well or it may enter
from above the restricting layer and exit below. Because direct monitoring
of saturation is time consuming and weather dependent, interpretation of
soil morphology is often used to estimate seasonal soil saturation.
Soil minerals, organic matter, and compounds of iron and manganese
contribute to soil color. If these materials are uniformly mixed, the soil
will have a uniform color. Colors are not uniform in many soils, but are
mottled in patches of reds, oranges, browns and grays. Soil mottles are
defined as "spots of color" (Soil Survey Staff, 1951) or "spots of contrasting
color" (Soil Survey Staff, 1975) and may result from segregation of soil
components by transport and precipitation during periods of changing moisture
conditions. Soil mottling or lack of mottling can usually be used as an indi-
cation of the soil moisture conditions throughout the year. Drainage classes
(Soil Survey Staff, 1951) and soil moisture regimes (Soil Survey Staff, 1975)
are defined using soil mottling and offer ways to classify moisture conditions.
Mottles form during soil saturation because of the chemical environment
that develops. When soils are saturated or nearly saturated, dissolved oxygen
in the soil solution can be removed by microorganisms if the conditions are
right. As 0 is removed, reducing conditions develop, and forms of Fe and Mn
become more soluble. Spots produced where Fe and Mn have been reduced or re-
B-70
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moved are gray and are generally referred to as mottles of chroma 2 or less
(Soil Survey Staff, 1975).
The more soluble reduced forms of Fe and Mn are free to go with moving
water until points are reached where oxidizing conditions exist. At this
point less soluble Fe and Mn compounds form. Just where they form in the
soil will depend on the configuration of the soil system. In the field,
oxidized forms of Fe appear red and those of Mn black. The oxidized Fe and Mn
compounds are stable and will persist in the soil even when the soil is dry.
Occurrence of low chroma mottling (chroma < 2) can be used in most cases
to predict the existence of significant periods of saturation. Correlation of
duration of annual periods of saturation with morphological characteristics
and low chroma mottles have been made (Daniels and Gamble, 1971; Simonson and
Boersma, 1972; Veneman et al., 1976) but just how long it takes to form
mottles is not known (Soil Survey Staff, 1975). Laboratory experiments
have shown that gleying (Daniels et al., 1973) and mottling (Vepraskas and
Bouma, 1976) can develop in very short time periods under proper conditions.
It is of primary importance to determine the degree and duration of saturation
required to produce and maintain a given morphological expression of soil
mottling so that this can be interpreted in terms of estimates of degree and
duration of saturation.
Though soil morphological characteristics, particularly soil mottling,
have been used successfully in many cases to estimate annual soil moisture
conditions (especially periods of saturation) there are times when it has
not worked. Errors can result because of a soil chemical environment not con-
ducive to generation of mottles or because mottles formed by a genetic pro-
cess not associated with the present moisture regime. Studies have shown that
correlations of the extent of saturation with mottling can be good (Daniels
et al., 1971; Simonson and Boersma, 1972), and that detailed morphological
description of mottles can be used to define soil moisture conditions more
precisely (Veneman et al., 1976; Vepraskas et al., 1974).
In Wisconsin, detailed studies of soil moisture and mottling have been
made around Madison. In these studies three broad categories of moisture
regimes and associated morphological features were distinguished (Veneman
et al., 1976).
Category 1: These horizons were saturated for only short periods
of time and generally less than one day. Mottles with chromas of two or
less (grayish) did not occur. Processes of reduction in this horizon were
strong enough to reduce Mn and form ped mangans (ped coatings high in Mn)
and Mn nodules.
Category 2: These soil horizons show saturation for periods of several
days at a time. They are nearly saturated for several days at a time
with only the largest pores drained. Mottling dominated by chromas
of two inside peds and iron cutans (ped coatings high in iron called
neoferrans or ferrans) along larger pores with a few manganese mottles
3-71
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is associated with this moisture condition. A drier but similar condi-
tion was discussed on a different soil (Vepraskas et al., 197U).
Category 3: The horizons in Category 3 were saturated for a
period of several months. All soil pores would be water-filled. Mottling
dominated by low chromas of one (gray) inside peds, ped and channels neo-
albans and virtual lack of manganese mottles are present when saturation
occurs for several months. "Neoalbans" was suggested as a name for the
gleyed zone around soil pores produced as water entering a ped carried
the surface iron away.
Though detailed morphological descriptions may be helpful to distinguish
detailed moisture conditions, they have not been used in routine on-site
evaluation. Instead soils with mottling have been considered saturated or
nearly saturated, and, if at a shallow depth, the site deemed unsuited.
Though direct groundwater observation may be the best method of establishing
zones of saturation, interpretation of soil mottling is usually adequate.
Bedrock—Determining the depth to bedrock in many cases is very easy
but in others the weathering process has resulted in a zone of questionable
character. The rock can become very soft or break down into gravel sized or
smaller pieces.
The soil conservation service defines lithic and paralithic contacts for
distinguishing bedrock based on crack spacing, hardness and slaking character
(Soil Survey Staff, 1975). Health codes have used the criteria of percent
hardrock and the ability to excavate with ordinary construction equipment.
Determining the percent hardrock may depend on what is considered hard.
This has not been well-defined. In many cases the hardrock may be distin-
guishable, but the percentage difficult to determine. A piece of wire mesh
placed over the profile face may be used to more accurately determine the
percent by counting the wire intersections that occur over hardrock. This
has been used successfully in areas of creviced limestone bedrock.
Excavation with ordinary construction equipment will indicate the
possibility of installation of a subsurface system and may indicate hardness
of the material. Soil material containing considerable rock and some wea-
thered bedrocks may be excavated but may be unsuited for a soil absorption
bed. Consideration of the soil material should be used as a deciding
criteria.
Slope—
There is concern that effluent may surface downslope from a soil
absorption system. This may occur if a flow restricting subsurface horizon
is present and the effluent passes above it to a seep area. In the absence
of a restricting horizon, flow is dominantly downward and should not create a
problem (Bouma, 1977). Steep slopes may place severe restrictions on the use
of equipment for construction.
B-72
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Land slope can be expressed and determined in many ways. Slopes have
been expressed as:
1. Percent of Grade - The feet in vertical rise or fall in 100
feet of horizontal distance.
2. Slope - The ratio of vertical rise or fall to horizontal
distance.
3. Degrees and Minutes - The angle of slope measured horizontal.
4. Topographic Arc - The feet of vertical rise or fall in 66
feet of horizontal distance.
Land slopes are usually determined by measuring the slope of a line
parallel to the ground with an Abney Level at some fixed height. The value
of the slope as percent or in degrees is read directly from te he instrument.
A hand level may be used on a horizontal line of site. If a survey of the
area is being made slopes may be determined from this information.
Landscape Position—
The location in the landscape such as at the shoulder (see Figure B-4), or
on the backslope or footslope influences the surface as well as subsurface
water (the landscape itself may be controlled by bedrock and thus certain
positions should be avoided). The shoulder of a slope is the best drained.
This is generally a convex slope. The backslope generally has surface water
running over it, but it generally continues on downslope. Depending on the
underlying stratigraphy at some places on the backslope, a groundwater seep
may be found. These spots can usually be seen as depressions on the slope.
The foot of the slope is where the water running off the backslope slows
down. Generally these areas are wetter than other segments of the slope.
These regions are concave in nature. Floodplains or bottoms also have exces-
sive surface water. Though any of these areas may prove to be suitable for
some type of on-site waste disposal, certain landscape positions are generally
better than others.
Position in the landscape can be determined visually or from a detailed
survey. aFactors that could be considered to give some indication of the
surface and soil water conditions should be recorded. These might include
the position, as illustrated in Figure B-43, and the shape of the landscape
element such as concave or convex.
Management History—
Man uses the soil for many other purposes besides on-site waste treat-
ment. Some of these activities do not alter the properties of the natural
soil appreciably, while others do. Heavy machinery or repeated trips over an
area with light machinery can compact the soil, increasing its bulk density
and decreasing its permeability.
B-73
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Divide
B
Al-olluvium
u-summit
Sh- shoulder
Bs- backslope
Fs - footslope
Ts • toeslope
Figure B-43. Terminology of hillslopes according to Ruhe (1969).
Cutting and filling is frequently done to change the nature of a land-
scape. This operation leaves an area with subsurface material exposed, which
might be quite different from what was once at the surface, and a filled area
of mixed material. The properties of the fill, particularly in fine-textured
materials, will be different than before it was moved and will change with
time.
Past use of an area is sometimes difficult to determine. Factors noted
during a site evaluation that might indicate that the site has been signifi-
cantly altered include the lack of surface soil horizons, sharp unnatural
changes in slope, soil material that appears to be a mixture of different
soil horizons or has artifacts mixed in with the material and layers that
appear compressed or compacted. Before testing, it should be determined if
the material has stabilized and properties will not change further with time.
Also, it should be established if the material is uniform. If these factors
are positive, normal site evaluation procedures can be performed.
B-74
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DETERMINATION OF SITE SUITABILITY BASED ON SOIL INFORMATION
Consideration of methods to utilize soil variability information for
predicting, with a certain probability, whether the hydraulic conductivity
at a given site will allow a liquid waste disposal system to operate
properly is necessary. Three possibilities have been discussed previously
(Bouma, 1974; Baker and Bouma, 1976a), and will be summarized briefly here.
The first of these is direct on-site testing of permeability at any new
site. This is already required in many health codes (USPHS, 1967) as a means
of evaluating a site. Use of the crust test would yield a K curve for the
soil. Sizing of the seepage system would then be based on the expected load-
ing rate and on the capacity of the soil to accept liquid. The latter char-
acteristic can be determined from observed tension corresponding to a steady-
state flow rate that occurs once a stable clogging layer is established.
Thus, this steady state conductivity can be found from the K curve. The
soil moisture tension under the bed can be measured and the value of the
conductivity extrapolated to other sites in similar soils.
A second possibility would require a knowledge of the mean conductivity
characteristic of soils at the soil series level and information on the
variability of K. To use these data, on-site determinations in specific soil
series would be necessary, and the data for the series would be used for
evaluation. The third scheme would eliminate most on-site field determina-
tions by the use of detailed soil maps already available in many areas from the
Cooperative Soil Survey, U.S. Department of Agriculture. All of these possi-
bilities have exceptions, reverting the process back to the previous scheme.
Figure B-4M- is a schematic breakdown of these systems of site evaluation,
indicating the major steps in each process. This figure is based on the
application of the conventional septic tank-seepage field system. It also
assumes that other limiting conditions are screened out separately, and that
the conventional percolation test is the means of measuring permeability. How-
ever, the scheme is also valid for crust test data, and this aspect is most
interesting. Using more advanced techniques to measure K could increase the
accuracy of any of these systems. This could also allow quantitative deci-
sions to be made such that alternate methods of disposal would be possible,
and would allow a more accurate basis for sizing of the field (Baker, 1976b).
The diagram is self-explanatory, but a few major points are stressed below.
System I—
System I is the decision-making process now used in Wisconsin and several
other states. Based on percolation test data, as well as other environmental
factors, construction is either approved or denied. Each site is tested
separately. If it does not meet requirements, the owner cannot construct
a conventional system. If it passes, the field is sized according to perco-
lation test data following empirical procedures which do not consider soil
permeability alone (USPHS, 1967). Use of the crust test would greatly
improve the sizing procedure.
B-75
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ON - SITE TESTING
I
USE OF SOIL CLASSIFICATION
USE OF SOIL MAPS
m
DETAILED ON - SITE
TESTING: SOIL BORINGS
AND PERCOLATION TESTS
USE OF RELEVANT
SOIL MAP
NAME OF MAPPING UNIT
IN WHICH SITE OCCURS
DETERMINE SOIL TYPE
AT NEW SITE
MAF
ASSUME SOIL AT SITE
HAS SAME NAME
(CLASSIFICATION)
CONSIDER DATA
OBTAINED FOR
IDENTICAL SOILS
ELSEWHERE
^
4
ASSUMPTION
CORRECT
*
ASSUMPTION
INCORRECT
I
DETERMINE SOIL TYPE
THAT OCCURS
SUITABLE
SOIL TYPE IS
PHYSICALLY
HOMOGENEOUS
1
*
^SUITABLE
SOIL TYPE IS
PHYSICALLY
NOT HOMOGENEOUS
1
GO TO I
STOP OR 11
| CONSTRUCTION
* RESEARCH NEEDED
Figure B-»m. Measurement of soil hydraulic conductivity and site selection.
System II—
In System II, based on accurate measurements from the crust test or other
methods, the hydraulic conductivity characteristics of major soil groupings
are determined including variability data. This could follow much the same
procedure as was described for the variability experiments presented by
Baker (1976a). Some soil series would coalesce into conductivity groupings
whose mean characteristics would be similar, so the number of these divisions
would not be too large. A field determination as to which soil series occurs
at the site would then lead to a realistic estimate of the conductivity char-
acteristics of the site in question. Sizing of the drainfield would proceed
based on the minimum expected hydraulic conductivity (after clogging). The
field percolation test could not be used effectively for this purpose.
Figure B-45 illustrates the range of possibilities that can arise under this
scheme. If soil series at a given site has the K characteristic shown in
B-76
-------
o
o
X
o
LOG SOIL TENSION
(a)
*
o
IN
O
O
LOG SOIL TENSION
(b)
bp
LOG SOIL TENSION
(c)
LOG SOIL TENSION
(d)
o
o
_J
Figure B-45.
LOG SOIL TENSION
(e)
Measurement of soil hydraulic conductivity and site selection
for liquid waste disposal.
B-7T
-------
(a), the soil is suitable because the lower limit for the prediction interval
(P.I.) is above minimum K required at saturation and at the equilibrium ten-
sion (bp) expected after clogging has occurred (Bouma, 1975; Bouma et al.,
1975a). In (a) the variability is high (large range between the limits for
P.I.), while in (b) variability is low. Both cases pass requirements because
the required probability of successful operation is satisfied. In the case
of (c) the variability is high. The lower limit (LL) of P.I. is below the
minimum K at the predicted clogging tension, so the required level of con-
fidence that the site will meet requirements does not exist. On-site testing
of K would then be required. In (d) the P.I. is below minimum K, even
though variability is low (narrow prediction interval). On-site testing
would be required, but the odds of finding a suitable site are less because
the probable range of values is almost entirely below the required minimum K
In (e) the entire prediction interval is below the minimum K, and the site
is rejected because of the high probability that it will not meet require-
ments. There is the outside chance that a given parcel of land might, with
on-site testing, yield a usable site, but these odds are low.
In such a scheme, a great deal of information is required to establish
the hydraulic conductivity characteristics of the possible soil series or
groupings. In areas of highly variable soil groupings it might be more
practical to simply perform on-site tests and not use this system.
System III--
System III is an extension of System II. Here soil maps are used for
identification of the soil series or grouping at a given site. For this
purpose, it is important to know the amount of mapping error involved. In
some areas mapping is more difficult than in others, leading to differing map
reliabilities. In cases where experience has shown the map is very reliable,
a decision is based directly on the data for that series, eliminating the
need for an on-site visit. This site is then evaluated according to the
advanced stages of System II. Mapping reliability could be too low to allow
this procedure, and an on-site identification of soil series would then be
needed. It should be noted that the mapping reliability and the level of K
probability for a site will compound. For certain soils this scheme can be
very useful. In the central sand plains of Wisconsin, for example, the
Plainfield series can be mapped with very high reliability, and its range of
conductivities is almost always above the minimum K required. In this case,
use of the soil map can save a great deal of time in site selection. Scheme
III then relies not only on soil mapping, but also on determination of K data
and variability of the soils involved.
Summary—
Soil suitability can be determined in a more quantitative and systematic
way than described here (Baker, 1976a). To do this, soil permeability and
wastewater system performance must be known, so that they can be treated
as probability terms. Since this information is only available for very
limited circumstances, the implementation of such a decision-making scheme is
not possible at this time. However, the potential improvement in accuracy
of prediction is well worth pursuing.
B-78
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PART II
WASTEWATER SOIL ABSORPTION SYSTEMS
On-site subsurface soil disposal of septic tank effluent is the most
common means of domestic liquid waste treatment in unsewered areas. In
19TO, approximately 16.6 million housing units or approximately 25 percent of
all housing units in the United States disposed of their wastewaters via
septic tank-soil absorption systems (Cooper and Rezek, 1977). The use of
these systems is growing at a rate of about one-half million new systems per
year (Patterson, Minear and Nedved, 1971). This rate is increasing due to
an emerging trend of population movement to rural areas (Beale and Fuguitt,
1975). Because of poor design, construction or maintenance practices, however,
a large percentage of these sytems are failing to provide adequate treatment
and disposal of the wastewater.
Failure usually manifests itself by seepage of septic tank effluent
over the ground surface or by sewage back-ups in the household plumbing due
to a severely clogged soil absorption field. Since the system is usually
near the dwelling, the poorly treated waste can become a nuisance, as well as
a health hazard. A more serious type of failure, however, occurs when there
is insufficient or unsuitable soil below the absorption field to properly
purify the wastewater before it reaches the groundwater. Contamination of
nearby wells by bacteria, viruses and chemical pollutants can result. This
type of failure can go unnoticed until illnesses or epidemics occur.
Increased emphasis on environmental quality and public health calls
for satisfactory treatment and disposal of domestic liquid wastes for all
homes in unsewered areas. This concern is expressed by regulatory codes which
limit the use of on-site disposal systems to soils which are often arbitrarily
defined as being "suitable" for the conventional septic tank system. Because
the pressure for development of unsewered areas is great, these codes are
difficult to enforce since it is estimated that only about 32% of the total
land area of the United States meet these accepted soil criteria (Wenk, 1971).
However, recent advances in soil physics, soil chemistry, microbiology and
engineering are leading to improvements in the conventional design as well as
alternative designs of on-site systems which overcome the limitations imposed
by many "unsuitable" soils.
MAINTAINING THE INFILTRATIVE CAPACITY OF THE SOIL
Soil Clogging
Proper performance of an on-site wastewater system utilizing soil ab-
sorption for ultimate disposal of the liquid depends upon the ability of the
soil to completely absorb and purify all the wastewater produced. Initially,
B-79
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the soil may have a high infiltration rate and is able to absorb a greater
quantity of liquid than applied. However, with continued application of
wastewater, a clogging mat usually develops at the infiltrative surface.
This creates a barrier to flow, restricting the rate of infiltration.
Clogging, per se, is not synonomous with failure because flow through the
mat will continue, albeit at a reduced rate. In fact, some clogging is bene-
ficial to enhance purification. Therefore, proper design requires that the
wastewater loading never be allowed to exceed the infiltration rate of the
clogged soil or that the extent of clogging be controlled to maintain the
desired infiltration rate.
Soil clogging is a complex phenomenon that is the result of many mecha-
nisms, often acting simultaneously. They can usually be grouped into physical,
chemical and biological processes. Not all mechanisms are equally significant,
however. In their review of the literature, McGauhey and Krone (196?) con-
cluded that biological agents and their activities are the most important
cause of soil clogging. This contention is supported by several investigators.
Allison (19^7) experimented with sterile and unsterile loam and sandy loam
soil columns, ponded with sterile and non-sterile water. Only the sterile
columns ponded with the sterile water did not show the characteristic decline
in infiltrative capacity usually seen in continuously inundated soil. Bac-
terial populations in the soils from the various columns used provided further
evidence that the clogging was caused by microbes.
McCalla (19^5, 19^6, 1950) also did work on the effects of micro-
organisms on the rate of percolation of water through soils. In one study,
three sets of columns containing a sand loam soil were prepared (McCalla,
1950). One set received distilled water only, another was covered with a
cotton gin waste mulch before distilled water was applied, and the third had
mercuric chloride added to the water to act as a disinfectant. All were
continuously ponded. Dramatic decreases in rates of infiltration resulted
in the control set and the set which received the mulch. Only the mercuric
chloride columns maintained infiltration rates near the initial rate, indi-
cating that clogging is largely due to biological activity. In another
study, permeability increased when organic matter was first added to the
soil, then wetted, incubated, and dried before water was applied (McCalla,
19^5» 19^-6). This increase was attributed to increased soil aggregation.
Therefore, McCalla (1950) concluded that under conditions of prolonged sub-
mergence, there appear to be two ways by which microorganisms may reduce
water movement through the soil. First, the microorganisms may produce gases
or organic materials, such as slimes, that may interfere with water movement.
Second, microorganisms may reduce water percolation by decomposing or changing
agents responsible for stabilizing soil structure, resulting in pedal
deterioration and loss of planar voids.
Other investigators also precluded the possibility that microbial cells
alone cause clogging. Bendixen, et al. (1950) observed that under continuous
inundation, clogging occurred only in the top few centimeters of the soil
and not throughout the column. Winneberger, et_ al. (i960) found that well-
aerated water applied at the infiltrative surface of the soil did not prevent
the development of an anaerobic soil system under continuous inundation.
Since no bacteria were added through the water and no action was involved
in concentrating microorganisms at the surface, the clogged layer which
B-80
-------
developed must have resulted from anaerobic activity on organic matter
originally in the soil.
Jones and Taylor (1965) studied the effects of intermittent dosing
versus continuous ponding of septic tank effluent on infiltration rates
through sand in laboratory columns. Loss of infiltrative capacity occurred
relatively soon in the columns continuously ponded while the columns in
which aerobic conditions were maintained clogged much slower, occurring in three
phases (See Figure B-U6). The first phase was attributed to physical blockage
of the interstices of the sand by the accumulation of organic deposits
because the rate of clogging was directly proportional to the volume of efflu-
ent percolated. In the second phase, clogging proceeded at a relatively slow
rate, as evidenced by small changes in conductivity over a period of several
weeks. It was speculated that a quasi-equilibrium condition was attained
where organic losses by decomposition were roughly equivalent to those added
by the liquid waste. In the third stage, clogging proceeded relatively
rapidly, and the rate of infiltration stabilized near 0.5 to 1.0 percent of
its original value. Jones and Taylor concluded that the duration of the
first and second phases were dependent upon the application rate and the
initial conductivity of the soil. Once into the third stage, clogging
rapid independent of the liquid loading or initial conductivity.
PONDED 15-25% TIME
EFFLUENT CONTINUOUSLY PONDED
0 300 600 1200 1800 2400
CUMULATIVE OUTFLOW, in
3000
3600
4200
Figure B-^6. Typical curve showing the effects of both physical and biological
clogging (after Jones and Taylor, 1965).
Jones and Taylor (1965) also found that under continuous ponding, the
second phase of clogging was either absent or of short duration. Initially,
the clogging rate was directly related to the volume of effluent absorbed.
B-81
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Later, the rate approached a minimum value which depended on the initial
conductivity of the sand. It was concluded that the conditions of Phase II
must be maintained by a proper loading rate and pattern, since excessive
clogging is inevitable once conditions of continuous ponding are reached.
Thomas, et_ al_. (1966) also observed the three phases of clogging in
sand lysimeters dosed with septic tank effluent. Once the third phase was
reached, however, waste application was interrupted for a period of time.
When loading was resumed, it was found that much of the infiltrative capacity
was regained. Upon analyses of the soil, the organic matter was the only
probable clogging agent found to have declined.
Since different organic compounds differ significantly in their biode-
gradability, partially degraded organic material could accumulate with time
to clog the soil. While this may contribute to long-term clogging, it
does not seem to be the dominating mechanism. Avnimelech and Wevo (196^)
and Mitchell and Nevo (196H) investigated the effects of prolonged percolation
of water containing high levels of organic matter through sand columns.
Initial results showed that polysaccharide-producing microorganisms pre-
dominated in the clogged layers of the sand. A direct correlation between
accumulation of polysaccharides and polyuronides in the soil and reduction of
the infiltrative capacity was found. If application of waste were inter-
rupted long enough for strictly aerobic conditions to return, the poly-
saccharides and polyuronides were broken down, and much of the infiltrative
capacity was restored. On the other hand, if strictly anaerobic conditions
were maintained in the column, no polysaccharides were produced and clogging
progressed more slowly.
Factors Effecting the Intensity of Clogging—
The accumulated evidence seems to indicate that the intensity of soil
clogging may be effected by the organic strength and the loading rate and
pattern of the wastewater applied. These are areas that more attention has
been given in an effort to maintain reasonable infiltration rates into the
soil.
The effect of applied wastewater quality—The effect of effluent quality
on soil clogging is unclear. It is reasonable to assume that if the suspended
solids and nutrient loading of the soil were reduced, less physical and bio-
logical clogging would occur. Weibel et_ a!L_. (195^0 found that the percolation
rate through packed columns of silt loam was reduced as the total suspended
solids of the wastewater was increased. Later studies by Winneberger, et al.
(i960) compared rates of infiltration reduction produced by septic tank and
extended aeration unit effluents. The aerobically treated waste had a
higher concentration of suspended solids and biochemical oxygen demand than
the septic tank effluent, and was found to produce an earlier but less
intense clogging in sand. The opposite was true in sandy loam, however.
Laak (1970, 1973) conducted similar experiments and found that the equilib-
rium infiltration rate did not differ between soil types but varied with
solids and nutrient loading.
The evidence seemed to indicate that effluent quality may affect the
rate or intensity of clogging under certain circumstances but it was still
B-82
-------
unknown which element in wastewater causes the clogging. Also it was unclear
if all soils are equally affected. To further elucidate, several laboratory
studies with packed and undisturbed soil columns were conducted.
The first phase of study attempted to test the hypothesis that
aerobically treated wastewater causes less intense clogging than septic tank
effluent (Daniel and Bouma, 197M • Since reduced infiltration is a more
severe problem in slowly permeable soils, a fine textured soil was used.
All previous studies used artificially aggregated soil fill materials rather
than undisturbed cores in which flow patterns of liquid are significantly
different (Bouma and Anderson, 1973). Therefore, to be meaningful, undisturbed
cores of soil were extracted in the field.
The soil used in the experiments were Almena silt loam (Aerie Glossaqualf)
which has an A2 horizon at 20-33 cm depth with platy structure, and a silt
loam texture. The B21t horizon at 33-68 cm depth has medium prismatic
structure and the B22t at 68-110 cm has coarse prismatic structure. Both are
silty clay loam in texture. Almena is a somewhat poorly drained and slowly
permeable soil.
Undisturbed vertical soil cores were taken in the field using a truck-
mounted hydraulic probe. The upper end of each core was at about 30 cm
depth corresponding with the middle portion of the B21t horizon. Upon sampling,
the soil cores were immediately coated with a layer of paraffin-petroleum
jelly mixture to prevent structural damage and loss of moisture. Each was
placed into lengths of 10 cm diameter plastic pipe, which were later sealed
with the paraffin-petroleum jelly mixture. The final dimensions of the soil
cores were 10 cm in diameter and 55 cm deep. Eight cm of medium gravel
was placed on the upper surface of the soil after the surface had been cleared
of loose soil.
The columns were wall-mounted in the laboratory. Tensiometers and
platinum electrodes were inserted in the columns at different levels to moni-
tor moisture and redox potentials (See Figure B-li7). A constant head of
5 cm of applied wastewater was maintained above the soil surface by
mariotte siphons. Suspended solids were kept in suspension by magnetic
stirrers.
Duplicate columns were subjected to constant ponding with (l) septic
tank effluent, (2) extended aeration effluent, and (3) distilled water
amended with sodium, magnesium and sulfate salts to simulate the salt content
of septic tank effluent. The chemical oxygen demand and suspended solids
concentrations of the extended aeration and septic tank effluents were 60 mg/L
COD, 33 mg/L SS and 150 mg/L COD, Uo mg/L SS, respectively.
A gradual reduction in flow occurred in all the columns (See Figure
B-U8), but comparison of data between columns is difficult due to differences
in initial flow rates. There was little difference between the other two
sets of columns.
B-83
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Inlet For
Conttont Head
Monotte Siphon
With Glott Cooling
Coil
Oxidation Reduction
Electrode!
Interface
2.5 Cm •
5.0 Cm •
Ptexigloii Column-*
Paraffin-**
Undisturbed Soil Core
Figure
Soil column with details of oxidation-reduction
electrodes, tensiometers, and cooling system
for constant head device (not to scale)
A more meaningful way for comparing relative degrees of clogging is to
consider the tensiometric data (Daniel and Bouma, 197^). This provides a
measure of the energy status of the liquid in the soil independently of the
permeability which varies between columns. The water potential above each
column was +5 cm. The rate of decrease of this potential with depth pro-
vided by tensiometry gives an absolute measure for the rate of development
of surface impedance.
The soil tensions after four months of ponding in the six columns are
presented in Figure B-U9. The potentials in the columns ponded with dis-
tilled water follow very closely the theoretical curves describing unin-
hibited flow of water under saturated conditions (Figure B-H9 )• The
tensions in columns ponded with extended aeration effluent resemble those
B-8U
-------
OIST H{0 ((ALT)
— Column I
— Column 3
too-
75
SO
23
100
79
SO
29
f4
»
MTSST
20 30 40 SO »0 70 80 90 100
Figure
Reduction in flow rate, in the columns, expressed
in cm/day and percent of original.
in the theoretical curve for crusted soil below 10-cm depth. The cores
ponded with septic tank effluent have an intermediate position indicating
the occurrence of some resistance to flow at the surface, but less than that
in columns ponded with the aerobically treated waste.
The difference in physical behavior between the columns loaded with
septic tank effluent and -those loaded with extended aeration unit effluent
may be due to different sizes and shapes of the suspended solids. Freeze
dried solids from both effluents were compared and were found to be coarser
in the septic tank waste. Finely divided particles in the aerobically
treated effluent may have more easily penetrated the relatively porous top-
soil to form "bottlenecks" in the pore system with depth, thus reducing the
overall permeability (Daniel and Bouma, 197*0 •
To test further what element in wastewater results in clogging, another
series of columns was set up. Undisturbed cores of Almena silt loam were
again used. In all, twenty-one columns were constructed and divided into
three groups as follows: Group A: seven columns for septic tank effluent;
Group B: six columns for extended aeration effluent; and Group C: eight
columns for synthetic effluents. Duplicate columns in groups A and B were
B-85
-------
SOIL MOISTURE PRESSURE (CM WATER)
SOIL MOISTURE PRESSURE (CM WATER)
UNSATURATEO FLOW
I CM/DAY
SATURATED FLOW
K) 20 30
DEPTH,CM
DEPTH ,CM
O DISTILLED WATER
A SEPTIC TANK
O EXTENDED AERATION
EFFLUENT
Figure B-Upa. Theoretical moisture pres- Figure B-U9b. Measured moisture
sure distributions in the columns pressures in six columns of
assuming saturated flow in a Almena silt loam, ponded with
homogenous porous medium (curves distilled water, septic tank
P and T) and in a two-layer effluent and aerated effluent
medium (I=topsoil, II=subsoil) (Daniel and Bouma, 197*0-
(curves P' and T1). Unsaturated
flow (left curve) was calculated
for a flow rate of 1 cm/day. P=
moisture pressure (cm), T=total
potential (cm). G=gravitational
potential (cm) (Daniel and Bouma, 197*0-
dosed with 1 cm/day (0.2 gpd/ft2) of raw effluent, sand filtered effluent
and paper filtered effluent. Compositions of these liquids are presented in
Table B-6. The sand filtered effluents were obtained from two laboratory
sand columns (10 x 60 cm) loaded with 5 to 7 cm (1.2 to 1.6 gpd/ft2) of the
respective effluents each day. The paper filtered effluents were prepared
by vacuum filtration through Whatman No. 2 filter paper.
Duplicate columns in Group C were subjected to the same dosing regime,
but with (l) unsoftened tap water, (2) tap water with glucose and glutamic
acid added to obtain a BOD^ at 250 mg/L; (3) tap water with 100 mg/L-N
ammonium and 50 mg/L-Pphosphate, and (U) tap water with BOD, nitrogen and
phosphorus added. There were no solids added in any of the prepared efflu-
ents for this group.
The columns were loaded daily for over 200 days. Prior to ponding
the rate of clogging appeared to be a function of the initial saturated
permeability of the cores which varied between 1 and 6 cm/day. There were
no specific trends as a function of effluent quality. When all columns
were ponded or about to pond, the columns were continuously loaded.
B-86
-------
TABLE B-6. CHARACTERISTICS OF WASTEWATER EFFLUENTS
APPLIED TO SOIL COLUMNS
Type of
Effluent BOD^ TOC TSS VSS MH + WO ~ Total N
mg/L mg/L mg/L mg/L mg/L-N mg/L-N mg/L-W
Septic Tank
Sand filtered
septic tank
Paper filtered
septic tank
Extended
aeration
300
100
100
30
75
20
70
20
15 15
5 1
10 10
1+0 30
50
1
50
1
Tr 55
5^ 55
Tr 55
75 76
Sand filtered
extended
aeration 20 5211 75 76
Paper filtered
extended
aeration 20 20 1 Tr 1 75 76
Some differences in clogging intensity were observed, "but were not striking.
The extended aeration effluent clogged more than the septic tank effluent,
while sand filtration of both the effluents reduced clogging, but more so
with the septic tank effluent. The paper filtered septic tank effluent
clogged more than all the septic tank derived effluents. Those columns
receiving synthetic wastes did not clog, but the infiltration rates for the
columns loaded with tap water with BODt- and nutrients added were reduced.
A third series of columns were set up to further investigate the effects
of effluent quality, as well as dosing and initial saturated conductivity of
the soil on the rate of clogging (Baker, 1976c). Twenty eight columns of
undisturbed Almena silt loam were set up at the pilot plant study laboratory
(Laboratory Site N). Aerobically treated effluent from the extended
aeration unit and septic tank effluent were used for the study. The two
wastewaters differed significantly in total suspended solids and oxygen
demand. Data showing their mean compositions are presented in Table B-7-
Tap water was also used for comparison. The three liquids were then auto-
matically applied to the surfaces of the soil columns at a loading rate of
1 cm/day (0.2U gpd/fl? ) in a single daily dose.
The saturated hydraulic conductivity (Kgat) of each column was measured
at the commencement of the experiment and after ko weeks of operation.
B-87
-------
TABLE B-T. CHARACTERISTICS OF EFFLUENTS USED FOR THIRD SERIES
OF CLOGGING EXPERIMENTS (Baker, 19?6c)
Total suspended
Septic Tank
Mean Standard Range
deviation
Extended Aeartion
Mean Standard Range
deviation
BOD (mg/L)
COD (mg/L)
U8
127
13
26
25-91
60-215
27
80
28
85
2-170
15-690
solids (mg/L)
Total nitrogen (mg/L-N)
NH3 (mg/L-N)
Total phosphorus (mg/L-P)
26.5
50.8
ko
3h
12
111
18
9
6-7U
11-87
0-83
13-55
61
UU
0.5
3U
105
21
2.U
13
11-8UO
2-8U
0-19
13-96
Measurements were accomplished by ponding tap water on the upper surface for
3 days to saturate the columns and by taking outflow recordings versus time.
In the cases where a barrier to flow developed, the conductivity of the
clogged column was determined. After this, the upper 1 cm of soil and barrier
was carefully removed, and Ksa^. was measured again.
The soil columns were arranged into groups according to their relative
initial saturated conductivity (Ksa^ j). Eight columns were assigned to
each effluent, four having similar low Ksat j values and four having high
K-sat I values. In this way each effluent was applied against a high or low
initial conductivity. The four extra columns were assigned to the water
subset bringing that group to 13 in all. The major purpose of this design
was then to determine whether Ksa^. j and effluent quality are major factors
in the development of a clogging zone and to see if these parameters
influence the length of time required for ponding to occur.
The decision to dose the columns at 1 cm/day was based on the previous
column studies and field work. The first series of columns indicated that
the long-term infiltration rate was 1.0 cm/day after U months of ponding
(Daniel and Bouma, 197*0. This takes into consideration the loss of area to
be expected with gravel "shadowing" a portion of the soil's infiltrative
surface.
The reduction in the soil's ability to accept effluent was soon ob-
served in some of the columns, notably in those with low Ksa^. j values.
Within a month, five columns had liquid continuously ponded on the surfaces.
Some of the columns with low Ksa^. j resisted ponding for considerable time.
Table B-8 shows data for the aerated effluent and septic tank effluent
groups. When a dose was initially applied to the soil surface, it ponded on
B-88
-------
TABLE B-8. HYDRAULIC CONDUCTIVITY DATA AND PONDING TIMES
FOR WASTEWATER-DOSED COLUMNS (Baker, 19T6c)
Treatments
Extended
Aeration
Septic Tank
Initial sat
•^ V « -fM- «« ->^~~
Column
No.
1
2
3
u
6
8
5
7
1
2
3
1*
5
8
6
7
;urated K
sat I
0.51
0.5^
0.60
0.71
1.33
1.89
1.20
1.1*3
.66
.57
• 52
.ko
2.00
2.77
2.97
2.79
K2 v3
^ p Ksat C
0.3 0.28
0.^0
0.1*8
0.11
<1 0.51*
0.1*0 0.86
<1 2.ll*
1.15 1.71
0.80 2.85
0.96 0.89
0.80 0.91
0.32 0.75
<1 2.41
5.96
<1 1.29
<1 0.21
Ponding
Time
(weeks)
3
3
12
38
28
32
16
38
28
21*
6
k
3k
not ponded
2k
2k
•* Saturated K after clearing surfaces of columns
the surface only temporarily before flowing into the soil. With continued
daily applications the amount of time required for the effluent to infil-
trate gradually increased until the liquid did not flow away in 2k hours.
From this point, on liquid was continuously ponded on the surface, a condition
represented here by PT, the ponding time.
Table B-8 shows that all effluent-dosed columns except one, ponded
during the course of the experiment. The mean ponding time for the septic
B-89
-------
group, eliminating the unponded column, was 20.6 weeks (s = 11.2 weeks) and
for the aerobic group was 21.3 weeks (s = 1^.7 weeks). Hence, the ponding
time was nearly the same for the two treatments. However, it should be noted
that the mean Ksa-f. j of the septic group was 1.1*2 cm/d (s = l.lU cm/d) and
for the aerated columns is 1.0U cm/d (s = 0.51 cm/d). Had they been equal, the
difference in PTs may have been greater. In either case only one of 16
columns remained unponded after 10 months of dosing. The Kp values are
generally lower than Ksat j values except for a few receiving septic tank
effluent which showed slight gains. After measurements were made, the infil-
trative surfaces were removed to a depth of about 1 cm leaving fresh surfaces.
These Ksa-t Q values are roughly the same as at the start of the experiment
with the exception of several of the columns which received aeration effluent.
It is believed that clearing the surface removed any shallow clogging mat,
and also accumulated solids and slaking. Since the extended aeration group
did not recover t o the extent the septic tank group did, this may indicate
that a more in-depth clogging occurred in the extended aeration group , as has
been suggested (McGauhey and Krone, 1967; Daniel and Bouma,
Table B-9 contains information for the water-dosed columns . Several of
these became ponded with a mean FT of 18.3 weeks (s = lU.5 weeks) roughly
equivalent to those of the effluent-dosed columns. The mean Ksa-^ j for these
ponded columns was 0.90 cm/day, (s = 0.12 cm/day). In this case, the lower
mean Ksa-j. j probably accounts for lower mean PT. As in the other columns,
Kp generally decreased, except for column 6. After clearing of the surface,
conductivities returned to initial or to slighly higher values, an indication
that the restrictive layer was at the surface, probably due to slaking. The
results of the ponding time data are summarized in Table B-10. The difference
in the length of time to ponding for the different applied liquids is not
significant. There appears, however, to be a relationship between Ksa-^ j_ and
PT. Table B-10 examines this relationship by grouping all ponded columns
into high and low groups of initial Ksa-^ . Although the individual data are
highly scattered, a significant difference in ponding time for the two groups
is clear. This indicates that for a 1 cm/day dose of liquid, higher
will in general lead to a longer acceptance time, but for the Almena
silt loam used here, this gain is only a few months.
Five of the columns dosed with water and one dosed with septic tank
effluent did not pond in the Uo week period. Their conductivities actually
increased with dosing before and after surface clearing. No visible surface
crust had developed, except for very slight slaking of a few surfaces.
Interpedal cracks and root channels were open to the surface allowing the
free flow of water into the column. Rapid movement of water through these
pores appears to have enlarged the flow paths, increasing their conductance.
Morphological evidence of this change was visible when the columns were
examined in detail. This may be viewed as a form of adaptation of the soil
morphology to the new moisture regime of pulse-loading 365 cm/year, versus
the 70-80 cm/year found naturally. A decrease in the daily minimum potential
(¥m min) with continued dosing indicates that flow has increased through
larger channels without having time to disperse into the pedal interiors
(Figure B-50). The ped interiors have in effect become more well-drained.
B-90
-------
TABLE B-9. DATA FOR WATER-DOSED COLUMNS, (Baker, 19760)
Treatments
Ponded
columns
Column
No.
1
2
3
k
6
12
13
sat I
0.7U
0.89
0.97
1.0k
0.96
0.96
0.71
K2
P
(cm/day)
0.60
0.9
0.7
0.95
lU.7
1.5
0.32
K3
sat C
1.07
2.25
0.70
1.0k
15.7
1.61
0.79
Ponding
Time
Weeks
10
32
12
36
32
3
3
Unponded
5
7
8
10
11
1.02
0.76
0.72
0.29
0.06
Ksat (Before
clearing surface)
3-59
6.U3
5-lU
3.0
7-82
3.65
7-^0
5-79
56.6
5-79
not ponded
ii
it
ii
n
Initial saturated K
2
K after ponding occurs
3
Saturated K after clearing surfaces of columns
Analysis of soil moisture potentials recorded by tensiometers at depths
below the surface sheds light on happenings within the columns. Figure B-51
represents the theoretical soil moisture profile for three possible situations
in a two-layered soil, such as AJjnena silt loam with a more permeable
upper horizon. Curve (a) represents saturated flow through the column, where
potentials are high in horizon I. Curve (b) represents a steady-state flow
through a restrictive barrier just below the soil surface (the upper portion
of the column is uniformly drained). Curve (c) represents the calculated
potentials expected at a constant flow rate of 1 cm/day (Bybordi, 1968) using
the K-curves for these two horizons. In natural soils the change in con-
ductivity with depth may not be as well defined as in this example but it is
often characterized by gradually decreasing with depth to the least permeable
horizon.
B-91
-------
TABLE B-10. SUMMARY OF PONDING TIME DATA AS RELATED TO TREATMENT AND INITIAL
HYDRAULIC CONDUCTIVITY, (Baker, 19T6c)
a)
Treatment Mean K (cm/d)
sat I
Extended
Aeration 1.03, (s = 0.51)
Septic
Tank 1.1*2, (s = l.lU)
Water 0.90, (s = 0.12)
Extended
Aeration and
Septic Tank
Conductivity Class
Low K . T (0.56 cm/d mean)
High Kgat j (1.9U cm/d mean)
Ponding Time1
( weeks)
PT = 21.3 s =
PT = 20.6 s =
PT = 18.3 s =
PT = 20.9 s =
Ponding Time
(weeks)
PT = lU.8 s =
PT = 28.0 s =
11*. 7
11.2
11*. 5
12.7
13.5
7.U
= mean ponding time, S = standard deviation
40-
30
>
UJ
20
10
TENSIOMETER DEPTH• 30cm
I " I
I I
-10 -20 -30 -40 -50
SOIL MOISTURE POTENTIAL (water cm)
+m min.
Figure B-50.
Plot of PT (ponding time) against ¥m min (daily minimum
moisture potential) for water column 8 (Baker, 19?6c)
B-92
-------
SOIL MOISTURE POTENTIAL, ^ min.
(cm water)
UNSATURATED FLOW SATURATED FLOW
-40 -SO -20 -10
10 20
20
\
Figure B-5L Calculated soil moisture potential profiles for three column
situations. Curve (a) represents an overloaded column, (b)
a column in which a clogging zone has developed restricting
flow, and (c) a non-ponded column receiving 1 cm/day of
liquid (Baker, 1976c)
Figure B-52 presents the soil moisture profile for three different
columns chosen to represent the three possible outcomes outlined above after
38 weeks of dosing at 1 cm/day on Almena silt loam columns. The values of
¥m (matric potential) used are the driest or minimum potentials reached that
day during the dosing cycle. Therefore,they represent the potential after
2k hours of drainage following the last dose. When these ¥m values are
plotted against subsurface depth, the resulting curves are similar to those
of Figure B-51. Each curve clearly illustrates the properties operating
within the columns. Column a' (Septic 2) had liquid ponded on its surface
because the loading rate of one cm/day exceeded the column's Koat p Some
clogging may have occurred, but the dominant effect expressed here is ex-
cessive loading. It took 2k weeks for continuous ponding to occur. Column
b1 (Extended aeration 5) clearly demonstrates the formation of a barrier
to flow near the surface, with ponding occurring at 16 weeks. In this case,
a uniform negative potential indicates the maintenance of unsaturated con-
ditions. Column c' (Water 8) did not pond, and the potentials are even more
negative than those predicted by calculation. The soil is more well-drained
which can be explained very simply by flow through a variety of pore sizes.
In the case of a daily dose, liquid is rapidly conducted away by the larger
pores such as interpedal cracks and root channels before much water enters
the finer pores or soil peds. The tensiometers record the potential of the
ped interiors and of the many small pores not exposed to the dose. In the
non-ponded columns the potential increased over the course of the study, as
did their Ksat values. This is easily explained by the enlargement of the
major flow pathways, allowing even faster conduction of liquid and reducing
further the potentials within peds.
B-93
-------
SOIL MOISTURE POTENTIAL,
-------
Contrary to findings of earlier workers, Kropf, et_ al_. (1975) reported
that infiltration rates through constantly ponded soil columns remained
higher than those in columns subjected to intermittent flooding. In an
earlier study, Mitchell and Nevo (1964) correlated clogging with poly-
saccharide accumulation in soil. The polysaccharides were produced by a
facultative bacterium of the genus Flavobactepiiffn which would be favored
under short periods of alternating aerobic and anaerobic conditions pro-
duced by intermittent dosing. Under strictly anaerobic conditions, no
polysaccharides were produced. If polysaccharides are a dominant clogging
agent, this might explain the results of Kropf, et al.
The results of these two investigations imply that the oxidation-
reduction potential in and around the clogging mat may be critical to main-
taining high infiltration rates. Totally aerobic conditions seem to promote
rapid degradation of the clogging materials, but totally anaerobic con-
ditions seem to prevent the buildup of an excessively resistant mat. Under
fluctuating anaerobic and aerobic conditions created by intermittent
dosing, polysaccharide-producing facultative organisms could be favored.
Therefore, if dosing and resting is to be used as a means for prolonging
the life of soil absorption fields, more must be known about the growth and
degradation dynamics of the clogging mat.
Much of the information on soil clogging has been obtained from column
studies designed to simulate a natural field clogging regime. Generally,
the studies use lysimeters with air tight walls, which create-anaerobic
conditions within the soil below the clogging mat. Walker, et_ ajU (l9T3a)
has shown that aerobic conditions exist under soil absorption systems
located in sand. Thus, most of the previous research has neglected to
acknowledge the impact of redox conditions in designing laboratory experi-
ments to evaluate the dynamics of soil clogging.
Recent work has shown that clogging mechanisms in aerated and non-
aerated columns can be quite different. Magdoff, _et_ al_. (l9T^a, 197^b)
showed that clogging was not delayed in aerated sand columns. The
resistance of the clogging mat in soil columns which were aerated by per-
forating the column sidewall were shown to more closely reproduce the
resistances measured below four clogged absorption fields in sands
(Magdoff and Bouma, 197^)- Thus, some of the reported work studying the
dynamics of soil clogging is of limited applicability to determining ac-
ceptable loading patterns.
To obtain the necessary information, column experiments were designed
which included column aeration as a variable (Perry and Harris, 1975).
The objectives of this study were to evaluate the dynamics of soil clogging
caused by continuous ponding with septic tank effluent and the dynamics
of infiltration rate recovery upon resting. Respirometric techniques
were also used to determine decomposition kinetics of the clogging mat to
aid in identifying parameters affecting the restoration of the infiltrative
surface.
Eighteen soil columns were constructed by uniformly packing plexiglass
columns (10 cm diameter x 60 cm long) with 50 cm of sand (U.C. = 1.99?
B-95
-------
E.S. = O.lU) obtained from the C horizon of a Plainfield loamy sand (Typic
Udipsamment) (See Figure B-53). Saturated hydraulic conductivity (Ksat)
values were approximately 500 cm/day which represented field conditions.
Stones were placed on the sand surface to prevent disruption of the surface
crust during effluent application. Soil water tension was monitored with
a flow-through tensiometer placed 5 cm below the soil surface.
To simulate the natural aerobic field situation beneath a seepage bed,
9 columns were subcrust aerated (SA) by perforating them with numerous 3 mm
diameter holes distributed 5 to 10 cm below the sand surface. The remaining
9 columns were maintained under anaerobic conditions and designated nonsub-
crust aerated (NSA).
Fresh septic tank effluent was obtained weekly from a residential house-
hold and stored in the laboratory at U°C until used. Average effluent
characteristics over the length of the study are presented in Table B-ll.
To apply the waste liquid, a Mariotte siphon apparatus was used to maintain
a constant head of 3 cm over the column surface.
During the clogging phase, effluent was applied at a rate of 127 cm/week
(It.5 gpd/ft2), until such time that clogging had intensified, reducing flow
rates. At that time, six of the columns were subcrust aerated. Continuous
effluent application was then initiated in all columns. The columns were
PLEXIGLASS COLUMN
0-
-5-
-35-
-45-
—EFFLUENT RESERVOIR
2 5 LITER
-PONDED EFFLUENT
-GRAVEL, 2 cm DIAMETER
-FLOW-THRU TENSIOMETER
-SUBCRUST AERATION
HOLES
-SAND FILL
GLASS WOOL
\ i| -VU RUBBER STOPPER
N DRAIN TUBE
D
Figure B-53.
Soil column schematic for respirometric studies
of soil clogging (Perry and Harris, 1975)
B-96
-------
TABLE B-ll. SEPTIC TANK EFFLUENT CHARACTERISTICS USED IN RESPIROMETRIC
STUDIES (Perry and Harris, 1975)
Property
Chemical oxygen demand
Biological oxygen demand
Total organic carbon
Total inorganic carbon
Volatile suspended solids
Total suspended solids
Total volatile solids
Mean
257
13k
10k
108
28
k2
303
RE
lUg,/ -Li — "
113
85
25
81
7
7
lUo
inge
- 39k
- 220
- 15U
- 105
- 60
- 72
- 1+60
maintained under this regime for an additional 7 to 9 months. After 8 to 10
months of clogging, infiltration rates were measured using tensiometry and
cumulative inflow and outflow from the columns. The rates were found to be
1 to 1.5 cm/day. At this time the unclogging phase was initiated whereby
effluent was no longer applied and columns were allowed to aerate. Infil-
tration recovery was monitored by adding effluent and measuring subcrust
water potential and inflow and outflow rates.
Also during this time samples of the clogging mat were removed from the
replicate NSA and SA columns analysis. Organic carbon was determined by
the autoclave, mercuric sulfate and silver sulfate modification of the reflux
dichromate oxidation method (Allison, 1965; Standard Methods, 1971; Unluturk,
197*0. Processing of crust samples for subsequent Q£ uptake analysis
involved sieving, gravimetric measurement, moisture adjustment to 50% maxi-
mum retentive capacity and reaction flask equilibration. Samples were incu-
bated at 22° C in a Gilson Differential Respirometer, Model SGR 20. Nitrogen
analysis was performed on the crust samples both before and after incubation
to correct oxygen uptake for nitrification: Total N was measured by the
#2 simimicro Kjeldahl digestion procedure (Bremner, 1965a), and NH^-N, NCU-N
and NOg-N by steam distillation (Bremner, 1965b).
The surface crust was removed in 1-cm sequential units and infiltration
through the freshly exposed surface was measured each time. This enabled
isolation of the regions within the crust responsible for clogging. The
complete history of a single column is shown in Figure B-5U.
Typical loading and flow characteristics for NSA and SA columns during
the clogging phase are presented in Figure B-55 and Tables B-12 and B-13.
The initial response to effluent application was a rapid reduction in
infiltration, followed by an increase in flow rate of short duration at 30
days and gradually culminating in an asymptotic decline in infiltration.
B-97
-------
S o.i
60
120
180 240 3CXT 2S 50 7B 100
TIME, day
Figure B-5^. Soil water potential and infiltration rate during
clogging, resting and crust removal phases for
a single column (Perry and Harris, 1975)
1000
ee.
cc.
100
10
O.I
-STEADY STATE
SUBCRUST AERATION
INITIATED
°» .•'
ANAEROBIC (II columns)
o SUBCRUST AERATED (6 column*)
-
0
°o" oej'o'o
° °° o S o 8 o
1 1
60 120
TIME, day*
«'o'?
8 °o 8 o ° §tg.g j8
i i
180 240
i
300
Figure B-55•
Infiltration rate reduction during clogging
phase (Perry and Harris, 1975)
B-S
-------
TABLE B-12. EFFECT OF CONTINUOUS EFFLUENT PONDING ON FLOW CHARACTERISTICS
OF A SUBCRUST-AERATED COLUMN OF PLAINFIELD SAND (COLUMN 3)
(Perry and Harris, 1975)
Cumulative loadl
Time
days
1
72
ll*
21
283
35
1*2
1*9)
5o
63^
70
77
81*
91
98
105
112
119
126
133
ll*0
ll*7
151*
161
168
175
182
189
196
203
210
217
22U
2315
23?
1 BOD:
VSS:
FSS:
Effluent
cm
26
127
25!*
381
508
635
762
889
1016
1096
1110
1125
1138
1152
1162
1171
1181
1191
1203
1227
1259
1288
1313
1327
1350
1361*
1377
1389
1398
ll*07
11*16
ll*22
ll*30
11*36
BOD VSS FSS
1*000 520 120
8067 880 120
8977 1100 130
91*83 1263 232
11163 1621* 366
12615 1998 512
Flov
rate
cm/ day
5^5
1*15
225
321
266
120
6.8
73
21*
5.1*
2.3
2.2
2.1
1.6
2.1
1.1*
1.3
1.1*
1.1*
l.S
3.8
1*.2
2.9
U.2
2.1
3.3
2.1
1.8
2.0
1.3
1.1*
1.2
1.0
1.2
1.0
Subcrust
moisture
potential
mbars
—
—
—
—
—
—
36
30
1*2
—
—
—
21*
29
28
30
31
32
31
30
26
27
28
21*
28
25
—
29
29
31
30
31
32
31
33
Standard 5-day biochemical oxygen demand
Volatile suspended solids.
Fixed (inorganic) suspended solids.
!: Appearance of black
vertical streaks below crust
, 8-12 cm
in length.
. Subcrust tensiometer installed.
c Subcrust aeration initiated.
g Continuous effluent
Aerobic rest regime
infiltration initiated.
initiated.
B-99
-------
TABLE B-13. EFFECT OF CONTINUOUS EFFLUENT PONDING OF THE FLOW CHARACTERIS-
,TICS OF A NONAERATED COLUMN OF PLAINFIELD SAND (COLUMN 11).
(Perry and Harris, 1975)
Time
H Q VC
U.cLj b
1
1
ll+
21
28
35
1+2
U9
56
63
TO
TT
81+
91
98
105
112
119
126
133
ll+O
1UT
15U
161
168
175
182
181+
196
203
1 BOD:
Cumulative load
Effluent BOD VSS FSS
26
51
102
152
203 151U 11+1+ 0
330
^57 .
581+
711 71+96 1061+ 1+1+
838
965
1092
1219 151+71 31+63 15^U
13i+6
1U73
1600
1727
1805 5016 2122
1932
1963 20100
1993
2010
2027
20UO
2052
2066
2078
2090
2103
2158 21+685 6216 2783
Standard 5-day biochemical oxygen demand.
T»_T _J_J T _ __._u.3_.a __T J 3 —
Flow
rate
rtVM / A QTT
CIU/ CLcLjr
525
1+50
320
200
100
90
100
50
35
53
36
18
17
18
27
16
15
5-9
13
1+.3
1*.2
2.6
2.2
1.7
1.7
2.0
1.8
1.7
1.8
1.9
Subcrust
moisture
potential
TTlT"M> T*Q
ZuUcLTS
3^
31+
32
37
38
38
39
l+l
1+3
1+3
k3
38
UU
1+1+
1+1+
1+5
1+6
U5
1+6
1+6
1+6
FSS: Fixed (inorganic suspended solids).
B-100
-------
The typical S-shaped curve (Figure B-55) resulting when infiltration is
plotted against time, has been previously identified by Allison (19^7)»
McGauhey and Winneberger (1965) and Robeck, et_ a3-_. (196^).
Six columns were subcrust aerated when continuous ponding occurred
to see what effect lateral (>> diffusion had on crust development. Prior to
the time of column perforation, a black ferrous sulfide coloration occurred
throughout the column. In response to aeration5the black coloration
disappeared except for the upper 0.5-cm crust layer. This was followed
by the formation of an amorphous light brown layer, 0.5 cm thick with a
sharp irregular boundary, directly beneath the upper black surface layer.
There was an immediate abrupt decrease in the infiltration rate (Table B-12
and Figure B-55) commensurate with the formation of this brown amorphous
layer. For the duration of the study, there was no change in the appearance
of the columns. In contrast, the NSA columns remained black and underwent
a more gradual decline in infiltration (Table B-13 and Figure B-55). These
results indicate that the initial response to aeration is intense clogging,
probably resulting from the production of microbial slimes and/or biomass
or the formation of oxidized iron compounds directly below the black surface
crust layer.
Perforated studies by others (Magdoff, et al., 197^a) indicate that
subcrust moisture tensions in columns are lower than in anaerobic non-
perforated columns at the time of initial clogging. The more intense crust
development within the initial clogging phases of aerated columns is con-
sistent with the observation by Perry and Harris (1975) of lower infil-
tration rates in aerated columns. These contrasting results between SA and
NSA systems also show that an effluent application regime that involves
alternating aerobic-anaerobic conditions on a short term basis, causes
rapid clogging and that infiltration capacity can be extended by maintaining
an anaerobic environment. This is consistent with observation by Kropf,
et_ al^. (1975) that continuously flooded soils,more often than not, infil-
trated more effluent than intermittently flooded soils.
Figure B-^g shows the cumulative effluent load for SA and NSA columns
during the clogging phases. In the 6 month period immediately after sub-
crust aeration, the NSA columns processed 3 times more effluent volume than
the SA columns.
An equilibrium infiltration rate of 1 to 1.5 cm/day was approached
in both SA and NSA systems at 5 and 7 months, respectively. These infil-
tration rates were maintained throughout the duration of the clogging phase,
aside from occasional crust breakthroughs. These rates are consistent
with values reported by other researchers (Jones and Taylor, 1965; Kropf,
et_ al_., 1975; McGauhey and Krone, 1967; and Thomas, et_ ajU , 1966) and are
independent of aerobic or anaerobic conditions.
The &2 uptake by samples taken from the clogging zone followed a
general pattern that can be divided into 3 periods. There is an initial
period consisting of an immediate high rate of (>> uptake followed by a
second period of rapidly declining 02 uptake. The final period consists of
B-101
-------
§150
u!lOO|
u.
UJ
UJ
5 50
13
1
..•A
•
o SA
• NSA
o o
-00
o»
60 120 180
CLOGGING TIME, days
240
300
Figure B-56".
Cumulative effluent loading for NSA and SA
columns (Perry and Harris, 197^)
a very low, but uniform rate of 02 uptake. This general sequence is con-
sistent with respirometric observations by others evaluating soil metabolic
activity (Bhaumik and Clark, 19^-T; Parr and Norman, 196U) and sewage decom-
position (Jenkins, I960; Ludwig, et_ al_., 1951) • In Figure B-59 it can be
seen that the initial period generally lasted less than 2h hours, the
duration being longer for those samples with higher concentrations of
organic carbon. During this period,the intense Cg uptake is usually attri-
buted to the metabolism of readily available carbon. Crust samples from
NSA columns showed a very high rate ,(80 yl/gm/hr) of 02 uptake. In contrast,
the SA sample had a lower initial uptake rate of less than 20 ul/gm/hr.
Large and rapid changes in rates of 02 uptake were common during this period.
Higher maximum rates of uptake were observed from samples containing
greater organic carbon. These initial Op uptake characteristics indicate
that the microbial population is abundant, active, and immediately capable
of utilizing the available substrate. Most importantly, data by samples
obtained from anaerobic clogging regimes lasting 200 days indicate the
facultative biomass was responsible for the immediate, high initial C^ uptake.
Further, this reveals the absence of microbial inhibition which is often
associated with the accumulation of toxic reduced sulfur compounds from sewage
organics under anaerobic conditions.
The second period lasted 3 to h days, during which time 02 uptake by
both NSA and SA samples decreased rapidly. The rate of decline tended to
be greatest within samples of higher initial organic carbon content. Toward
the later portion of this period, rates approached a lower maintenance
level of 02 uptake. It is generally assumed that the initiation of the
second period is due to the exhaustion of an essential or readily available
nutrient. The final period consists of a uniformly low rate of 02 uptake
B-102
-------
20
15
K
o o SA
• • NSA
10
20
ISO
200
INCUBATION TIME, days
Figure B-57.
Rate of C>2 uptake by crust samples from NSA and SA
columns (Perry and Harris, 197*0
and may reflect the maintenance level of metabolic activity. The rate curve
shows an assymptotic decline during this period and tends to approach the
level of endogenous G£ uptake at approximately 60 days. Millar, et al.
(1936) observed that rates by amended systems approached those of endogenous
systems between 120-190 days.
First-order organic carbon decomposition kinetic data (McCabe, I960;
Eckenfelder, I960), extrapolated from 02 uptake data based on initial organic
carbon content (Tables B-lU and B-15) are plotted in Figure B-58. Rate
constants for different biodegradable fractions were similar to those ob-
tained from previous incubation studies using crust samples from clogged
columns under a variety of conditions (Daniel and Bouma, 197*+; Magdoff,
et al. , 197**a; Magdoff, et_ al. , 197^b; Unluturk, 197*0. However, it was
not possible to relate different biodegradable fractions to any specific
infiltration trend because of saturated hydraulic conductivity variability
between columns.
Figure B-59 shows the cumulative 02 uptake for SA and NSA column crust
samples during the resting phase. The decomposition is extrapolated from
Og uptake data, corrected for nitrification, and based on initial organic
carbon and an assumed respiratory quotient of 1. The cumulative values
reflect the high initial rates of 02 uptake.
The infiltration rates during the resting sequence are presented in
Figure B-60. All columns showed a 100 fold increase in the infiltration
rate within the initial three weeks of resting. These infiltration trends
are consistent with values reported in the literature (Thomas, et al.,
1966).
B-103
-------
2.0
50
100 ISO 50
RESTING TIME , days
100 150 200
Figure B-58. First order organic carbon decomposition for SA and NSA
columns (Perry and Harris, 1975).
f
I 300
E
o" 100
Ld
-J
0-1 cm ZONE OF SA COLUMN 5
(2.4g VSS LOAD)
eo!
40:
20
UJ
o
40 80 120
RESTING TIME, days
160
^x
s
40 80 120
RESTING TIME, day*
Figure B- 59. 02 uptake rate by samples from SA and NSA
columns during resting phase (Perry and
Harris, 1975).
B-1C&
-------
TABLE B-ll*. 02 UPTAKE BY CRUST SAMPLES FROM A SA COLUMN
DURING RESTING (Perry and Harris, 1975)
Oxygen uptake
Cumulative organic C decomposition
Incubation
time
hr
5
6
8
11
26
27
1*9
97
100
ll+l+
1U5
ll+8
169
176
186
19!*
270
271
289
292
306
312
313
315
317
319
322
330
336
361
1+1*0
652
1058
1395
181*3
191*0
2022
3096
1*200
51*23
Rate
10~3um/g/hr
11 1*3
911
969
15k
696
6l6
1*61*
303
295
277
301*
286
295
281
263
277
219
165
152
183
138
129
125
11*7
13U
156
129
125
116
111
89
63
38
25
2k
19
22
20
17
15
Cumulative
Um/g
6.0
6.5
8.1*
10.1*
20.9
21.1*
33.1*
51-9
52.9
65.3
65.7
66.6
69.8
71.9
71*. 6
76.6
95.1*
95.7
98.5
98.9
101.3
102.0
102.2
102.5
102.8
103.0
103.1*
10U.5
105.2
108.0
115-9
132.1
152.3
162.9
173.1
175-2
176.9
199.1*
219.6
238.7
Total amount
decomposed
mg/g soil
.07
.08
.10
.12
.25
.26
.1*0
.62
.63
.78
.79
.80
.83
.86
.90
.92
l.ll*
1.15
1.18
1.19
1.21
1.22
1.23
1.23
1.23
1.2k
1.2k
1.25
1.26
1.30
1.39
1.59
1.83
1.95
2.08
2.10
2.12
2.39
2.61*
2.81*
Amount left of
initial organic C
%
98.1*
98.3
97-8
97.3
91*. 6
91*. 5
91.3
86.5
86.2
83.0
82.6
82.6
81.8
8l.2
80.5
80.0
75.3
75.1
71*. 3
71*. 2
73.6
73.1*
73.1*
73.1*
73.2
73.2
73.1
72.8
72.6
71.8
69.8
65.6
6o.k
57.6
51*. 9
51*. 3
53.9
1*8.2
1*2.8
37.8
Log %
1.99
1.99
1.99
1.98
1.97
1.97
1.96
1.93
1.93
1.91
1.91
1.91
1.91
1.90
1.90
1.90
1.87
1.87
1.87
1.87
1.86
1.86
1.86
1.86
1.86
1.86
1.86
1.86
1.86
1.85
1.81*
1.81
1.78
1.76
1.71*
1.73
1.73
1.68
1.63
1.58
Initial organic carbon = l*.6o mg/g.
B-105
-------
TABLE B-15. 02 UPTAKE BY CRUST SAMPLES FROM A NSA COLUMN
DURING RESTING (Perry and Harris, 1975)
Oxygen uptake
Cumulative organic C decomposition
Incubation
time Rate
hr
6
26
1*9
97
ikQ
170
192
270
321
331
350
369
k29
kkQ
652
1058
1395
18U3
19^0
2022
3096
k2QO
5^23
10 3ym/g/hr
2U19
2205
661
1009
290
156
165
156
103
9k
85
80
76
63
5^
38
28
2k
18
23
15
11
8
Cumulative
um/g
20.0
66.3
9U.1
133.2
163.3
168.2
172.3
18U.8
191.0
191-9
193.6
195.2
199.8
201.1
213.0
231. k
2k2 . k
25^.0
256.0
257.6
278.2
282.5
293. U
Total amount
decomposed
mg/g soil
0.2k
0.80
1.13
1.60
1.96
2.02
2.07
2.22
2.29
2.30
2.32
2.3k
2.39
2.U1
2.56
2.78
2.91
3.05
3.07
3.09
3.3)1
3.39
3.52
Amount left of
initial organic C
%
97.1
90.0
86.3
80.6
76.2
75.^
7^.8
73.0
72.1
71.9
71.8
71.5
70.8
70.6
68.9
66.2
6^.6
62.9
62.6
62. k
59-^
58.8
57.2
Log %
1.98
1.96
1.9k
1.91
1.88
1.88
1.87
1.86
1.86
1.86
1.86
1.85
1.85
1.85
1.8U
1.82
1.8l
1.80
1.80
1.79
1.77
1.77
1.76
-1- Initial organic carbon = 6.85 mg/g.
No increase in infiltration rates occurred during a 1 cm sequential
removal of 6 cm of surface crust in the NSA columns. The apparent in-depth
crust development is a result of anaerobic conditions and/or the higher
amounts of effluent application prior to resting. In contrast, removal of
the 0-1 cm surface crust in SA columns resulted in an additional 13 percent
increase in the infiltration rate, showing that thin crust with high
crust resistance developed within the surface region of aerobic columns.
The results of this study indicate that substantial differences exist
regarding the nature and mechanisms involved in clogging and resting-induced
infiltration surface restoration between aerated and non-aerated columns.
This has implications with respect to extrapolation of data and conclusions
derived from non-aerated column experiments to field conditions in coarse
textured soils where aeration below the clogging mat usually prevails.
Non-aerated columns clogged slower than aerated columns but infiltration
B-106
-------
1000
u
SA
oCOLUMN2 (l.6g) ^COLUMN 3(2.0g)
-a COLUMN 4(5.9g) • COLUMN 6(2.
NSA
o COLUMN 7(6. Ig) A COLUMN 9(6.1 g)
irvvj_ DCOLUMN 11(6.2) 'COLUMN 14(5.7g)
1000 ~ "COLUMN 15 (6.lg)
40 80 120
RESTING TIME (days)
160
I
40 80 120
RESTING TIME (days)
160
Figure B-60.
Infiltration rate recovery for SA and NSA
columns during resting phase. (Values in
parentheses are cumulative volatile
suspended solids load for the respective
column) (Perry and Harris, 1975)
rate recovery during resting vas more rapid in the aerated columns (Perry
and Harris, 1975)- Therefore, extrapolation of data from laboratory columns
for recommending design and operational requirements of soil absorption
fields must be done with care.
The aerated column studies indicate that effluent application regimes,
characterized by alternating anaerobic-aerobic conditions on a short term
basis (dosing and short cycle alternating seepage systems),could result in
reduced infiltration associated with the formation of an intense crust
directly below the surface which develops during the aerobic (resting)
phase. Once clogged, restoration of the infiltrative surface by resting re-
quires at least 3 to U weeks in sands. This appears to be sufficient time
to decompose 30 to 35 percent of the organic carbon present in the mat and
reestablish acceptable infiltration rates (Perry and Harris, 1975). This
implies that dosing and resting frequencies must be selected with care to
prevent excessive clogging. It is yet unknown what these frequencies should
be.
Design of Soil Absorption Systems
If a septic tank-soil absorption system is to operate satisfactorily,
the soil must continue to absorb wastewater at an acceptable rate over a
reasonable length of time. This would be a simple matter, if the pores in
the soil would remain open, but when wastewater is applied to the soil, a
clogging mat often forms at the infiltrative surface. The clogging mat
B-107
-------
becomes a "barrier to flow, restricting the movement of water into the soil
by closing the entrances to the pores. This is beneficial to a point, for
it enhances purification of the wastewater, but it does slow absorption.
Fortunately, the clogging mat will continue to transmit water, albeit at a
reduced rate. The flow rate seems to reach an equilibrium value when the
system is operated under uniform conditions. Thus, the problem becomes one
of managing the infiltrative surface to prevent the clogging mat from
becoming excessive by proper design and operation of the system.
Sizing the Infiltrative Surface—
Loading rates—Direct measurement of how the soil will respond to
continuous wastewater loading cannot be done practically, Instead, equil-
ibrium flow rates through clogged soils usually must be estimated from a
short term soil test. The test most commonly used is the percolation test.
It was first developed in 1926 by Henry Ryon in an effort to prevent septic
tank system failure by establishing a rational method of soil absorption
field design. Ryon plotted the loading rates of systems experiencing
problems in the New York area versus percolation rates measured in the soil
adjacent to the system (Federick, 19^8). An enveloping curve was drawn
to include these points. Separate curves were developed for tile fields
(trenches and beds) and cesspools. Ryon used these curves to estimate
soil absorption field loading rates for septic tank effluent (See Figure
B-6l). Adoption of this design procedure by the New York State Health
Department led to its wide acceptance since few other design criteria
existed.
Ryon's design curves were used with varied success for many years
throughout the United States. However, after World War II an increasing
number of families moved out to the suburban fringes of metropolitan areas
onto small lots beyond the reach of sewers. Failures of septic tank
systems became a common occurrence. This led to the reevaluation of Ryon's
percolation test by the U.S. Public Health Service as part of their broad
study of septic tank systems during the years of 19^7 to 1953 (Weibel,
et al., 19^9; Bendixen, et al., 1950; Weibel, et al., 195*0.
The Public Health Service investigated U5 tile fields in much the same
manner as did Ryon (Bendixen, _et_ al. , 1950). Of the systems investigated,
27 had no history of difficulties, 9 had a history of occasional surface
seepage while 9 had continuous problems. The results of this study, plotted
over Ryon's original curve (Figure B-6l) showed the curve to fit fairly
well, but the failure rate would be too high if the use of Ryon's curve
were to be continued. It was speculated that changes in sewage character-
istics since Ryon's original work and climatic factors different from
those of New York were influencing the infiltration rates (Weibel,
Bendixen and Coulter, 195M • The new data suggested that the equilibrium
loading rate was equivalent to a 9Q% reduction in the percolation rate.
This relationship was used in part to develop a new design curve (Figure B-6l)
(Weibel, Bendixen and Coulter, 195*0, which was later published with
further modifications (See Table B-l6) in the USPHS Manual of Septic Tank
Practice (1967).
B-108
-------
]. RYON DATE
POINTS-*
Q
UJ
O.
Q.
Q
<
O
m 9 —
LINE USED
LINE INCLUDING ALL
A HISTORY OF NO DIFFICULTIES
A HISTORY OF OCCASIONAL SEEPAGE
x HISTORY OF CONTINUOUS DIFFICULTIES,
MANUAL OF SEPTIC TANK PRACTICE (1967)
U.S.PH.S.
SURVEY
i- FIELD
DATA
10 20 30 40 50 60 70 80 90
TIME FOR WATER SURFACE TO FALL ONE INCH, MinutM
x-i
A-A-
100
Figure B-6l.
Relationship of tile field loading rates to percolation
test rates (after Bendixen et_ al., 1950)
In addition to decreasing Ryon's recommended maximum loading rates,
other significant changes were made. Loading rates were expressed in
terms of required absorption area per bedroom served, rather than square
feet per capita or gallons per day per square foot. This change required
that the potential future use of the home be designed into the system,
rather than basing it on present use. Also, it was recommended that soil
absorption systems not be permitted in soils with percolation rates slower
than 60 minutes/inch and seepage pits not be used where the percolation
rates are slower than 30 minutes/inch.
The revised design loadings alleviated the problem to some degree, but
many failures still occurred which could not always be correlated to soil
type or loading rate. Some of the failures could certainly be attributed
to poor construction techniques or lack of septic tank maintenance by the
owner, but many others indicated inadequacies of the percolation test
itself, which is highly variable. Tests run at the same site by the same
technician have been shown to vary as much as 90 percent (Bouma, 1971).
B-109
-------
TABLE B-16. ABSORPTION-AREA REQUIREMENTS
FOR INDIVIDUAL RESIDENCES
(Manual of Septic Tank Practice, 196?)
Percolation rate (time)
required for water to
fall one inch
in minutes)
Required absorption
area, in sq. ft. per
bedroom, standard
trench, seepage beds,
and seepage pits
1 or less
2
3
h
5
10
15
30
60
TO
85
100
115
125
165
190
250
300
330
B-110
-------
Modifications of the percolation test have "been tried in an attempt
to reduce variability but they have met with little success (Weibel, et al.,
19*19; Bendixen, e_t al., 1950; Weibel, e_t al., 195^; Winneberger, et_ al_.,
I960; Bouma, et_ aJ^., 1972). Other attempts have been made to correlate
loading rates to specific soil properties, such as the saturated permeability
(Healey and Laak, 197^; Bouma, et_ al., 1972) or soil texture sieve analyses
(Norwegian Department of the Environment, 1975), but while these may reduce
the variability of the test, interpretation still must rely on an empirical
relationship to arrive at an acceptable design loading rate. Saturated
hydraulic conductivity tests do not reveal how the soil will conduct waste-
water under prolonged loading because the clogging mat restricts liquid
movement, with the effect that the soil below the mat is unsaturated. Thus,
the flow rate through the soil is governed by the soil's unsaturated
hydraulic conductivity which will vary with texture, structure and mineralogy.
Soil texture sieve analyses also give limited insight to the percolative
capacity of the soil because structure and mineralogy are not taken into
account.
With no reasonably simple alternative to determine the equilibrium
infiltration rate of soils under wastewater application, the percolation
test continues to be favored. However, other information, such as soil
borings and soil maps, is often used to increase its reliability. In light
of this, Machmeier published an extensive literature review to determine if
more recent research and field experience since the publication of the
Manual of Septic Tank Practice (1967) would suggest modified loading rates
(Machmeier, 1975)- His recommendations departed little from the Manual of
Septic Tank Practice (1967), but they represent the most current design
loadings (See Table B-17).
If the soil's ability to accept liquid during wastewater application
is to be accurately predicted, consideration of unsaturated flow phenomena
due to soil clogging mats or compaction is essential. Clogging mats or
compacted soil layers of progressively higher resistances will allow
progressively lower rates of infiltration through the soil. While a method
does not yet exist to measure this rate directly, it can be done indirectly
with some accuracy by use of Darcy's Law:
Q = KAdH
dZ
in which Q = flow rate (cm3/day); K = hydraulic conductivity (cm/day); A =
cross-sectional flow (cm2); H = gravitational + matric potentials (cm);
Z = vertical distance from datum (cm); and dH/dZ = hydraulic head gradient
(cm/cm) (Bouma, 1975)-
The hydraulic conductivity, which is the one-dimensional flow rate through
a unit area under a unit hydraulic gradient, is a reliable measure or any
saturated or unsaturated soil to accept and conduct liquid. The crust test
was developed for field measurement of K values in terms of the soil
moisture potential. Figure B-6"2 presents the general K-curves developed
for the major textural groupings in Wisconsin. These curves relate K
to the soil moisture potential. Continued research may result in different
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B-112
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groups at a later date. Through the use of tensiometry, the soil moisture
potential and gradient can be measured. This technique does not require
disruptive removal of soil samples and, therefore, is very suitable for
continuous in situ monitoring of moisture conditions in soil surrounding
absorption systems. Thus, the moisture potential and its gradient measured
in situ can be translated into a flow rate by using Darcy's Law (Bouma,
1975).
This relationship between hydraulic conductivity and soil moisture
potential can be used to provide sizing criteria for conventional septic
tank systems. Assuming steady infiltration through a barrier of semi-
infinite length into soil, the flux through the barrier, Q^, should equal
the flux in the underlying soil, Qs:
= Qs
or
(dH) =
Wb
in which K and K
underlying soil respectively and
(Bouma, 1975)-
are the hydraulic conductivities of the barrier and the
the hydraulic gradient in both materials
The hydraulic gradient in the soil is approximately unity
1000- 245 -
_ 100 -
I
X
o
10-
t-
o
O
O
1.0-
0.1-:
20 40 60 80 100
SOIL MOISTURE TENSION (MBAR)
ORYIN6 ^
Figure B-62.
Hydraulic conductivity (K) of the major soil texture groups
in Wisconsin as a function of soil moisture tension
measured in situ with the crust test procedure (Bouma, 1975)
B-113
-------
under steady infiltration (Baver, et_ al_. , 1972):
This permits the equilibrium loading rate to be estimated from measured
soil moisture potentials under operating systems when K-curves for the
underlying soil are available.
Moisture potentials were measured under several ponded conventional
septic tank-soil absorption systems to determine equilibrium flow rates
through clogging mats in different soils (Bouma, 1975; Bouma, et_ al., 1972;
Bouma, et_ al . , 1975a; Magdof f and Bouma, 197^; Walker, et_ al . , 1973a). The
tensiometers consisted of 5 cm long porous cups attached to 2 cm diameter
plastic tubing. These were connected to mercury manometers with fine
tubing (See Figure B-63). Small excavations were made adjacent to ponded
systems and the tensiometers were installed at different points in the
soil below and to the side of the systems. Measured potentials were used
to estimate infiltration rates into the soil through the bottom and side-
walls of the system, using the appropriate K-curve. Where direct measurement
of moisture potentials was not possible, soil samples were taken next to the
bed to obtain moisture contents, which were translated into moisture
Figure B-63.
In situ measurement of soil moisture tensions in soil adjacent
to subsurface seepage systems. Porous cups inserted in the
soil are connected through fine tubing with a mercury
reservoir. Moisture tensions are derived from the mercury
rise along a calibrated scale (Bouma, et al., 1972).
B-114
-------
potentials using moisture retention curves (Bouma, et_ al_., 19T2). The
moisture potentials were used to obtain K-values from K-curves derived from
the particular soil found at each site, rather than referring to the
general curves shown in Figure B-62•
This technique is valid if the water table is deep and the flow in the
underlying soil is vertical and one-dimensional under unit gradient. These
conditions are closely approximated immediately under the clogging mat some
distance from the edge of the system. However, in most cases it was
necessary to make measurements 5 to 10 cm below the mat and near the edges
of the absorption areas because of difficulties in excavation. In this
location, flow might not be one-dimensional but diverging with the effect
that the gradient would be greater than unity. Thus, in equating K to Q^
as in the previous equation, the estimated flow rate would be less than the
actual flow rate. This results in a conservative estimation of the in-
filtration rate.
Characteristics and performance indicators based on in situ monitoring
data for 12 septic tank-soil absorption systems are presented in Table B-l8.
All systems, except as noted,used 10-cm perforated pipe to distribute the
septic tank effluent in the absorption field by gravity. Thirty centimeters
of gravel lay under the pipe.
Hydraulic characteristics of the soil in terms of K-curves could be
broadly classified into four groups as shown in Figure B-62. Results of
the studies presented in Table B-18 are discussed for each group.
Conductivity Type I (sands)—Eleven conventional systems were investi-
gated in this soils group. All those over 9 months of age were found to be
ponded due to clogging of the infiltrative surface (Bouma, et_ al_. , 1972).
Four were selected for additional monitoring of the moisture tensions below
the clogging mat. Results of this monitoring showed that moisture tensions
and associated flow rates in soil surrounding clogged trenches or beds were
not very different for the different systems, despite their differences in
system age. This would seem to indicate that a mature clogging mat is es-
tablished early in the system's life and that flow rates through the mat
change little as the system ages. The results also show that clogged sands
accept significant quantities of septic tank effluent through both bottom
and sidewall surfaces. However, the hypothesis that sidewalls are more
effective than bottom areas as infiltrative surfaces (McGauhey and Winne-
berger, 1965) is not supported by these data. The choice of which surface
should be favored in design may depend on the local climate.
Based on these data, 5 cm/day (1.2 gpd/ft2) is recommended as a maximum
loading rate of the bottom area for systems with 30-cm (12 inch) sidewalls
constructed in sands (Bouma, 1975). This rate compares closely with that
commonly used when assuming 150 gpd/bedroom (See Table B-17). It is
further recommended that the effluent be applied uniformly over the entire
bottom infiltrative surface in four or more daily doses, particularly
during system start-up, if bacterial and viral contamination of a shallow
water table is a concern. The uniform application in small volumes will
insure unsaturated conditions in the sand necessary for good purification.
B-115
-------
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B-116
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Conductivity Type II (sandy loams; loams)—Soils of this type have
rapid percolation rates initially but they have a tendency to clog quite
severely. This may "be due to their particular pore size distribution and
structural instability. Relatively low clay contents do not allow signifi-
cant swelling and shrinking of the soil necessary to form structural
units or peds with associated interpedal cracks. Tubular worm and root
channels are formed, but they tend to be more unstable and much less
permanent than those formed in clayey soils. Thus, the packing pores between
particles, which are much finer than in the sands, are the principal voids
through which the water moves (Bouma and Anderson, 1973). The finer pores
may result in greater accumulation of solids at the infiltrative surface
and the development of anaerobic conditions in the clogged layer due to the
reduced air diffusion compared to sandy soils (Magdoff, et_ alU , 197^a).
Seven operating systems were investigated in these soils, and all were
ponded with septic tank effluent. Systems 5, 6 and 7 were selected for
more detailed study (See Table B-l8). The moisture tensions measured below
the bottoms of the systems increased with increased ponding depth within
the systems indicating that the clogging mat resistance increased with
ponding depth. The estimated rates through the bottom areas varied from
0.1* cm/day (0.09 gpd/ft2) to 1.9 cm/day (0.^5 gpd/ft2). The estimated rates
through the sidewalls were similar.
These data indicate that relying on the percolation rate alone for
sizing the system is not sufficient, for soils of this type clog much more
easily than the percolation rate would seem to indicate. To maintain
reasonable infiltration rates,the data further suggest that ponding levels
within the system should be kept to a minimum.
This finding is contrary to what has been reported by others (Healey
and Laak, 197^i Kropf, et. al., 1975)- Kropf, et_ al., (1975, 1977) found
that during 70-day laboratory column studies, increasing the ponding depth
over the infiltrative surface increased the amount of wastewater absorbed,
but not as great as would be predicted by Darcy's Law. Increasing the
ponding depth in finer textured soils was not as effective (Kropf, et al.,
1975). This fact was attributed to the nature of the stresses placed on
the mat which would have more of a disruptive effect in sands because of
the poor supportive matrix due to the large pore size. If the tests had
been run longer, however, the increased infiltration rate may have been
found to be temporary. This transient increase is suggested by the more
recently published data (Kropf, et_ a^., 1977)- If true, these data would
confirm that increasing ponding depths lead to a corresponding increase in
clogging mat resistance.
To reduce ponding levels, intermittent periods of aeration between
applications should be provided to allow aerobic decomposition of the
clogging mat. To test this hypothesis,one trench of System 5 was drained
and allowed to dry before wastewater was reapplied in once per day dosings
(System 5A, Table B-l8). After several months of operation in this mode,
the moisture tensions below the clogging mat had dropped from 80 mbar to
60 mbar indicating the mat was passing more liquid. When the operation
B-117
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returned to continuous application,the moisture tensions again increased
to 80 nibar (Bouma, et^ al_., 1972).
Absorption fields designed for bottom area loadings of 3 cm/day (0.7
gpd/ft2) with 30-cm (12-in) sidewalls have functioned well in Wisconsin.
Trenches are preferred to beds, with once daily dosing recommended if this
rate is used (Bouma, 1975). This rate is somewhat lower than design rates
used elsewhere (See Table B-17).
Conductivity Type HI (silt looms, some silty olay loams)—Although
these soils are more finely textured than either Type I or Type II soils,
their more strongly structured nature can maintain relatively high infil-
tration rates if the system is constructed and managed properly. Nine
systems were investigated (Systems 8-l6, Table B-l8). Four of these systems,
all bed designs, were failing or about to fail. The cause of the failures
were traced to construction problems (Bouma, 1975; Bouma, et_ al. , 1975a).
Construction of beds often involves several passes over the infiltrative
surface by machinery while excavating and placing of the rock. This
practice can result in severe compaction and puddling if the soil is wet,
because these finer textured soils exhibit a plastic consistancy over a wide
range of moisture contents, which occur naturally in the field (Bouma, 1975).
Observations made at the installations indicated that excavating equipment
had been driven over the bottom areas of the beds during construction. The
presence of a compacted layer was confirmed by moisture tension measurements
taken below the beds. These indicated a restricting layer with a resistance
reasonably close to resistances through layers of manually puddled fine
silty soil materials used in the original version of the crust-test procedure
(Bouma, et. al_., 1971; Bouma, et_ al., 1975a). The other five systems studied
were functioning satisfactorily and did not contain ponded effluent. Two
were beds both of which were dosed. Samples taken of the soil from the
bottom of the systems showed well exposed soil structure with open planar
voids between peds as well as worm and root channels. The exposure of these
larger pores explains the lack of ponding. For example, one tubular root
channel with a diameter of only 2 mm (0.008 in.) can conduct 285 L/day
(75 gal/day) at a hydraulic gradient of 1 cm/cm (Bouma and Anderson, 1973).
This points to the importance of construction practices which minimize
damage to the structure of the soil.
The results from these investigations also demonstrate the advantages
of dosing. Systems 11 and 13 through l6 were all dosed by pumping effluent
through the distribution piping. Conventional 10-cm (U-inch) pipe,perforated
near the inverts, was used in each of systems 11, 13 and 14. System 15 used
10-cm (H-inch) pipe perforated at the crown of the pipe, requiring the pipe
to fill before discharging liquid, and System 16 used small-diameter pipe
with small orifices. These designs were used to achieve more uniform dis-
tribution. None of these systems were ponded, indicating that infiltration
rates were greater than the application rate. Since ponding did not occur,
it was necessary to estimate infiltration rates from the daily volume of
wastewater discharged (Bouma, et_ al_., 1975a). Bottom areas were the only
infiltrative surface in these instances. The reported infiltration rates in
Table B- for Systems 11, 13 and lU do not reflect the true rate, but merely
its minimum, because the loading could not be changed. To provide more
B-118
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flexibility in loading, Systems 15 and 16 were constructed in a deep fine
silty loess deposit overlying a calcareous permeable sandy loam glacial
till as experimental systems (Bouma, et_ al_. , 1975a). By dosing once daily,
uniformly over the surface, infiltration rates of 7.2 cm/day (1.8 gpd/ft^)
and 6.8 cm/day (1.7 gpd/ft^) were realized after more than 2 years of
operation. These rates are nearly three times those recommended in most
areas (See Table B-17). Excavations into the trenches revealed recent
worm and other fauna activity which left large vertical channels through
the infiltrative surface. Dosing and uniform distribution,with drying
periods under aerobic conditions between applications, may stimulate this
activity, as organisms seek the nutrients deposited at the infiltrative sur-
face. This would seem to suggest that while good construction practices
are necessary to expose an open infiltrative surface, periodic application of
effluent is essential to keeping the surface open. This is in opposition to
the conclusion reached by Healey and Laak (197^) and Kropf, et_ al_., (1975»
1977) who worked only with Type I and Type II soils.
While the data are not conclusive, they suggest that maximum permissible
loading rates would vary according to the method of distribution employed.
If once daily dosing were employed, maximum rates of 5 cm/day (1.2 gpd/ft^)
might be acceptable based on bottom area only (Bouma, 1975). Uniform
distribution would be crucial in this case to maintain unsaturated flow so
that deep penetration of pollutants through the large exposed pores will not
occur. If conventional gravity trickle distribution is used, the conventional
loading rate of 2 cm/day (0.5 gpd/ft^) should not be exceeded. In both cases,
shallow trench designs H5 to 60 cm (l8 to 2k in) deep are preferred because
the upper soil horizons are usually more porous and less subject to damage
during construction. Shallow systems also enhance evapotranspiration.
Conductivity Type IV (clays, some s-ilty etay loams}—Low conductivities
in these soils at saturation drop strongly in the 0 to 20 mbar tension
range due to the emptying of the interpedal voids and tubular channels as
in Type III soils (See Figure B-62). However, lower Ksat values indicate
the lack of many large pores. Thus, the soil itself, rather than the clogging
mat, becomes the dominant controlling factor (Bouma, 1975; Healey and Laak,
197*0.
Only two systems of this type were investigated. System 17 was observed
to be slightly smeared and compacted during construction while System 18
was installed under ideal conditions. Effluent from an aerobic treatment
unit was dosed into System 12 using pressure distribution.
Because soils of this type are severely limited, it may be more crucial
to maintain an open infiltrative surface to utilize the large interpedal
cracks and tubular channels. Dosing frequencies of once per day or longer
may promote soil fauna activity between dosings to maintain an open surface
(Bouma, et_ ajL_. , 1975a). If conventional gravity distribution is used, load-
ing rates of 1 cm/day (0.2 gpd/ft^) based on the bottom area only would seem
to be acceptable, assuming 33 percent of the flow would be through the side-
wall (Bouma, 1975). If expandable clays are present, a lower rate should
be used.
For a summary of recommended loading rates, see Table B-19-
B-119
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TABLE B-19. RECOMMENDED MAXIMUM LOADING RATES FOR SEPTIC
TANK SOIL ABSORPTION FIELDS BASED ON IN SITU
MEASUREMENTS1 (After Bouma, 1975)
Conductivity
Type
Soil Texture
Loading
Rate2 cm/day
(gpd/ft2)
Operating Conditions
II
III
IV
Sand
Sandy Loams
Loams
Silt Loams
Some Silty Clay Loams
Clays
5 (1.2)
3 (0.7)
2 (0.5)
5 (1.2)3
U doses/day
Uniform Distribution
Trenches or Beds
1 dose/day
Uniform Distribution
Trenches Preferred
Conventional Distribution
Shallow Trenches
1 dose/day
Uniform Distribution
Shallow Trenches Only
~ 1 dose/day
1 (0.2) Uniform Distribution Desirable
Shallow Trenches Only
Assumes that the high water table is > 90 cm (3 ft) below the infiltrative
surface.
2
Bottom area only.
3
Should not be applied to soils with expandable clays.
Bottom versus sidewall area—Both the horizontal bottom area and verti-
cal sidewalls of a subsurface soil absorption system can act as infiltrative
surfaces for wastewater absorption. When a conventional gravity system is
first put into operation, the bottom area is the dominant infiltrative sur-
face. However, after a period of wastewater application, this surface can be-
come clogged sufficiently to pond liquid above it, at which time the sidewalls
become infiltrative surfaces. Because the gradients and resistances of the
clogging mats at the two surfaces are rarely the same, the infiltration
rates will be different. Which surface would have the greatest infiltration
rate will depend on a number of factors. Vertical and horizontal hydraulic
conductivities and gradients in the soil, clogging mat resistances, and soil
moisture contents of the surrounding soil are factors that will effect the
direction and rate of liquid movement through the soil. Thus, the more
significant infiltrative surface may vary between sites. The objective in
design is to maximize the area of the surface expected to have the highest
flow rate.
B-120
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Based on investigations done at the University of California in
Berkeley, McGauhey and Winneberger (1965) have reported that the sidewall is
". . .by far the most effective infiltrative surface." They concluded from
various studies vith packed lysimeters (Winneberger, Saad and McGauhey,
196l) and columns (Winneberger, Menar and McGauhey, 1962) of Hanford fine
sandy loam, Yolo sandy loam, and Oakley sand that (l) suspended solids in
the effluent do not contribute to sidewall clogging, (2) rising and falling
liquid levels vithin the system allow alternate loading and resting of the
surface while the bottom is often continuously inundated, and (3) sloughing
of the clogging mat can occur during resting periods. Therefore, they
recommend that subsurface soil absorption systems should provide a maximum
of sidewall surface per unit length of trench and a minimum of bottom surface
(McGauhey and Winneberger, 1965).
The Manual of Septic Tank Practice (196?) recognizes the contribution by
the sidewall but recommends the bottom area as the principal infiltrative
surface. A statistical allowance for the sidewall is included in the
recommended bottom area per bedroom, assuming a 15-cm (6-in) vertical side-
wall (See Table B-1T). If deep trenches are used, the total bottom area of
the trench can be reduced by a factor determined by the relationship:
Percent of length of Standard Trench
[15-cm (6-in) sidewall] = ^ * j" 0. x 100
w + 1 + do.
where w = the width of the trench and d = the depth of the gravel below the
distribution pipe. While this gives credit for sidewall absorption, it assumes
that the infiltration rate is less than that of the bottom. No allowance is
made for deep beds.
The extent to which the sidewall becomes an infiltrative surface would
depend upon the prevailing hydraulic gradient and clogging mat resistance.
The hydraulic gradient is largely determined by the soil type and soil wet-
ness surrounding the system. At the bottom surface»the gravitational po-
tential, the pressure potential of the ponded water above, and the matric
potential of the soil below each contribute to the total potential of the
liquid, while at the sidewall the gravitational potential is zero since it
operates only vertically and the pressure potential of the ponded water
diminishes to zero as the liquid surface is approached. The lower hydraulic
gradient across the sidewall can be offset if the clogging mat is less
resistant. This would be expected since the rising and falling liquid
levelsjin effect, alternately dose and rest the sidewall as pointed out by
McGauhey and Winneberger (1965). Monitoring of operating absorption fields
by Bouma, et_ ajL. (1972), seems to confirm this fact. Estimated flow rates
through the sidewalls and bottom areas were not significantly different in
most cases though the hydraulic gradients did vary. However, in temperate
climates, frequent rainfall, particularly in the spring and fall, may reduce
the matric potential at the sidewall to low levels due to percolating
precipitation. During such times, the horizontal gradient could be reduced
to a very low level with the effect that the bottom surface becomes the only
B-121
-------
reliable infiltrative surface. Healey and Laak (197M recommend that in
temperate zones subsurface absorption systems be designed to function under
gravity potential only, because of the problems during wet portions of the
year.
To increase the hydraulic gradient across the sidewall, deep narrow
trenches could be constructed as recommended by McGauhey and Winneberger
(1965). However, this would diminish the advantages of shallow trenches
which enhance evapotranspiration and avoid construction in the deeper soil
horizons where puddling and compaction are often more likely. It might be
concluded that in humid regions systems should be designed on bottom area
while maximizing the sidewall by utilizing trenches rather than beds. In
more dry regions, with deep permeable soils, the sidewall area could be maxi-
mized at the expense of the bottom area.
Shallow versus deep absorption systems—Shallow soil absorption systems
offer several potential advantages over deep systems: l) the upper soil
horizons are usually more permeable than the deeper subsoil because of clay
migration to the deeper horizons and because of greater plant and soil fauna
activity; 2) evapotranspiration is greater; 3) the upper soil dries more
quickly than the subsoil so construction can proceed over longer periods of
the year with less smearing, puddling and compaction; and H) less excavation
is necessary, reducing the cost. Deep systems are desirable when the side-
wall is determined to be the better infiltrative surface, more permeable soil
exists with depth, or freezing is a danger during cold periods of the year.
Freezing of shallow absorption systems does not seem to be a problem,
even when frost penetration is quite deep. Weibel, et_ al_., (19^9) reviewed
the literature and made contacts with health authorities and plumbers in
the northern states to determine if failures of shallow systems due to
freezing were frequent. They concluded that carefully constructed shallow
systems H5 to 60 cm (l8 to 2.k in) in depth would not freeze even in areas
where frost penetration reaches 1.5 m (60 in), if the tile lines were gravel
packed, insulated under driveways or other surfaces usually cleared of snow,
and kept in reasonably continuous operation.
This was confirmed by a field study in which three adjacent trenches
were monitored for temperature. The trenches where each 75 cm (29.5 in)
deep, with 33 cm (13 in) of gravel placed below the distribution pipe. Four
centimeters (1.6 in) of gravel covered the pipe. Topsoil was filled over
the gravel to a depth of 38 cm (15 in) which brought the top of the system
10 cm (U in) above the original surface. Thermocouples were placed at the
top of the gravel, within the pipe, and in the natural soil beside the
trench 15 cm (6 in) above the trench bottom and 10 cm (U in) below the
trench bottom. Only Trench #2 was loaded by dosing once daily. The other
two trenches stood idle.
Temperatures have been monitored weekly since July, 1972. The winter
of 1976-77 was the most severe. Average daily ambient air temperature
remained below 0°C (32°F) from late in November, 1976 to early February,
1977. During much of this period,the average temperatures were between
B-122
-------
-18° and -26° C (0° to 15°F) (See Figure B-64), The temperatures in the
pipe and below the bottom of the unloaded trench dropped below freezing for
over a 6-week period as the frost penetrated the ground. However, in the
trench which was dosed daily with septic tank effluent temperatures remained
above freezing throughout this period.
Trench versus bed design—Though the seepage bed is often more
attractive than seepage trenches in terms of total land area requirements,
cost, and ease of construction for the same bottom area, it is less desirable
in terms of maintaining the infiltrative and percolative capacity of the
soil. This is particularly true in soils with significant clay contents
(>25$ by weight). The principal advantages of trenches over a bed are:
l) more infiltrative surface is provided for the same bottom area and 2) less
damage to the bottom infiltrative surface occurs due to compaction, puddling
and smearing during construction.
For the identical bottom areas, trench designs of absorption fields can
provide more than eight times the sidewall area. This can be of benefit
in preventing failure through clogging. In humid climates there may be
portions of the year that the sidewall looses much of its effectiveness for
absorption, which necessitates designing the system to function on bottom
area only. However, it is recognized that the sidewall is beneficial, and
it is certainly recommended to maximize it in any system (Bouma, 1975;
McGauhey and Winneberger, 1965).
In addition, the seepage bed design can cause severe damage to the
natural soil structure during installation. This is a particular concern in
clayey soils. Rapid absorption of liquid by the soil depends on a suitable
soil structure being maintained (Bouma, 1975; Bouma, et_ al_., 1975a). When
mechanical forces are applied to moist or wet soil, the structure is partially
or completely destroyed because clay particles in the soil are able to slip
relative to one another. This movement, referred to as compaction, puddling
or smearing, closes the larger pores between soil aggregates and those made
by roots, or burrowing soil fauna.
To construct a seepage bed, it is common practice to first scrape off
the topsoil using a front end loader and then return with a backhoe for
digging to final grade in an attempt to leave a fresh soil surface. However,
these two operations may require several passes over the bed area by the
construction machinery, often with heavy loads. When digging is complete,
trucks may be backed into the bed to unload aggregate, which is spread over
the bottom of the bed by machinery. After the distribution piping is laid,
additional gravel is placed over the pipe and covered with soil. By the time
the bed is completed, the soil structure may be destroyed.
This problem is further compounded when soil conditions are wet. A
busy contractor is unable to always schedule his work when the soil is dry,
so construction often proceeds when conditions are marginal at best. The
trench design reduces the severity of these problems because the construction
machinery is able to straddle the trench so that the future infiltrative
surface is never driven upon.
B-123
-------
80
70
60
50
40
30
20
10-
UJ
a.
S
UJ
-10
-20
-30
UNLOADED TRENCH _
AMBIENT AIR TEMPERATURE
I L
M-1976 A
M
S 0 N D J-1977 F
Figure B-6U.
Temperatures recorded in a loaded and unloaded
trench during 1976-1977-
Unfortunately, many state and local codes favor the construction of "beds
over trenches. The codes usually follow the recommendations of the Manual
of Septic Tank Practice (1967), which limits trenches to 1.5 m (5 ft) widths
with 1.8 m (6 ft) separations "between sidewalls. Thus, a 100 m2 (1076 ft2)
absorption bed can be laid out in a 8 m x 12.5 m (26 ft x 38 ft) rectangular
area while a trench system would require a 6.6 m x 33.3m (22 ft x 110 ft)
area assuming 1 m (3.3 ft) trench widths. These larger areas required by
trenches are often undesirable. In addition, trench systems cost up to 25%
more in Wisconsin because additional time is required for construction.
To encourage the use of trench systems, codes could be changed, A
reasonable approach might be to require more bottom area for beds than
trenches for the same size household. Two methods might be used: l) give
credit for sidewall area, thereby reducing the bottom area required for
trenches, or 2) increase the bottom area now required for beds in proportion
to the amount of sidewall area lost by not using the trench design.
A trench or bed can be represented by a rectangle with sides of x and y.
The bottom area becomes:
AB = xy
If Ag is set constant, x and y can vary. If x is the width, when it varies
between 0.3 m to 1.5 m (l ft to 5 ft) the system is defined as a
trench. If x is greater than 1.5 m (5 ft) then the system is defined as a bed.
B-12U
-------
If it is assumed that 60 cm (12 in) of gravel is laid below the inlet
of the distribution pipe, the side-wall area is:
Ag = 2x + 2y
Therefore, the sidewall area, Ag} is a minimum when x = y (a square bed), and
a maximum when x approaches 0.
A useful means of comparing sidewall areas for different shape and size
of beds is a ratio of sidewall area to bottom area:
R = 2x + 2y
xy
Substituting y = AB
R = 2x2 + 2A
•B
This analysis indicates that trenches 1.5 m (5 ft) wide can provide
25$ more sidewall area than beds for 30 cm (12 in) deep systems. Since bed
designs are most unfavorable in finer textured soils, a 25$ increase in
bottom area required for beds is reasonable. This would have the effect of
reducing the advantages of cost and land area required which beds offer
over trenches.
Liquid distribution—
Dosing and uniform application of wastewater effluent over the infil-
trative surface may be critical to the proper functioning and long term life
of the soil absorption system. Localized overloading due to continuous
inundation and poor distribution may result in inadequate purification of
the effluent in very permeable soils and accelerated clogging in all soils
(Bouma, 1975; Bouma, et al., 1972; Robeck, et_ al., 196U; McGauhey and
Winneberger, 1.96k}.
In conventional subsurface soil absorption systems, distribution of
the effluent within the field is usually provided by perforated drain tile
laid below the elevation of the septic tank outlet to permit gravity flow of
the liquid. The pipe is commonly 10 cm (U in) in diameter and perforated
with two rows of 1 cm (3/8 in) diameter holes spaced 7-5 cm (3 in) apart.
It is laid level or on a slope of 0.167 to 0.333 percent such that the rows
of holes are positioned downward k5° either side of the vertical center line
of the pipe. One pipe is used per trench, but in the case of a bed, two or
more pipes may be installed with a spacing of 90 cm to 180 cm (3 ft to 6 ft)
between centers. In a bed or multi-trench system the pipes are usually
interconnected by a common solid wall header pipe or through a distribution
box (Manual of Septic Tank Practice, 1967).
This method of effluent application provides very poor distribution.
McGauhey and Winneberger (196*0 and Bouma, e_t_ a-IU , (1972) observed a
B-125
-------
phenomenon of "creeping failure" within trenches and beds. It was attri-
buted to the discharge of effluent out the holes in the pipe nearest the
inlet to the absorption field. The soil below this point becomes overloaded,
receiving a more or less continuous trickle of effluent. Biological
clogging soon occurs which reduces the rate of infiltration below the rate
which the effluent is discharged, forcing the effluent to flow along the
bottom of the system until it encounters unclogged soil. This process con-
tinues until the whole system is ponded (See Figure B-65). Failure does
not necessarily occur at this time if the system is sized to account for
the reduced rate of infiltration. However, the initial overloading of the
unclogged soil may result in groundwater contamination in sands while con-
tinuous inundation which ultimately occurs may cause severe clogging, leading
to surface seepage in some finer textured soils.
In an attempt to improve distribution, several full-scale distribution
systems were evaluated in the laboratory (Converse, 197*0 • A gravel trench
was constructed such that water passing through the gravel from each ^5-cm
(18 in) segment could be measured. Both gravity flow and pumped discharge
systems were tested.
The conventional 10 cm (U in) diameter bituminous fiber pipe with two
parallel rows of holes located downward provided very poor distribution.
Figure B-68 shows a typical distribution pattern for a lH.6 m (U8 ft)
length of pipe laid on a 0.215 percent slope when 57 L (15 gal) of water
were allowed to flow by gravity. The liquid distribution was concentrated
at the head and end of the pipe with little or no flow between. The first
holes, as well as the holes with the lowest elevation, received the greatest
proportion of flow. When water was pumped into the pipe at the rate of
U8 L/m (13 gpm), 97 percent of the liquid was distributed over 63 percent of
TRADITIONAL SUBSURFACE SEEPAGE BED
Gravity flow, continuous trickle of effluent
t I t I t I
) t I I I I I I
V
Equilibrium
i I i i t i i t i i i
Figure B-65.
Progressive clogging of the infiltrative surfaces in
subsurface seepage beds with gravity distribution
characterized by continuous trickle flow (Bouma, et
al., 1972)
B-126
-------
the bed (See Figure B-*$7). A lesser slope resulted in less than 4 5 per-
cent of the bed receiving effluent.
The trials were repeated using a single row of holes located in the
crown of the pipe. This configuration improved distribution. The most
important factors affecting distribution were the slope of the pipe, vari-
ation in hole elevation, flow rate and pumping time. Gravity flow was not
as effectual (Figure B-gs) • The results indicated that the pipe should be
laid level and a high flow rate provided with few holes in the pipe (See
Figure 6-69). A minimum flow rate of 95 L/m (25 gpm) for no less than
2.5 min is recommended for a pipe with hole spacing of 90 cm (3 ft)
(Converse,
The results with inverted pipe (holes at the crown) configuration
indicate that "better distribution is achieved when the pipe is under pres-
sure. When the number of holes are decreased and the flow rate increased,
more uniform distribution results. This suggests that the best method of
distributing liquid uniformly over a large area would be to utilize a
pressure network.
Pressure networks have been used for years in fixed nozzle trickling
filter units to uniformly apply wastewater over the filter media. The ob-
jective in design is to balance the headlosses to all parts of the network.
This is done by maintaining one to two psi of pressure within the perforated
laterals at their terminal ends and sizing the perforations and pipe
chambers such that the headlosses incurred in delivering the water to the
holes does not exceed 10 to 15 percent at the in-line pressure. The pump
or siphon used to pressurize the network is sized to supply the necessary
flow against the network losses plus the elevation head and friction losses
incurred in delivering the liquid to the network (Otis, et_ aJ^. , 1977).
The pressure networks were designed and constructed for evaluation.
The networks had single manifolds with h to 6 perforated laterals (See
Figure B-70a and B-70b). The perforated pipe was 2.5 cm (l in) diameter,
with 0.52 cm (13/6^ in) or 0.6U (lA in) diameter holes spaced every 75 cm
(30 in) (Converse, 197*0. Distribution was improved through these net-
works, though irregularities in the holes due to drilling caused some
fluctuations (See Figure 3-71a and B-71b). Since the networks are laid with
the holes at the pipe inverts allowing the system to drain between dosings,
dosing volumes should be large enough to fill the network within 10 percent
of the total dosing time.
Six pressure networks were installed at private homes to evaluate
their performance under field conditions (Converse, et_ aJ^. , 1975a)- After
two years of operation, the principal problem encountered was in pump
sizing. One-third horsepower submersible pumps were used but were not
always sufficiently large to achieve adequate pressure throughout the system.
Plugging of the lines occurred in only one system, which was found to be
due to improper installation (Otis, et al. 197^).
B-127
-------
C 0.10
I
^
U
SJO.OO
5.0
g 4.0
COLLECTED -
10 c*
b b
ac
1 ''°
O
S
FLOW - GRAVITY
HOLES - Q
SLOPE - .215 %
\ Jh n r
j
12 18 24 SO 36
DISTANCE ALONG PIPE - FEET
42
48
H 0.10
i
3;
uj
SJO.OO.
5.0
tL
FLOW - 1.71 CFM
HOLES - Q
SLOPE - .215 %
12 18 24 30 56
DISTANCE ALONG PIPE - FEET
42
48
Figure B-66. Gravity distribution
of 15 gal. of water from a h-in
perforated bituminous pipe
(Converse, 197*0.
Figure B-67. Pumped distribution
of water along a l|-in perforated
pipe (Converse, 197*0-
n- O.K)
3t
Si0-00;
z.o
FLOW - GRAVITY
HOLES - 6
SLOPE - LEVEL
HOLE SPACING
3.0 FT.
l~l .75 FT
f! .25 FT.
FLOW RATE
.033 CFM
.025 CFM
.026 CFM
12 18 24 3O 36
DISTANCE ALON6 PIPE - FEET
QUANTITY
15 SAL.
15 GAL.
10 SAL
42 48
FLO* -
HOLES -
SLOPE -
Figure B- 68. Gravity distribution
of water from a level U-in per-
forated bituminous pipe with one
row of holes at the crown of the
pipe (Converse, 197*0
Figure B- 69. Pumped distribution
for a level U-in perforated
bituminous pipe 100 ft long with
one row of holes at the crown of
the pipe (Converse, 197*0-
B-128
-------
INLET
INLET
-x
L*J
Figure B-70a. The top view of a bed
system consisting of a 2.5-cm (l-in) PVC
manifold and four laterals, each with six
0.5-cm (l3/6i|-in) holes spaced 75-cm (30-
in) apart. The laterals are U m (13.5-ft)
long and spaced l.k m (k.^-ft) apart. The
5.3-m (17.5-ft) square dashed area repre-
sents the seepage bed perimeter (Converse,
197*0.
• 2.94 CFM
• 2.11 CFM
• 1.02 CFM
IS
FOUR
Figure B-70b. The top view of a
trench system consisting of a 7.5-cm
(3-in) PVC manifold with six 2.5-cm
(l-in) PVC laterals. Each lateral
has eight 0.6-cm (lA-in) holes
spaced 75-cm (30-in) apart. The in-
let is on the end or center. Each
6.1-m (20-ft) lateral is spaced U.6-m
(15-ft) apart. The three 0.9-m (3-ft)
dashed areas represent the trench
perimeters (Converse, 197*0.
I"
to m to s sa 5 Jo~
w » re B s m is to~
Figure B-71a. Distribution for three flow Figure B-71b. Distribution for the
rates at the bed network (Converse, 197*0. trench network at two flow rates.
The top portion is the distribution
pattern for the center inlet, and
bottom pattern for the end inlet
(Converse, 197*0.
B-129
-------
Limited monitoring of the field systems suggests that this method of
effluent distribution retards clogging of the infiltrative surface.
Several of the systems excavated did not show signs of a clogging mat
developing, even after two years of operation. The application of effluent
at a rate below the saturated conductivity of the soil in infrequent doses
should allow rapid drainage and nearly continuous aerobic conditions at
the infiltrative surface. Further work is needed to confirm this.
Restoring the Infiltrative Surface
Assuming that a system has been properly designed, sized, installed
and maintained by necessary periodic tank pumping, the only reason it can
fail is by excessive clogging or sealing of the soil in the absorption
field. Short of installation of a new or extended seepage area, the only
way to rehabilitate a failed system is to unclog the soil and restore its
infiltrative capacity. Laboratory and field experience has shown that there
are only two methods to do this. The two options are: l) prolonged resting
and 2) unclogging of the soil with chemical agents. Only these two
approaches reach the problem where it is occurring, namely in the clogged
portion of the soil.
Resting—
Several researchers have observed beneficial effects on infiltration
following resting of clogged soil in laboratory columns (McGauhey and
Winneberger, 1965; McGauhey and Krone, 1967; Jones and Taylor, 1965; Thomas,
et_ al_., 1966; De Vries, 1972; Perry and Harris, 1975; Harkin and Jawson,
1976). The practice of intermittent resting is recommended in HUD's (197*0
handbook on "Methods of Preventing Failure of Septic Tank Percolation
Systems." However, the increase in soil permeability produced by short-
term resting is usually lost again within about 5 to 10 days after loading
is resumed (McGauhey and Krone, 1967; Harkin and Jawson, 1976). The final
infiltration rate is usually lower than that before resting is commenced
(See Figures B-72 and B-73).
The main problem with resting is the provision of the long period neces-
sary for beneficial resting, which may be days, weeks, or months, depending
on the soil in question and the status of the clogging mat. If a new
system is being installed or an older system is being upgraded, plans
should be made to provide for future periods of resting by construction of
a dual or alternating bed system. This obviously increases the cost of the
basic septic system and is not always a viable alternative if the lot is
too small to accomodate alternating beds. In some cases, the system may
simply not drain rapidly enough. In finely textured soils, J+5 to 60 cm
(2.5 to 3.0 ft) of unsaturated soil below the infiltrative surface is
necessary for the system to drain after effluent applications are stopped
(Klein, et_ al_. , 1962; Bendixen, e_t al., 1962; Winneberger, et_ al_. , 1962).
This depth of unsaturated soil is necessary to create a sufficiently high
hydraulic gradient across the clogging mat. In areas of seasonally or
permanently high water tables, drainage of the soil and reaeration may not
occur at all during periods of resting.
B-130
-------
25
20
E
u
.15
a.
UJ
a
g
o
10
JULY
20 25
H-
AUGUST
I 5 10 15 20 25 30 5
SEPTEMBER
10 15 20 25 30
10 20 30 40 50 60
DAYS FROM START
70
80
OCTOBER
10 15
^
92
Figure B-J2.
Ponding of septic tank effluent in Hanford fine sandy loam with
periodic resting (Winneberger, et_ al_., 1962)
Chemical Treatment—
Even before the concept of restoration by resting was created, efforts
had been made to restore the efficiency of ailing septic systems by additions
of chemicals or other materials to the system through the household plumbing.
Over the years a myriad of processes and agents have been used to try to
improve septic tank performance.
The use of some techniques and materials is based on misconceptions
of the problem and incorrect logic as to measures that could be taken to
correct the situation. For example, many people, including officials ad-
ministering health and plumbing codes and installers, believe that it is
blockage of the perforated pipes or tiles in distribution lines by solids
spilling over from badly maintained septic tanks that cause sluggishness
or backups in septic systems. They think that snaking of the lines will
restore functionality to the system. There is a simple test to determine
whether blocked lines are the cause of a failure: if water is ponded in
the seepage area, it has free access to the soil and the lines are not
3-131
-------
900
*, 800
E
700
600
500-
Th
WEEKEND RESTING
PERIODS
M T W Th F S S M T W Th
DAY OF THE MONTH
S S M
Figure B-T3-
Effect of anaerobic resting periods (surface ponded) on flow
rates of wastevater through partially clogged columns
(after It months of dosing) (Jawson, 1976)
plugged, the soil is. Others believe that it is invasion "by roots of nearby
trees that causes system sluggishness, and make efforts to poison the tree
roots with chemicals, such as copper sulfate. In fact, the likelihood of
tree roots invading a septic system is remote (Bendixen, et_ a^., 1950).
Although septic tank effluent is a source of moisture and the plant macro-
nutrients N and P, tree roots need air and consequently do not, in fact
tend to invade anaerobic ponded seepage areas. Inspection of systems in-
stalled so close to trees that the tree crowns spread over the drainfield
area (so that an equivalent spread of the roots should be expected) have
revealed that roots grow profusely in aerobic soils around, but outside,
the clogged soil layers, but do not invade the ponded strata inside the
clogged soil. Failure in such systems was again found to be due exclusively
to soil clogging. The problem that has to be addressed, therefore, is soil
clogging, although this may be complicated by other secondary factors.
Processes—Basically, there are three approaches to applying chemicals
designed to unclog soils in drainfields: l) through the household plumbing
system to the septic tank and thence to the clogged field; 2) to the ponded
water in the drainfield; and 3) directly to the clogged soil. Addition to
the ponded water is less convenient than addition through the tank, but the
principle is the same with less dilution of the chemical. Maximum effect
of any additive can only be expected from direct addition to the clogged
soil. What is more important is the avoidance of pernicious side effects
of the chemicals on the operation of the tank, on the soil or on the ground-
water quality.
B-132
-------
Agents—The types of materials used to try to improve the performance of
sluggish septic systems includes various categories of compounds: aggressive
chemicals such as acids, bases, and strong oxidizing agents; biological
agents or biochemicals such as yeasts, bacterial inocula, or enzymes; and
surfactants. Proponents of these treatments usually recommend that the
materials be added to the tank by flushing down drains or toilets. A few
practitioners, realizing that the problem lay in clogging of the soil, have
added enzymes, acids, or oxidizing agents directly to the drainfield or soil.
Effects—The Manual of Septic Tank Practice (196?) warns that over a
thousand preparations which allegedly improve the performance of septic
systems have been tested, but that not one has been found to be efficacious.
Perhaps because no documentation of this contention is given, many manu-
facturers continue to concoct, market and advertise - often with the help of
testimonials - a multitude of preparations that are purported to prevent
or cure septic tank "sluggishness" or failure. Many are "guaranteed" to
work. The producers of these nostrums usually suggest that a dirty tank is
the problem and that addition of their product will clean the tank and create
or stimulate bacterial action which will speed up liquefaction of the wastes
in the tank, producing a more infiltrable, higher quality effluent. Such
products are nationally advertised and sold. Most large department stores,
hardware stores, and plumbing supply retail stores sell septic tank "cleaners"
or "activators" of this type, despite the fact that the Manual states that
!'. .there are no known chemicals, yeasts, bacteria, enzymes, or other sub-
stances capable of eliminating or reducing the solids and scum in a septic
tank so that periodic cleaning is unnecessary. The addition of such
products is not necessary for the proper functioning of a septic tank/soil
absorption system."
To determine the efficacy of commercially available treatment, a series
of 39 uniformly clogged sand columns were prepared (Jawson, 19?6). The
columns were continuously ponded for a total of 19 months before the treat-
ments were tried. Flow rates were reduced to 0.02 cm/day.
The directions for use of most of the products recommend that a portion
of the package contents be emptied into a drain or toilet and flushed.
The amount added depends on the septic tank capacity. Based on the quantity
stated for use, a proportional amount was added to 19 L (5 gal) carboys of
septic tank effluent for each treatment. This "unclogging" potion was then
added to the column in place of the raw septic tank effluent. In addition,
some preparations were added directly to the clogged layer. After receiving
direct applications, influents containing these preparations were used to
load the columns.
The types of material tested included one or more examples of a "drain
cleaner" containing strong sulfuric acid, a "septic tank and cesspool cleaner"
containing a crude technical grade of sodium hydroxide, a "beneficial
bacteria additive," a "root killer" (CuSO^^H0 crystals), a "bacterial
cleaner," a "bacteria enzyme" product, a "bacteria-enzyme activator,"
another "activator," a "bacterial sensation," a "septic tank conditioner,"
a complex commercial enzyme mixture designed for addition to drainfields,
an emulsifying agent, a detergent, a chlorobenzene fat solvent, and
B-133
-------
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various experimental grades of stabilized hydrogen peroxide.
When applied directly to clogged soils, only the sulfuric acid, the
caustic alkali and the peroxides increased the soil permeability (See
Table B-20). The peroxide preparations were invariably the most effective.
Suitable applications restored the soils to almost the initial infil-
tration rates, and allowed increased percolation for several months after
treatment. The acid and alkali also increased the infiltration rate
initially, to an extent comparable with short-term resting, but not as
effectively as the peroxides. However, the flow rate after one month had
fallen to a lower level than that of the original clogged soil in the
column treated with acid and to zero in that treated with alkali. The
sodium hydroxide caused deflocculation and dispersion effects of the soil.
Chemical analysis showed that the sulfuric acid and resting removed much
less organic matter from the clogging layer than did the mild peroxide
treatment.
None of the other materials produced any significant increase in in-
filtration. This is not surprising. The clogging mat is rich in hetero-
trophic bacteria and their enzymes so that addition of a few extraneous
bacteria, bacterial spores, or enzymes cannot evoke a significant change.
Even if the bacteria or enzymes present in the preparations happened to be
adapted for optimum growth or action under the temperature, pH and redox con-
ditions present in clogged soil, it is unlikely that they will be able to
compete effectively with or supplement substantially the massive amounts of
bacteria and enzymes already in the clogging zone. It is more likely that
the commercial bacteria are not adapted to the peculiar environment of the
clogged soil and the commercial enzymes are either inactivated by the sul-
fides present in the clogged soil or, as proteins, digested by the proteolytic
bacteria in the clogging zone.
It is also not surprising that the surfactants or emulsifying agents do
not increase infiltration. The rationale behind the use of surfactants is
to reduce the surface tension in the ponded water and help it "slip through"
the clogged soil or to help dissolve the hydrophobic fatty constituents of
the clogging material. Some manufacturers apparently think that water-
resistant fats and grease are a major constituent of the clogging material.
Normally, this is not true. Chemical analyses show that lipids constitute
only 10-15 percent of the organic material in clogged soils (See Table B-21).
Moreover, there are already substantial levels of detergents present in
undecomposed form in normal septic tank effluent. The low lipid content of
the clogging zone also explains why the chlorobenzene does not unclog soil.
There is also little sense in adding emulsifying agents or organic solvents
to the system to dissolve fats and grease for the same reasons.
In practice, people use these preparations only after their system has
developed problems, i.e., the soil is already clogged, and they normally
add them to the tank through their household plumbing instead of directly to
the clogged soil or the ponded water. Therefore, tests were conducted with
clogged soil columns to see whether septic tank effluent treated according
to manufacturers' prescriptions with various chemical and biochemical prepar-
ations would gradually unclog soil (Harkin and Iskandar, unpublished data,
B-137
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1977)- In n° case was an increase in infiltrative capacity obtained. On
the contrary, sealing was accelerated and failure occurred more rapidly
than with columns dosed with unamended effluent.
The only treatment that was found effective in unclogging soil was
hydrogen peroxide when applied directly to the clogged soil. Most of the
reagent is uselessly expended if applied to the ponded water or to the
septic tank, because it is destroyed by reaction with materials in solution
or suspension in the water. The reagent is much more effective if properly
stabilized and correctly applied. It destroys most of the organic matter
in the clogging zone, and it reestablishes aerobic conditions in the infil-
tration area, so that aerobic bacterial digestion of undissolved clogging
material can take place. Peroxide treatments have also been found to be
successful for rehabilitating failed absorption systems in the field
(Harkin, et_ al_. , 1976; Harkin and Jawson, 1977). Peroxide treatments are
the basis of the POROX TM system for reviving failed septic systems (Harkin,
1977) which is now being commercially marketed.
Concern has been expressed that treatment with peroxide could cause
organic matter, bacteria and other substances to move deeper into the soil
and into groundwater with adverse affects, since a large amount of puri-
fication occurs as effluent passes through the clogged layer (McGauhey and
Krone, 1967; Bouma, et_ al. , 1972). To test this possibility, BOD and
bacterial analyses were performed on column effluents before and after Ho Oo
treatments (Jawson, 1976). Effluent samples were collected for several
days following successful treatment to determine when and for how long
these substances filter through sandy soil. Results from these columns are
presented in Table B-22. The data do seem to indicate that both bacteria
and organic matter are eluted in the treatment effluents. However, the
concentrations of BOD and coliforms found do not appear to be high enough
to cause alarm, especially since the columns were only 60 cm (2 ft) deep.
It appears that any strong oxidizing agent, acid or base could be a
successful declogging agent. However, hydrogen peroxide appears to be the
best choice based on very limited data thus far available. It works more
effectively than other chemicals so far tried, with no major drawbacks
apparent so far. One of its most positive properties is that it is reduced
to water and oxygen, while most other chemicals tested have by-products
which may be undesirable. Probably the biggest unknown is the secondary effects
such as the release of toxic metals or virus during and immediately after
peroxide treatment.
In all cases, direct application to the clogging mat was necessary for
successful operation. This methodology treats the problem where it occurs,
viz., in the seepage bed itself. Addition of a declogging agent to the septic
tank itself would cause most or all of its beneficial effects to be dissi-
pated through reagent degradation and/or dilution long before the problem
symptoms are attacked.
TOROX is a trademark of the Wisconsin Alumni Research Foundation, Madison,
Wisconsin 53706.
B-139
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ALTERNATIVE SYSTEM DESIGNS FOR PROBLEM SOILS
The Mound System
There are many areas where the conventional septic tank-soil absorption
field is not a suitable system of wastewater disposal. For example, sites
with slowly permeable soils, excessively permeable soils, or soils over
shallow bedrock or high groundwater do not provide the necessary absorption
or purification of the septic tank effluent. However, these limitations
often can be overcome by constructing the soil absorption field above the
natural soil in a mound of medium sand fill (See Figure B-7^).
There are several advantages to raising the soil absorption field.
The fill below the absorption trenches within the mound provides additional
soil material necessary to purify the wastewater before it reaches the
groundwater at sites with shallow or excessively permeable soils. At sites
with slowly permeable soils, the purified liquid is able to infiltrate the
more permeable natural topsoil over a large area and safely move away
laterally until absorbed by the less permeable subsoil. Also, the clogging
mat that eventually develops at the bottom of the gravel trench within the
mound will not clog the sandy fill to the degree it would in the natural
soil. Finally, smearing and compaction of the wet subsoil is avoided since
excavation in the natural soil is not necessary.
The mound system was originally developed in North Dakota where it
became known as the NODAK disposal system (Witz, et_ al_., 197^ )• The mounded
design was proposed to overcome slowly permeable soil conditions by util-
izing the more permeable topsoil. The seepage bed was constructed in gravel
fill which was placed over the original soil after the topsoil had been
removed. These systems were first installed in 19^7 and have since appeared
to function properly. However, monitoring data has been lacking, and design
criteria based on the potential of the soil to absorb and conduct liquid
have not been defined.
To develop sound design criteria, several mound systems of various
designs were evaluated both under field and laboratory conditions (Bouma,
et_ al., 1972; Bouma, et_ al., 197^c; Bouma, et_ al., 1975b; Magdoff, et_ al.,
197^4-a; Magdoff, et_ aJ-_. , 197Ub). Six mound systems installed prior to 1970
were first investigated (Bouma, _et_ al., 1972). These were similar in
design to the NODAK system constructed to overcome both slowly permeable
soil conditions and permeable soils over shallow creviced bedrock where
groundwater contamination was a danger. The conclusions made from these
initial investigations were that the gravelly fill was too coarse to provide
adequate filtration where groundwater contamination was a problem and that
inadequate distribution, sizing and/or construction was resulting in sur-
face seepage during wet periods of the year.
To correct these shortcomings, changes were suggested in the design
and construction of mounds. To provide better filtration and treatment,
medium sand was specified for fill material. Loamy sands or sandy loams
have better filtration properties but their potential for clogging is
-------
DISTRIBUTION —^ CAP-
LATERAL
MOUND
SEPTIC TANK
PUMPING CHAMBER
x
NN
/\-\n IN-ZIM
/ PIPE FRO
V CHAMBER
PLAN VIEW
Figure B-7^. A plan view and cross-section of a mound system
for slowly permeable soils
greater (Bouma, et_ al_. , 1972). Crust tests were performed in the soils at
each site to determine the soil's capability for conducting water, providing
better sizing criteria. It was also specified that the original soil be
disturbed as little as possible. The vegetation should be removed and
raked, but the topsoil should remain in place and not be driven upon.
Full-scale mounds and laboratory models were constructed to test the
modifications made. Models were designed to represent the vertical cross-
section of a mound (Magdoff, et_ al_., 197^a). Large 1^.7 cm (6 in) diameter
columns were filled with 15 cm (6 in) of gravel followed by 30 cm (12 in) of
silt loam topsoil, 60 cm (2^ in) of sand, 30 cm (12 in) of gravel and
another 30 cm (12 in) of silt loam. This model represented a mound con-
structed over a shallow silt loam with underlying creviced bedrock (See
Figure B-75). The upper gravel layer of each column was dosed with 8 cm/day
(1.92 gpd/ft2) of septic tank effluent. Monitoring included moisture tensions,
gas sampling, redox potential measurements and liquid samples for COD,
nutrients and bacteriological analyses with depth in the column.
-------
+ 60 cm
+ 30 cm
60 cm
90cm
TENSIOMETER
LIQUID
PORT
INFLUENT
»PT
ELECTRODE
MONITORING COMPLEX
gp-GAS PORT
mc-MONITORING COMPLEX
Figure B-75.
Column model of mound over shallow creviced
bedrock (Magdoff, et al. , 197*0.
The results of the laboratory studies indicated that a mound using
60 cm (2h in) of sand fill would provide adequate treatment (See Figures
3-76, B-77» B-78 and Table B-23). Essentially complete removal of fecal
indicators, and COD were realized with significant decreases in nitrogen
and phosphorus. Only in situations where nitrate contamination of the
groundwater is undesirable would such a design be technically unsuitable
(Magdoff, et al., 197^>) •
Several experimental mounds were constructed to test the suggested
modifications. A rational design method was developed (Bouma, et al.,
1975b). Different design considerations are dictated during the spring
and fall in slowly permeable soils when natural water tables occur at a
shallower depth than in summer and winter. Dimensions of the seepage trench
are designed to avoid rising of the perched water table into the fill when
the groundwater is high, and the total basal area of the mound should be
sufficiently large to absorb and conduct the effluent downwards through
slowly permeable subsoil horizons when the groundwater is low.
The calculation of the required basal area of a mound should be based
on the Ksat of the least permeable soil horizon within 90 cm (3 ft) below
the proposed site for the mound. Maximum flow is estimated by using 568
liters/day (150 gallons/day) per bedroom in the home served.
The second step in the design is to size the absorption system within
the mound. The system should consist of one or a series of small parallel
trenches, rather than one single absorption bed containing all the distribution
laterals. Widely spaced trenches are superior than beds because they
distribute the liquid over a larger area causing a smaller rise of perched
-------
400-
•* 300
o»
jl 200
O
o
o 100
INLUENT
EFFLUENT
20 40 60 80 100
DAYS AFTER
CONTINUOUS PONDING
20 40 60 80 KX)
DAYS AFTER
CONTINUOUS PONDING
Figure B-?6. Chemical oxygen demand
(COD) of influent and effluent
from column (Magdoff, et al.,
Figure B-77. N concentrations in
influent and effluent from
column (Magdoff, et al.,
30r
£20
OL
10
/•A
INFLUENT
•--EFFLUENT
20 40 60 80
DAYS AFTER
CONTINUOUS PONDING
100
Figure B-78. Total-P concentrations in
influent and effluent from column
(Magdoff, et al., 197^ ) •
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liquid in the topsoil. A standard trench width (v) of 60 cm (2 ft) is
recommended as a result of applying the Dupuit-Forchheimer assumption for
horizontal flow applied to the topsoil (Childs, 1969). Figure B-79 shows a
schematic cross section of one-half of a mound on top of a permeable top-
soil of thickness h- cm, resting on an "impermeable" subsoil B horizon.
Infiltration of effluent from the seepage bed (l, cm/day) results in a rise
of the groundwater in the topsoil. Below the center of the bed, the ground-
water level is equal to the depth of the topsoil (t^), below the edge of the
bed the level is h-, . The calculation is designed to prevent groundwater
from rising into the fill. Trench width (w) is calculated by the following
equation, assuming 1=5 cm/day, b^ = 30 cm, and h-[_ = 25 cm, and K from the
K-curves for the particular soil.
(h02 - hx2)= (I
This analysis is approximate because: l) the subsoil B is not im-
permeable; 2) the soil usually has some slope; and 3) the liquid is not
applied as a steady flow, but as a dose. However, calculations do indicate
the need for small seepage trenches rather than large seepage beds. The
total bottom area of the trenches is calculated by using a liquid appli-
cation rate of 5 cm/day (1.2 gpd/ft2). The height of the gravel-filled
trench should be at least 20 cm (8 in) above the natural soil surface to
allow for sufficient liquid storage. If parallel trenches are used, their
spacing is determined by the hydraulic characteristics of the underlying sub-
soil. The area between the trenches should be sufficient to absorb all
the liquid contributed by the upslope trench, and trenches should be laid
parallel to the slope. In more permeable soils, beds rather than trenches
can be used because the water table is less likely to rise.
The selection of the most appropriate dosing regime is closely corre-
lated with the type of fill, its hydraulic characteristics, and economic
considerations. For example, dosing once every two days would require a
MOUND SURFACE
PERCOLATION ZONE
(UNSATUATED) 60CM
I lunaAiuM
ORIGINAL SOIL SURFACE
HIGH
GROUNOWATER
A - HORIZON
B - HORIZON
Figure B-79.
Schematic cross-section through a mound system used to
calculate the required width of the gravel bed in the mound-
B-ll+6
-------
relatively large pumping chamber, while instanteous introduction of this
large quantity of liquid would probably result in saturated flow conditions
in the fill and associated unsatisfactory purification (Bouma, et_ al_., 1972).
On the other hand, more frequent dosing, e.g. four times per day would
result in better purification and require a smaller pumping chamber. How-
ever, the fill may then not have sufficient time to drain, and relatively
high moisture contents at the interface of seepage bed and fill could lead
to early clogging. Clogging can be at least partly removed by introducing
a period of aeration in which clogging components are decomposed by aerobic
bacteria. A long period between successive dosages would be advantageous
in that it would provide relatively long intermittent periods of aeration.
The laboratory column experiments indicated that a once-a-day appli-
cation of 8 cm of effluent was quite effective in removing fecal indicators,
pathogenic viruses, BOD, and significant amounts of N and P (Magdoff,
et_ al., 19?Vb;Green and Oliver, 1975).
Based on these column studies, the application rate of the field
system to be used for sizing purposes was chosen to be 5 cm/day. This daily
loading rate was derived from independent field measurements of soil
moisture tensions below clogged seepage beds in sand (Bouma, et_ al., 1972).
These tensions, which can be translated into flow rates by using the
appropriate K-curves were approximately 25 mbar, corresponding with a flow
rate of about 8 cm/day. The lower rate of 5 cm/day was used here to
include a safety factor. The concept of using this rate is to ensure ade-
quate infiltration of effluent, even if the seepage bed were to become
clogged at some future time, assuming that the clogged layer would still
allow percolation of 5 cm/day.
Five experimental mounds were constructed based on the rational design
approach. Mounds I and II were constructed in September, 1971 in the slowly
permeable Hibbing silt loam. Modifications based on experience with these
systems were made in Mound III, also constructed in the Hibbing silt loam
during June, 1972. Mounds IV and V were again modified to improve per-
formance. Mound IV was constructed in the tight Almena silt loam, while
Mound V was designed primarily to provide purification because of its
location over a shallow, creviced bedrock. Salient characteristics of these
systems appear in Table B-24.
As shown in Table E-2h, the total bottom area of the mounds is much
larger than the area required on the basis of the limiting conductivity
of the subsoil. This discrepancy is caused by the requirement for 60 cm
(2h in) of fill below the seepage trenches to purify the liquid. Addition
of soil cover results in a mound that is 1.2 m to 1.5 m (H.5 to 5 ft) high
at the center. Slopes at the side of the mound should not exceed 3:1 to
insure stability which create large basal areas.
At slowly permeable soil sites, the depth of fill can be reduced
because purification is not a problem. This was done in Mound IV (See
Figure B-8l). This reduces the basal area somewhat. The seepage areas
within the mound are much smaller because they are based on flow character-
istics of the sand fill. Mounds I and II were constructed as shown in
-------
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Figure B-8Q, except the clay dam was not used and distribution was provided
by the conventional 10 cm (^ in) perforated pipe. Some seepage occurred
in localized spots at the sides of these mounds in the spring and fall,
indicating that short circuiting was occurring either from unequal distri-
bution of the effluent within the trench or inadequate absorption in the
natural soil. Excavations into the side of Mound I after 2.5 years of oper-
ation indicated the occurrence of a slight compacted slimy surface layer
formed from decomposed grasses at the original soil surface, even though
grasses were cut and removed before applying the fill. The in situ soil
below the original soil surface was not saturated and infiltration rates
into the soil were, therefore, reduced (Bouma, et_ aJ^., 1975b). The large
diameter distribution pipe provided local overloading within the mound,and,
coupled with the organic mat which developed at the original surface,
seepage resulted.
To correct this problem, a clay dam was constructed inside Mound III
to force the liquid over a wider area, and a pressure distribution network
was tried to uniformly apply the liquid in the trench (See Figure B-80).
This prevented any seepage, but monitoring standpipes extending down to the
original soil surface showed 2.5 cm to 5 cm (l to 2 in) of ponded water.
To further improve infiltration into the soil, the topsoil was first
plowed under Mound IV. This was done when the soil was dry to a depth of
20 cm (8 in). The contour of the slope was followed, throwing the soil up-
slope to prevent an channeling. By using this construction technique,
it was felt the clay barriers around the perimeter of the mound could be
eliminated (See Figure B-8l). This modification proved satisfactory (Bouma,
et al., 1975 "h).
I IN PEKFORATCD PIPt
CROSS SECTION A-A
1"
iZ I IN PERFORATED! ^ SEEMGE GRAVEL BED
n flK I
HM m PLASTIC PIPt »SFT('I
mm PUMPINO CHAMKR
TO 9CEPAOE KO
PLAN VIEW
Figure B-80 . Section view and plan view of Mound III.
-------
STRAW OR
MARSH HAY
.2301 PERFORATED , B CM TOP90IL
SECTION VIEW
25 CM DEEP
WITH CONTOUR
PLAN VIEW
( \
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MANIFOL
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PIPE
|" TRENCH
TION
Figure B-8l. Section view and plan view of Mound IV
A second modification in system IV was the construction of a more com-
pact seepage system consisting of one manifold with three laterals, feeding
three small trenches. The trenches were built perpendicular to the
direction of the slope. The distance between the trenches was U.5 m (15 ft),
which was considered adequate to allow infiltration of applied liquid
during downslope movement before the soil area beneath the second trench
was reached. One advantage of this system was its more attractive shape
(21 m by 2k m) as compared with Mounds I through III (13 m by 38 m), even
though total bottom areas are identical. Seepage has not occurred in Mound
IV, even though several problems were encountered in operation due to a
careless homeowner who damaged the septic tank and dosing chamber while land-
scaping the yard. Unknown quantities of surface runoff water have seeped
into the dosing chamber and have .been pumped into the mound.
Mound V was constructed prior to the inception of plowing, but because
of the more permeable soil, no seepage has occurred, even through the clay
barriers around the perimeter of the mound were eliminated. In addition,
the more permeable soil allowed a bed rather than trenches to be constructed,
making a more attractive mound (See Figure B-82).
All five mounds were monitored for performance. Liquid samples were
taken of the septic tank effluent applied and of any seepage that occurred
(Bouma, et_ al_., 19T5b). Since purification was of major concern with Mound V,
soil samples beneath the mound were taken for bacteriological analyses as
well (Bouma, et_ al_., 197^c). Results of these analyses appear in Table B-25
showing that adequate purification was achieved with this design.
Winter operation is a concern with these systems because of the danger
of freezing. Thermocouples were installed at various points within Mounds
B-150
-------
NO 2 GRAWELxx'SRASS
25 CM PERFORATED PIPE
'LATERALS SPACED 45FT
8-IOCMLAYER
OF BLACK DIRT
^EXISTING GRADE LINE
I--I* LOCATION OF THERMOCOUPLES
X LOCATION OF AIR SAMPLE PORTS
Section view and plan view of Mound V showing
location of thermocouples and gas sampling
ports (Bouma, et_ aJ^. ,
Figure B-82.
Ill and V as shown in Figures B-80 and B-82. Results from this monitoring
indicated that although freezing temperatures did occasionally occur,
freezing did not result because the trench and distribution pipe drained
between dosings (See Tables B-26 and B-2J. However, a tighter fill material
(such as silt loam) over the trenches is recommended to improve insulation.
Based on the success of the experimental mounds, their use for on-site
disposal was recommended for sites with: l) slowly permeable soils; 2)
permeable soils over shallow creviced or porous bedrock; and 3) permeable
soils with high water tables. A detailed manual describing the design and
construction procedures was written for use by regulatory personnel and
contractors (Converse, et_al. , 1975b, 1975c, 1975d
Curtain and Underdrain Systems
Hydrodynamic Design Considerations—
The placement of drains and trenches in small scale waste disposal
systems are geometrically and hydraulically similar to the system shown in
Figure B-83- (Only half of the subsurface system is shown due to symmetry
about the z-axis). Two design questions are considered, with due consider-
ation given to the satisfactory disposal of the liquid waste.
In order to ensure adequate purification of the effluent (Bouma, et al.,
1972), effluent draining from the trench must pass through a partially
saturated zone of sufficient thickness to allow for treatment of the waste-
water. Current health codes require a minimum distance of 0.9 to 1.2 m
B-151
-------
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B-152
-------
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B-153
-------
Position
TABLE B-27. TEMPERATURES OF MOUND V (Bouma, ejb al. , 197Uc) .
Temperature (°C)
Nov. 12, 1972 Dec. 1^, 1972 Jan. 29, 1973 May 18, 1973
1
2
3
U
5
6
7
8
9
10
11
12
13
lU
11
11
10
10
11
8
8
11
12
11
10
11
9
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8
7
7
6
7
2
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8
7
7
6
6
3
U
5
5
U
U
5
2
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5
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10
10
10
11
11
10
10
9
10
10
11
11
10
11
(3 to h ft) between the source of the effluent, i.e., the trench, and the
phreatic surface of the fully saturated groundwater "below. However, in
order to maintain generality, the design procedure will include an unspeci-
fied unsaturated thickness - T.
Design problem no. 1—Consider a waste disposal trench (See Figure B-8s)
of given width, 2w, located at a given distance, d, above a horizontal,
impermeable layer. Liquid waste is released steadily from a bottom of this
trench at a given infiltration rate, pQ (flow rate/unit area of the trench
bottom), into a soil with a given hydraulic conductivity, K. Upon reaching
the saturated zone the effluent flows toward the two drains, in which the
flow depth, a, (which may be negligible) is maintained.
Find the drain spacing, 2b, which will provide a sufficient thickness,
T, of the unsaturated zone to meet health standards.
Design problem no. 2—consider a waste disposal trench (See Figure B-83)
of given width, 2w. Liquid waste is released steadily from the bottom of
this trench at a given infiltration rate, p (flow rate/unit area of the
trench bottom), into a soil with- a given hydraulic conductivity, K. Upon
reaching the saturated zone the effluent flows toward the two drains which
are spaced a given distance, 2b, apart, and in which a given flow depth, a,
(which may be negligible) is maintained.
Find the distance, d, which must separate the trench and the impervious
layer to meet health standards.
-------
.
rx.- -^.^ /"-f-,-*' -f *, * ~7 f >
V i * I.* if I
~«
TRENCH
PARTIALLY SATURATED ZONE
Figure B-83 • Subsurface waste disposal system.
In order to solve these design problems it was necessary to devise an
equation that described the shape of the groundwater mound which is formed
below the trench. Once the shape of the phreatic surface is known, the ele-
vation of the peak of the mound, h,-,, can be calculated such that the unsat-
urated zone, T, will be of sufficient thickness to satisfy health standards.
Development of the Equation Describing the Phreatic Surface—
In order to develop the equation describing the shape of the phreatic
surface, the non-linear Dupuit-Forchheimer approximation was employed.
Details of this method of analysis may be found in the literature (Decoster,
19T6). Only a summary will be offered here.
The following simplifying assumptions were made to establish a basis
for the analysis.
1. The porous medium above the impervious layer is homogeneous and
isotropic.
2. The impervious stratum is horizontal.
3. The effluent is released uniformly across the entire width of the
trench at a constant rate. It percolates uniformly and vertically
downward through the unsaturated zone.
k. The porous skeleton is considered rigid, and the water is
essentially incompressible.
5. The flow obeys Darcy's Law.
B-155
-------
6. The drainage ditches are fully penetrating to the impervious
layer or if drain tiles are planned, they completely intercept
the effluent.
7. A fixed water level at a depth, a, is maintained in the drains,
which may be determined by an analysis of the flow conditions in
the drainage ditch. The seepage face is neglected. Under some
circumstances the depth, a, may be negligible, i.e., a - 0.
The fundamental equations describing flow at any point in the field are
the continuity equation,
V . q = 0 (1)
and Darcy's Law,
q = -
->•
where q is the vector specific discharge, K is the hydraulic conductivity,
and cj> is the piezometric head. Therefore,
4> = y + Z (3)
where p is the fluid pressure, y is the specific weight of the effluent and
z is the vertical coordinate, measured upward from the impervious base.
By substituting Eq. (2) into Eq. (l) and integrating the resulting Laplace's
Equation over the depth, z, the Dupuit-Forchheimer Equation may be obtained.
The sole additional restriction in the analysis is that the pressure dis-
tribution throughout the saturated zone must be essentially hydrostatic.
In other words, the flow must be essentially horizontal and the phreatic
surface may slope only moderately in the flow direction. The resulting
equation for steady flow with infiltration, p, as developed by Decoster
(1976) is:
d2hg/2 = - I (10
dx2 K
with boundary condions
0 £ x _< w
p = 0 w < x 1 b
and compatibility conditions at x = w to assure that there is no discontinuity
in either the phreatic surface elevation or the flow rate at this section.
Solutions to Eq. (U), subject to Eq. (5) and the compatibility conditions
are:
B-156
-------
h. = {£° (2b - (i)2 - 1) + (a) 2}1/2 for 0 < x < w (6)
w K w w w
and
h {Po (£. - 2E.) + (S.) 2}l/2 f or w < x <_ b (T)
w K w w w
These two equations decribe the elevation of the phreatic surface, h, as a
function of position, x, with the constant values, po, K, b, w and a des-
cribing the effluent rate, hydraulic conductivity of the porous medium, and
the geometry of the system components.
In as much as we are primarily concerned with the elevation of the
phreatic surface at x = 0, i.e., at the peak of the mound, Eq. (6) can be
evaluated at this point to give:
5° = {£o (Zb.-L) + (a)2}l/2 (8)
w K w w
Eq. 8 is the basis for the design of the system since it contains the terms
that describe the flow of the effluent, po, the hydraulic conductivity of the
porous medium, K, and the terms that describe the system geometry, hg, w, b
and a. In fact, one could rely entirely on this equation to determine either
the unknown distance, d, between the trench and the impervious bottom
(since d = h,., + T) as explained in Design Problem 1, or the drain spacing,
2b, as described in Design Problem 2.
However, to simplify the process of solving Eq. (8), a graphical pre-
sentation is preferable, and this can best be accomplished by dividing
both sides of Eq. (8) by (po/K)l/2, and introducing so = h-, - a. This results
in:
(!°. + £)2 K_ = (2b _ i) + (a,)2 K_ (9)
w w p0 w w p0
or (S + A)2 = §_ - 1 +A2 (10)
B
where the three dimensionless parameters are identified as follows:
S = so K
A = a K
w P0
(11)
B-157
-------
Eq. (10) which consists of only three variables is presented in Figure B-8U.
Decoster (1976) also developed solutions to several unsteady flow
problems and sought a verification of the steady flow ease considered here.
By comparing the Dupuit-Forchheimer results with those from a finite-element
analysis and a Hele-Shaw analog, he concluded that the Dupuit-Forchheimer
approach is very satisfactory for A >_ ^.0 while for values of A <_ U.O the
phereatic surface elevation may be underestimated by as much as 15 percent.
Design Procedure—
With Figure B-8U and Eq. (ll), it is now possible to solve the two
design problems previously posed.
Design problem 1—Let us assume that a given disposal system consists of
a 250 cm wide trench placed 200 cm above the impervious stratum, with the
water elevation in the drains not exceeding 50 cm. The rate of effluent
discharge is limited to 1 cm per day (0.2 gpd/ft^) and the hydraulic con-
ductivity is everywhere equal to 3 cm per day.
The problem is to find the appropriate drain spacing, 2b. In this
example, calculation of S and A, based on the given data, is as follows:
5 = f°. JL_ = (200-90-50) 1 = 0.82
v P0 125 1
A = a. K_ = 50 3 = 0.70
w PQ 125 1
Therefore from Figure B-8U, B = 0.85 and 2b = 295 cm.
The drains may be spaced less than 295 cm apart, and a satisfactory
distance T will be maintained between the trench and the phreatic surface.
In fact, since A is less than U.O, it might be appropriate to design for a
somewhat smaller value of b. However, it would appear that sufficient
spacing should be maintained to assure that none of the effluent from the
trench is released beyond either of the drains, i.e., outside of the drainage
system.
Design problem 2—Assuming that a second disposal system consists of
a 220 cm wide trench with water elevations in the drains so small as to be
negligible, e.g., 5 cm. The drains are spaced U^O cm apart. The rate of
effluent discharge is limited to 0.8 cm per day (O.l6 gpd/ft^), and the
hydraulic conductivity is everywhere equal to 3.2 cm per day. The problem is
to find the elevation of the bottom of the trench above the impervious layer
required to assure that health standards are met.
In this example calculations of A and B, based on the given data, are
as follows:
B-158
-------
0.000 .200 .400 .600 .800 1.000
Figure B-Qh. Subsurface waste disposal design graph (Decoster, 1976)
B-159
-------
A = a K = 5 3.2
v i^ 220 F^=
(this is close enough to 0.0 to permit the use of the limiting curve)
B=w= 110 =Q<5
b 220
Therefore from Figure B-8U , S = 1.73 and so
S0 = ^ _£. = 1.73 • no !_ = 95.2 cm
K U
The total elevation of the trench is therefore
d=sQ+a+T=95.2+5+90= 190 cm
The fact that the surface elevation may be underestimated "by as much as
might suggest a depth of 220 cm.
The trench may be located higher, and a satisfactory distance, T, will
still be maintained. However» if it is lower, there may be an insufficient
thickness of the partially saturated zone.
B-160
-------
APPENDIX C
THE FATE OF BACTERIA, VIRUSES AND NUTRIENTS IN SOIL
Since the link between disease outbreaks and the presence of pathogenic
organisms in waste-contaminated drinking waters was first established, there
has been considerable effort to reduce the numbers of bacteria and viruses
in potable waters by proper treatment of wastewaters. In addition, eutro-
phication from excessive nutrient concentrations in surface waters and the
public health hazard of increased nitrate concentrations in groundwater has
directed much attention to methods of controlling point and non-point dis-
charges of nitrogen and phosphorus.
From the standpoint of public health, removal of bacteria and viruses
is the most critical function of a wastewater treatment system. Yet, the role
of bacteria in the biodegradation of the wastes also must be recognized. With-
out bacterial enzymes, the hydrolysis of organic solids and their subsequent
oxidation would not occur. The biodegradation is the very basis of biological
waste treatment, and so bacterial growth and metabolism are to be encouraged
under controlled conditions. It is only in the final treated wastewater that
there is a concern for eliminating bacteria and viruses which pose a potential
danger to public health. This becomes a particular concern when partially
treated wastes are applied to the soil for final disposal. Therefore, know-
ledge of the fate of bacteria and viruses in soil and the mechanisms of
removal, is essential for preventing contamination of groundwater in areas
employing subsurface wastewater disposal systems.
Nutrients in wastewater are also of concern. Nitrogen,in the form of
nitrate or nitrite, found in private water supplies has been linked to cases
of methemoglobinemia in infants. Also, accelerated eutrophication can occur
if nitrogen and phosphorus are allowed to reach surface waters.
Therefore, the fate of bacteria, viruses and nutrients in the soil is
of paramount importance. A knowledge of the soil capabilities to remove
these contaminants, as well as the mechanisms involved, is necessary to
properly design and operate soil absorption systems for wastewater disposal.
THE FATE OF BACTERIA IN SOIL
Wastewater Bacteria and Their Detection
Human Intestinal Bacteria—
The normal intestinal tract of man and all other warm-blooded animals
contains a characteristic population of bacteria. At birth the tract is
sterile, but it is quickly invaded (certainly within the first day of life)
by bacteria from the mother's skin, food and water,and other objects put
into the infant's mouth. With the first food in the tract, these bacteria
C-l
-------
grow and the typical numbers and great variety of bacteria in the intestinal
flora are quickly established. All of this is quite normal, unless there
is a gross unsanitary handling of the infant, involving the risk of intestinal
diseases. In fact, it serves to establish the natural intestinal flora that
will persist throughout the child's life, which is believed both beneficial
for the mechanical functioning of the gut and in vitamin synthesis.
While the infant is fed milk, the dominant bacteria are lactose fermen-
ters, e.g., fecal coliforms and lactic acid bacteria, including the fecal
streptococci. Later, as non-sterile foods in great variety are ingested,
many other types of bacteria are introduced, but they do_ not displace the
fecal streptococci and fecal coliforms. These bacteria co-exist in a complex
mixture of many types of bacteria, somewhat affected in numbers, but not
in kinds, as diet varies throughout life (Haenel, 196l).
Many of the bacteria of this mixture are the same kinds as those found
in natural soils and waters. These intestinal bacteria become the general
flora in sewage and do not pose any danger to either health or the environ-
ment. In bacteriological testing of sewage, they appear in the Total Bac-
teria Count (Standard Methods, 1971). It is recognized that the count is
far from "total," but it is representative of the main bacterial populations
involved in general biodegradation.
Indicator Bacteria—
Superimposed on these normal groups of intestinal bacteria may be patho-
gens, if the individual is infected and shedding them via the feces.
Detection of these pathogens is difficult, due to their variety and low pop-
ulations. Therefore, to protect the public health, it is common practice
to determine if fecal contamination has occurred, thus indicating a
potential presence of pathogenic bacteria.
Fecal coliforms and fecal streptococci are commonly used as indicators
of fecal pollution, since they satisfy four important criteria:
1. They are always present in very high numbers in the feces of man
and other warm-blooded animals and do not naturally occur in high
numbers elsewhere in nature.
2. They are able to survive for sufficiently long periods of time
outside the body to be still present in wastewaters under treatment.
3. They can be monitored because quantitative methods for their
detection and quantitative pollution standards based on these
methods have been developed.
h. They generally outnumber the pathogens, and thus detection is
more likely to be successful. They can serve as "indicator bac-
teria: because where they are found there is a possible presence
of pathogens.
C-2
-------
However, there are some limitations to the interpretation of indi-
cator bacteria counts as an indicator of significant pollution. First,
in natural soils and waters, there may be contamination from wild animals,
resulting in a low background count (Geldreich, et_ al_., 1962). In an
effort to distinguish between animal and human sources of the indicator
bacteria, Geldreich (Geldreich, et_ al., 196^, Geldreich, 1967) proposed a
ratio of fecal coliform to fecal streptococci of U:l or greater as indi-
cating human intestinal pollution, whereas a 0.6:1 ratio implicates live-
stock, poultry, cats, dogs and rodents. But this distinction has never
been widely tested and has not been incorporated into Standard Methods (l97l)<
Another approach for determining the identity of human vs. animal intestinal
pollution is based upon determination of the species of fecal streptococci
in the sample. StTeptoooeous faeeali-s occurs in both animals and humans, but
predominates in humans, whereas it is found in relatively low numbers in
lower animals. Therefore, only higher and repetitive counts should be
considered to indicate human source pollution. This consideration is useful
when following decreasing numbers of indicator bacteria from the high counts
at the waste source through stages of treatment and final disposal.
There is one additional point to be kept in mind in the interpretation
of coliform bacteria counts, that is the distinction between fecal coliform
(FC) and total coliform (TC). Standard Methods (1971) defines the coliform
group of comprising "...all of the aerobic and facultative anaerobic, gram
negative, non-spore-forming, rod-shaped bacteria which ferment lactose with
acid and gas formation within kQ hr. at 35°C." This total coliform group
is heterogeneous and includes bacteria of several genera: Esaher'io'h'ia,
Enterobacter, Citrobactei>3 Klebsiella, Hafnia, Peotoba.eteiri.ian, and
Erwin-La. Although any of these coliforms may occur in the human intestinal
tract and, therefore, in the feces, some of them also occur in soil and water
and on green plants. Their best growth temperature is lower than that of
Escherich-ia coli, i.e., about 37°C. The other coliforms prefer 30 to 35° C,
which is, of course, still well within the optimum growth range for E. eoli.
Thus, the total coliform count run at 35°C, includes both E. aoli and other
coliforms. However, the higher more optimum temperature for E. ooli- allows
one to make a separate count by running tests at UH.5°C in a medium favoring
E. col-i. This represents the fecal coliform (FC) count which generally
account for only about one fifth of the total coliform (TC) count on fresh
feces or raw sewage. The significance of the total coliform count varies.
When applied to natural soils or green plant samples, the TC count reflects
mainly the Enterobaoter, Peotdbaotein-wn3 and Evwini,a members of the
complex, but when applied to human feces, the count has the same significance
as the fecal coliform count. When applied to unpolluted soil and water,
it reflects the low background count attributable to a scattering of wild
animals and possibly some surviving or free-living coliforms. Thus, there
is some significance in high total coliform counts. For the final effluent
or the soil absorption bed samples, where counts are low, greater reliance
is given to the FC count. Even so, testing for both E. coli, and S. faeoalis
(fecal streptococci, FS) is even more reliable and has been used in most
of these investigations.
When the indicator bacteria are released into soil at the disposal
site, a new complication arises. They may survive temporarily, or grow if
C-3
-------
conditions permit, or die off in competition with the soil bacteria.
Rudolfs, et_ al_., (1950) have reviewed these aspects of sewage bacteria in
soils. More recently, others (Geldreich, 1967; Van Donsel, et_ al_., 196?;
and Gerba, et_ al_., 1975) have discussed conditions which may determine sur-
vival or die off of the indicator bacteria in soils. Many of these con-
ditions are operative in the sewage/soil systems reported in this investi-
gation and will be discussed later.
Pathogens—
Man is subject to several intestinal or enteric diseases, meaning that
the gut is the infected site. Typhoid and paratyphoid, food poisoning and
other diarrhoeas and dysenteries, caused by several bacterial, viral and
amoebic pathogens, are examples of enteric diseases. The causal agents,
whether animal parasites, pathogenic bacteria or viruses, may be present at
times in feces and in wastewaters (Craun, 1975)-
There are three groups of pathogenic bacteria which can be monitored
directly in sewage studies; i.e., Salmonella spp., Pseudomonas aeruginosa
group and Staphylooooaus aureus group. Their incidence in healthy humans
are: salmonellae O.OU$ (Geldreich, 1970; Hall and Hauser, 1966; Craun, 1975);
P. aeruginosa 12-lU$ (Hoadley and McCoy, 1968); and S. aureus about 18% in
adults and UO+$ in children under 2 years old (Elek, 1959; Ziebell, et al.,
1975b; and Smith and Crabb, 1975). Because of their incidence and significance
to public health, these were the pathogens chosen for monitoring in this
investigation. The rationale of choice was:
1. Significance of salmonellae: If related to even a small number
of disease cases, its proven occurrence constitutes an outbreak
and is reportable to authorities;
2. Usefulness of P. aevuginosa and S. aureus monitoring: When present
in feces in sufficient numbers to allow detection, reduction in
numbers during waste treatment and disposal is easily monitored.
3. Quantitative measurement: Physiology of any of the above species
allows selective media and culture methods on which to base
detection and enumeration in the presence of other sewage and soil
bacteria; and
U. Low human risk: The risk of human infection during laboratory
handling is present but low, and safeguards can be provided by
employing proper techniques.
Salmonella spp.—The salmonellae comprise a large and complex group of
species and/or varieties, whose classification is based upon serological
typing (Bergey's Manual, 197M. A general term for salmonella infection is
salmonellosis. Some salmonellae are linked to specific diseases, and all are
suspect pathogens. Therefore, the finding of any salmonellae, whether in
foods, animal or human carriers, sewage waters or in the polluted environ-
ment, calls for elimination in order to protect the public. An extensive
review of the Salmonella problem in relation to sewage was done by Nero (197*0 <
C-U
-------
Pseudomonas aeruginosa group—Pseudomonas aeruginosa is an "opportun-
istic pathogen" and a common cause of ear, sinus and burn infections
(Forkner, I960; Frier and Friedman, 197*0- P- aerug-inosa infections are
persistent and can be serious due to its resistance to many antibiotics
(Artenstein and Sanford, 197** and Brown, 1975). Its occurrence in lower
animals is not common unless such animals have frequent contact with man,
e.g., domestic animals and especially young animals which are most likely to
be handled by man (Hoadley and McCoy, 1968). P. aeruginosa is regularly found
in wastewaters (Hoadley, et al., 1968).
Staphylocooaus aureus group— Staphyloaocous aweus is also an opportun-
istic pathogen which is capable of producing a variety of infections and a
form of food poisoning (Elek, 1959> Frier and Friedman, 197*0. While it was
originally susceptible to penicillin and many antibiotics, it is prone to
develop resistance, and such resistant populations are now found in many
hospital-acquired infections. Recently, several other species of Staphylooooous
associated with the human body have been reported (Kloos and Schleifer, 1975
and Schleifer and Kloos, 1975). Not all of these species are yet known to be
pathogens. Coagulase positiveness is generally indicative of pathogenicity
in S. awceus, but cases of coagulase negative staphylococcal infections are
known (Quinn, ert al_., 1965). It is, therefore, probable that the familiar
S. awceus is one of a group of staphylococci of potential pathogenicity.
The approach taken for this investigation was to enumerate all Staphylococcus
colonies on a specific growth medium (Kloos and Schleifer, 1975, Schleifer and Kloos,
1975) and to confirm true S. aureus3 if present by the coagulase test. The situ-
ation is thus comparable to that for the total coliform (TC) and fecal coli-
form (FC) bacteria in wastewater.
Laboratory and Field Studies
Materials and Methods—
Samples and handling before testing—Bacteria are living cells with
potential for either growth or death after sampling, thereby differing from
viruses. Special precautions are needed if bacteriological counts are to
represent the bacterial populations at the time and point of sampling.
Error can occur in two ways: l) growth or die-off after sampling or 2) fail-
ure to detect the target bacteria. The latter is a particular problem in
the counting of certain pathogens, which are always few in number and
generally unable to compete in the massive bacterial population in sewage.
In some cases, the actual numbers of the target counts are important in
order to compare with national standards, e.g., the fecal coliforms (FC).
More often in these investigations the numbers are important only to cal-
culate bacterial density (numbers per ml or per 100 ml) before and after
treatment so as to determine the effectiveness of certain treatment tech-
niques. Thus, accurate bacteriological enumeration can only be accomplished
through proper sampling, preservation, rapid transport and prompt testing
in the laboratory.
If the bacteriological sample is to reflect the actual bacterial count
of the waste in question, the sample must be taken in a sterile container
and in a manner to avoid contamination, i.e., aseptically. Wide-mouthed
C-5
-------
polypropylene "bottles of 500 or -1000 ml capacity are convenient; they are
autoclava"ble and non-breakable in the field. Their screw top closure is
also leakproof and is a safeguard against spreading of possible pathogens in
the laboratory.
The method of sampling depends on the nature and accessibility of the
sevage to be tested. The choice of type of sample is determined in part by
the conditions and purpose of testing.
Flaw composited samples were preferred where feasible, since they pro-
vide more uniformity and thus, minimize the need for replicating. In general,
the composite samples were taken from a holding vessel (originally sterile),
to which a portion of the sewage being treated was diverted continuously or
periodically over a 24-hr time. Such a composite sample was preferable to a
grab sample.
Grab samples were often taken to represent aerobic unit mixed liquors
or septage. In such cases, care was taken to well mix the liquid before
sampling so that suspended solids were uniformly distributed. However, non-
uniformity of grab samples is inevitable, since the solids themselves are
heterogeneous in nature, size and settling characteristics. Large volumes of
sample, mechanical blending in the laboratory and replication of tests (even
of the sub-samples for each laboratory test) were required to minimize error
in results based upon grab sampling.
Grab samples of septic tank sludge are sometimes desired. They can be
taken by a sterile bottle, lowered to the point of sampling and then opened,
or by a lake mud sampler which is also opened in, situ. The mud sampler was
used which is made by the Martek Co. and consists of a cone-shaped chamber
covered by a larger diameter disc. When the apparatus is in place, a rod
pushes the cone down and allows the sample to enter. Raising the cone closes
the chamber and protects the sample from contamination as the apparatus is
withdrawn. The sample was transferred by sterile spatula to a sterile
plastic bag, such as the Whirl-Pak type. The apparatus was rinsed in water
and alcohol and flamed to sterilize before the next sample was taken.
Soil samples were sometimes taken from various points surrounding soil
absorption systems. If the systems were opened by excavation, samples were
taken from the clogged zone just under or at the lower sidewalls of the
systems. This zone is usually only a few centimeters in thickness. Soil
adjacent laterally or below the systems were sampled by exposing to the
desired point (30 to 60 cm or more) by further excavation. Exposed surfaces
were then sampled with a sterile spatula or trowel, and the soil promptly
transferred aseptically to a sterile Whirl-Pak bag. Occasionally, a core of
soil was preferred and such a core was extracted by a simple open-ended
brass cylinder closed at both ends with rubber stoppers. The stoppers were
removed before insertion and the outer one replaced before withdrawal while
the other one promptly after withdrawal. Another convenient sampler consisted
of a longer cylinder cut-away along one side with a sheath to close this
opening before sampling. After withdrawal the sheath could be rolled back
to allow sampling at desired points within the core.
c-6
-------
Well-point water samples were also used in monitoring absorption fields
without excavation. The well points were driven to the desired depths and
left in place. When a sample was taken, water was withdrawn through sterile
tubing by vacuum. The first sample drawn was discarded so that the sample
taken afterward would represent the free water in the bed or ponded trench,
not the stagnant water in the "well." The well-point type of sampling was
often preferred to excavating, since the sites need not be disturbed.
Samples taken by any of the above methods were promptly ice-refrigerated
in the field and during transportation to the laboratory. For local samples,
the testing began as soon as possible, always within 2k hours. Freezing with
dry ice was not done, because such a procedure causes a serious reduction in
the counts (Calcott, et_ al., 1975).
Analytical Methods—Standard Methods (1971) recommendations are helpful,
but not always strict enough or broad enough for purposes of specific investi-
gations. Therefore, in some instances, the "standard method" was adapted or
new procedures developed for both sample handling and analysis. A brief
statement of the tests conducted is given here.
The following counts were routinely done for the bacteriological moni-
toring:
1. Total Coliforms (TC)
2. Fecal Coliforms (FC)
3. Fecal Streptococci (FS)
k. "Total" bacteria count (TBC)
5. Salmonella spp.
6. Pseudomonas aevuginosa group
7. Staphyloaoacus aureus group
Depending upon the need to know these counts, choices were made from the
list. Usually the TC, FC, and FS as indicator groups were most useful.
Usually tests also were made for one or more of the pathogens, most often
Pseudomonas for reasons given later. In general, the counts were done on the
MPN (Most Probable Number) basis, a practice approved in Standard Methods
(1971)- For some tests, the conventional plate count was preferred, especially
when a selective growth medium would allow selection of colonie for confirm-
ation of the bacterial type. The newer more rapid Membrane Filter (MF)
technique is becoming popular, but it is most applicable to clear liquid
samples. With turbid samples, clogging of the filter with slime, sludge or
soil is a problem. If high counts of a specific bacteria are expected,
dilution of the sample in sterile, peptone-buffered water blanks before fil-
tration is helpful, but not always feasible.
Table C-l summarizes the tests used.
C-7
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Results of Field and Laboratory Studies—
Bacterial quality of various wastewater effluents—In fresh raw waste-
water, the kinds and numbers of bacteria are predominantly those of intestinal
origin. As the waste passes through treatment, conditions change and new
types of bacteria flourish and compete with the intestinal bacteria. The
microflora of sewage, therefore is a complex mixture of bacteria growing and
dying in response to their environment. In the aggregate, they are capable
of biodegradation of numerous chemical compounds in the waste. In this
respect, they differ from the viruses which are merely carried along with-
out multiplication after leaving the body.
Anaerobic} treatment—The septic tank is anaerobic with the majority of
the functioning bacteria being facultative, capable of growth with or without
free oxygen. Because the wastewater is a high protein/low carbohydrate
substrate, proteolytic bacteria becomes dominant. The intestinal indicator
types are at a disadvantage, since they are fermentative, growing preferen-
tially when carbohydrate is available. Their numbers may decline during
septic tank treatment, but they are still present in significant numbers in
the effluent (See Table C-2). In addition, the pathogens, Staphylooooous
aureus and Salmonella spp. have been isolated in septic tank effluent (See
Table C-3).
Aerobic treatment—Aerobic treatment of wastewater offers a more advanced
degree of degradation where aerobic bacteria become dominant. These also
compete with intestinal indicator bacteria and pathogens but as Tables C-2 and
C-3 indicate, high numbers can still survive through aerobic treatment units
and sand filters. Ps. aeruginosa was found in higher numbers in the mixed
liquor of extended aeration units than in septic tanks, which indicates that
conditions are more suitable for its survival or growth in aerobic tanks
(Ziebell, et al., 19T5b).
Thus, it is evident that if soil is to be used for ultimate disposal,
it must be capable of removing the remaining harmful bacteria.
Bacterial removal from wastewater by soil—It is well known that soils
have a tremendous capacity to remove bacteria from wastewater. However, it
is difficult to specify the depth of soil through which the wastewater must
percolate to remove potentially hazardous levels of bacteria. Soil type,
temperature, and pH; bacterial adsorption to soil and soil clogging; soil
moisture and nutrient content; and bacterial antagonisms are factors which
affect bacterial survival and movement.
Laboratory studies—To study bacteria removal from septic tank effluent
by different soils, eight soil columns were set up for study under controlled
laboratory conditions (Ziebell, et_ aJ^., l9J5a). The columns were 10 cm in
diameter and 60 cm in depth. Columns 1 through U were hand packed with sand
from the C horizon of Plainfield loamy sand. Columns 5 through 8 combined
undisturbed cores of the A2 and B21 horizons of Almena silt loam which had
been taken in the field and coated with paraffin to facilitate handling
(Daniel and Bouma, 197M• The particle size distribution of these soils and
other relevant physical characteristics are presented in Table C-U. The
sand had a single grain structure, and the Almena silt loam had a prismatic
structure (2 to 5 cm wide and 5 to 10 cm high, relatively compact natural
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soil aggregates or peds, separated "by planar voids). The sand columns had
one tensiometer at a depth of 5 cm "below the sand surface. Six air exchange
tubes were placed at various levels in the column walls to ensure aerobic
conditions in the sand (Magdoff, et_ al_., 1975a). The silt loam columns had
four tensiometers at depths of 5, 10, 20 and 30 cm below the surface (Daniel
and Bouma, 197^-)• All columns were covered with vented plexiglass caps to
restrict drying.
The columns were subjected to different dosing regimes of septic tank
effluent at various temperatures (See Table C-5). The sand columns received
daily dosages of 5 and 10 cm of effluent. These loadings were chosen on the
basis of field monitoring studies. The infiltration rate through the clogged
layer in sands is approximately 5 cm/day (1.2 gpd/ft2) (Bouma, et_ al_., 1972).
This loading rate, therefore, is applicable to soil disposal systems, including
mound systems, in the field to allow continued functioning even when clogged
(Bouma, et_ a!L_. , 19T^b; Bouma, 1975). However, irregularities in liquid dis-
tribution may result in local overloading and the higher loading rate was,
therefore, also included in the experimental plan to investigate its effect
on purification.
TABLE C-5. EXPERIMENTAL DESIGN FOR COLUMN STUDIES INVESTIGATED
REMOVAL OF PATHOGENS BY SOIL (Ziebell, et al., 1975a).
Column
Soil
Temperature
1
2
. ..Plainfield
25
25
3 k
loamy sand. . .
5 5
5 6
. . .Almena silt
25 25
7
loam. . .
25
8
25
Loading
(cm/ day)
10
5
10
5
cont.
ponding
cont.
ponding
1 1
Soil disposal systems must function during the entire year, under vari-
able temperature conditions. In situ measurements of soil temperatures in
mound systems were found to range approximately 5 to 25°C suggesting the
temperatures to be used in these experiments (Bouma, et_ al_., 197^c; Bouma,
1975).
The type of silt loam tested has a low hydraulic conductivity at satur-
ation, generally less than k cm/day (l gpd/ft2) and sometimes even lower
(Daniel and Bouma, 197U). A dosing rate of 1 cm/day (0.2U gpd/ft2) applied to
columns 7 and 8 permitted complete infiltration within a day, thereby
allowing the infiltrative surface to be exposed to the air so that aerobic
decomposition of clogging compounds could occur. Columns 5 and 6 were con-
tinuously ponded by maintaining a constant head above the infiltrative surface.
The ponded columns simulated conditions where the loading rate exceeded the
capacity of the soil to conduct the liquid downward.
Travel times of liquid were determined in the columns with a 300 mg/L
KC1 solution as a tracer, used as described by Converse, et_ al_. , (l975a).
C-13
-------
The calculated retention times versus loading rates are given in Table C-6.
Septic tank effluent was obtained weekly from a single family residence
and stored at U°C until used. Since it contained relatively low numbers
of fecal coliforms and fecal streptococci, additions of each were made.
An isolate of each indicator organism was obtained from the sewage incubated
for 20 to 2U hours in shake flasks with Nutrient Broth (Standard Methods,
197l)5 and added to the septic tank effluent to obtain average concentrations
of 5-1 x 106 FC/100 ml and 7-3 x 106 FS/100 ml. Sewage, thus fortified,
was prepared every two days and stored at U°C, with insignificant die-off
occurring in this period.
Staphylocooous aureus (S.a.) generally was not present in the septic tank
effluent from this site. An isolate of this organism (S.a. FDA 209) was also
grown in nutrient broth and added to obtain initial concentrations of loVlOO
ml of septic tank effluent; this number is similar to those found in some
septic tank effluents (Ziebell, et_ al., 1975b). However, rapid die-off of
this organism occurred, dropping the counts by approximately 2 logs during
the 2 day storage. Nevertheless, the numbers of S.a. applied to the columns
were still in a realistic range for S.a. in sewage, i.e., 10^-10^/100 ml.
Pseudomonas aeruginosa (Ps.a.) was present and survived in the septic
tank effluent; no attempt was made to alter its numbers. The average concen-
tration was 1UOO/100 ml.
Before the start of experiments, tap water was applied to wet all columns
at the respective loading volumes for three days prior to initial septic tank
effluent application. The prepared fortified septic tank effluent was then
applied once daily to all columns except #5 and #6 which were kept ponded by
using Mariotte bottles filled every two days with fortified septic tank
effluent. Samples were collected in sterile polypropylene bottles with screw
cap lids attached by tubes to the base of the column.
The numbers of bacteria in the fortified septic tank effluent and in
column effluents were monitored regularly over a period of 200 days. Soil
moisture tensions and column effluent volumes were recorded prior to each
dosing. Occasionally, soil moisture tensions were recorded periodically
throughout a day to establish diurnal column performance and to relate
changes in the soil moisture recovery pattern in terms of moisture conditions
within the column as the experiment progressed. For example, these data were
helpful in judging whether clogging was developing.
Figure C-l and C-2 compare results from Columns 1 and 2 packed with
Plainfield loamy sand: both at 25°C with Column 1 receiving 10 cm and
Column 2 receiving 5 cm of effluent per day. Both columns initially removed
bacteria effectively, but after the first 5 to 10 days, they began to release
FC in their effluents. During the first 100 days of the experiment, the
number of effluent FC reached a plateau of approximately 3 x 105 FC/100 ml
from Column 1 and 103/100 ml from Column 2, as compared to the influent
waste containing 5.1 x 10° FC/100 ml. While these are unacceptably high for
a final effluent, they still represent removals of 9^-1 and 99-98% respectively.
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I
8 2
50
S
E 30
10
COLUMN 1
LOADING= 10 cm/day
*.«.'—-"*"•*./* "• *
20
60 100
Time (days)
140
180
Figure C-l. a. Bacterial data from Column 1 (Plainfield Is, 25° C);
FC = Fecal coliforms, FS = Fecal streptococci.
b. Soil moisture tension 5 cm "below the infiltrative
surface "before daily dosing (Ziebell, et_ al_., 19T5a).
Fecal streptococci appeared in the effluent from Column 1 (high loading) on
day U8 and reached a peak of 13,000/100 ml on day 95- Fecal streptococci,
however, were never detected in the effluent of Column 2 (low loading). At
approximately 100 days and thereafter, the effluent FC counts of "both
Columns 1 and 2 and the FS of Column 1 began to decline until the end of the
200-day experiment.
Pathogen removals were also detected through the columns. Pseudomonas
aeTug-inosa was detected in three effluent samples from Column 1 out of 19
tested: 23/100 ml on day 91, 3/100 ml on day 96, and 3/100 ml on day 128.
Staphyloeoecus aupeus was not found in any of the 15 Column 1 samples tested,
although 200 to 600 ml samples were analyzed. These pathogens were never
detected in the outflow from Column 2, although sample volumes of 30 to 50
ml for Ps.a. and of 100 to 350 ml of S.a. were tested.
The performance of these columns can also "be judged by the volume of
outflow and the moisture tension characteristics. The hydraulic data for
these columns showed sustained equilibrium conditions in terms of volume of
effluent collected daily and moisture tension stability (-^50 cm of water).
Column 1, after 100 days, showed some lag in recovery of tension after each
application, thus suggesting some flow impediment or early stages of clogging
(Figure C-lb). Column 2 tensiometer data did not show evidence of this condition
(Figure C-2b).
C-16
-------
H
COLUMN2
LOADING - 5 cm/day
FC
20
60
100
Time (days)
140
180
Figure C-2. a.
Bacteria from Column 2 (Plainfield Is, 25°C);
LC = Loading change, i.e., first change from
one 5 cm/day dose to three applications per
day of 1.7 cm each, and the second change re-
storing the original dose regime.
Soil moisture tensions 5 cm below infiltrative
surface before daily dosing (Ziebell, et al.,
1975).
Toward the end of the experiment, a change in the dosing regime was made
for Column 2 in order to test multiple dose application. On day 137» the
same daily quantity of 5 cm was applied, but it was divided into three 1.7 cm
doses. The first was applied in the morning, and the remaining two at
approximately h-hr intervals. There was only a slight reduction in bacterial
counts and on day 176 the original once-a-day rate of 5 cm/day was restored.
Columns 3 and h also packed with Plainfield loamy sand were maintained
at 5°C. They presented a somewhat different pattern including a drastic
change when a malfunction of the refrigeration occurred on day k&. (See
Figures C-3 and C-k). Thus, the data should be analyzed with respect to the
temperature effect, remembering the at 5°C bacterial growth and metabolism
are very slow.
C-17
-------
In the first days of operation, both Columns 3 and h removed at least
k log numbers of FC, before allowing a peak of about 10^ FC/100 ml to pass.
The peak period of release was short, about 10 to 20 days, followed by
rapid decline, which coincided with ponding in both columns. It is reason-
able to assume that this ponding resulted from accumulation of organic
compounds which were not decomposed very rapidly at the low temperature.
During this ponded period, tensions in both columns stabilized at approxi-
mately 30 cm, and the volumes of effluent dropped to 400 and 200 ml for
Columns 3 and U, respectively.
The refrigeration failure, which resulted in a rise in temperature on
day U8, caused impending with a consequent rise in bacterial numbers in the
effluents, high tensions after daily drainage, and larger daily volumes of
effluent, corresponding with the total daily applied volumes. Column k re-
ceived lower dosages and, therefore, could probably remain unponded for a
longer time. Both columns, when restored to 5°C, returned to the ponded
state and so remained for the duration of the study, during which Column 3
passed very little liquid (about UO ml/day) or bacteria (approximately 5
FC/100 ml). Column k (originally the lightly loaded one), on the other hand,
functioned better in terms of liquid outflow, but still poorly in terms of
bacterial removal. The higher FC counts in Column k effluent (as compared
to Column 3) are a reflection of shorter liquid retention times. Effluent
volumes from Column h of 100 to 200 ml/day can be associated with approximate
retention times of 3 to k days, while liquid entering Column 3 would require
approximately 12 days (at a flow rate of kO ml/day) before leaving the column.
Associated with these outflows, moisture tensions for Column 3 remained
between 35 and kl. cm, while tensions in Column U reached ^3 cm, then dropped
to 22 cm with the erratic outflow volumes and FC remaining at the high
10-ViOO rol' Gas bubbles were observed between the sand grains in the clogged
zone of Column h, and disruptions resulting from their release were believed
to cause these irregularities.
Although FC were present in the effluents of Columns 3 and k, these
columns functioned very efficiently in removal of FS and the pathogens,
Pseudomonas aeruginosa and Staphylocoocus aureus. Fecal streptococci were
found in only 2 of 21 samples of Column 3 (3/100 ml on day 9, and 58/100 ml.on
day 50) and in only 1 of 32 samples from Column U (1/100 ml on day 62).
Pseudomonas aeruginosa was present in 2 of 18 samples from Column 3 (3/100 ml
on days U2 and 1*5) and in only 1 of 20 samples from Column U (3/100 ml on day
9*0- Staphylocoocus aureus was not detected in either column effluent
(30 samples analyzed).
In summary, data for the sand columns indicate that only 60 cm of sand
can remove large numbers of fecal indicators and pathogens. Flow regime, and
soil temperature clearly affect the removal process, in part by inducing
early soil clogging at low temperatures. Removal below normal detection
levels was generally not achieved, especially during the early weeks of
operation of the columns (in this study, the first 100 days). This first
period, before clogging occurs, can be a critical phase of operation.
During this time, high loading rates and localized overloading may effect
transport of pathogenic organisms deep into the soil. A newly constructed
septic tank disposal system was implicated as the source of well water
C-18
-------
7
» 6
E
8 5
2
1
50
30
10
COLUMNS
LOADING =10 cm/day
20
60
100
Time (days)
140
180
Figure C-3. a.
b.
c.
Bacterial and physical data from Column 3 (Plainfield Is,
5°C: PD = continuous ponding after the indicated time,
UPD = unponded conditions after the indicated time.
Moisture tension 5 cm below the infiltrative surface.
Volume of column effluent collected (Ziebell, et al. ,
1975a).
contamination causing 60 cases of gastroenteritis in an Illinois State Park
(Morbidity and Mortality, 1972). The septic tank system had been installed
at the required distance from the veil as specified in the local code, how-
ever, during installation, groundwater was observed at 10 feet from the soil
surface and the well water was reported to be turbid for a short period after
installation.
The retentive power of the columns improves as bacterial films build up
on the sand surfaces. However, such columns can allow escape of FC and FS
and pathogens. Therefore, for safety, more than 60 cm of sand is required.
Low dosing rates significantly enhanced removal of fecal indicators
and pathogens, indicating that field system overloading, as represented by the
columns loaded at 10 cm/day, should be avoided.
Results of the chloride tracer study with silt loam columns are reported
in Table C-6. Columns 5 through 8 show a significant difference between the
ponded Columns 5 and 6 and the columns which received daily dosages of only
1 cm, i.e., Columns 7 and 8. Five and 15 days were required for displacement
of liquid present in Columns 5 and 6, respectively, as evidenced by the
first appearance of chlorides. The longer retention time for Column 6 was
C-19
-------
7
6
at
I 5
8
I 4
0)
CO
fr 2
°, 1
50
I 30
tu
O O
UI z
Q O
Z Q.
O Z
O
Z
COLUMN 4
LOADING = 5 cm/day
20
V V_ H _^— ^— ---"
60 100 140 180
Time (days)
Volume (mis)
Figure C-H. a.
b.
c.
Bacterial and physical data from Column U (Plainfield Is,
5°C): PD = continuous ponding after the indicated time,
UPD = unponded conditions after the indicated time.
Moisture tension 5 cm below the infiltrative surface.
Volume of column effluent collected (Ziebell, et al.,
1975a).
was due to its low hydraulic conductivity at saturation. The saturated hy-
draulic conductivity is controlled by the size and continuity of few,, but
relatively large, planar and tubular voids in the soil. These are the only
pores conducting significant quantities of liquid at saturation since water
moves very slowly through the soil aggregates (Bouma and Anderson, 1973).
Columns 7 and 8 received a daily volume of liquid at a rate less than
the saturated hydraulic conductivity. Therefore, these columns drained
successfuly in one day, as evidenced by an unponded surface several hours
before the next liquid addition. The total volume of water-filled pores
after drainage, i.e., at equilibrium, was 1^55 and 1575 cm^ for Columns 7 and
8, respectively. However, chlorides appeared in the column effluent after
passage of only TOO and 6HO cm3 of liquid, or about half the volume of liquid
present at equilibrium.
This can be interpreted by considering the nature of flow processes in
aggregated soils. Immediately after dosing, the large air-filled pores fill
with liquid and conduct this liquid considerable distances, depending on
pore-continuity. The liquid present inside the aggregates is bypassed.
C-20
-------
If such short-circuiting extends deep enough it could have implications on
sewage purification. The retention data reported for Columns 7 a and 8 in
Table C-6 were determined at the start of the experiment, indicating rela-
tively long retention times of 10 days. However, changes occurred in the pore
structure of Column 7- Interconnection of larger pores, perhaps caused by
faunal activity in these undisturbed cores, resulted in significant short-
circuiting. After the bacteriological experiments were completed, chloride
tracer studies were again conducted on Column 1. Results presented in Table
C-6 (Column Tb) show that chlorides appeared in the effluent within 3 hours,
after only TO cm^ of liquid had passed through the column. Field measurements
have been reported indicating similar phenomena in undisturbed soils below
seepage systems (Bouma, et_ a^., 197^b; Bouma, 1975).
Bacteriological analyses of effluents from Column 5 and 6 indicated
excellent removal of fecal indicator bacteria from sewage after continuous
ponding occurred. Two of 22 effluent samples from Column 5 contained 10 to
13 FC/100 ml and of these only 13 contained FS (2/100 ml). Pseudomonas
aeruginosa was found in four of the 13 samples, with highest numbers occurring
after day 100 (23, 15, 1 2*10, and >_ 2^,000/100 ml on days 100, 10U, 1^3 and
1^8, respectively). These data indicate conditions within this column were
favorable for survival and possible growth of this bacterium. Staphylocoeaus
aureus was not detected in lU samples analyzed.
Even better results were found for Column 6. An average of 15 samples
were tested for each organism (FC, FS, Ps.a. and S.a.}, none of which
contained detectable numbers of these bacteria.
Fecal coliforms, FS and Pseudomonas aevugi-nosa were found in the effluent
of Column 7, as indicated in Figure C-5- The concentrations of these bac-
teria reached 83,000 FC/100 ml, 100 FS/100 ml and greater than 2 x 10° Ps.a./
100 ml in Column 7 effluent on day 91- The numbers of Pseudomonas aeruginosa
were often greater than those of the influent sewage, indicating (as in
Column 5) conditions favorable for survival and potential growth. The
large number of fecal bacteria in the effluent implied short-circuiting
between soil aggregates or through channels formed by roots or worms as dis-
cussed earlier. On day 93, the loading was changed to 3 mm/day to determine if
a reduction of the loading rate would reduce the amount of liquid available
for vertical flow along cracks and channels, by allowing lateral capillary
forces to pull the liquid into the aggregates. Movement of sewage through
the aggregates would be expected to result in longer liquid retention, more
contact of sewage bacteria with soil particles and better purification. The
results confirmed this hypothesis. After the loading change, fecal indicator
bacteria were undetectable in the effluent within 30 days, and similarly
Pseudomonas aeruginosa within 90 days. Staphyloaooaus aureus was never
found in Column 7 effluent.
Fecal coliforms and FS were also found in the effluent of Column 8 during
the first ^0 days when unsaturated flow conditions existed (See Figure C-6).
However, the flow rate through this column gradually decreased below 1 cm/day,
and ponding resulted with unsaturated flow below the infiltrative surface as
indicated by tensiometer data (See Figure C-6). At this point, Column 8 was
C-21
-------
o
o
m
*
Q:
UJ
I
2
o
8
7
6
5
4
3
2
I
40
20
g
to
UJ
COLUMN 7
I CM/DAY
(A)
FC
(B)
20
CM/DAY
(C)
j i i u
100
50
60
100 140
TIME (DAYS)
180
Figure C-5. a. Bacterial data from column 7 (Almena sil, 25°C):
FC - fecal coliforms, FS - fecal streptococcus,
Ps. a. = Pseudomonas aerug-inosa.
b. Moisture tensions, 5 cm below the soil surface,
prior to daily dosing.
c. Volume of column effluent (Ziebell, et_ al. , 19T5a).
operating under conditions similar to Columns 5 and 6. Indicator organisms
were no longer detected in the effluent. Pseudomonas aeruginosa and
Staphylocooaus aweus were never found in 12 and lU respective samples from
this column.
In summary, data derived from the silt loam columns indicate that 60 cm
(2k in) of a slowly permeable silt loam soil can remove fecal bacteria very
effectively under certain flow regimes. However, the heterogeneous pore
structure of these aggregated clayey soils affects removal efficiency. Short-
circuiting of effluent through large air-filled pores resulted in rapid move-
ment of fecal indicators for considerable distance, as demonstrated in
Columns 7 and 8. These observations have practical implications for con-
struction of on-site disposal systems in slowly permeable soils having
seasonally high groundwater tables. Bacterial contamination of groundwater
from septic tank-soil absorption fields under such conditions in similar soil
has been shown by others (Viraraghaven and Warnock, 1973). The theoretical
pore continuity patterns in clayey soils indicate that the large pores,
through which short-circuiting occurred in this study, would not extend into
the soil indefinitely, and problems of groundwater contamination are unlikely
C-22
-------
50
30
10
COLUMNS
LOADING=1 cm/day
H
20
??9 99 ? 9? 9 ¥9 9 ?? 9 ? 9??? ? ? ? 9 ? 7?
3
0 -
60 100
Time (days)
140
180
Figure C-6. a. Bacterial data from Column 8 (Almena sil, 25°C):
FC = fecal coliforms, FS = fecal streptococcus.
b. Moisture tensions, 5 cm below soil surface prior
. to daily dosing.
c. Volume of column effluent (Ziebell, et_ aL., 1975 a )„
in slowly permeable soils having deep groundwater tables (Bouma and Anderson,
1973).
Removal of high groundwater tables by draining, with surface discharge
of the drainage water, is being used as a procedure to improve on-site con-
ditions for disposal of septic tank effluent (Bouma, 1975). However, short-
circuiting of effluent could lead to pollution of the water in these drains
and to surface water contamination following drainage discharge. One such
field system has been investigated, and, it was found that liquid in the
curtain drain had a high content of fecal indicator bacteria (Ziebell, et al.,
1973). This problem is particularly relevant because drains in slowly
permeable soils have to be deep and within a few feet of seepage trenches to
function properly from a hydraulic standpoint.
Field studies—The field studies included investigations of 19 conventional
subsurface soil disposal systems (Bouma, et_ al_., 1972). Some of the systems
were sampled at different times of the year, thus, they reflect in some degree
the seasonal variation in biological activity and consequent problems. The
general purpose of the bacteriological investigation was to monitor the number
of coliform and enterococcus organisms in septic wastes, in soil samples
taken at various points in drainage fields, and in test wells located around
C-23
-------
a number of such systems. A total bacterial count (TBC) was also obtained
in order to evaluate the interaction of the general soil microflora and
the sewage microflora in the area. The enterococcus count was assumed to be
equivalent to the fecal streptococci (FS) as Streptococcus faecalis. These
counts, and total (1C) and fecal (FC) coliform counts gave an indication
of bacterial movement and density in the field system. Movement of any of
these pollution-indicating bacteria to the surface of the soil or to the
groundwater was considered a priori evidence of unsafe conditions, i.e.,
failure of the system.
Detailed data on the bacterial populations for a single system in Plain-
field loamy sand illustrates the general characteristics of all 19 investi-
gations . Additional data from other systems studied may be found in a
report (Bouma, et_ al., 1972). The counts on the septic effluent entering
the seepage field were typically high for all of the bacterial tests. All
three of these pollution bacteria were rapidly removed by soil adsorption
below the trench (See Figure C-7),as were a great many of the general bacteria
of the septic effluent, as shown by a drastic drop in the TBC count. The
population in the seepage bed is reduced within 30 cm below or to the side
of the trench to about the level of the population in control soil. The
abrupt drop in numbers occurs between the clogged zone and 30 cm horizontally
or vertically.
FT
0 -
ABSORPTION FIELD
CROSS SECTION
2 -
TRENCH
o
-?
LIQUID
BACTERIA/100 ml OR PER 100g
OF SOIL
• I f t. -H
*
FECAL FECAL
STREPTO- COLI-
COCCI FORMS
< 200 < 200
^CLOGGED ZONE *:' :•'*>
TOTAL TOTAL
COLI- BACTERIA
FORMS x I07
<600
06
160,000 1,900,000 5,700,000 3.0
54,000 4,000,000 23,000,0004,400
<200 17,000 23,000 67
<200 <200 <600 3.7
<200 700 1,800 2.8
Figure C-7. Cross-section of an absorption field in Plainfield loamy
sand with typical bacterial counts at various locations
(Ziebell, et al., 1975t>).
-------
A darkening due to the presence of iron sulfide defines the clogging zone,
which implies anaerobic conditions within the zone. However, the bacteria
within the zone are not necessarily obligate anaerobic but are predominantly
facultative types functioning anaerobically (Bouma, et_ al_. , 1972). The
coliforms, fecal streptococci and many of the TBC bacteria are facultative.
From inspection of bacterial counts in the clogged zone, it is not possible
to say whether the bacteria living there result from trapping by adsorption
or from growth. Probably both processes occur, since nutrients, moisture,
pH and temperatures are favorable. One bit of evidence for growth of bacteria
in the zone is found in the high numbers of pseudomonads (Pseudomonas spp.,
including P. aevugi-nosa but also the P. fluopesoens group which is common in
soils but not in the feces). These pseudomonads are found in even greater
numbers in the adjacent soils below and at the side of the trench/soil inter-
face. In fact, they and certain yellow and orange Flavobaeterium spp. and
red Sepratia spp. can comprise up to 70% of the TBC counts. The high
pseudomonad count (it is as high as the low millions per gram of soil just
beyond the clogged zone) is probably important in the final "purification" of
the percolating water. Pseudomonads are known for the many carbon substrates
they can use, e.g., proteins, fats, carbohydrates, and many more resistant
carbon compounds like chitin, waxes, hydrocarbons, etc. (Stanier, et_ al_. , 1966)
The pseudomonads also produce pyocyanins, fluorescein, HCN, phytotoxic factors
and a number of endo- and exotoxins as yet not well defined (Artenstein and
Sanford, 197*0. Thus, they are probably a factor in the die-off of the
indicator bacteria and pathogens in the percolating wastewater. Field studies
also showed that within the first foot of soil, either downward or laterally,
soil actinomycetes, bacilli, and molds begin to appear and they are very
numerous in the second foot of soil (Bouma, et_ al_., 1972). These are anti-
biotic producers and no doubt contribute to the die-off of pathogenic indi-
cators. It is interesting that the TBC platings of soil taken beyond 30 cm
from the infiltration surface appear typical of the soil flora, rather than
of the sewage flora, which was still dominant in the first 30 cm. The
striking difference is:
Soil TBC: high proportion of gram positive bacteria, actinomycetes
and molds.
Sewage TBC: high proportion of gram negative bacteria, esp. pseudomonads
and other yellow-orange pigmented gram negative bacteria.
Summary
While remarkable purification can be achieved in non-aggregated soil
under conditions of established clogging and proper flow regime, it must be
remembered that many soil conditions are less efficient in providing bacterial
removal. During initial periods of operation (prior to clogging), conventional
soil absorption systems do not provide ideal removals. Similarly, channel-
ing due to voids between soil aggregates can result in movement of bacteria
to depths of 60 cm (2 ft) or more in aggregated soils, especially under dry
conditions. Under such conditions a deep soil profile or further treatment
of effluent must be present to insure adequate purification.
C-25
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THE FATE OF VIRUS IN SOIL
Background
Viruses differ fundamentally from other kinds of infectious agents. The
"life-cycle" of a virus includes a transmission phase and infecting phase.
Virus in the transmission phase is a small, inert particle which can only be
made visible with the aid of an electron microscope. Virus in the infecting
phase is a virtually formless presence inside cells of the host's body, serving
as a pattern for production of more virus particles. Cells which are infected
and producing virus tend to abandon their special functions in the body, and
they sometimes die. If enough cells die or are diverted functionally, the host's
body may undergo an abnormality called disease. Because the course of virus
disease can seldom be influenced by therapy, there is a tendency to blame all
intractable disease upon virus infections, even in the absence of any positive
evidence. Most human hosts develop immunity and recover from virus infections
despite the lack of effective therapeutic agents.
Virus in the infecting phase evokes the most concern; however, only virus
in the transmission phase can be forestalled. The inert particles of the virus
range upward from approximately 25 nm (one millionth of an inch) in diameter,
depending upon the kind of virus. A particle consists of nucleic acid coated
with protein. There may be some enzyme present, and (though not in the viruses
with which we are concerned) some particles are enveloped with a lipid-containing
material. The particle is significant because it may cause infection. Virus
transmission may be prevented either by precluding the particle's passage from
one host to another or by depriving the particle of its infectivity along the
way.
Intestinal Viruses—
Not all viruses are transmissible through the environment. Many lose their
infectivity so rapidly outside the host that they can only be transmitted by
person-to-person contact. To be transmissible in vehicles such as water and
food, viruses must maintain their infectivity through time and distance outside
the host; those which can do so are principally those produced in the intestines.
The intestinal viruses are shed by the infected host in feces; if the virus
contaminates water or other material ingested by another person, infection may
result.
Human feces do not always contain viruses because the human intestines
are not always infected. In countries where sanitation is not advanced,
children's intestines may harbor viruses more or less continuously during the
first 5 years of life. Survivors of these first 5 years show a progressively
lower incidence of intestinal virus infection.
Intestinal virus infections are less common in the United States but
still tend most frequently to involve young children. There is also a seasonal
trend: infections are most prevalent during the months of July, August and
September, at least for the enterovirus group. A person who is infected with
an intestinal virus may shed the virus in his feces for several weeks, perhaps
with no sign of illness, before developing a level of immunity which terminates
the infection. Immunity to that specific virus is durable, so that the person
C-26
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cannot usually be infected with it again. However, there are approximately
100 known types of intestinal viruses, so few persons acquire immunity to all
of them. In the United States, most people's intestines are without virus most
of the time, not because of immunity but because of sanitation. Americans are
relatively vulnerable to viruses to which they may be exposed as a result of
lapses in sanitation, as the experience of travelers to certain foreign countries
seems to verify.
The overall rate of virus infection and shedding in the United States
population is difficult to estimate accurately. A fairly recent survey in
Seattle involved families with very young children (Cooney, et al., 1972). The
overall incidence of viruses other than polioviruses in fecal specimens was 3.5
percent compared to 8.8 percent for polioviruses (presumably of vaccine origin).
A little over 2 percent of fecal specimens from parents contained any virus;
adults not closely in contact with young children would probably have shown a
lower incidence. Adenoviruses showed a higher prevalence than coxsackieviruses
or echoviruses; no reoviruses were reported. This is not typical of the dis-
tribution of kinds of enteric viruses reported to be detected in raw urban
wastewater, but this may be as much a function of sampling and testing techniques
as of the true relative incidence of different viruses. These findings do not
provide a very firm basis for estimation, but it seems likely that not over 1
to 2 percent of stools produced in the United States contain virus at all. If
all of this virus were enterovirus, one might expect a mean daily output of 10
plaque-forming units (PFU) per person per day, which is approximately 10~9g Of
virus material per person per day (at 100 particles per PFU). The weight of
virus shed might be greater by a factor of 10 to 100 because most other virus
particles are larger than those of enteroviruses. Given a number of additional
assumptions, one can predict, very approximately, the presence of 1 PFU of virus
per milliliter of urban raw wastewater.
There is no reason to believe that the rate of virus infection would
differ significantly among the 25 percent of the United States population that
is served by private waste disposal systems. However, intestinal virus in-
fections are likely to occur in a family on an all or none basis, (most usually
none) so that average levels of virus incidence are not meaningful. The great
majority of private waste disposal systems would be expected to receive no virus
at all on a given day; whereas those that do receive virus are probably getting
a hundred-fold higher level than that in urban sewage.
Waste Disposal—
The main line of defense against transmission of viruses shed in feces is
proper waste disposal. A private waste disposal system most often comprises
a septic tank and a soil absorption field. The virology of the septic tank is
virtually unknown; whereas, studies on transport and inactivation of viruses
in soils abound. There have been three general kinds of studies:
a. Batch studies, in which the virus is added to a slurry of sand or
soil particles in some type of fluid — The mixture is stirred for
a period of time; the fluid is separated from the solids by settling,
centrifugation, or filtration; the quantity of virus remaining in
the fluid is measured; and the degree of virus adsorption to the
solids calculated. Batch studies are not of direct applied value
C-27
-------
because the extent of virus removal is small. They enable deter-
mination of how ions, pH and interfering substances affect virus
adsorption.
b. Column studies in which virus-containing fluids are passed through
tubes packed with sand or soil. These simulate the filters of
disposal beds being evaluated. Columns are especially useful in
measuring the effect of flow rate on adsorption. Virus adsorption
is orders of magnitude greater in columns than in batch tests.
This is probably due to the increased opportunity for contact
between virus and fill material in the columns.
c. Field studies, in which samples are taken from wells dug at known
distances from a virus-application site. These studies document
infectious virus movement under natural conditions. Insofar as they
are meant to characterize the movement of naturally-occurring virus
in wastewaters, they may be limited by the infrequent incidence of
viruses in individual household wastes. Negative test results may
not mean anything, and positive test results may not mean what they
seem.
Virus Adsorption—
Some general principles emerge from the studies on virus adsorption to
particles of soil and sand.
Batch studies—Drewry and Eliassen (1968) and Eliassen and Drewry (1965)
carried out batch-type adsorption studies with three 32p_]_abeieci bacteriophages
suspended in distilled water containing various concentrations of sodium and
calcium salts. Five soils were tested. Virus adsorption decreased with in-
creasing pH, in the range from 6.8 to 8.8, and increased with increasing cation
concentration. Three soils showed greater than 90 percent adsorption at all
concentrations. Virus adsorption also increased with increasing ion-exchange
capacity, clay content, organic carbon and glycerol-retention capacity of the
soil. However, one soil, which ranked low in these properties, had the greatest
adsorptivity for viruses.
Carlson, et al., (1968) measured adsorption of poliovirus 1 and bacterio-
phage T2 on clay suspensions. Adsorption was negligible if the suspending
medium was distilled water; cations enhanced adsorption as a function of their
concentration. Their relative effectiveness was Al3+>Ca2+>Na+. The process was
90 percent complete in 5 min and essentially 100 percent complete in 20 min.
Adsorption could be prevented or reversed by adding albumin to the mixture.
Adsorbed virus remained infectious.
Schaub and co-workers (197^, 1975) studied the adsorption of enteroviruses
poliovirus 1, coxsackievirus B-2 and encephalomyocarditis virus to clays. With
respect to cation concentration, adsorption to bentonite was maximized (91%}
with 5mM Ca2+i 100 times greater concentration of Na+ was required for equivalent
adsorption. Enterovirus adsorption to montmorillonite did not vary signifi-
cantly over a pH range of 3.5 to 9-5- The virus association appeared to be
stable over a prolonged period, but 22 to 30 percent could be eluted readily by
diluting the suspension with 99 volumes of estuary water from which solids had
C-28
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been removed by filtration. Inactivation of sorbed and free virus proceeded
at similar rates. Sorbed virus was infective to laboratory animals.
Column studies—Robeck, et aX,(l962) applied poliovirus 1 (Po-l) in 80 to
160 cm/day of dechlorinated tap water to a column filled with 60 cm of California
dune sand. The column removed 2.7 to k.Q log1Q of virus continually for 98 days.
With 60-cm columns of fine and coarse Ottawa sand, virus removal increased as
flow rate decreased; there was a large variation from run to run at some of the
rates, however. In the coarse (O.J8 mm) sand column, virus removal varied from
1 percent at a flow rate of 1.6 cm/min to greater than 98 percent at k3 cm/day.
Each run was continued long enough to displace 2.5 times the volume of liquid
held in the column.
In upflow studies, columns containing 60 cm of coarse (0.38 mm) Chillicothe,
or fine (O.l8 mm) Newtown sand were dosed with water containing 10 plague
forming units (PFU)/ml and flowing up through the columns at a velocity of 90
cm/day. Complete displacement of the fluid in the column occurred in l6 to 2k h.
The effluent from the fine sand column was "virtually" virus-free; the effluent
from the coarse sand column averaged 8 PFU/mL . No exhaustion of virus-removal
capacity was observed during seven months of continuous operation. Addition of
alum to a virus suspension before filtration through coarse sand resulted in
virus-free effluents for a limited time, but after 6 to 7 h both the floe and
the virus broke through.
Drewry and Eliassen (1968) and Eliassen and Drewry (1965) reported studies
in which ^P-labeled bacteriophages Tl and T2 were applied to U3- to 50-cm soil
columns. The columns were operated at 20° C under saturated, continuous down-
flow conditions (l8 to Ul cm/day). The phage was suspended in distilled water
containing 1.0 mM Ca++ and 1.7 mM Na+. The columns removed from 79 to over 95
percent of the label, depending on the type of phage and soil tested. Most of
the phage was adsorbed in the first few centimeters. A significant amount of
inactivation occurred as a result of passage through the columns: PFU to ^2p
count per minute (SSI) ratios were 2 to k log-io lower in the effluents than
in the feed solutions.
Hori, et al., (1971); Tanimoto, et al., (1968) and Young and Burbank (1973)
tested the adsorption of coliphage TU and poliovirus 2 (Po-2) to three types
of soil, packed into 3.8 to 15-cm deep columns. The soils were two clay-type,
low humic latersols, and a volcanic cinder. The virus was suspended in distilled
water and the columns were washed with distilled water before dosing at 15 cm/day.
Virus breakthrough occurred in all the columns and the levels of virus in the
effluents increased with time. The clay-type soils were similar to each other
in performance, and more retentive of virus than the cinder. TU was retained
more effectively than Po-2. After 5 bed volumes of the suspension had been
treated, the 15-cm clay-type columns still retained over 99 percent of the polio-
virus, whereas only 22 percent was retained by the cinder column. All of the T^
was retained by the 15-cm clay-type columns, and more than 52 percent by the
15-cm cinder column.
Nestor and Costin (1971) constructed 70-cm columns with fresh sand and with
sand from operating waste-treatment filters. The sand was analyzed for organic
matter: the fresh sand contained 0.21 percent and the used sand 1.U5 percent.
C-29
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About U.7 cm of water was used to moisten dry, fresh sand columns. The columns
were dosed with 15-6 cm of tap water containing coxsackievirus A-U. Two dry (sic)
fresh sand columns reduced the titer of the virus suspension "by 11 percent; two
moistened fresh sand columns reduced it toy 80 percent; used sand from an un-
washed sand filter removed 95 percent; and used sand from a washed filter
removed 98 percent of the virus.
Kott and co-workers [Goldsmith., et al,, 1973; Lefler and Kott, 1973. 1971*)
dosed 10-cm fresh sand columns with Uo cm of salt solution containing Po-1
or bacteriophage f2 with similar results. Virus retention was related to cation
type and concentration. With l.OmM NaCl, 18 percent of the poliovirus was ad-
sorbed; with 500 mM NaCl, 83 percent of the virus was retained. Retentions were
U5 and lU percent respectively, with 0.5 mM Ca Cl2 and MgCl^. Increasing the
divalent cation concentrations to 5-0 mM resulted in virus retentions of 99-98
percent, which was similar to results observed with tap water.
Duboise, et al., (197^) studied migration of Po-1 and bacteriophage T7
through relatively porous sandy soil cores 19-5 cm high and 6.3 cm in diameter.
The cores had been washed with deionized water. The viruses were suspended
in deionized water and applied in small bands at the tops of the columns,
followed by either continuous (U-cm pond) or intermittent application of deionized
water. Three cores receiving T7 under continuous flow conditions retained
99 j 96 and 93 percent of the virus. There was no correlation between virus
breakthrough and the quantity of fluid accepted by the columns. Virus break-
through was rapid, decreasing gradually with time. Poliovirus behaved in a
similar fashion; 98 and 99-5 percent were retained by two columns. Under inter-
mittent flow conditions (l cm of dionized water every k hours), 99 percent of
the T7 and 99.6 percent of the poliovirus were retained.
The most important factor in virus retention by soil columns appears to be
flow rate: rapid flow systems generally removed only a small percentage of the
applied virus, while columns receiving moderate amounts of fluid reduced virus
levels by several orders of magnitude. Increasing cation concentration in the
suspending fluid also enhanced virus adsorption.
Field studies—In a wastewater reclamation project at Vhittier Narrows,
California (McMichael and McKee, 1965), wastewater containing 3 x 10^ PFU of
poliovirus 3 (Po-3) per liter was applied to a percolation basin. Samples
were collected from a central well with sampling pans at 6l to 2HH cm depths.
The soil in the basin was described as "dark brown very fine to medium silty
sand and soil, with an abundance of organic material." None of the samples
were positive for virus; but, because concentration techniques were not used,
the results could only be reported as less than one PFU per milliliter.
Wastewater containing added Po-3 was reclaimed by percolation through soil
in another California study (Merrell, et al., 1967). Wells were installed in
a sand and gravel formation at 6l, 12U and ^58 m from the edge of the disposal
bed to sample the upper 15 to 30 cm of groundwater. Approximately 5-3 x 10?
liters of wastewater containing 10^ tissue culture infective doses per ml were
applied to the percolation bed. No virus was detected in any of the samples
taken from the wells over a ^9-day period. Later tests showed that a salt
solution applied to the percolation bed reached the wells in less than kQ hours.
C-30
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Poliovirus 2 (Po-2) was isolated from drinking water from a well located
92 m from the edge of a septic tank drainfield (Mack, et al., (1972);
Vander Velde, 1973). A geological survey of the area revealed that the soil
underlying the absorption field was shallow and clayey, so there was probably
little treatment of the wastewater before it reached the groundwater and traveled
rapidly through cavernous limestone to the well.
Wellings,et al., (197^) sampled water from wells draining a spray irrigation
site which consisted of about k ha (10 acres) of sandy soil irrigated with
effluent from an activated-sludge waste-treatment plant. Application rates
ranged from 5 to 28 cm per week. Virus traveled up to 6 m in the sandy soil.
Most of the isolations were made following heavy rains.
Wellings, et al., (1975) also investigated the virological aspects of a
scheme to discharge treated wastewater into cypress domes, which are continuously
ponded. The dome under study had been drained, however. The soil profile
showed alternating clay and sand layers; the major groundwater flow occurred in
the sand layers. Sampling was by means of eleven drilled wells 3 m deep, lined
with polyvinyl chloride pipe. Most of the samples were negative, but a grand
total of 3 PFU were detected in the course of the entire study. The isolations
demonstrated percolation of virus to 3 m depth, plus lateral flow of at least
7 m. Virus passage through the clay could have been aided by the construction of
an observation tower, the support pilings of which cut through the clay layers.
Two of these 3 PFU were detected 28 days after the last effluent was applied,
indicating virus persistence of at least that long in the dome. These isolations
followed heavy rains, which might have aided in the transport of the virus.
Dugan, et al.,(l975) analyzed leachates from 150 cm deep lysimeters dosed
with wastewater. The lysimeters were filled with various types of soil. One
sample out of 28 was positive for virus. When "high concentrations" of Po-1 were
added to the wastewater, virus was found to penetrate as deep as 117 cm in one
case (sod lysimeter), and 15 cm in another (bare soil lysimeter). Another bare
soil lysimeter was seeded in two ways: either the virus was diluted in a large
volume of wastewater or the concentrated virus was applied directly to the soil.
In the first case, virus was detected as deep as 10 cm; in the second, the virus
had penetrated to 91 cm depth.
These field studies, although mostly uncontrolled, indicate that while soil
disposal beds are generally effective in preventing virus entry into groundwater,
heavy rains or breaks in the soil strata might reduce the effectiveness of the
system.
Summary—In terms of the objectives of the Small Scale Waste Management
Project, a number of important questions remain unanswered by the investigations
reported in this section. A few of the studies used wastewater as the suspending
medium for the virus, but little attention has been paid to the changes which
might occur in the system after many months of wastewater application. These
changes could alter the ability of a soil to remove viruses. Secondly, it is
not possible to predict, on the basis of the information available, just how
much virus would be removed by a given system. Although flow rates seem to
influence virus penetration into soil, the available data do not allow selection
of a rate which would ensure complete safety. There is no information on the
C-31
-------
effect of low temperatures on virus retention, and the question of whether or
not the virus is inactivated after sorption has not been addressed. Recent
reviews pertinent to this subject have been written by Bitton (1975) and by
Gerba, et al., (1975).
Laboratory and Field Studies
Areas of Study—
Several aspects of the virology of on-site disposal systems have been
studied. The virology of the septic tank and the virology of septage were
examined briefly. The principal focus has been on the removal of virus from
septic tank effluent (STE) by slow percolation through 60 cm of sand, as in a
mound. The virology of systems which might be used to prepare STE for surface
disposal was also investigated.
Materials and Methods—
Virus preparation and assay—Poliovirus type 1 (Po-l)» strain CHAT, was
obtained from the Viral and Rickettsial Registry of the American Type Culture
Collection. Po-2 and Po-3 were isolated from feces of a recently vaccinated
child. A swine enterovirus, ECPO-6 was obtained from Dr. E. H. Bohl at the Ohio
Agricultural Research and Development Station, Wooster.
The polioviruses were propagated in primary rhesus (Macaca mulatta) monkey
kidney (PMK), established African green (Cercopithecus aethiops) monkey kidney,
or established human cervical carcinoma (HELA) cell cultures. An established
swine kidney cell culture lines (MPK) was used to detect the ECPO-6 virus,
which served as a model contaminant in the feces of an infected pig. Methods
for preparing the cultures, propagating the viruses, detecting viruses in cultures
maintained with fluid medium, and quantification of viruses by the plaque tech-
nic in cultures maintained with semisolid medium were largely as described
earlier (diver and Herrmann, 1969; Salo and Cliver, 1976).
Po-1 was sometimes labelled with 32p so that the virus particles could
still be located, even if they were no longer infectious. The procedures
used have been described in detail elsewhere (Cliver and Herrmann, 1972; Herrmann
and Cliver, 1973; Salo and Cliver, 1976).
Sample processing—The samples to be examined in a study such as this
differ considerably from those ordinarily encountered in laboratory virology.
Special procedures had to be developed to make the samples suitable for the
detection and assay of virus that was present.
Samples derived from an experimental septic tank at the Park Street Labor-
atory (site N) presented unusual contamination problems. Trial and error led
at last to a procedure for coping with this contamination. To a 10 mL sample in
a large screw-cap tube were added 0.05 mL diethyl ether. The mixture was treated
for 15 sec with the tube immersed in ice water in a sonic cleaning bath. After
2 hours of inculation at room temperature, air was sparged through the sample
for 1 hour to remove the ether residue. This reduced the microbial population
but did not eliminate it. When the sample was tested in tissue cultures, it was
necessary to include the following in each milliliter of maintenance medium:
C-32
-------
5 yg amphotericin B, 1500 y penicillin, 60 yg tetracycline, and 100 yg genta-
micin.
Samples of septic tank effluent (STE) from an operating septic tank at the
Arlington Experimental Farms and of fluids partly or completely treated in a
sand or soil column were processed somewhat differently. If such samples were
frozen before testing, a precipitate would often form; when this precipitation
occurred, most of the virus that had been present was lost in some unexplained
way. Therefore, samples were ordinarily stored in the liquid state, at tempera-
tures <_ 8° C. If the level of virus in the sample was expected to be fairly
high, the sample might be diluted with 9 volumes of phosphate-buffered saline
PBS) plus 2 percent fetal calf serum (PBS-FC2) and then frozen. Either of two
means were used to rid these samples of bacteria before testing in tissue culture:
l) adding chloroform (5% by volume) to the sample, mixing and then removing all
traces of chloroform by sparging air through the sample, or 2) filtration at
0.20 ym porosity (Gelman GA-8) (Cliver, 1968). The latter method required that
suspended solids be removed from the sample by prefiltration. Effective pre-
filters tended to adsorb virus. This could be prevented by adding 2 percent
fetal calf serum to the sample before prefiltration (Cliver, 1965); however, the
presence of the serum would preclude later concentration of virus by the ad-
sorption- elut ion method (Cliver, 1967). If the virus had adsorbed to the solids
which were to be removed by the prefilter, the adsorption could usually be
reversed by adding 10 percent fetal calf serum. Virus could be concentrated from
a sample by adsorption to a cellulose nitrate membrane filter (0.22 ym porosity,
Millipore GS or 0.^5 ym porosity, Millipore HA and elution with a small volume
of fetal calf serum or cold pH 11.5 buffer. However, adsorption was likely to
be poor if calf serum had been added to the sample to enable prefiltration, and
elution was often less than complete.
Sorbed virus was removed from sand and soil column fill samples by stirring
with 1.0 mL of fetal calf serum per gram of fill. This procedure was tested
by adding 5-0 mL of ^P-iateledi Po-1 to 22.6 g of sand, conditioned as described
below by use in STE treatment, in a chromatography column. The virus was allowed
to adsorb overnight, eluted as above, and the eluate counted. Recovery was
77 percent. Recovery was not improved by adjusting the pH of the serum to 8, 9»
10, 11 or 12. Recovery with pH 11.5 glycine buffer was 71 percent; with PBS as the
eluent, recovery was 20 percent.
Yet another procedure was used to recover virus from septic tank sludge
with relatively little admixture of supernatant after experimental inoculation
and attempts at disinfection. An equal volume of fetal calf serum was added to
the sample, and the mixture was stirred with a magnetically-driven bar while
the pH was adjusted to 9 with IN NaOH. After another 15 minutes of stirring,
the mixture was treated with 5 percent chloroform by volume for 1 hour in an ice
bath. Settled solids were resuspended and the suspension was decanted from the
chloroform. Residual chloroform in the suspension was removed during 15 minutes
of treatment in a sonic cleaning bath filled with ice water; the flask containing
the sample was subjected to a vacuum of 500 mm of mercury to encourage vapor-
ization of the chloroform. The treated sample was stirred for 15 minutes with
an equal volume of phosphate-buffered saline (PBS) and assayed by the plaque
technique. Using ^P-labelleA. Po-1, this procedure was shown to recover all of the
virus particles, but more than Uo percent of the infectivity was lost in the
C-33
-------
process. Sodium sulfite (^2803) was used to neutralize glutaraldehyde in
samples from the disinfection experiments. The final concentration of 1.26
g/L (lOmM) was shown not to affect the infectivity of Po-1.
Columns — The majority of experiments were so varied that the procedures
can best be described together with their results. However, the operation of
the various sand and soil columns used in treating STE had enough features in
common to merit a general description.
The first columns (A and B) were the largest. They were constructed from
lU.6 cm ID PVC pipe, 150 cm in height and were capped at the bottom end (Figure
C-8). The cap was fitted with an outlet tube. The columns were filled with 15
cm of gravel at the bottom; 30 cm of a Batavia silt loam soil; 60 cm of a
medium (0.2 aim) sand from the C horizon of a Plainfield loamy sand; and 30 cm of
gravel (Magdoff, et al. ,
Below the sand surface were rings of 1 cm diameter aeration holes spaced 8
cm apart. Also below the sand surface were 2.H-cm holes (plugged with rubber
stoppers) for fill sampling. Samples were obtained by removing a stopper and
digging out some fill with a bent-tipped spatula. For fluid sampling, fritted-
glass tipped gas-dispersion tubes were embedded in the fill at the same depths
as the fill sampling ports; fluid samples were drawn by applying a vacuum.
— FLUID SAMPLING PORT
AERATION HOLE
FILL SAMPLING PORTS
Figure C-8. Diagram of Column A (lU.6 cm inside diameter)
-------
All columns were maintained at room temperatures (l8° to 2it°C), unless
otherwise stated, and were dosed manually once a day with STE from a family
residence. The STE was delivered to the laboratory weekly in a 19 L glass car-
boy. This volume was divided into dose-size units and stored at 6° to 8° C.
Units were warmed to room temperature, and virus was sometimes added just before
dosing the columns. Columns A and B initially absorbed approximately 3.5 L of
STE before any effluent began to flow out the bottom port.
The 60 cm of sand in the lk.6 cm ID columns occupied a volume of 10,000 cu
cm and weighed 17.2 kg when dry. When a fill sample was saturated with water,
its weight increased to 121 percent of its dry weight, so the void volume of a
60 cm, lU.6 cm ID sand column was approximately 3.6 L. In normal operation, the
columns were never saturated. Fill samples taken 2h h after dosing with 5
cm of STE showed that the sand at the top of the column was about 25 percent
saturated, increasing to 100 percent at 60 cm. Calculations indicated that a 5
cm dose resided in the sand for two full days.
Columns C, D, E and F were 1.6 cm ID and were filled with 60 cm of sand,
without any underlying silt loam. Columns C, D and F were filled with fresh
sand, whereas column E (also containing 60 cm of sand) had been dosed with 5 cm
of STE/day since its construction 3 weeks earlier.
Two columns contained Almena silt loam cores which had been collected in situ.
The cores were U8 cm (column G) and 5^ cm (column H) high and were set in 66 cm
sections of 10 cm ID acrylic pipe. They received 0.6 cm (50 ml) of STE daily,
the maximum they would accept being 65 mL. NaCl (300 ppm) was added to the STE
to determine its rate of passage through the columns; the results indicated that
column G may have been short-circuiting.
Shorter, smaller columns (minicolumns) were sometimes used in order to get a
clearer picture of the movement and inactivation of viruses in sand columns.
Cylindrical filter holders (Millipore Corp. or Gelman Co.) were found to be ideal
for this purpose. The Millipore holders consisted of a 1.6 cm ID glass cylinder
which clamped to a glass base containing a stainless steel mesh filter support.
The Gelman units were composed of 1.9 cm ID polypropylene tube which attached to
a stainless steel base fitted with a steel mesh. For the Millipore columns each
milliliter of dose volume was equivalent to 0.50 cm height; in the Gelman units
a 1.0 mL dose was equivalent to 0.35 cm.
The units were assembled without a filter, and packed with 1 to 5 cm of
sand or soil, as required. The approximate void volume of the minicolumns was
determined by dosing a moistened and drained 3 cm fresh sand column with 0.5 cm
(l.O mL) of PBS labelled with 36ci~ . This was followed by 0.5 cm doses of label-
free PBS. The first 0.5 cm of effluent contained none of the label; the second,
3 percent; the third, 55 percent; diminishing thereafter. From these data the
void volume was calculated to be 0.3 cm of fluid per cm of fresh sand. The
experiment was also performed using conditioned sand, which showed a similar void
volume.
C-35
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Results—
Septic tank inoculation—Infectious swine feces (25g) containing 10 7 PFU of
ECPO-6 were added to the input end of the 1000 gallon septic tank at the Park
Street laboratory (site N). If the tank had contained exactly 1000 gallons of
liquid and if mixing had been instantaneous and complete, each milliliter of the
contents should have contained ~ 65 PFU of the virus. None were detected in
effluent samples taken on 18 successive days thereafter. No firm conclusions
can be drawn from this because the contamination problems described previously
had not been solved fully by the time of this experiment. However, it does
appear that this septic tank may have inactivated much of the virus with which
it was inoculated.
Column studies—The purposes of these studies were to determine the degree
to which virus in STE was removed by passage through sand and other soils, the
effect of prolonged use upon sand and soil performance, the influence of the
STE loading rate, the influence of temperature and the extent to which the re-
tained virus is inactivated (loses infectivity).
The sand or soil into which STE is discharged starts in a "fresh" state and
gradually becomes "conditioned with use." The study first tested retention of
virus by these media when they were in the "fresh" state. Two 5.0 cm ID columns
were filled with 10 cm of fresh sand, and two with 10 cm of fresh Batavia silt
loam soil. Each was dosed daily with 5 cm (100 mL) of STE containing 12,000 PFU
of Po-l/mL. Effluents were collected daily and assayed for virus infectivity
(Table C-T). The sand column effluents contained fewer than 7 PFU/mL for three
days; then the titers increased by an order of magnitude. This was perhaps a
result of the columns becoming conditioned. The daily dose exceeded the func-
tional void volume of the sand. Virus remained low or undetectable in the
effluents from the Batavia silt loam columns.
Further, to establish the degree of virus retention by fresh soils, two 1 cm
minicolumns were constructed. They were packed with Almena and Batavia silt
loams respectively. Each was dosed with 1.8 cm of Whatman #1 filtered STE con-
taining 8 x 10? PFU of Po-l/mL. The effluent from the Almena column contained
1 PFU/mL, a 7.9 log reduction; the Batavia column effluent contained 1.7 x 102
PFU/mL, a 5.7 log reduction.
The effect of conditioning—Penetration of the virus into the fresh sand
columns progressed with time. This could have been the result of repeated
desorption, transport and readsorption with each STE dose. Another possibility
was that as the columns became conditioned, their retentiveness for virus
decreased.
To test the effect of conditioning on virus retention, the performance of
60 cm of fresh sand (column F) was compared with 60 cm of sand (column E) which
had received 5 cm of "virus-free" STE daily for 3 weeks. Column F was given
a single virus-free STE dose, and both columns were placed in the cold room
(6° to 8° C) to retard conditioning in column F. The next morning (day 0) both
columns were dosed with 5 cm (250 mL) of (<_ 8° C) STE containing 6.0 x 10° PFU
of Po-l/mL. Thereafter, each column received daily 5 cm doses of cold (<_ 8° C)
virus-free STE. Titers of fluid samples taken from various depths in these
C-36
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TABLE C-7. REMOVAL OF Po-1 FROM STE BY
10 cm FRESH SAND AND SOIL
COLUMNSl
Effluent titers in PFU/mL from
Sand Columns Soil Columns
Day
#1 #2 #1 #2
0
1
2
3
U
5
6
7
8
9
10
o2
0.3
1
7
19
5^
50
36
33
35
51
0
0
2
2
32
20
32
12
2
0
0
1
0
0.2
0
0
0
0
0
0
2
0
0
0
0
1.5
0
0
6
0
1.7
0
1
2
0
Daily dose: 5 cm of STE containing 12,000 PFU/ml.
2
No PFU detected = 0.
Column ponded.
columns are reported in Table C-8. The conditioned column was less retentive
of virus than the fresh sand column.
To examine further the difference in virus adsorption between fresh and
conditioned sand, two sets of minicolumns were constructed. Each set consisted
of three columns in Gelman filter holders, packed with 2, h or 6 cm of fill.
One set contained fresh sand, the other conditioned sand removed from columns
A and B. Each column was dosed with 3.5 cm of labeled virus. The effluents
were collected and counted. Results are presented in Table C-9. The fresh
sand was 1.8 times more effective in removing virus than the conditioned sand,
and the removal was proportional to column length.
C-37
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TABLE C-8. VIRUS TITERS OF FLUIDS FROM COLD SOIL COLUMNS"
Column E (Conditioned)
(cm depth)
Column F (Unconditioned)
(cm depth)
uay
1
2
3
5
8
111
21
35
175
180
205
362
363^
5
62
5.5U
5-36
—
—
5.28
5-32
11.95
2.90
U.79
3.93
2.3
2.3
15
6
5.81i
5.23
—
5.00
5.59
5.18
5.U2
3.36
U.7U
3.23
2.9
2.8
30
1.3
3. Oil
2.8
—
2.5
2.8
3.65
3.61*
3.01
3.53
2.U5
2.58
2.0 .
*5
o3
0
0.2
1.57
0.3
0.6
0.2
0.0
1.53
0.6
0.0
0
0
5
5.011
3.95
3.77
U.56
—
5.00
5.08
5.00
3.63
U.99
3.76
3.51
3.0
20
0.5
0.95
0.2
0.8
0
0.8
1.3
1.U3
2.93
2.5
2.00
2.88
1.8
30
—
—
0
—
0
0.0
1.76
0
1.58
0.0
1.00
0
0
^5
—
—
0
—
—
—
0
0
0
0
0
0
0
Dosed daily with 5 cm of STE, vhich contained 8.78 Iog10 PFU of Po-1 per mL on
day 0 and 7.00 Iog10 PFU of Po-2 per mL on day 176. On day 175 they received
20 cm of virus-free STE. They were maintained at 6-8° C, "but column E had
been preconditioned at room temperature.
2
Iog10 (PFU/mL)
No virus detected = 0
u
The viruses in these samples were mostly Po-1.
Two minicolumns were filled to 1 cm with fresh Almena silt loam, and two
with fresh Batavia silt loam. The soils were conditioned by dosing the columns
for 28 days with 0.35 cm of filtered STE/day. On the 29th day, 0.9 cm of filtered
STE containing 9.0 x 10? PFU was added, followed by daily 0.35 cm doses of virus-
free filtered STE. Accumulated effluents were collected 1 and 9 days after the
C-38
-------
TABLE C-9. COMPARISON OF Po-1 RETENTION BY FRESH AND
CONDITIONED SAND COLUMNS
Fill
Fresh
Conditioned
Column Length
(cm)
2.0
U.O
6.0
2.0
U.O
6.0
Recovery in
Effluent (%)
15
2
0.5
50
22
11
Loss/cm
(log1Q)
o.>a
O.li3
0.39
0.15
0.16
0.15
the virus dose. The day 1 effluents from the Batavia columns contained totals of
2TO and 300 PFU; by day 9, only another 1^0 PFU had washed out of the first
column and 22 PFU from the second. Approximately 5-^ l°§io °^ virus were re-
tained by the columns. No virus was detected in the effluents from the Almena
columns, showing at least a 7-9 l°§io reduction in virus titer. These values
correspond quite closely to the results obtained with the fresh soils, there was
no indication that conditioning had reduced their retentiveness for virus.
Effect of hydrautic loading—Fresh 10-cm sand columns had removed \ log-m
of virus from a daily 5 cm dose of STE. The next problem examined was the effect
of a 10-fold increase in hydraulic loading rate. At higher loading rates
the pores between the sand grains would be filled with fluid, and this could
affect virus adsorption. Two 60 cm fresh sand columns were dosed daily with STE
containing ca. 10° PFU of Po-l/mL. Column C received 5 cm/day and column D
50 cm/day. Virus concentrations in the columns are represented in .Figure C-9.
At 10 cm depth on the first day (day 0), the 5 cm dose was reduced in titer by
^.U log-j_Q; the 50 cm dose was reduced by only 3.2 log-]_Q. As time progressed,
virus penetrated deeper and in greater numbers in both columns, but column D
samples were always one or more logs higher in titer than the comparable sample
from column C (Tables C-10 and C-ll).
An experiment to determine the effect of an STE overload on a conditioned
60 cm column, was carried out on column A which had 30 cm of Batavia silt loam
below the sand zone (Figure C-8). An 8.0 L batch of STE was inoculated
with Po-1 to a titer of U.6 x 105 PFU/mL. This amount of STE was equivalent
to a 50 cm dose, 10 times the "normal" amount. One-tenth of this was applied to
the column, and as soon as no fluid remained on the surface, fluid samples were
taken from ports 1 through 8 and 12. An additional Uo percent was then applied
and was followed by an identical sampling procedure. The final 50 percent was
then applied; it percolated through the column during the night. The next
morning, before dosing, a third set of samples was collected. A fourth set
C-39
-------
DAY 0
DAY
DAY 6
DAY 13
DAY 21
0
10
e 20
o
a.
ui
o
30
40
50
60,
036 036 036 036 036
log,0 (PFU/ml)
Figure C-9- The effect of dose size on Po-1 penetration into 60 cm fresh
sand columns. Symbols: 0, 5 cm of STE/day; 50 cm of STE/
day until day 11, when crusting reduced the flow rate to ca.
20 cm/day.
was collected five days later, after normal dosing (5 cm of virus-containing
STE/day) had resumed. The data showed that as the dose increased, the virus
penetrated further and in greater numbers through the column. By the second
sampling (5 cm + 20 cm STE applied) the virus had penetrated as far as the
bottom of the sand; and by the third sampling (5 cm + 20 cm + 25 cm = 50 cm STE
applied) virus was detected in the effluent, having passed through the silt
loam in the bottom of the column as well. After returning to normal dosing,
the virus levels dropped at all depths, but still had not returned to pre 50 cm
dose levels after 5 days (Table C-12).
Next, the effect of flow-rate on virus retention by conditioned sand was
studied. Two minicolumns were filled to 3 cm with sand from columns A and B.
Each was dosed with 3.5 cm (10 mL) of PBS containing 5,^00 CPM of 32p_la-kele(i
Po-l/mL. One of the columns had the entire dose applied directly: This passed
through the column in less than one minute. The dose for the other column was
applied dropwise over a 2.5 h period (l.H cm/h). The rapid flow column retained
6l percent of the virus; whereas the slow-flow column retained 96 percent. The
slow-flow column was 2.2 times as retentive per centimeter of column length as
the rapid-flow column, in terms of l°g-,n virus titer reduction.
-------
TABLE C-10. VIRUS TITERS OF FLUID SAMPLES FROM COLUMN C
Sampling depth
Day
0
1
6
13
20
21 3
22aH
22b
23
26
30
57
TO
8it
92
99
107
Hit
120
137
Iit2
Iit7
15it
160
175
182
191
200
208
217
1
log
_ 10
2
STE
5.61
6.15
6.00
—
—
—
—
5.48
6.it5
—
5-93
5.85
—
—
—
—
—
—
—
—
—
—
5.2
—
—
—
(PFU/mL)
No virus detected
3
5 cm
dose
10 cm
1.23
1.8
2.81
3.5
—
U. 00
lt.80
it. 81
it. 58
5.08
5.68
5.65
6.3U
5.^5
—
5.26
—
—
—
—
—
—
—
—
—
—
—
—
—
—
= 0
20 cm
2
0
0
1.18
1.60
—
2.6
3.15
3.58
3.8
it. 63
it. 5U
5.3
6.3it
it. 78
—
5.11
—
—
—
—
—
—
__
—
—
—
—
—
—
— —
30 cm
0
0
0
0
0
0
l.itO
2.6lt
2.0
3.32
3.18
3.6
—
3.it9
—
it. 8
—
—
—
—
—
—
__
—
—
—
—
—
—
— —
40 cm
0
0
0
—
0
0
0.8
0.3
2.6k
3.08
0.7
__
1
5.84
it
—
—
—
—
—
__
__
—
—
—
—
—
—
—
50 cm
—
—
—
—
—
0
0
0
0
0.8
0
0.7
1.11
l.Oit
—
—
—
—
—
__
—
__
—
—
—
—
—
—
—
60 cm
0
__
—
0
0
0
—
0
—
0
0
0
1.08
0
2.8
2.6
1.95
1.8
1.70
2.63
0.3
0
0.6
0
1.70
—
0
0
0
it
50 cm dose
C-itl
-------
TABLE C-ll. VIRUS TITERS OF FLUID SAMPLES FROM COLUMN D
Day
0
1
6
13
21
26
30
57
70
84
92
99
lilt
120
136
137
142
147
15l*
160
175
191
200
208
217
1
2 ]
STE
5.61
—
—
—
5-0
—
—
5.48
6A5
—
5-93
5-85
—
—
—
—
—
—
—
—
—
5-2
—
—
—
LO (PFU/mL)
10 cm
2.38
2.58
4.15
3.8
U.53
14.18
5.02
5.614
6.28
5.54
—
5.67
—
—
—
—
—
—
—
—
—
3.5
—
—
—
20 cm
O2
0.8
2.95
2.5
3.69
3.8
4.63
5.71
5.65
5.U6
—
5.47
—
—
—
—
—
—
—
—
—
1.7
—
—
—
Sampling
30 cm
0.6
0
1.80
1.81
2.95
2.5
3.3l|
5.69
5.26
5.30
—
14.60
—
—
—
—
—
—
—
—
—
0
—
—
—
depth
40 cm
0
0
0
0.95
0
2.67
2.84
5.36
—
5.20
4.7
4
—
—
—
—
—
—
—
—
—
1.5
—
—
—
50 cm
0
—
—
—
0
0
0
2.11
4.00
4.62
4.5
4
—
—
—
—
—
—
—
—
—
0.7
—
—
—
60 cm
0
—
—
__
0
0
0
2.48
4.08
3.90
4. 3
3.1
3.1
2.8
1.3
1.9
1.28
0.3
0
0.7
0.8
0.5
—
0
0
0, no virus detected.
If virus retention is a function of flow-rate, then virus adsorption may be
related to the degree of fluid saturation of the pores between the sand grains.
To investigate this, a minicolumn filled with 2 cm of fresh sand was washed with
PBS and drained; the last free liquid was forced out with compressed air.
Labeled virus in 0.35 cm (0.6 times the void volume of the sand in this mini-
column) of phosphate buffer was added, followed immediately by 3.2 cm (5 times
the void volume) of PBS. Approximately 98 percent of the virus label was retained
in the column. The then saturated column was again dosed and flushed in the
same manner. Ninety-six percent of the virus was retained. Next, 3.5 cm (6
void volumes) of the virus in PBS was added. The column retained 93 percent of
the labelled virus. A second 3.5 cm dose of PBS (without virus) eluted only 0.2
percent of the sorbed virus. These data suggest that even though fresh sand
retains virus quite effectively, adsorption per unit depth of sand is somewhat
reduced under conditions of saturated or rapid flow.
C-142
-------
TABLE C-12. VIRUS TITERS OF FLUID SAMPLES FROM COLUMN A,
TAKEN AFTER INCREASING STE DOSE VOLUMES
Depth
(cm)
0
6
13
21
28
37
44
52
60
90
Cumulative
5
5.662
It. 26
3.26
2.23
2.08
-0.30
O3
0
0
0
STE dose
in one
25
5.66
5.40
4.95
3.96
3.45
2.1+6
1.34
0.70
0.84
—
(cm)
day
50
5.66
—
—
—
4.15
3.59
3.28
3.00
2.72
0.30
51
5.30
5.04
4.6
3.3
—
—
0.0
0
1.20
0
Five days after return to 5 cm/day dose.
2 Iog10 (PFU/mL)
No PFU detected = 0
Removal of virus from STE by vested conditioned sand—Columns C and D had
"crusted" (were unable to pass 50 cm of STE per day) after 4 weeks of operation.
To determine if the columns could be restored to their original state by
letting them rest, dosing was stopped. Four weeks later (day 57) the columns
were cooled to 6°to 8° C, and dosing with virus-containing STE resumed at the
original rates (See Figure C-10).
Virus was detected in the effluent from column D immediately (See Table C-ll)
and in the effluent from column C after 27 days (See Table C-10). After 22 days
(day 79 of total), column D was moved to room temperature, and 27 days later
(day 106 of total) its dose was reduced electively to 5 cm/day. (it had not
crusted.) The effluents from both columns continued to contain low levels of virus
until days 125 (182 of total) and 134 (191 of total), respectively, after this
experiment began.
To examine different ways in which resting could have modified column per-
formance, barrels from 3 mL plastic syringes (Becton-Dickinson) were filled with
C-43
-------
50
30
^^
o 10
-
'///////m
V/\
%
I
%
'/A
COLUMN C
f
COLUMN D
60
90
DAY
120
217
Figure C-10. Dosing and temperature regimes for Columns C and D.
Shading under curve operation at room temperature;
open, operation at 6-8° C;Q , column would no longer
accept previous dose within 2H h; , mean dose
accepted per day during period when column was
ponded.
3.5 cm (2.0 cm3) of: fresh sand; conditioned sand; air-dried conditioned sand;
and acid-washed, conditioned sand. There were two replicates of each treatment.
The conditioned sand columns were dosed with 0.5 mL of filtered STE for 7 days
to restore the conditioning before use. Then 3.5 cm (2.0 mL or 3.3 void volumes)
of 32p_ia-be]_ea p0_]_ j_n GA-8 filtered column effluent was added. The first
milliliter of effluent was discarded; the second was collected and assayed for
label and infactivity. The columns were then dosed with 3.5 cm or filtered
column effluent containing 32p_iabeie
-------
TABLE C-13. RETENTION OF VIRUS AND E. COLI IN 3.5 cm SAND
COLUMNS UNDER DIFFERENT FILL CONDITIONS
Recovery in effluent
Fill
Po-1 E. coli
Fresh
Conditioned
Cleaned conditioned
Dried conditioned
0.02
0.^7
0.26
0.30
0.20
0.19
30
U6
11
23
6U
63
58
57
68
67
Long-term operation of aolwms—Columns A and B contained 60 cm of sand and
over 30 cm of of silt-loam soil. The columns received 8 cm (13^0 mL) of STE
daily for 25 days, to "condition" them. They then (day 0) were dosed with 8 cm
of STE containing 3.0 x 10? PFU of Po-1, followed by daily 8 cm doses of STE with-
out virus. Each day's effluent was assayed, as was the uninoculated STE. No
virus was detected. Beginning two weeks after the Po-1 dose, k.2 x 105 PFU of
Po-3 were added each day for a week, followed by daily 3.^ x 10" PFU doses of
Po-2. On day 28 the virus was switched to Po-1 again, at levels greater than
10T PFU/day. No virus had been detected in the effluents up until this time
(2 mL/day were tested), but on day 28 there was a virus PFU in the effluent sample
from column B. No further PFU were detected from this column. Beginning on
day 37, concentration techniques were incorporated to increase the amount of
effluent that could be assayed. One hundred mL or more were tested weekly, there-
after. A sample from column A collected on day 92 produced one plaque (900 mL
were tested). Effluent assays were performed at intervals until day 536. From
day ii76, column A samples were collected from port 8, at the sand/silt-loam
interface. No further PFU were detected. By day 536 the columns had each
received 5 x 1010 PFU of poliovirus (Table C-lU). A total of 23 liters of efflu-
ent had been examined for virus, and 2. PFU; one from each column were detected
(Table C-15).
Effects of low temperature—Columns E and F, containing 60 cm of sand,
were used to study this topic. Column E had been dosed with STE for 3 weeks at
room temperature before being placed in a cold (6 to 8° C) room; the sand in
in column F was fresh. Both were then dosed with 5 cm (250 mL) of STE containing
1.5 x 1011 PFU of Po-1; thereafter they received 5 cm/day of virus free STE.
C-U5
-------
TABLE C-lU. VIRUS APPLIED TO COLUMNS A AND B
Day Virus
0 Po-1
1-13 None
lit - 20 Po-3
21 - 27 Po-2
28 - 59 Po-1
60 - 76
77 - 80 "
81 - 153 "
15it - 223 "
22it - 295 "
296 - 299 "
1
300 - 385 "
386
387 - 575 "
576 - 6ll None
612 Po-12
1
Columns dosed six
2
Column A only.
"•^ *+ -i T-i -\ r\ £ r\
Daily Dose
Titer Volume
(Iog10 PFU/mL) (mL)
it. 36 13UO
__ ii
2.51
3.U2
3.60
it. 02 "
It.it5
U. 15 "
it. 32
it. 23
5-36
5.57 8itO
5.66 SltOO2
5 . 30 8Uo
-
8.2lt "
days per week after day 300.
Total
(Iog10 PFU)
7.it8
—
5-62
6.53
6.72
7.15
7.57
7.26
7- it 5
7« 3it
8.U8
8.1t8
9.56
8.20
—
11.17
Cumulat i ve
dose
(Iog10 PFU)
7.U8
7.it8
7.52
7.76
8.36
8.65
8.78
9.30
9.59
9.7U
9.83
10. U6
10.51
10.79
10.79
11.323
C-U6
-------
TABLE C-15. VIRUS ASSAY OF EFFLUENT FROM COLUMNS A AND B
Day
1-27
28
29
31
37
38
39
i+o
1+3
1+1+
^
52
60
73
77
87
92
103
108
110
115
128
Volume
assayed (mL)
A
2
2
2
1+
i+oo
200
100
200
0
100
200
200
200
200
200
200
900
200
200
200
200
100
B
2
2
2
U
1*00
200
100
200
100
100
200
200
200
200
200
200
200
200
200
200
200
100
Cumulative volume
assayed (mL)
Method -—
A
Direct 5^
56
58
62
3% "beef extract 1*62
662
762
962
962
1062
1262
11+62
1662
1862
" 2062
" 2262
3162
3362
3562
3762
" 3962
1+062
(continued)
C-l+7
B
51*
56
58
62
1+62
662
762
962
1062
1162
1362
1562
1762
1962
2162
2362
2562
2762
2962
3162
3362
31+62
PFU
detected
A
0
0
0
0
0
0
0
0
-
0
0
0
0
0
0
0
1
0
0
0
0
0
B
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-------
TABLE C-15 (continued)
Day
133
156
165
172
193
220
228
2UO
21*1*
261
300
313
325
328
3l*2
393
1*76
1*81
519
536
Volume
assayed (mL) Method
A
100
200
200
200
500
500
1*50
600
650
550
380
900
31*0
31*0
320
280
320 -1
320 1
21
l1
B
100 3% beef extract
200 "
200 "
200 "
500 "
500 pH 11.5 glycine
500 "
600
600
550
320 Fetal calf serum
1150 "
31*0
1*00
320 "
31*0
260
200 "
2 Direct
1
Cumulative volume
assayed (mL)
A
1*162
U362
1*562
1*762
5262
5762
6212
6812
71*62
8012
8392
9292
9632
9972
10292
10572
10892
11212
11211*
11215
B
3562
3762
3962
1*162
1*662
5162
5662
6262
6892
7l*12
7732
8882
9222
9622
99l*2
10282
1051*2
1071*2
1071*1*
1071*5
PFU
detected
A
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
B
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
Sample collected from sand/silt loam interface.
C-U8
-------
Fluid was collected periodically from the sample ports and assayed for virus
infectivity.
Virus penetration was greater in the conditioned than in the fresh column
(Table C-8); this pattern persisted throughout the experiment. On day 175
the columns were dosed with 20 cm (l.O L) of virus-free STE. The next day
they received 2.5 x 109 PFU of Po-2 in 5 cm of STE. Application of 5 cm/day
of virus-free STE continued thereafter. The final samples were taken on day
363. Most of the virus in these samples was Po-1, which had been applied on
day 0. Virus is less rapidly removed (and, as shown below, more slowly in-
activated) in sand at 6-8° C than at room temperature. This seems unlikely
to present a problem except in cases of hydraulic overloading.
Virus mobility in Qondit-loned sand—Column A was dosed with 5 cm (QkO mL)
of STE containing a higher titer of virus (1.7 x 10° PFU/mL), followed by daily
5 cm doses of virus-free STE. The passage of the virus down the column was
monitored for 2k days by assay of both fill and fluid taken from the sampling
ports. The column had been in operation 21 months, so it was fully conditioned.
There was no indication of crusting or ponding. The last virus had been applied
one month earlier, and samples were taken to determine residual virus levels
before the experiment commenced. Fill samples were taken just before dosing,
and fluid samples shortly after dosing. Virus distribution in the fill is
illustrated in Figure C-ll, and fluid sample titers are shown in Figure C-12.
Numerical data from the experiment are recorded in Table C-l6.
Residual virus infectivity from previous applications was measurable in
fluid samples down to 28 cm depth, but in fill samples only as deep as 21 cm.
Titers decreased exponentially with depth in the fill samples. The fluid samples
on day 1 (after dosing) displayed a different pattern. The virus was uniformly
distributed from 6 to 28 cm depth, dropping off sharply below that point. On
day 3, the fill titer at 6 cm depth had decreased by 50 percent but had increased
at all depths below that down to 37 cm, suggesting that virus had relocated
downward. Fluid sample titers had decreased at all depths to 28 cm, but at
37 cm were higher on day 3 than on day 1.
Samples taken on or after day 7 all showed lower titers than samples from
day 3. This pattern continued through day 2k, when the experiment was termin-
ated. As shown by the percentages quoted in Figures C-ll and C-12, most of the
virus inoculated did not penetrate the column as far as the sampling ports,
at least in an infectious form.
Inaotivation of virus retained in conditioned sand—The above experiment
showed that migration of infectious virus through conditioned sand columns
receiving moderate (5 cm/day) doses of STE was extremely limited. Furthermore,
as time progressed, less and less of the infectivity could be recovered from
within the column. The virus was clearly being inactivated in the column.
This inactivation was explored further using eight 3.5 cm minicolumns. They
were packed with 20 g of conditioned sand and dosed with 0.7 cm of filtered
STE/day for 10 days to restore the conditioning after packing. Each minicolumn
was then inoculated with 1.0 x 10' PFU of Po-1 suspended in 0.7 cm of filtered
STE. The following day, the fill from two of the columns was removed and
-------
DAY-I
30-
40
50
60
DAY I
DAY 3
( I \ L I I I I I 1 1 I
11%
73%
DAY 7 DAY 24
22%
036 036 036 036 036
loglo(PFU/g)
Figure C-ll.
Po-1 distribution in a conditioned sand column (fill samples),
The percentage shown compare the amount of virus represented
"by the area within the curve to the total amount of virus
that was applied in the dose on day 0.
DAY -1 DAY 1 DAY 3 DAY 9 DAY 24
0
10
1 2°
H 30
O.
g
40
50
fin
-
A
-1
{
f
-
1 I I I I I
-
0.08%
4
-
Y
h
-
1 1 > 1 1 1
P
002"/
-
^
;/
t
-
1 1 1 1 i i
r
000
- ,
t
3%
1
-
r
000007%
_
-
036 036 036 036 036
loglo (PFU/ml)
Figure C-12.
Distribution of virus in a conditioned sand column (fluid samples).
The percentages shown compare the amount, of virus represented "by the
area within the curve to the total amount of virus that was applied
in the dose on day 0.
C-50
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TABLE C-16. TITERS OF SAMPLES FROM COLUMN A
Sample
Type
Fluid
Fill
(cm) -1
6 2. II2
13 1.77
21 0.3
28 0.8
37 O3
44
52 0
60
6 3.67^
13 1.89
21 0.0
28 0
37 0
44
52
60
Po-1 dose: 11.17 log.. . PFU
2 -LU
log1Q (PFU/mL)
No virus detected = 0
4 ,
Days after virus dose
1379
4.95 4.36 — 3.59
4.95 4.34 — 3.48
5.00 4.00 — 3.23
4.68 4.32 -- 3.08
0.5 2.58 — 1.2
00—0
o
0
7-52 6.81 6.34
4.90 6.38 5.76
1.8 3.65 2.94
0.8 3.59 2.52
2-3? 3.04 2.36
0 0 0 —
—
—
in 5 cm of STE; 8.24 Iog10 ( PFU/mL).
24
2.08
1.32
1.87
0.3
0
—
—
—
4.8
4.45
1.08
1.51
1.45
0
—
—
(PFU/gram)
stirred with 10 mL of fetal calf serum to elute the virus. The serum suspension
was GA-8 filtered and assayed as were the effluents from the two columns. The
other six columns each received 0.7 cm/day of virus free filtered STE. At 7» l4
and 28 days two more columns were sacrificed and assayed as above.
C-51
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After 7 days the infectivity recoverable from the fill had dropped to 55
percent of the day 1 recovery; by day lU it was 10 percent and by day 28, 2.5
percent. The effluent which accumulated in 7 days contained only 0.06 percent
of the virus input; later accumulations were no higher. One column was dosed
with 32p_la-beled Virus; after 7 days only 0.2 percent of the label was recovered
in the effluent. This indicates that the inactivated virus particles (or viral
RNA, at least) were remaining in the columns.
To determine how disposal systems in sandy soils or mounds might be expected
to perform during the winter, a set of eight minicolumns (similar to those just
described) was run at 6 to 8° C. The duration of the experiment was extended
from U to 8 weeks. The results presented in Figure C-13 include those of the
room temperature experiment for comparison. The sorbed virus was not inactivated
to any great extent in the cold, even after 8 weeks. After k weeks at room
temperature, only 2.5 percent of the infectivity was recovered, whereas 57 percent
of the virus was still infective after k weeks at 6 to 8° C. The cold columns
also allowed approximately 10 percent of the virus input to pass into the effluent.
Virus inaotivat-ion rates in sand oolyncns and fluid suspensions—The Po-1
retained in column A became inactivated at a daily rate of 0.088 log]_Q units, or
18 percent per day (from Figure C-ll). The daily inactivation rate in 3.5 cm
conditioned sand minicolumns was 0.062 Iog10, or 13 percent per day (Figure C-13).
Virus in similar minicolumns operated at 6 to 8° C was inactivated at a rate of
0.0005 Iog10 (1.1$) per day.
Lefler and Kott (197*0 studied the survival of Po-1 in fresh sand columns
saturated with distilled water, tap water or oxidation pond effluent. The rate
of Po-1 inactivation was 0.038 Iog10 (8.3$) per day with distilled water, 0.0^0
l°SlO (8.8$) per day with tap water, and 0.031 log-,Q (6.9$) per day with oxidation
pond effluents. The experiments were run at 20° C, and samples were taken over
COLD FILL
o
LU
cr
o
o
cr
> 001
ROOM TEMP FILL
ROOM TEMP EFFLUENT
20 30 40 50 60
DAYS
Figure C-13.
Effect of temperature on inactivation of Po-1 in
conditioned sand columns 3.5 cm deep.
C-52
-------
a 175 day period. Columns at h to 8° C (fluid unspecified) had a Po-1 inacti-
vation rate of 0.00*1 Iog10 (0.92$) per day. The authors pointed out that even
drying did not inactivate all the virus. Sand columns to which Po-1 was sorbed
were tested after 77 days of dryness, and 0.02 percent of the infectivity was
recovered.
Rates of Po-1 inactivation in fluids at room temperature have been compiled
from several of the experiments in the present study. Median daily rates were
0.146 Iog10 (29$) in STE, 0.237 Iog10 (1*2$) in column effluent or port samples,
and 0.037 I°g10 (8.1$) in PBS or PBS - FC2. At 6 to 8° C, the median daily virus
inactivation rates were 0.01*7 Iog10 (10$) in filtered STE and 0.020 Iog10 (1*.5$)
in PBS. Inactivation rates were generally greater in STE and its fluid derivatives
than in the columns.
Mierobial role in the inaotivati,on of sorbed virus—Oliver and Herrmann
(1972) observed the inactivation of coxsackievirus A-9 when mixed with a pure
culture of Pseudomonas aeruginosa. They did not observe inactivation with other
viruses (including poliovirus) or other bacteria, but their study does suggest
that microbial activity in the columns may have a role in virus inactivation.
To test this, six different types of bacteria were isolated (on the basis
of colony morphology) from fill samples. Pure cultures were grown overnight
in 0.1* percent nutrient broth powder (Difco) dissolved in filtered STE. The
cultures were diluted 100-fold in the same medium, Po-1 was added, and the six
flasks were agitated on a shaker at 30° C for 7 days. One additional flask
was a bacteria-free control. The virus titer was reduced by approximately 2 log-^Q
in all the flasks: The concentration in the control was 3.8 x 10^ PFU/mL, and
the cultures contained from 1.0 x 103 to 3.1* x 103 PFU/mL. These data indicate
that the bacteria played a minimal role in the inactivation of the virus.
The question was explored further by comparing Po-1 inactivation in sterile
and non-sterile minicolumns. Six Millipore cylinders were filled to 3 cm with
conditioned sand. All openings were covered with foil and the columns autoclaved
at 121° C for 30 min. After cooling, 1.0 cm of sterile phosphate buffer contain-
ing 2.2 x 10' PFU of Po-1 was added to each column; the columns were resealed
and the virus allowed 2 days to adsorb to the fill. Three of the columns were
then seeded with STE bacteria by dosing them with 2.0 cm of Whatman #1 filtered
STE (F-STE). The three sterile control columns were dosed with 2.0 cm of sterile
Whatman #1 filtered, autoclaved STE (the filtration was necessary to remove the
precipitate induced by autoclaving). On subsequent days all six columns received
2.0 cm of sterile, filtered STE. To assure that sterile conditions were main-
tained in the control columns, the STE also contained antibiotics (0.1 mg genta-
micin, 200 units penicillin, 0.2 mg streptomoycin, and 0.01 mg fungizone per
milliliter).
After 33 days the effluents from all the columns were collected and tested
for sterility in trypticase-soy broth. The samples from the seeded columns were
not sterile, whereas all samples from the control columns were. The fill from
each of the columns was removed and stirred with 10 mL of fetal calf serum to
elute the virus. The effluents and the serum eluates of the fill were assayed
for infectivity. There was no statistical difference (t-test at 95$ confidence
level) between the virus recoveries from the two sets of columns (Table C-17).
C-53
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TABLE C-1T. INACTIVATION OF SORBED Po-1 IK STERILE AND
NON-STERILE 3 cm CONDITIONED SAND COLUMNS
Recovery
Column
Sterile
Non-sterile
Fill
12
22
9
13
IT
12
Effluent
19
19
8
6
2
3
There was no indication that the bacteria in the non-sterile columns caused a
reduction in virus infectivity.
Adsorption of virus to floe fowned in condit'ioned sand—When minicolumns
were being filled with conditioned sand from larger columns, a light, flocculent
material settled out of the slurry last and formed a layer on top of the sand.
A series of experiments was undertaken to determine the role played by this floe
in the retention of viruses by the columns.
•30
Ten grams of conditioned sand were placed in a beaker, and 1.0 mL of J P-
labeled Po-1 in phosphate buffer was added. After a 1.5 h adsorption period,
the material was shaken with 10 mL of filtered column effluent to separate the
floe from the sand grains. The floe was dried on a planchet and counted. It
contained 93 percent of the labeled Po-1.
Next, a Gelman minicolumn was filled to 5 cm with fresh sand and dosed with
filtered STE daily for 2U days for conditioning. The column was then dosed with
1.8 cm (1.2 void volumes) of 32P-labeled Po-1 in phosphate buffer. This was
followed by 31 daily 0.7 cm (0.5 void volumes) doses of virus-free filtered STE.
The accumulated effluent was collected, and the fill was removed and shaken with
two 10 mL portions of divalent cation-free, buffered physiological saline to
separate the floe from the sand. Ninety-one percent of the labeled Po-1 was
recovered in the floe and U.O percent in the accumulated effluent. Homogenization
of the floe suspension in a Sorvall Omni-mixer released only U.5 percent of.
the bound virus.
To determine if virus adsorbs to floe in the absence of sand, a sample of
floe was collected from conditioned sand removed from column B. The floe was
packed into a small column (9 mm inside diameter, Pharmacia K9/15), and U.7 cm
(3.0 mL) or 32p_;]_abeled Po-1 was added. Less than 3 percent of the label passed
-------
through the ^ cm of floe. The column was frozen; and the cylinder of floe
was removed and cut into slices which were dried, weighed and counted. Sixty-
one percent of the virus was located in the top l6 percent of the column. The
floe was strongly retentive of the virus and appears to be the primary site of
virus adsorption in conditioned columns.
Summary
This study has examined the virology of septic tank waste treatment systems,
with emphasis on the fate of virus during the soil phase of the treatment.
Further study of the septic tank itself is merited: it seems to do a rather
good job of removing fecal virus from wastewater.
Poliovirus type 1 in septic tank effluent (STE) was percolated through
columns containing silt loam or sand. The silt loam removed the virus very
strongly (not less than a 10-thousand fold reduction in 10 cm depth) and were
unimpaired in efficiency after priods of use. Fresh sand also retained virus
very efficiently; but after being "conditioned" by a few weeks' applications
of STE, the sand was less retentive of virus, especially at temperatures as low
as 6 to 8° C.
The assumed standard loading conditions in this study were 5 cm/day of STE
applied to a 60 cm depth of sand. If the sand had been conditioned and was
subjected to a ten-fold hydraulic surge overload, some virus was carried through
the 60 cm of sand, especially at 6 to 8° C. Well over 99 percent of the virus
was removed from the STE by the sand under the worst conditions that were devised
and tested. Surge loading was not a factor in virus removal by silt loam because
their low hydraulic conductivity precludes too-rapid infiltration of the STE.
Further applications of STE cause very little displacement of virus which
has been retained in sand. The virus is gradually inactivated in the sand;
the rate is lower at 6 to 8° C than at room temperature. The many bacteria
present seem to have very little effect upon virus inactivation.
A floe which accumulates in conditioned sand appears to be the principal
substance to which the virus adsorbs. Under standard loading conditions,
virtually all the virus the STE might contain was removed by the conditioned
sand during at least a period approaching 2 years.
In the design and operation of a slow sand treatment system, it is impor-
tant to avoid large hydraulic surges or very uneven distribution of the waste,
especially in cold weather. The results of this study indicate that virus
reductions of 6 to 10 Iog10 are reasonable to expect of a properly designed and
operated system.
THE FATE OF NUTRIENTS IN SOIL
The wastes from a household contain all the nutrients required for sustaining
life processes. Disposal problems arise when high concentrations of these
nutrients are discharged to relatively small areas. The nutrients which have the
greatest potential of creating environmental or health problems are nitrogen (N)
C-55
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and phosphorus (P). This discussion will be concerned with reactions of
these nutrients in the soil below septic tank-soil absorption fields. Water
(the septic tank effluent) is the primary transport mechanism. Since vertical
downward movement dominates in the unsaturated zone, the receiving body is the
saturated zone or aquifer. The effect of this discharge on the aquifer is of
importance, since the aquifer may be used as a drinking water supply source or
may be eventually discharged as a surface flow.
There is no evidence that P in drinking water constitutes a threat to
human health. Rather, P is of chief concern in relation to surface water quality,
as it is one of the two major nutrients limiting algal productivity of lakes
and impoundments. Because of the wide distribution and transformations of N in
the natural environment, many fresh water lake eutrophication control strategies
are based on P control, particularly where numerous point-sources of P repre-
sent a significant portion of the P budget in the lake.
Nitrogen, on the other hand, is a potential threat to public health. Nitrate
(NOg), the end product of nitrification which readily occurs under aerobic con-
ditions in soils, and nitrite (NC^), the intermediate form, can be toxic to
humans particularly in infants, if ingested in excessive amounts. This toxicity
arises from the hypoxia associated with the reaction of N02 with hemoglobin to
reduce the oxygen carrying capacity of the blood. The NOg arises from microbial
reduction of ~NO^ in the human gut. With adults, lethal toxicity is virtually
nonexistent, while clinical recognition of NOo toxicity in infants has resulted
in essentially complete elimination of this problem. However, much less is
known of the chronic toxicity (i.e., subclinical effects) of NOo. Therefore, the
U.S. Public Health Service recommendation of an upper limit of 10 mg/L of NOj-N
in potable water is almost certain to be retained for the foreseeable future
(National Acad. Sci., 1972). Nitrate may also be toxic to livestock, but this
appears to be of limited occurrence and is primarily associated with animal feed
rather than water (Haz. Mater. Adv. Comm., 1973).
Recently a number of N-nitroso compounds have been found to be carcino-
genic to laboratory animals, and msfn is probably also susceptible (Tannenbaum,
1976). This class of compounds, commonly referred to as nitrosamines are formed
from the reaction of NOg with secondary amines. Formation of significant
amounts of these compounds in the natural environment has not yet been demon-
strated, but they are resistant to microbial attack (Tate and Alexander, 1976).
A more likely mode of human exposure is formation in the body by reaction of
ingested NOo with amines in the stomach (Tannenbaum, 1976). Saliva contains
significant N02, which increases markedly on ingestion of NO?,. Tannenbaum (1976)
indicated that NOg in food and water represents a high carcinogenic potential
and noted that there is strong epidemiological evidence in several countries
that high NOo intake is casually related to gastric cancer.
Background
Phosphorus Transformations—
Phosphorus in household wastes—Phosphorus in septic tank effluent origin-
ates mainly from detergents with phosphate builders and from human excreta.
The relative contribution of detergent P will vary with the amount of detergent
C-56
-------
used and its P content, but Sawyer (1965) has estimated that detergent-based
P accounts for about 50 to 75 percent of the total P in domestic wastewater.
The contribution from human excreta has been estimated by Sherman (1952) to
range from 0.23 to 1.05 kg per person per year with a mean of about 0.6 kg.
These estimates were based on dietary data. The results of the raw wastewater
characterization phase of this study (Appendix A) indicated the collective
contribution of P in bathing, clotheswashing and dishwashing wastewaters to be
approximately 3.U g/cap/day (86 percent) with toilet usage contributing 0.6 g/
cap/day (lU percent).
The anaerobic digestion which occurs in the septic tank, converts most of
the organic and condensed phosphate forms, to soluble orthophosphate. Magdoff,
et al., (I97^b) and Otis, et al., (1975) found more than 85 percent of the
total P in most septic tank effluents to be in this form. The relatively small
amounts of organic P and also the condensed phosphates present in many septic
tank effluents will eventually be converted to orthophosphate. The condensed
phosphates such as meta-, pyro-, and tripolyphosphate will react with soils in
a manner similar to orthosphosphate (Black, 1970). Magdoff, et al., (l97^b)
found that the total P concentration in the septic tank effluent used in their
column studies ranged from 15-6 to 2U.5 mg/L with a mean value of 20.6 mg/L.
Otis, et al., (1975) in detailed studies of 6 septic tank systems, found average
effluent concentrations of total P to range from 11.0 to 31.H mg/L with a median
value of about 12 mg/L. This concentration, coupled with the measured average
flow rate of 182 liters per person per day gives the total of 0.8 kg of P per
person per year.
Chemisorption reactions—At low P concentrations (< 5 mg/mL-P) in the soil
solution at equilibrium, the phosphate ion becomes chemisorbed on the surfaces
of Fe and Al minerals in strongly acid to neutral systems, and on Ca minerals
in neutral to alkaline systems. The pH of septic tank effluent is nearly
neutral. Viraraghavan and Warnock (197*0, and Walker (personal communication)
found pH values of non-calcareous sandy soils under seepage fields to range
from 6.2 to 7.0. In this pH range, all of these metal cations (Fe+++, Al ++,
Ca++) could probably participate in P immobilization reactions, with Fe and Al-
bound P dominating in non-calcareous soils and Ca-bound P in calcareous soils.
Precipitation reactions—As the P concentration in the soil solution in-
creases, there comes a point where one or more phosphates precipitates may
form. This point can be predicted from the ion activity products (solubility
products) if all of the relevant ion activities are known. Ion activity pro-
ducts of some of the more important compounds are given by Lindsay and Moreno
(i960). These compounds include strengite (FePOk • 2HpO), variscite
(AlPOj, • 2H20), dicalcium phosphate (CaHPO^ • 21^0), octacalcium phosphate
[Ca^H(PO^)o • 3HpO] , and hydroxyapatite [Ca-^PO^XOHp)] . In acid soils, most
of P sorption involves the Al and Fe compounds vhile in calcareous or alkaline
soils, Ca compounds predominate.
In the pH range encountered in septic tank seepage fields, hydroxyapatite
is the stable calcium phosphate precipitate. However, at relatively high P
concentrations similar to those found in septic tank effluents, metastable
compounds such as octacalcium phosphate are formed initially, followed by slow
C-57
-------
conversion to hydroxyapatite (Lindsay and Moreno, 1960).
Phosphorus reactions under anaerobic conditions—Although the phosphate ion
itself is not chemically reduced under redox conditions normally occurring in
nature, subjecting a previously well-aerated, non-calcareous soil to reducing
conditions will almost invariably result in an increase in dissolved inorganic
P. This is to be expected since much of the P in soils is bound to ferric
iron, which is converted to the soluble ferrous form under reducing conditions.
The P is then released to the soil solution where a new equilibrium is estab-
lished with the Al- and/or Ca-bound phosphates. Patrick (196U) found that ex-
tractable P increased rapidly as the redox potential decreased from +200 to -200
mv. This is the same redox potential range over which ferric compounds are
reduced.
Magdoff, et al., (I97^~b) found different results in soil columns dosed with
septic tank effluent. The soil used in this case contained free CaCOo, and
they postulated that the lower P values in the leachates after the columns crusted
and became anaerobic were due to increased Ca ion concentrations resulting from
dissolution of CaCOo by organic acids formed under the anaerobic conditions.
The P concentrations in the leachates were very close to those predicted from
the solubility product of octacalcium phosphate.
Time dependence of P immobilization—The rate at which P is sorbed from
solution onto the surfaces of soils and soil constituents has been shown to con-
sist of a rapid initial reaction followed by a much slower reaction which appears
to follow first order kinetics. Kuo and Lotse (1973) reported that 80 percent
of the P sorption by CaC03 was completed within 10 seconds, while Chen, et al.
(1973), found that the initial reaction on kaolinite required about 2U hours.
Chen, et al, (1973), found that the slow sorption reaction continued for several
weeks. This slow reaction has been attributed to diffusion of P into the sorbing
material (Scholten, 1965), or a slow decomposition-precipitation reaction
(Hsu and Rennie, 1962; Kuo and Lotse, 1973; Griffin and Jurinak, 197*0 • Soil
material directly under the absorption bed will be exposed to relatively high
concentrations of P throughout the life of the system, so that this slow reaction
is important in determining the amount of P immobilized.
Capacity of soil to immobilize P—Investigators attempting to describe P
movement in soils have utilized models involving: l) a first order kinetic
equation, 2) a series of exponential terms, 3) a second order kinetic equation
based on the Langmuir adsorption isotherm, U) the Elovich equation, 5) a
kinetic equation based on the Freundlich adsorption isotherm, and 6) mass trans-
fer (Kuo and Lotse, 1973; Novak and Adriano, 1975). All of these equations
predict a relatively sharp boundary between a zone of near-maximum P adsorption,
extending down from the surface or layer of introduction, and the underlying
soil. The coefficients for the equations have usually been derived from labora-
tory experiments involving relatively short equilibration times. As a result,
the slow decomposition-precipitation reactions which should occur with the
high P concentrations in septic tank effluent are not taken into account, and
maximum immobilization values are underestimated. Adriano, et al. (1975),
studied the P retained by soils subjected to wastes from a food processing
plant and a dried milk and cheese plant. They concluded that the amount of P
retained by the soils greatly exceeded the Langmuir adsorption maximum, and
C-58
-------
attributed the excess to precipitate formation, particularly of Ca phosphates.
Sawhney and Hill (1975) also found that soils retained P in excess of the
Langmuir adsorption maxima, and that the P sorption capacity of a soil could
be rejuvenated by drying and wetting the soil following saturation with P. This
procedure apparently exposes more sorntion sites probabxy as a result of pre-
cipitate nucleation and migration of sorbed P to the precipicate nucleation
sites. Similar results were obtained in the Netherlands by Beek and deHaan
(197*0.
Nitrogen Transformations—
Nitrogen in household wastes—Ammonium N and organic N constitute the most
prevalent forms of N in household wastes (dissolved I^j though always present,
is not considered here). Urine is the major source of N, and this N is largely
in the forms of urea, uric acid and creatimine. The remainder of the N is
largely in undigested foodstuff and bacterial cells (HMAC, 1973). The results
of the raw wastewater study (Appendix A) indicated an average daily nitrogen
contribution ranging from 6.1 to 16.8 g/cap/day. In a daily flow of 170 L/cap/
day this yields a concentration of approximately 36 to 9^ mg/L-N. Effluents
from 6 septic tanks showed a range of 26 to 76 mg/L-TT (Appendix A).
Septic tank and seepage bed—Anaerobic conditions prevail in the septic
tank, and the soluble N compounds of low molecular weight are mineralized
rapidly to NH^ by enzymatic and microbial degradation. The N in the effluent
as it leaves the tank is about 15% NH^-N and 25% organic N (Otis, et al., 1975)
with a C:N ratio of about 10. Some of the N is associated with the sludge
solids and thus remain in the tank, although mass balance studies indicate this
is a small fraction of the total. Particulate N leaving the tank is retained
at the seepage bed-soil interface to become part of the crust layer. This N
will be slowly mineralized to NHi|-N.
Below the seepage bed—Since crust formation approaches an apparent steady
state condition, additions and removals of N are essentially equal. Thus, in
a stable system, N input to the soil below the seepage bed is equivalent to N
output from the tank, with little or no net N removal. When the bed is crusted
or if effluent is added by dosing, the normally underlying soil will be aerobic
and moist. Temperature will vary depending on the season, but even in mound
systems, is always above freezing in the winter. Thus, under these conditions,
nitrification will occur within the underlying soil.
Optimal nitrification in soil occurs when the soil moisture tension is in
the range of 300 cm to 100 cm (Sabey, 1969; Stanford and Epstein, 197*0. Bouma
(1975) found tensions of 60 to 100 cm in sandy loams, loamy sands and loams
and 30 to 35 cm in finer-textured soils under properly functioning seepage beds.
Thus, finer-textured soils will have less air-filled pore space and the possi-
bility of zones with anaerobic conditions exists. These anaerobic areas may
be the site of some denitrification. Since soil textures are rarely homogeneous
vertically, moisture tension discontinuities at textural boundaries also could
result in zones of high water content and subsequent anaerobic conditions.
Because the effluent is under anaerobic conditions in the tank and seepage
bed, there is no opportunity for nitrification until the effluent reaches the
C-59
-------
soil. Thus, the inorganic N is present only as Nlfy-N on the soil cation ex-
change sites and in solution. The continuing input of cations (Ca++, Mg++, Na+,
K+ and UH^+) from the effluent will maintain a constant ratio of NH^-W in
solution to NH^-N on the exchange sites. Therefore, NH^-N will move downward
with the percolate once equilibrium of the effluent with the cation exchange
sites is achieved. Unless the soil is submerged or oxygen diffusion into the
soil is limited b'y some other means, aerobic conditions will prevail in the
unsaturated zone within a very few cm below the bed. At this point nitrification
will commence. The point at which complete nitrification of the NH^-H occurs
will be a function of the contact time of the effluent and the rate of nitrifi-
cation. Factors which affect the rate of nitrification include pH, aeration
and moisture conditions, number of nitrifiers, and temperature (Alexander, 1961).
The pH of the soil beneath the seepage bed is near neutrality (Walker, personal
communication) which is optimal for nitrification.
Denitrification would be desirable, since it is the only feasible mechanism
of N removal. However, energy (available organic carbon) is required. The only
sources of organic matter under the bed are organic matter native to the soil
and that from the effluent. Since subsoils are typically low in organic matter
and organic matter from the effluent is rapidly oxidized under the seepage bed
(Magdoff, et al. , 197^-a), denitrification would not be expected to be a signifi-
cant N removal mechanism.
Thus, as a first approximation, all of the IT leaving a household can be
expected to eventually exist as NC^-N under the seepage bed. Nitrate is not
retained by soils, and it will move with the percolate to the groundwater. The
resulting groundwater NOj-N concentration and ultimate fate of this ET is depend-
ent on the hydrogeology of the region and other sources and sinks of N.
Previous Investigations of Groundwater Pollution by IT and F from Subsurface
Seepage Beds
Woodward et al., (l96l) reported on an extensive survey of over 63,000
private water supply wells in 39 communities in Minnesota. The majority of these
wells were shallow, and most of the communities were served by individual
septic tank systems. Forty-eight percent of the wells sampled had NO^-N con-
centrations above background levels and 11 percent had concentrations above
10 mg/L-N. The authors explained the variable results on the basis of soil
profile properties, well depth, population density and hydrogeology. One com-
munity, which was located in an area where there was a continuous clay layer
in the soil profile, had no ground water contamination. A general relationship
of increasing water quality with well depth also existed. More contamination
was found in older communities (pre-19^0) than in post World War II communities.
The reasons for this were not clarified in their study. Crabtree (1972) found
that 15 percent of the wells in an area in central Wisconsin where the population
was served exclusively by septic tank systems had greater than 10 mg/L of NO^-N,
and Miller (1972) found that groundwater in an urbanizing sandy soil area of
Delaware contained 10 to 30 mg/L of NO^-ft.
Several investigations have been reported which verify the rapid nitrifi-
cation of septic tank effluent in sandy soils. Robeck, et al., (19&U) obtained
80 percent nitrification of added NH^-N in 150-cm soil lysimeters, while
C-60
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de Vries (1972) and Pruel and Schroepfer (1968) found essentially complete
nitrification within 30 to 60 cm.
Dilution by uncontaminated groundwater is the only significant mechanism
of lowering NOj-W concentration in the groundwater below seepage beds overlying
aerobic soils. Polta (1969) found a rapid decrease in WOo-N concentration in
groundwater with increasing distance from a septic tank-dry well system, with
NOo-N concentrations decreasing from 30 mg/L directly under the system to 5 mg/L
at k3 m down gradient. Pruel (1966) obtained data from septic systems on sandy
soils, which showed that about a 30 m distance down-gradient from the seepage bed
was required to lower NOo-N below 10 mg/L. Similar findings were reported by
Childs (1973), although Polkowski and Boyle (1970) found that 20 m was required
for the system they evaluated.
While NOo-N usually is the major N form found in groundwater under septic
tank absorption fields, high concentrations of WH^-N have been reported occasion-
ally. This has usually occurred where the depth of the aerobic zone between the
bed and the groundwater was shallow (< 0.6 m) . Ammonium-N concentrations should
also increase in winter when low temperatures slow the rate of nitrification and
thus effectively increase the distance required for complete nitrification. Also,
conditions under which saturated flow might occur (such as in a new system or
one which did not have a clogging mat) could permit movement of
Chloride (Cl~) moves through soils much like NOo-N, and is present in house-
hold wastes at concentrations much higher than background levels. Thus, its
presence can also indicate the rate and direction of effluent movement. Dudley
and Stephenson (1973) noted consistently high correlations between NOo-N and Cl~
concentrations in groundwater below a number of seepage beds. They investigated
11 sites in Wisconsin and found significant CT~ contamination at all sites.
The average NOg-N concentration in the groundwater below systems installed in
sands was 15 mg/L, and a distance of about 15 m down-gradient from the system was
required before the concentration decreased to less than 10 mg/L. Significant
NHlj-N concentrations occurred at two sites, one located on impermeable glacial
till soil, and the other on a site with a high water table.
Ellis and Childs (1973) investigated 19 septic tank sites on sandy soils
around Houghton Lake, Michigan, and found significant NOo-N input to the
groundwater from 6 of these sites. Significant concentrations existed from 30
to 100 m from the sources and generally affected the upper 2.h m of the ground-
water aquifer.
Several reports have noted a high degree of variability in results of
groundwater sampling, both in terms of time and space. This can be explained
by a number of factors . A groundwater mound usually develops under the system
(Bouma, et al. , 1972; Dudley and Stephenson, 1973) which can markedly affect the
flow pattern. Also, different usage patterns and temperature effects on the rate
of nitrification result in differing concentration patterns of IfO -N in the
groundwater.
Several cases of significant P contamination in groundwater below seepage
beds have been reported. Ellis and Childs (1973) found significant P movement
(up to 30 m) from a number of systems, with PO^-P concentrations ranging from
2 to greater than 20 mg/L for up to 1.2 m into the groundwater aquifer directly
C-6l
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under the systems . Phosphorus was moving into a nearby lake from a number of
these systems. Dudley and Stephenson (1973) found significant concentrations
(> 1 mg/L total P} above background levels (< 0.2 mg/L total P) in k of the 11
sites they examined. Three of the sitet, were in coarse-grained outwash sands
and gravels, but one was in an impermeable glacial till. None of the newer
systems had significantly increased concentrations of P in the groundwaters im-
mediately below them.
Experimental Approach
Results of the project research activities designed to evaluate the fate of
P and N from subsurface disposal of septic tank effluent are summarized below, as
related to other research and to the potential for contamination of groundwater.
Evaluation of Existing Systems in Sands —
Five study sites, located in permeable sandy soils in central Wisconsin
were investigated. Details of the methodology have been reported by Walker, et al.,
(I973a; 1973b). The forms and amounts of N in the soil under a seepage bed were
determined from samples obtained by excavation adjacent to each system. Ground-
water samples, direction of flow and gradients were obtained using observation
wells.
Columns Representing Fill Type Disposal Systems —
Detailed description of this research is given by Magdoff, et al., (l9?Ha;
197^"b) and Magdoff and Keeney (1975). Large polyvinyl chloride (PVC) columns
(lH.7 cm inside diameter) were filled with soil materials to represent those used
in a mound (See Figure C-1^0 . The fill material consisted of either a sand or a
sandy loam subsoil. The columns were equipped with tensiometers, sampling ports,
air entry ports and redox electrodes. They were loaded with 8 cm/ day of effluent
from a household septic tank. Room temperature was about 15° C.
Monitoring of Existing Fill Systems--
Concentrations of N and P in experimental fill systems were determined by
in situ sampling of the liquid. One mound was designed for use in areas under-
lain by creviced bedrock (Bouma, et al. , 19jUc), The others were designed for use
on slowly permeable soils (Bouma, et al. ,
Analytical Procedures —
Ammonium-N and NOg-N concentrations in water samples or 2N KC1 extracts of
soil samples were analyzed by the steam distillation procedure of Keeney and
Bremner (l965b), Organic C was measured as described in Standard Methods (1965)
and total N by Kjeldahl (Bremner, I9_65al, Chloride was determined by the pro-
cedure of Cotlove, et al., (1958).
Oxygen, No and C02 were determined on a Barber-Coleman Model 23-P gas
chromatograph (Chen, et al. , 1972) and methane was determined on a U07 Series
Packard gas chromatograph with a flame ionizer detector (Macgregor, et al. , 1973).
Platinum electrodes for Eh measurement were prepared by fusing 0.6 cm segments of
a 20-gauge Pt wire to a 12-gauge solid Cu wire. After replacing the original
rubberized outer sheath of the Cu wire, the Cu-Pt junction was coated with epoxy
cement to give a water tight seal. The electrodes were replatinized with black
platinum and checked according to the procedures of Quispel (19^+6).
C-62
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+ 60 cm
+ 30 cm
9P
60 cm
90cm
TENSIOMETER
LIQUID
PORT
INFLUENT
PT
ELECTRODE
MONITORING COMPLEX
gp-GAS PORT
mc-MONITORING COMPLEX
Figure C-l4. Column design for mound simulation
Results
Phosphorus—
Existing systems in sands—The results of monitoring studies of P concen-
trations in groundwater under and adjacent to existing systems in sands were re-
ported by Bouma, et al., (1972). Two of the 5 systems studied had relatively
high groundwater concentrations of P. One of the systems was 12 years old, and
the other had been functioning for 8 years. Both had coarse sands and gravels
between the seepage system and the water table. Background PO^-P ranged from less
than 0.02 to 0.03 mg/L, and PO^-P in wells just adjacent to the systems ranged
up to 9-5 mg/L. Phosphorus above background was not found in groundwater under
a new system (< 1 year old) or under the systems which had an intervening layer
of clay between the system and the aquifer. These findings largely confirm those
reported in the literature.
Existing mound systems—Three experimental mound systems, based on preliminary
designs, were monitored in 1970 and 1971 (Bouma, et al., 1972). Well water samples
were obtained in the vicinity of one of the mounds which was located on a somewhat
poorly drained sandy loam. One of the wells adjacent to the system had elevated
PO^-P concentrations (0.37 mg/L). The fill for this system was sand, and the
groundwater was less than 1 m below the mound. No other groundwater P data under
existing mounds are available. However, P concentrations of percolate within the
fill of several existing mounds was determined. Phosphorus (PO^-P) concentrations
generally ranged from 0.2 to 0.6 mg/L at the fill-soil interface (Bouma, et al.,
1972). Phosphorus was also measured in the soil solution in a sandy loam fill
system installed over creviced bedrock (Bouma, et al., 197^c). The data showed
that, after 18 months of operation, total P in solution was about 8 mg/L, indi-
cating that the P removal capacity of the system was low.
C-63
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Columns representing mound systems—Considerable data are available on P
retention in laboratory columns using sand or sandy loam fill (Magdoff, et al.,
197^a; 197^b; Magdoff and Keeney, 1976). This research showed that P was not
completely retained in the fill, and that after only 3 months of loading, P con-
centration in the effluent was about 12 mg/L in a sand fill (100$ sand) and 2
mg/L in calcareous sandy loam fill (68$ sand, 22$ silt, 10$ clay) (See Table
C-18). Initially, most of the P was retained and P concentrations in the efflu-
ent were less than 1 mg/L. This was undoubtedly due to sorption of P by soil
constituents. Once the sorption capacity was exceeded, precipitation reactions
dominated. Solubility product considerations indicated that octacalcium phos-
phate was being formed.
After the experiment, the columns were dissected. The total P distribution
profile (See Figure C-15) showed that P was being removed in the sand fill and
in the underlying soil.
Nitrogen—
Existing systems in sands—The results of a monitoring study on existing
systems located in sands in central Wisconsin were reported by Walker, et al.,
(l973a; 1973l>). The findings confirmed other reports that nitrification will
readily occur if 1 to 2 m of unsaturated soil are present above groundwater.
Table C-19 summarizes the findings and indicates that nitrification was complete
at 5 to 15 cm below the clogging mat.
The effect of septic tank systems on NOo-N in the groundwater was also
evaluated (Walker, et al., 1973b). The results demonstrated the heterogeneity
of the groundwater regime, even in an area with sandy soil profiles. Results
for three of the systems are given in Figures C-l6, C-17 and C-18. Below
System 1 (Figure C-16), both NHj^-N and NOg-N were found in the groundwater.
This was a large system, but loading from the household decreased markedly during
TABLE C-18. PHOSPHORUS CONCENTRATIONS IN SOLUTION IN UNCLOGGED SAND
AND CLOGGED SANDY LOAM COLUMNS
Total P in solution (mg-P/L)
Depth Unclogged1 Clogged2
(cm) Sand Sandy loam
Influent 23.9 18.3
5 22.1 1^.5
Fill 30 21.6 13.7
55 17.0 8.2
65 9.8 1.0
83 11.0 1.2
Effluent 11.8 1.6
2 After 9^ days of loading.
After 73 days of loading.
-------
TABLE C-19. N03-N CONCENTRATIONS IN UNSATURATED SOIL SOLUTIONS"
AT SELECTED DEPTHS BELOW SEEPAGE BEDS (Walker,
et al., 1973a)
Depth
Below Crust System 1 System 3 System h
System 5
cm mg/liter
5 20 50 100
15 50 160 70
U5 50 ikO 70
75 50 80 80
Avg. U3 110 80
130
120
80
90
105
The concentrations (yg/g dry soil) of NOg-N in unsaturated soil
solutions were obtained on field-moist samples.
0
o
Q_
LJ
O
30
60
90
CRUST
INITIAL
FINAL
SILT LOAM
0.2 0.4 0.6 0.8 .10
TOTAL-P (% OF DRY WEIGHT)
Figure C-15. Total phosphorus profiles in laboratory columns.
C-65
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25
SYSTEM I
. . •" ( (<30 cm in groundwater)
NOg-NJ
^ANH4-N? (|.5m in groundwater)
,20
_£
z
g
£
£
o
o
10
ONH4-
Q
o
H J
1 K
o o « •
i iihiJKig.
.F
.P /•*.
/Q-
, * -0 >
>%:
"L
•B *M
.E .D .C .N
R .T
S
•u
10m .
N
PLAN VIEW 1
N
• * •
• A
A
io o 9
20 10 0 10 20 30 40
DISTANCE FROM SYSTEM (METERS)
50
Figure C-l6. Concentrations of NH^-Ef and NOo-N in ground water as a function
of distance to the seepage bed (Walker, et al., 1973b)•
SYSTEM 2
, .
\
E
^
O
t-
§
f—
z
LU
z1
o
o
z
80
70
60
50
40
30
20
10
0
• NOj-N (<30 cm in groundwater)
O NH4-N (<30cm in groundwater)
D
o
E
0 0
o
_
o
o
O o
1
o
.L »M
.K to
HG->f
Hc
D->
u :
li
• 1
t-F i
•T *J
' — F
[ F
\ *B
1
1
10m .
' ' I1
PLAN ' .
VIEW ••• ft i i i _5_(i_5_
70 20 10 5 0 5 10 15 20
DISTANCE FROM SYSTEM (METERS)
25 50
Figure C-17. Concentrations of NHj^-W and WCU-N in ground water as a function
of distance to the seepage "bed (Walker, et al. , ""
C-66
-------
the study. The bed was probably aerobic during periods of low loading, and,
when used, the effluent percolated so rapidly through the soil that nitrification
did not always occur. System 2 (Figure C-17) was constructed in the groundwater
and,therefore, little nitrification could occur. Another system not shown was
constructed over a clay layer 8 m below the bed. Groundwater below this layer
had little NOg-N indicating that the clay layer acted as a barrier to vertical
water movement immediately below the system, causing the percolating waste to
move along the layer and emerge or percolate downward at some other place.
System k (Figure C-18) provides a classical picture with maximum NOg-N (about
1*0 mg/L) directly adjacent to the bed. The NOo-N concentration was still about
10 mg/L at 70 m from the bed.
Existing mound systems—From investigations at one mound system, Bouma,
et al., (l97Uc) found that nitrification was complete within the fill (0.7 m of
fine sand). Influent total N to this system averaged 62 mg/L. There was 66 mg/L
of NOj-N in the liquid reaching the interface between the fill and the silt loam
topsoil and 5^ mg/L of WOg-N 20 cm below the interface, indicating some NOo-N
retention (possibly denitrification) by the topsoil. Ammonium-N decreased to
below detectable levels. Interestingly, the NHi^-N concentration 20 cm below
the interface in the winter was 8 mg/L. During this sampling period,
30 mg/L, and organic N was 10 mg/L. By May, this had changed to 3 mg/L of
Nlfy-N, 57 mg/L of N03~N, and 0.3 mg/L of organic N. Thus, mineralization and
nitrification were inhibited by the low temperatures in the middle of winter.
Columns representing mound systems—Results of this study (Magdoff, et al.,
also showed that nitrification in the sand fill is rapid and complete,
and that some denitrification may be occurring at the fill-topsoil interface
where nearly saturated conditions exist (Magdoff, et al., 197^-a). After the
experiment, the columns were sampled for total N. The results show that, with
the exception of the clogging mat, very little N was retained in the sand fill,
and that N was mineralized and removed from the silt loam topsoil (See Figure
C-19). Similar results were obtained for the distribution of carbon.
SYSTEM 4
ONH4-N? (< 30 cm jn groundwater)
NO^-N was
• NO
-N?
-NJ
O
O
50
40
30
20
10
0
ANO,-N (1.5 m in ground
k-
£ H
- .:: g
m B«
e •
o;:o:
• 08° 8S 2s
7 Boo, oo , 9 15
water)
H" /f
•° EJ2f t
§
1 1 *A
10m T.
i— i N
c 1
• PLAN VIEW
i i i
C
8
10 0 10 20 30 40 50 60 70
DISTANCE FROM SYSTEM (METERS)
Figure C-l8.
Concentrations of NH^-N and NO^-N in ground water as a
function of distance to the seepage bed (Walker,
et al., 1973b).
C-67
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s
o
"•* 30
Q.
IU
Q RO
90
• i i 1 i > i i
— i CRI|«?T
SAND
INITIAL
FINAL
SILT LOAM *i I
, i i 1 i 1 i 1 :
0.4 0.8 .12 .16 .20
TOTAL-N (% OF DRY WEIGHT)
Figure C-19- Total nitrogen profiles in laboratory columns.
Discussion
Phosphorus—
Results of this project and of other investigations have shown that septic
tank soil absorption systems, whether conventional or mounded, can represent a
significant source of P to the local ground water system. However, P is tightly
sorbed by most soils (Black, 1970), and significant inputs to surface water would
be likely only if the soil had a very low sorptive capacity> e.g., sand, and
the system were in close proximity to surface water.
The depth of penetration of the P "saturated" layer can be calculated if
the P loading rate and the P immobilization capacity of the soil are known. The
extreme case would be a seepage field in a sandy soil. The Wisconsin State Board
of Health minimum soil absorption area requirements for a 3 bedroom house are
about 21 m2 of bottom area for«a sandy soil with a fast percolation rate. If an
effluent input of 727 liters/day at an average P content of 12 mg/L is assumed,
the total P load would be 3.2 kg per year or about 1500 kg/ha per year (The
input and median P concentrations are calculated from data of Otis, et al.» 1975
for a family of M. For a sandy soil with a bulk density of 1.6 g/cm3, and a
Langmuir adsorption maximum of 90 ug P/g soil (Peck, 1962) the soil would be P-
saturated to a depth of 10U cm in one year.
The Langmuir adsorption maximum is a minimum value for potential P immobili-
zation. Walker (personal communication) determined that P extracted from sandy
soils beneath septic tank seepage fields in central Wisconsin ranged from about
100 to about 300 ug/g. Magdoff and Keeney (1976) reported immobilization of 121
ug P/g by a sandy^ soil in a column study which ran for less than a year. Based
on a P immobilization value of 200 Ug/g, the depth of P penetration would be
about 52 cm per year in the hypothetical system. The depth of penetration would
be less on finer textured soils because the maximum P immobilization values
would be higher, and the loading per unit area would be less as larger absorption
areas would be required. Peck (1962) found that the average Langmuir adsorption
C-68
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maximum for silt loam surface soils in Wisconsin was 186 Ug/g. If such a soil
has a relatively slow percolation rate, an absorption bed of about TO m2 would be
required to handle the volume of effluent used in the hypothetical sand system.
Thus, the areal P loading rate would be decreased to about 0.3 that of the sand,
and the adsorption maximum would be increased by a factor of about 2.1. This
would result in P penetration of about 15 cm per year if only the adsorption maxi-
mum values were considered, and less than 10 cm per year if additional immobili-
zation from precipitation were assumed. The data of Magdoff and Keeney (1976)
would suggest that P immobilization in excess of the adsorption maximum is signif-
icant on silt loam soils, as they found 307 mg/g-P immobilized compared to the
mean adsorption maximum value of 186 yg/g obtained by Peck Cl96"2).
This analysis supports the experimental findings that P movement is the most
extensive on coarse sandy soils. If sufficient systems are located adjacent to
a lake or impoundment and sandy soils predominate, P removal from the effluent
would seem necessary to protect the water quality of the lake.
Nitrogen—
Nitrogen loading to ground waters from septic tank disposal fields is a
certainty in nearly all cases. The seriousness of the situation is essentially
a function of the hydrogeology of the area and the level of background contam-
ination. The movement and mixing of nitrate in the ground water is complicated,
and prediction of problem areas is difficult. Problems are most likely to exist
in areas with higher housing densities (Walker, et al., 19T3b). Even in these
situations, proper well construction (deep casing) might be sufficient to negate
or reduce NO^-N contamination of drinking water. The uncertainties about the
severity of NOo-N toxicity, and the lack of documented evidence of the relative
contribution of septic tank-soil absorption systems to the NOo-N contamination of
ground water would indicate that, at this time, there is not a widespread need
for NOo-N removal systems. However, continued monitoring of areas with rela-
tively high development densities employing this form of wastewater disposal,
especially in coarser soils, is recommended as a prudent course of action by health
authorities.
C-69
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APPENDIX D
INSTITUTIONAL AND REGULATORY ASPECTS OF TREATMENT
AND DISPOSAL OF SMALL WASTEWATER FLOWS
CURRENT REGULATIONS
The typical means of implementing control of the various on-site sewage
treatment and disposal systems in use today is via a regulatory program which
imposes requirements and/or restrictions upon the systems and upon those who
design, install, own or operate them. While the regulatory programs used in
different jurisdictions appear to vary greatly, there are many basic similarities
(Patterson et al., 1971). This variety of programmatic approaches exists due to
preferences for (or against) certain departments and agencies, as they exist in
any municipal or state government. The existing local departments and/or agencies
which typically have responsibility for supervision of on-site systems vary ex-
tensively including: departments of health, plumbing, building, development,
planning, zoning, environmental protection, public works and drainage and con-
servation commissions. (For convenience, the terms municipal and municipality
will be used here to mean all general purpose governmental units, i.e., city,
town, village, borough, county, etc., and any special purpose districts which are
empowered to control on-site sewerage.)
The institutional approach also varies with the degree that on-site sewerage
is perceived as a problem and with the extent and nature of regulation to which
the citizens are accustomed. The emphasis of this initial discussion of regu-
latory programs centers almost exclusively upon local municipal and state pro-
grams; because, aside from surface water discharge from on-site sewage treatment
systems, there are no federal statutes or regulations which are directly appli-
cable to these regulatory programs.
Each local or state program contains common elements such, as; l) the
type of regulations, and 2) the regulatory or enforcement mechanisms used. These
two elements will be discussed briefly below.
Type of Regulations
Regulations for the control of on-site sewerage may be effected in a number
of ways. These include the use of specification standards; performance standards
or regulations which indirectly control on-site systems, i.e., land use controls,
subdivision regulations, etc.
Specification Standards—
Design standards establish detailed requirements and/or restrictions for
specific components or location of on-site sewerage systems. This type of
D-l
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regulation is found in almost all regulatory programs, i.e., minimum septic
tank volume shall "be 750 gal, soil absorption field shall be set back 50 ft from
any water course, etc. However, these standards have been found to vary widely
from one regulatory program to another (Flews, 1977). This is especially so
when comparing one state's program to another. One must logically assume that
those individuals regulated by these programs and those involved in the regu-
latory programs could reasonably question this variance, since all programs are
intended to have the identical purpose, the protection of public health. How-
ever, despite this singular purpose, the fact remains that difference in speci-
fication standards does exist.
Additionally, the use of specification standards has often been objected
to by the designers of these on-site systems because the standards deny any
opportunity to truly "design" the system for the existing situation. This ob-
jection is quite valid in those instances where a competent designer is, in
fact, stymied by the codification of the design parameters of an on-site system.
However, in fairness, the use of specification standards has been defensible
because the previous designers of these systems did not understand or were not
concerned with proper design of these systems (Winneberger and Klock, 1973).
Performance Standards—
These standards establish requirements for the performance of on-site
sewerage systems without specifying how such standards are to be met. Perform-
ance standards generally are not a type of regulation used in on-site system
regulatory programs. Examples of performance standards are: effluent standards,
equipment standards and operation standards. Systems which discharge effluents
to surface waters have effluent standards as established by P.L. 92-500 and the
regulations adopted pursuant to the act. Since these standards simply impose
effluent limitations without establishing specific requirements for design,
they are clearly performance standards. The National Sanitation Foundation's
(1970) NSF Standard No. UO for individual aerobic wastewater treatment plants
is an example of equipment performance standards. Implicit in all regulatory
programs is the principal purpose of protection of public health. Often, this
purpose is expressed or implied as a performance standard by prohibiting the
creation or maintenance of a nuisance or unhealth condition. While nuisances
are quite difficult to prove in legal actions, on-site systems typically are
subject to this operational standard.
Indirect Controls—
Land use or zoning controls may result in indirect or de facto regulation
of on-site systems. For example, in Wisconsin, state regulations for unsewered
subdivisions impose minimum lot size and soil characteristic requirements upon
nearly all land parcels created in the state. As a consequence of this direct
regulation of the land subdivision process, on-site system controls are
strengthened by assurance that building lots will be adequate for an on-site
system. Similarly, a unit of government could effect indirect control over
on-site systems by adoption of comprehensive land use or water quality plans.
Under these types of plans, the use of on-site systems would be restricted by
land use or water quality goals. However, the indirect control also includes
regulation of systems by restricting or completely prohibiting their use in
certain areas. Thus, comprehensive planning could result in a reduction of the
D-2
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pressure upon the regulatory program by restricting or excluding on-site systems
due to land use or water quality criteria.
Regulatory Techniques
By necessity, any regulatory program must contain certain administrative
and enforcement techniques. The purpose of administrative mechanisms is to aid
in efficient and thorough regulation of on-site sewage systems within the juris-
diction of the administrative agency. Further, to assure that the regulatory
programs are successful in controlling on-site sewerage, it is necessary to
include enforcement mechanisms in the program. Often the distinction between
these two types of techniques becomes blurred and somewhat arbitrary.
There are only a limited number of generic regulatory techniques available
for use in any type of control program. Thus, existing and recommended alter-
native on-system regulatory programs are constrained to be selected from the same
"laundry list" of available regulatory techniques. Most of these techniques
may be included in one of the following:
1. Direct controls over the on-site system itself;
2. Controls upon the actors (i.e., designers, installers, owners, etc.);
3. General or indirect controls; and
k. Unfair or unlawful controls.
It must be noted, however, that the regulating agency must have the authority
to impose these controls. This authority might be in the form of statutory
enabling legislation enacted by the state legislature granting the regulatory
agency (at either the state or local level of government) the necessary power
to implement the regulatory program. This legislation may or may not be
obligatory, that is the delegated agencies may decline to regulate on-site
sewerage. Further, the legislation might specifically designate the exact regu-
latory techniques which are to be used and in some cases might even prescribe
the procedure to be used and establish a fee structure.
Alternatively, certain types of governmental agencies possess adequate
authority either via the state's constitution or by their general grant of
statutory authority (i.e., "police power") to implement a regulatory program
consisting of many, if not most, of the available regulatory techniques. One
example of such an agency might be the state agency responsible for protecting
public health and/or water quality. As a second example, incorporated communi-
ties in many states, i.e., cities and villages, have the authority to impose
the controls needed for an adequate regulatory program and the courts' will
likely hold this to be a valid exercise of their police power (See Louisville
v. Thompson, (Ct. App. Ky.) 339 S.W. 2d 869 (i960); Early Estates, Inc. vT
Housing Board of Review, 93 R.I. 277, 1971* A. 2d 117 (l96l); City of St. Louis
v. Nash (S. Ct. Mo.) 260 S.W. 985 (192*0). In many states, these "home rule"
powers are also available to other units of local government, such as towns
and counties.
D-3
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Obviously then, it is necessary to first determine what unit of govern-
ment is attempting to actually regulate on-site sewerage and then to carefully
assess what authority it has. To be absolutely correct, this assessment must
look at statutory and case law, as well as the State Constitution. Often the
assessment is made more difficult because more than one unit of government is
involved in the program, i.e., a state-county program.
Direct Controls—
Direct controls may be thought of as those techniques which the regulatory
agency imposes directly upon the on-site systems, itself.
Permit—A permit is a written warrant granted by a governmental unit or
agency which conveys the right to conduct a specific activity usually at an
identified location and normally for a given fixed period of time, i.e., for
installation of on-site systems, construction must commence typically within one
or two years or the permit becomes void. The legislation, ordinance or regu-
lation which establishes the permit process also should impose an additional
requirement making it unlawful to conduct the regulated activity without first
obtaining a validly issued permit. This permit technique can be used to ad-
minister and enforce technical and performance standards, simply by making
compliance with these standards a necessary prerequisite for issuance of a
permit. Clearly most permit processes places the burden of obtaining and supply-
ing all necessary data and information upon the permit applicant, and often
require the applicant to pay a fee as precondition to permit issuance.
Permit issuance is a technique which is often used to regulate on-site
sewerage. Generally, the program requires that a permit must be obtained prior
to commencing installation of any on-site system. The permit requirements may
be varied for different types of on-site systems. In addition, some programs
require "use" or "occupancy" permits prior to occupancy of the residence served
by the on-site system. It has been proposed that a permit program also be
employed to assure adequate and timely maintenance of the system (Stewart, 1977).
For example, in Wisconsin a county permit is required for the installation
of an on-site system (Wis. Admin. Code H62.20). This county permit program is
similar to the programs in Pennsylvania and Maine (State of Maine Plumbing Code
Sec. 2.2, Dept. of Health and Welfare; Penn. Sewage Facilities Act, P.L. 1535
as amended by 35 P.S. 750). The use of permits either at the local or state
government level is desirable because it presents the regulatory agency with
notice of all proposed system Installations. This is also an inexpensive means
of providing the agency with data about the system. Such data is available
for compliance checks of the system during construction. Also included under
the rubric of this technique are conditional permits, defined as one which is
valid only until the occurrence of an event or the failure to comply with a
requirement. The placard, stop work order or "red tag" might be used to show
this occurrence or failure.
Plan review and approval—A review of project specifications and drawings
is a second direct control which may be required prior to undertaking specified
activities. Control is assured since the review process can be used to make
sure that the regulatory standards will be implemented as part of the activity.
D-U
-------
Plan review and approval are frequently included in on-site sewerage
regulatory programs. For example, Wisconsin does not require the submission
of plans for state approval of conventional on-site systems serving single
families; however, pursuant to a recent amendment, the state now requires
county review of such plans (Wis. Admin. Code H62.20).
Installation inspection—Inspection is a third technique which is used to
assure that other control requirements are met. The types of inspections
which have been used range from the inspection of the proposed site prior to its
approval for installation of an on-site system, to compliance inspections made
after the system is completely installed. Included within this range are one
or more inspections during construction, e.g., the "pre-coverup" inspection
would be included here. The inspection technique can be included as part of
the permit or licensing process whereby the permittee is required to give notice
to the regulatory agency at specified periods in the construction of an on-site
system. Of course, ,the application for the permit clearly puts the regulatory
agency on notice and as a condition of permit issuance, the applicant may be
deemed to have given his consent to a pre-issuance inspection, as well (See v.
City of Seattle, 387 U.S. 5Ul, 5U6 (1967)). In addition, inspections may be
performed by the regulatory agency upon a random basis or upon receipt of a
complaint. For example, Dane County, Wisconsin now makes a minimum of two
inspections for each septic tank system installed: one at the proposed site
prior to issuance of a permit and the other during construction. Other
inspections may be made when deemed necessary. The county regulatory agency
charges a fee for the permit to cover the cost of these inspections.
Access to the property for the purpose of making inspections has been the
subject of several court cases. As a result of these cases, the United States
Supreme Court has held that under certain circumstances, inspections of property
might be a "search" within the meaning of the fourth and fourteenth amendments
of the U.S. Constitution. Unless consented to, such an inspection could only be
conducted or compelled under a search warrant, [see Camara v. Municipal Court
of San Francisco, 387 U.S. 523 (1967) and companion case See v. City of Seattle,
387 U.S. 5^1 (1967).] . Clearly,,under the U.S. Constitution a nonconsentual
inspection of a residence would require a search warrant. The courts have
also extended this fourth amendment protection to include out-buildings and
surrounding land (English law recognized this land as the curtilage or court-
yard area). Thus, it is likely that a warrant might be needed if permission
cannot be obtained. For non-criminal proceedings, many state statutes now
prescribe the procedure for the issuance of an administrative warrant, since the
standard search warrant procedure is generally not available. For an example
of such a search warrant see: Wisconsin Statutes, 1975, Section 66.123 for
specific wording and Section 66.122 for the procedure which must be used to
obtain such a warrant.
Maintenance assurance and monitoring—Maintenance assurance and monitoring
requirements are direct control techniques similar to the installation inspection
techniques. These techniques can be used to assess the compliance with the
regulatory program and to assess the success of enforcement of various types
of other regulatory techniques. These maintenance and monitoring techniques
might involve sanitary surveys, chemical or dye tests and aerial photography to
determine the effectiveness of other control techniques as well as water quality
D-5
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monitoring. The same constitutional constraints would apply to nonconsentual
access to property as was discussed for inspections in general. For example,
the Auburn Lake Trails Subdivision in Georgetown Divide Public Utility District,
El Dorado County, California, undertakes a water quality monitoring program to
determine whether any of the septic tank systems are effecting the surface
water quality (Georgetown Divide Public Utility District, 1972). In addition,
the El Dorado Irrigation District has provided maintenance assurance programs
to several subdivisions within the district (Winneberger and Anderman, 1972).
Their program involves both annual physical inspection and maintenance of septic
tank systems within the district.
Bonding or other surety—The technique of requiring the posting of a bond
or other surety as a guarantee that the requirements of the regulatory program
will be complied with must be mentioned as a direct regulatory control technique.
Typically, the enabling legislation, ordinance or regulations contains either a
schedule listing the amount of the bond or surety or it provides a formula, from
which the regulatory agent can calculate the amount. Usually the bond or surety
is a condition precedent to issuance of a permit. It is generally returned
after a certain time, e.g., 6 months to 1 year after occupancy of the dwelling
and use of the system.
This technique is not without its shortcomings. In particular, while a
bond might be posted to assure the proper installation and/or function of an
on-site system, the regulatory agent might be reluctant to attempt to collect
on the bond in the event of improper installation and/or failure of the system.
The nature of the bond always involves a question of fact, i.e., was the
installation improper, did the system fail to function, and why. Such questions
of fact invite court actions and, thus, posting a bond or requiring a surety
does not always bring about the regulatory result desired by the municipality
or state agency.
Controls Upon Actors—
On-site regulatory programs may use techniques other than direct controls,
as discussed above, to obtain the primary objective of public health protection.
The most important method of so doing is to regulate those who act on the
systems. The actors most likely to be regulated are the soil testers, designers
and installers of on-site systems, as well as those who service or maintain
the systems, i.e., liquid waste pumpers/haulers.
Licensing—Lieensure of qualified individuals has long been recognized as
a legitimate function of the state under its police power. The United States
Supreme Court described this power as follows:
"The power of the state to provide for the general welfare of its
people authorizes it to ... secure them against the consequences
of ignorance and incapacity, as well as deception and fraud.
As one means to this end it has been the practice of different
states, from time immemorial to exact in many pursuits a certain
degree of skill and learning upon which the community may confi-
dentially rely, their possession being generally ascertained upon
an examination of parties by competent persons, or inferred from a
certificate to them in the form of a diploma or license from an
institution." Dent v. West Virginia, 129 U.S. Ill*, 122 (1889).
D-6
-------
As stated by the Supreme Court, the requisite degree of skill may be ascer-
tained by an examination or inferred from a diploma or license from an insti-
tution.
Some of these regulatory programs have required that the designers of the
on-site systems be licensed professional engineers, architects or plumbers.
Additionally, some programs limit those who may actually install the systems
to those who are licensed plumbers, architects, septic system installers, etc.
For example, in Illinois the contractors who install on-site systems pay an
annual fee of 50 dollars and are licensed by the state (State of Illinois,
Private Sewage Disposal Licensing Act). In Wisconsin, state law prohibits anyone
other than a licensed master plumber from installing on-site systems (Wis. Stat.
1975, Sec. 11+5.06).
However, it is important to realize that the regulatory program is not con-
strained to rely on pre-existing licensing programs, but may, in fact, provide
a training and/or examination program and establish its own licensing program.
For example, Wisconsin recently created a program to license those who perform
the soils evaluations for the suitability of sites for on-site soil disposal
systems (Wis. Admin. Code H62.20, H6U). Similarly, several agencies have
apparently incorporated the licensure of the liquid waste haulers/pumpers into
their regulatory programs. The State of Delaware annually licenses liquid waste
pumpers (Del. Water Poll. Contr. Reg. No. 12) as do the states of Florida (State
of Fla. Dept of Poll. Contr. Rules, Chap. 17-13), Illinois (State of 111. Private
Sewage Disposal Licensing Act) and Wisconsin (Wis. Admin. Code, Chap NR 113
and Wis. Stat. 1975, Sec. 1U6.20). The Commonwealth of Pennsylvania has a certi-
fication program similar to licensing for sewage enforcement officials because
each municipality in Pennsylvania is required to employ such an official (Penn.
Sewage Facilities Act P.L. 1335 as amended by 35 P.S. 75 and Dept. of Envir.
Res. Rules and Reg., Chap. 7l). Also many states license sanitarians.
Registration—Registration requirements are sometimes used as a regulatory
technique. Generally, the difference between this and licensure is that regis-
tration is often only a bookkeeping, non-discretionary listing of those who are
performing certain functions. That is, registration might be nothing more than
the keeping of an updated list of all those who have applied to the agency or
otherwise indicated an interest in performing these functions.
However, there appears to be a shift in preference from licensing to
registration based upon the fact that licensing is only as good as its follow-up.
Some licensing boards have tended to become co-opted by the licensees, and,
even if not so controlled the regulating boards generally have been quite
reluctant to revoke a license. Therefore, licensing often gives a false sense
of security to the consumer. Thus, there is a movement toward regulation and
away from the previously preferred policy of licensing.
One spinoff technique available to those agencies which impose licensure
requirements upon some or all of those who perform actions related to on-site
systems is to limit the issuance of permits solely to those who are properly
licensed or registered.
D-7
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General or Indirect Controls—
General or indirect controls are those which the regulatory agency seldom
has the ability to influence or determine completely. Examples of these controls
are zoning and land use policies. While the regulatory agency might have the
enforcement or administrative responsibilities for zoning or other land use
techniques, it is unlikely that the agency itself can adopt zoning land use
ordinances. One exception to this would be the denial of the issuance of build-
ing permits until all on-site requirements have been complied with. It is possible
that the same regulatory agency would process both permits. Along these lines,
some local governmental units have in place, highly structured interlocked pro-
cedures for the review of development proposals. Thus, this procedure acts as an
indirect control upon on-site systems included in any development proposal.
A second example of an indirect control would be the existence of public
policies in favor of or against certain regulated actions. These policies might
aid or hinder the regulatory agency in the administration of its program, e.g.,
the "aggressiveness" and priority placed upon enforcement; budget and authori-
zation for the agency will influence the number and professionalism of the
administrative staff, as well as the quality of their program.
Unfair or Unlawful Controls—
The regulatory agency might seek to control certain portions of its on-site
system regulatory program by establishing excessive fee requirements, by delay
in processing applications or by unjustified denial of permits. These techniques
are not desirable control techniques and are just mentioned to point out that
they do exist and have been used in the past.
Summary—
In conclusion, it can be seen that a typical regulatory program to control
on-site wastewater treatment and disposal systems could consist of direct controls
such as permit issuance, inspection, plan review and possibly bonding, and/or
maintenance assurance and monitoring. Note, that the program could and probably
should, involve most of these direct control techniques. In addition, the
program should preferably require licensing or at least regulation of system
designers, installers and pumpers as well as the persons enforcing the program.
The types of regulations would principally involve specification standards and
possibly some performance standards especially for surface discharge units.
Thus, while each regulatory program would be unique, each would contain
many of the same regulatory techniques and standards.
Theory of the Regulation of On-Site Systems
The previous section gave a brief introductory examination of the types of
regulations and the regulatory techniques which are contained in regulatory
programs. This section examines the theory of these regulatory programs by
first examining the three regulatory phases of on-site systems and concludes
by briefly exploring the wide spectrum of types of regulatory programs used to
control on-site systems.
Three Regulatory Phases of On-Site Systems—
The three phases where regulation of any on-site system is needed are the
initial installation phase, the operational phase and the failure phase.
D-8
-------
However, before an examination of these phases of a good regulatory program
can "be meaningful, it is necessary to briefly examine the problems which arise
or have been attributed to the use and misuse of on-site systems. A good regu-
latory program is one which addresses these problems and adequately deals with
them.
Problems—The threat to public health due to water-borne diseases is
generally the major problem raised when discussing on-site sewerage. Typically,
those individuals who supply their own water have the highest risk of water-borne
disease. In the United States, from 1961 to 1970 there were a total of 128
known outbreaks of water-borne disease (defined as at least two reported cases)
attributed to drinking water which caused about U6,000 illnesses and 20 deaths
(Craun and Me Cabe, 1973). Ninety-four of these outbreaks occurred in private
water supplies and the majority of these outbreaks were classified as gastro-
enteritis. This same source compiled outbreak data for the 25 year period of
19^6 to 1970 and concluded that 71 percent of the outbreaks (of a total of 358)
occurred in private water supplies. It is important to note that many outbreaks
of water-borne illness go unreported, so that the true incidence of disease may
be assumed to be much higher.
Disease outbreaks could be drastically reduced by eliminating the travel
of pathogens into water supplies. It has been argued that improper siting and
design of the on-site system in the initial installation phase and failing
systems at the end of their life cycle are the major sources of contamination.
For this reason, these systems pose a potential threat to public health. Thus,
many health officials have adopted the attitude that the use of on-site systems
is to be generally discouraged — seeking replacement where possible with
central systems.
Another potential problem associated with on-site systems is their inability
to remove potentially troublesome chemicals found in the wastewaters, typically
nitrogen and phosphorus. These chemicals represent both a potential public
health threat (i.e., nitrates causing infant methemoglobinemia) and a source of
undesirable nutrients affecting both surface and groundwaters. There are
two stages in the life cycle of on-site systems where this problem may occur.
The first is due to improper siting and design of the system. The second is
the end of the life cycle of the system when it has failed. Either improper
siting or a failed system may result in contamination of surface or groundwaters
with unwanted chemicals. Neither the public health aspects nor the contamin-
ation of surface or groundwaters will be discussed in detail here; however, it
should be noted that since 19^5 about 2,000 cases, including fatal poisonings,
of methemoglobinemia have been reported worldwide (Shuval, 1970). Further
note that there are many other chemicals which might occur in wastewaters which
are not discussed here.
Most on-site systems have the attendant problem of limiting development.
On-site systems which rely on soil for final disposal function properly only
if located on suitable sites. In many places in the United States, suitable
sites for on-site soil disposal are not available. In those jurisdictions
which have a good administrative program of limiting installations to only
suited sites, the resulting limited development has been referred to by some as
D-9
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de facto zoning. That is, the siting requirements necessary for soil disposal
tend to limit the amount of land available for development. In the past, many
jurisdictions have relied on these requirements to provide them with a means of
land use control. As innovative systems, which do not have as stringent siting
requirements or do not rely on the soil for disposal become more widely accepted,
this technique of land use control will be lost.
This problem of limiting development arises only at the initial or first
phase in the life cycle of an on-site system. However, the magnitude of this
problem is quite large. One source estimated that about 68 percent of the United
States is unsuited for the conventional soil disposal system (Wenk, 1971)•
Thus, the potential for a problem of limiting development is great, especially
as more and more jurisdictions improve their programs of limiting installations
to only suited sites.
Economic and financial hardship problems often arise when on-site
systems are employed. Again, these problems generally occur during the initial
phase in the life of an on-site system; however, these same type problems may
occur in the failure or final phase in the life cycle. A typical example of this
problem arises when the homeowner, after purchasing his site, discovers that it
is unsuited for an on-site system. Several things may occur, first, the value of
his lot and home, if already built, is greatly diminished. Second, he may plead
financial hardship to the regulatory authorities in an effort to receive approval
to install the system despite the lack of suited soil. This same type problem
may also occur when an existing homeowner's system fails. He, of course,
has a. much stronger financial hardship argument to raise if he is unable to
find suitable soil on his lot; because very few regulatory authorities will ever
require a homeowner to vacate his home. Of course, if the homeowner prevails,
the installation of systems on unsuited sites may cause the public health and
chemical problems as discussed.
Regulatory phases—The initial installation phase consists of proper siting,
design and construction of the on-site system. Through proper controls the
potential danger to public health and pollution of surface and ground waters may
be avoided, as well as controlling economic hardship problems.
It is during this first phase that the regulatory program can be most
cost effective in minimizing public health and water pollution problems. Regu-
latory emphasis must be given to assuring that on-site systems are installed
only on suitable sites, but assurance of proper design and construction techniques
are necessary as well.
While the regulation of this first phase is ideally suited to avoid health
and water quality problems, the program, also can avoid possible economic
hardships. This is possible because landowners are better served if the regu-
latory program prevents them from installing on-site systems on unsuitable sites.
Thus, even though the owner of undeveloped land might argue financial and
economic hardships if he cannot develop the land, the hardships may be minimal
when compared to the hardships which would result if the on-site system were
permitted and later failed.
D-10
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The second regulatory phase is concerned with operation and maintenance.
The problems of public health and pollution of the surface and groundwater may
occur if there is inadequate control over proper operation and maintenance.
While there are very few operational or maintenance requirements for a septic
system, some of the more innovative on-site treatment and disposal systems have
more extensive requirements. Whether the system's operation and maintenance
requirements are straightforward or elaborate, a good regulatory program should
impose controls at this second phase in the life cycle.
The third phase occurs when a system fails. This phase involves both the
detection of failure and the imposition of the necessary corrective actions.
Detection may result from an active role taken by the regulatory agency such as:
l) a systematic, scheduled inspection of every on-site system in its jurisdiction,
2) random inspections of systems, or 3) a sanitary survey of a given region or
area for purposes of both locating systems and determining whether they are
functioning properly. In addition, failing systems may be brought to the
attention of the regulatory agency by citizen complaints or self-reporting by
owners of failing systems.
Despite the manner of detection, an adequate regulatory program must be
empowered to take necessary action once the failing systems are noted. At a
minimum, the regulatory agency must have the authority to order repair, replace-
ment or abandonment of failing systems.
This is the most difficult phase to regulate. However, the problems
of public health, water pollution and economic hardships may be attenuated or
avoided by proper regulatory control.
Spectrum of Regulatory Programs—
The regulatory program to control on-site systems varies widely from state
to state and is probably subject to at least an equal amount of variation
among local regulatory authorities within each state. Existing regulatory
programs vary from total regulation of all on-site systems to almost no regu-
lation whatsoever. Within this spectrum, are several intermediate programs
which split responsibilities for setting standards, inspection, permit issuance
and enforcement provisions between the state and local authorities.
Despite this wide range of state programs, it is possible to categorize
them into four general types (Patterson, et al., 1971): l) complete state
regulation of all on-site systems, 2) split of regulatory control between
state and local agencies, 3) delegation by the state to local governmental units,
and h} virtually no state action (not even delegation to local authorities).
Some of the states with complete state level regulatory programs include
(Plews, 1977):
Connecticut New Hampshire
Delaware Oregon
Hawaii Rhode Island
These states typically require a permit for on-site system installation and
require an inspection by the state agency (Patterson, et al., 1971).
D-ll
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This type of regulatory program is generally considered to "be the most
effective because the pressures to weaken on-site regulatory programs are not
usually as effective at the state level as at the local level. In addition,
since states typically have or can obtain greater expertise and technical
knowledge than most local units of government, state agencies should assist
or perform many of the regulatory control techniques.
States which divide the regulatory control between state and local
authorities include (Plews, 1977):
Alaska
California
Colorado
Florida
Maine
Montana
Nevada
New Jersey
New Mexico
Oklahoma
Pennsylvania
South Carolina
South Dakota
Texas
Utah
Vermont
West Virginia
Specifically, Pennsylvania has a strong state program, but it requires that
each municipality employ at least one state trained official to implement
the program at the local level ("Perm. Sewerage Facilities Act" P.L. 1535 as
amended by 35 P.S. 750 and Dept. Environ. Res. Rules and Reg., Chap. 71).
Similarly, Maine requires a local plumbing inspector to issue permits for
residential systems (Maine State Plumbing Code, Part II, Sec. 2.2).
States which have delegated regulatory responsibility to the local govern-
mental or health authorities include:
Alabama
Arizona
Georgia
Indiana
Iowa
Kentucky
Louisianna
Michigan
New York
North Carolina
Ohio
Tennessee
Virginia
Washington
Wisconsin
These states have been identified as deferring functions such as the permit and
inspection responsibilities to local regulatory agencies (Plews, 1977). Some
states, such as Ohio, have adopted a state code of minimum standards and
specifications for on-site systems (Ohio Health Dept. H.E. 20). In states
having adopted minimum standards, the local health authorities' codes and
standards generally must be as stringent as the state codes.
States which have been identified as having virtually no state regulatory
programs include (Plews, 1977):
Missouri
Nebraska
North Dakota
Wyoming
Wyoming apparently only has a limited advisory educational program in which
the state attempts to provide assistance to the general public regarding
on-site systems. North Dakota only takes enforcement against owners of systems
which result in a water pollution or public health problems (Patterson, et al. ,
1971).
D-12
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Analysis of Current State Regulatory Programs
While the range of regulatory programs in the 50 states is quite broad,
the on-site system standards and specifications imposed by the states vary
to an even greater degree. Many of the states use the Manual of Septic
Tank Practice (USPHS, 196?) as the basis for their standards. However, many
states and localities have diverged significantly from this basic standard
(Plews, 1977).
This large variation in the standards and specifications has been docu-
mented by Plews (1977). He analyzed the state codes, regulations and guide-
lines governing on-site sewerage in the following states:
Alabama
Alaska
Arizona
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Plews concluded that:
Illinois
Indiana
Iowa
Kentucky
Louisianna
Maine
Michigan
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
"... the Manual of Septic Tank Practice has had some influence.
However, the diversity in certain requirements is questionable
and obviously many of the documents have been developed through
political compromise rather than by sound technical advice."
Tables D-l, D-2, D-3S D-^ and D-5 show the wide range of variation in
the specification standards currently used in the various states to regulate:
l) septic tank capacity, 2) absorption field setback distances, 3) absorption
field percolation restrictions and sizing methods, U) soil depth and surface
discharge restrictions, and 5) absorption field design requirements, res-
pectively.
Licensing—
The licensure of those who interact with on-site systems is a valid regu-
latory technique which might be used to control both conventional and non-
conventional on-site systems. Several programs exist which currently license
those individuals who install, inspect, operate and/or service on-site
systems. The use of licensure programs can be an efficient method to assure
control over the individual who interacts with the on-site system. However,
caution must be exercised. Each licensure program must be evaluated individ-
ually before incorporating it as a regulatory technique because such programs
may suffer from lack of policing of the licensee and excessive use of
"grandfather" privileges.
D-13
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1000
750
960
1000
750
960
1000
900
960
1200
1000
1200
lUoo
1250
1500
750
1000
750
750
750
750
750
750
750
750
500
750
750
1000
750
750
750
750
750
750
750
750
750
750
900
1000
750
900
900
1000
900
900
1000
900
900
900
1000
1250
1000
1000
1000
1200
1000
1100
1250
1000
1150
1000
1250
1500
1250
1200
1250
1350
1250
1250
1500
1250
1^00
1250
TABLE D-l. SEPTIC TANK DESIGN STANDARDS USED IN THE U.S. (Flews, 1977),
Septic Tank Capacity in Gallons By Number of Bedrooms
States 1 2 3 H 5
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
750
750
1000
750
750
750
750
750
1000
1000
750
900
750
890
1000
750
750
750
1000
750
750
1000
750
750
750
750
750
1000
1000
750
900
750
890
1000
750
750
750
1000
(continued)
900
900
1000
900
900
900
900
900
1500
1000
900
900
900
890
1000
900
1000
900
1000
1000
1000
1000
1000
1000
1000
1000
1000
2000
1000
1000
1000
1000
7
1250
1000
1250
1000
1000
1250
1250
1250
1250
1250
1250
1250
1250
2000
1250
1250
1100
1250
?
1500
1250
1500
1250
1500
D-lU
-------
TABLE D-l (continued)
Septic Tank Capacity in Gallons By Number of Bedrooms
States !_ 2 3 U. 5.
Virginia 30 Hour Detention - 100 Gallons Per Person
Washington 750 750 900 1000 1250
West Virginia 750 750 900 1000 1250
Wisconsin 750 750 975 1200 1375
Wyoming 750 750 900 1000 1250
D-15
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TABLE D-2. ABSORPTION FIELD DESIGN STANDARDS USED
IN THE U.S. (Flews, 1977)
States
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Setback Distance Drainfield To
Well In Feet
50-75
50-100
50-100
100
75
50-100
75-100
100
50
100
50-100
100-200
100
100-300
100
100
100
75
50-100
100
100
100
50
50-100
50-100
100
100
100
100
50
100-150
100
Setback Distance Drainfield To
Surface Wa^er In Feet
7
50-100
100
50
50
50
50
50
50
100-300
50
25
7
50-100
100
50
100
75
50
50
100
50
7
50
50-100
50
50
50
100
25
75
100
(continued)
D-16
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TABLE D-2 (continued)
States Setback Distance Drainfield To Setback Distance Drainfield To
Well In Feet Surface Water In Feet
Vermont 100 50
Virginia 35-100 50-100
Washington 75-100 100
West Virginia 100 100
Wisconsin 50-100 50
Wyoming 100 50
D-17
-------
TABLE D-3. ABSORPTION FIELD DESIGN STANDARDS USED IN
THE U.S. (Flews, 1977)
States
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Minimum. Percolation Restriction
None
None
None
None
None
Yes
None
None
None
None
None
None
None
None
Yes
No
Yes
None
Yes
Yes
None
None
None
None
None
Yes
None
None
Yes
None
Yes
None
None
Sizing Methods
Perc
Perc & Soils
Perc
Perc
Perc
Perc
Perc & Soils
Perc & Soils
Perc
Perc & Soils
Perc
Perc & Soils
Perc
Perc
Soils
Perc & Soils
Perc
Perc
Perc
Perc & Soils
Perc & Soils
Perc & Soils
Perc & Soils
Soils
Perc Test
Soils
Perc
Perc
Perc & Soils
Perc
Perc & Soils
Perc & Soils
Perc
Perc & Soils
(continued)
D-18
-------
TABLE D-3 (continued)
States Minimum Percolation Restriction Sizing Methods
Virginia None Perc & Soils
Washington Yes Perc & Soils
West Virginia None Perc
Wisconsin None Perc & Soils
Wyoming None Perc
D-19
-------
States
TABLE D-U. SPECIAL SITE RESTRICTIONS MADE IN
THE U.S. (Plews, 1977)
Required Soil Depth Below Bottom
Of Trench In Feet
Allows Surface Discharge
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska*3
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
U
U
No Minimum
1.5
1.5
No Minimum
No Minimum
U
7
i.5a
None
2
2
1
u
1.5a
U
3
6"
U
l^a
U
1
(continued)
No
No
Yes
No
No
No
Yes, Conditional
No
No
Yes
No
Yes
Yes
No
No
No
No
No
No
Yes
Yes
No
No
No
No
No
No
No
No
D-20
-------
TABLE D-l* (continued)
States Required Soil Depth Below Bottom gurface Discharge
Of Trench In Feet "—
Vermont k No
Virginia No Minimum Yes
Washington 3a No
West Virginia h Wo
Wisconsin 3a No
Wyoming k Yes
&
Allows less with special design
Guidelines
D-21
-------
TABLE D-5. ABSORPTION FIELD DESIGN REQUIREMENTS AND SIZING METHODS
USED IN THE U.S. (Plews, 1977)
States Minimum Spacing
Between Lines In Feet
Minimum Soil Cover Range of Drainfield
Over Trench In Inches Widths in Inches
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
6
6
6
6
6-9
6.5-7.5
6-8
10
6
6
6-7.5
7.5
7
10
6
6
6
6-7.5
6-7.5
6
8
6
8
10
6
6
10
6
6
7
6-7.5
6
6-9
6
12
12
12
6
9
12
12
12
12
12
12
None
6-12
2-6
(continued)
12
6
U-6
6
12
12
12
6
10
6
12
12
9
?
12
6
12
6
None
18-36
12-36
12-18
18-36
18-36
12-36
18-2U
18-36
18-36
12-36
18-36
18
12-18
12-36
18-36
12-2U
12-36
18-36
2k
18-36
8-30
12-36
18
18-36
7
18-36
18-36
12-36
12-U8
18-36
D-22
-------
TABLE D-5 (continued)
States
Washington
West Virginia
Wisconsin
Wyoming
Minimum Spacing In Feet
Between Lines In Feet
6
6
10
6-7.5
Minimum Soil Cover Range of Drainfield
Over Trench In Inches Width In Inches
6
12
12
6-12
18-36
12-36
18-36
12-36
D-23
-------
Table D-6 lists the states which register sanitarians (Winston, 1975).
Registered sanitarians, it is assumed, have the requisite knowledge and skills
to adequately deal with the public health aspects of on-site systems. Thus,
it is possibly this official who is chosen to administer on-site regulatory
programs. Of course, this assumption varies from state to state depending upon
the quality of the licensure program.
While Registered Sanitarians may be qualified to administer a regulatory
program for on-site systems, at least one state has perceived the need for a
more specialized individual. Pennsylvania adopted a program to certify sewage
enforcement officials to directly administer the bulk of its on-site regulatory
program ("Penn. Sewage Facilities Act" P.L. 1535 as amended by 35 P.S. 750).
Table D-7 lists those states which have either a mandatory or voluntary
certification program for wastewater treatment plant operators. This is germain
because a certified treatment plant operator may be required to operate alter-
native treatment systems which are more complex than the conventional septic
tank system. For example, in Wisconsin, a licensed treatment plant operator
is required to operate all treatment plants in the state. Many on-site systems
(other than septic tank systems which are excluded by specific wording in the
rule) are defined by Wisconsin as "treatment plants" and, therefore, would
require a licensed operator (Wis. Admin. Code Chap NR 11*0.
Suggested Improvements in Qn-Site System Regulatory Programs
Several recommendations can be made to improve regulation of on-site sys-
tem. However, due to the variation in state regulatory programs and different
state constitutional limitations and requirements, some of these recommendations
may not be applicable or possible in all states. Where applicable, enactment
of enabling legislation may be required.
These suggestions are discussed under the headings of the three regulatory
phases of an on-site system discussed previously. In some cases, incorporating
a suggested improvement in one phase may bring about improvements in another.
Such suggestions are discussed in the phase where the most improvement might be
effected.
Initial Installation—
State Permit Program—Many local regulatory officials are subjected to
political pressure to approve the installation of systems on unsuited sites.
Also, some local authorities have reported that their boards of appeal are
subject to similar pressures and consequently often override denials made by the
local authority. In a survey made of 31 county regulatory officials in
Wisconsin, 2h expressed the need for increased job security indicating the
existence of political pressure (Stewart, 197*0.
A state permit program is a method of avoiding undue pressure to approve
system installations on unsuited sites. The chance for direct political
pressure should be considerably less at the state level. Additional advantages
-------
TABLE D-6. STATES WHICH REGISTER SANITARIANS (Winston, 1975)
Alabama
Arkansas
California
Colorado
Connecticut
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Kentucky
Louisiana
Maryland
Massachusetts
Michigan
Mississippi
Montana
Nebraska
Nevada
Nev Jersey
New Mexico
North Carolina
Oklahoma
Oregon
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Virginia
Washington
West Virginia
Wisconsin
TABLE D-7. CERTIFICATION PROGRAMS-BY STATE (DASHES INDICATE
NO INFORMATION AVAILABLE) (Commission on Rural Water,
197*0
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Mandatory Voluntary
X
— -
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-
X
State
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Mandatory
X
-
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-
Voluntary
X
X
-
X
X
X
X
X
-
D-25
-------
arising from such a program are: l) uniformity of regulations throughout the
state, 2) possible increase of available resources for commitment to the regu-
latory program, and 3) increased number of experienced personnel, or at least
an increase in the ability of the state to retain such personnel experienced
in soils and on-site system regulation.
While these advantages exist, disadvantages have been put forth by state
regulatory program detractors. Principally, these include: l) failure at a
state permit program to take into consideration local variables such as soil
conditions, etc., and 2) loss of responsiveness to local needs. Both of these
should not be real disadvantages since the basis for on-site regulation is the
protection of public health regardless of the regulatory level.
The use of a permit represents the basis of almost all regulatory programs
regardless of the administering level of government. Its widespread use arises
because of obvious enforcement advantages. The permit application gives the
regulatory agency notice of intended system installation. Therefore, if a
landowner installs a system without obtaining a permit, the regulatory agency
could establish a prima facia case simply by establishing in court that l) under
the regulatory program a permit is needed, and 2) the landowner did not have a
permit. This makes enforcement much easier because it is not necessary to
prove that the system constituted a nuisance or threat to public health.
The previous section listed states having a complete regulatory program
at the state level, which likely includes a permit program. For example, the
Delaware Department of Natural Resources and Environmental Control issues
installation permits (Del. Water Poll. Cont. Reg. #2). Similarly, the Hawaii
Department of Health requires landowners to obtain written approval prior to
installation of an on-site system (Hawaiian Publ. Health Reg. Chap. 38), and
the New Hampshire Water Supply and Pollution Control Committee issues installa-
tion permits (W.H. Rev. Stat. Annot. Chap 1^9-E).
In summary, permits are used as a regulatory technique to control the
location of on-site systems and to facilitate enforcement. Further, if the
program is administered at the state level, presumably there is less chance
for local political pressure to be exerted to obtain permits for unsuited
sites. Such a program would not represent any increased costs to the state
if the permit fee were set to recover the costs of administration.
Review of local permits—As an alternative to a state permit program,
a state agency could provide similar insulation against local political
pressures through a program of review of installation permits issued by the
local regulatory agencies. This regulatory technique would not require that
all permits be reviewed but only some of the permits selected at random.
However, it would be necessary to require each local agency to submit a copy
of every permit issued to the state. The state agency would then have a
limited period of time to act on the permits. Thus, the permit issued by the
local agency would: l) not become effective for a given number of days to
allow time for review by the state agency, and 2) be subject to revocation
by the state agency.
D-26
-------
It is likely that enabling legislation would be required in most states
to provide for a state review program. The legislation should mandate that:
l) all local regulatory programs must contain an installation permit require-
ment, 2) copies of all permits must be forwarded to the reviewing state agency,
and 3) the state agency shall review a random selection of all of the permits
received within a set time period.
It is not known whether any state currently employs a permit review
program. Stewart (197^) proposed statutory language for Wisconsin, which,
if adopted, would have required the Department of Health and Social Services
to review all local (county) installation permits. The language was as follows:
SECTION 1. 59-07 (51) of the statutes is amended to read:
59.07 (51) Building and Sanitary Codes. Adopt building and
sanitary codes, make necessary rules and regulations in relation
thereto and provide for enforcement of such codes, rules and regu-
lations by forfeiture or otherwise. Copies of all permits issued
pursuant to sanitary codes adopted under this section shall be sent
to Department of Health and Social Services and shall be issued
subject to the requirements of s. 11*5.025. Such codes, rules and
regulations shall not apply within cities and villages which have
adopted ordinances or codes concerning the same subject matter.
SECTION 2. 1U5.025 of the statutes is created to read:
1^5.025 REVIEW OP COUNTY PERMITS. (l) Counties Shall Forward
Copies of Permits. Each county shall within 5 days from the date
of issuance, forward a copy of the permit application for each
permit issued pursuant to sanitary codes, rules or regulations
adopted pursuant to s. 59•07(51) •
(2) Departmental Review. The department, either at its central
or district offices, shall review all permits; and from information
contained on the permit application, soil surveys, and its own
information, the department shall make a finding that the issuance
of the permit is or is not in compliance with the plumbing code.
The department is empowered to make its own investigation of any
facts necessary to make such a finding.
(3) Department May Overrule. When the department makes a find-
ing that the issuance of the permit does not comply with the state
plumbing code, the department shall within 15 days after receipt
notify the county which issued the permit that said permit is can-
celled. Further, the department shall notify the applicant that
the permit has been cancelled and such notice shall inform the appli-
cant of the enforcement and review provisions of this section.
(U) Enforcement. Upon receipt of notice of cancellation, the
applicant may not proceed with the construction, alteration or ex-
tension for which the permit was required. The circuit court of
any county where a permit has been cancelled shall have jurisdiction
to abate the use of a constructed facility and to halt further con-
struction and use by injunctive or other appropriate relief. The
district attorney shall bring an action to halt all such construction.
D-27
-------
(5) Review. Any applicant who has a permit cancelled under
this section may obtain judicial review as provided in ch. 227.
The costs of this permit review program could be included as part of the
permit fee. A portion of the fee collected by the local agency would be for-
warded to the state reviewing agency along with the permit.
Minimum standards for local regulatory programs—As a second alternative
to the state permit program, a state agency with appropriate regulatory
authority could establish minimum standards by which local regulatory programs
could be reviewed. As with the programs discussed previously, this program
would insulate the permit process from local political pressures.
Enabling legislation probably would be necessary to implement this program
also. Stewart (197*0 proposed statutory language which would have empowered
the Wisconsin Department of Health and Social Services to evaluate each local
(county) regulatory program on the basis of installation permits issued. If
after its review, the Department found the local agency ineffective, it was
empowered to suspend the local agency's authority to issue permits. Thus,
the penalty for failure to avoid local political pressure in issuing permits
is the loss of authority to administer the program and henceforth permit
applications must be made directly to the state. The specific statutory lang-
uage is as follows:
SECTION 1. 1^5.025 of the statutes is created to read:
1^5-025 MINIMUM STANDARDS FOR COUNTY SANITARY PROGRAMS. (l) The
department is empowered to require each county to forward a copy of
all permit applications for permits issued pursuant to sanitary
codes, rules and regulations adopted pursuant to s. 59.07 (51)'
Further, the department is empowered to require each county to cert-
ify which of these permits were issued.
(2) The department shall require the counties to forward all
permit applications which were granted for a period of 1 year from
the effective date of this section, and the department shall review
all of said permit applications.
(3) After this 1 year period, the department shall within 60 days
issue findings of fact about the effectiveness of each county's sani-
tary program. The department shall find a sanitary program ineffect-
tive if the review of the sanitary permits in subs. (2) established
that permits were issued in violation of the site requirements of the
state plumbing code. Further, the department may find that a county
sanitary program is ineffective for other reasons.
(U) Based on its findings of fact, the department shall issue
an order to each county found to have an ineffective sanitary program,
ordering it to cease issuing permits.
(5) No person may construct, alter or extend a private domestic
sewage treatment and disposal system in any county found to have an
ineffective sanitary program, unless that person has first obtained
a permit from the department authorizing that system.
(6) The department may issue the permits in subs. (5) and may
set a fee for the issuances of the permits.
D-28
-------
(?) Review. Any county found to have an ineffective sanitary
program may petition the department for a review, under ch. 227.
(8) The department may at any time rescind its order and allow
a county to begin issuing permits. However, the department shall
review all county permits issued as provided in subs. (2) and the
department shall make a finding of fact as required in subs. (3).
This minimum standards review is currently being used by the Commonwealth
of Pennsylvania. The local agency issues the installation permit and the
Pennsylvania Department of Environmental Resources is responsible for review-
ing the administrative performance of the agency. The Department may order
a local agency to modify its permit issuance practices to correct any
deficiencies found (Penn. Dept. Environ. Res. Rules and Reg. Chap. 71 and 73).
Uniform citation and complaint—The issuance of citations for sanitary
ordinance or code violations can be an important regulatory technique. The
citation system is currently used by building inspectors in several major
American cities to "ticket" owners of buildings who violate local codes
(National Institute of Municipal Law Offices, Municipal Law Review 33:3^2).
In essence, the uniform citation is similar to a speeding ticket issued to the
violator of an ordinance (or state statute). Depending on the enabling langu-
age, the violator usually signs the citation, posts a bond in accordance with
an established schedule and agrees to appear in court to enter his plea or
forfeit his bond.
If the violator choses to forfeit the bond which he has posted, generally
no court appearance is made (though the court may refuse to accept the bond
and issue a summons or warrant for the violator). However, if the violator
wishes to defend against the charge, he may appear in court, enter his plea
and be assigned a court date for his trial.
The principal advantage of the uniform citation and complaint is that
the local or state regulatory official now has a means to begin an enforcement
action (law suit) against the violator immediately. The action is commenced
simply with the issuance of the "ticket" without going through the regulatory
authority's attorney (district attorney, county attorney, attorney_general,
etc.). The obvious benefit is the avoidance of delays typically experienced
when seeking action by the authority's attorney.
It must be noted that the uniform citation and complaint is used only
to commence the enforcment action. If the violator wishes to plead not guilty,
time for the trial must be scheduled on generally crowded court calendars.
The regulatory authority's attorney also must find time to prepare and present
the case at the trial. Thus, enforcement delays are not avoided completely
if the violator pleads not guilty.
Delays are avoided if the violatory pleads guilty, but in such instances,
the authority has succeeded only in collecting a forfeiture. No injunction or
other equitable relief may be imposed. Therefore, if the regulatory authority
desires injunctive relief, use of the citation and complaint poses a serious
disadvantage. The violator could chose to post and forfeit a bond and continue
the violation.
D-29
-------
Wisconsin has recently enacted statutory language which enables local
regulatory officials to use the citation and complaint process against violators
of on-site system ordinances and rules. Section 66.119 of the Wisconsin
Statutes (1975) provides the following:
66.119 Citations for certain ordinance violations
(l) Adoption; content, (a) the governing body of any county, city
or village may by ordinance adopt and authorize the use of a citation
to be issued for violations of ordinances other than those for which a
statutory counterpart exists.
(b) An ordinance adopted under par. (a) shall prescribe the form of
the citation which shall provide for the following:
1. The name and address of the alleged violator.
2. The factual allegations describing the alleged violation.
3. The time and place of the offense.
k. The section of the ordinance violated.
5. A designation of the offense in such manner as can "be readily
understood by a person making a reasonable effort to do so.
6. The time at which the alleged violator may appear in court.
7- A statement which in essence informs the alleged violator:
a. That * * * the alleged violator may make a cash deposit of a
specified amount to be mailed to a specified official within a specified
time.
b. That if * * * the alleged violator makes such a deposit, * * *
he or she need not appear in court unless * * * susequently summoned.
c. That * * * the alleged violator makes a cash deposit and does
not appear in court, * * * either he or she will be deemed to have
tendered a plea of no contest and submitted to a forfeiture not to exceed
the amount of the deposit or * * * will be summoned into court to
answer the complaint if the court does not accept the plea of no contest.
d. That if * * * the alleged violator does not make a cash
deposit and does not appear in court at the time specified, an action
may be commenced against * * * the alleged violator to collect the
forfeiture.
8. A direction that if the alleged violator elects to make a cash
deposit, * * * the alleged violator shall sign an appropriate statement
which accompanies the citation to indicate that * * * he or she read
the statement required under subd. 7 and shall send the signed state-
ment with the cash deposit.
9. Such other information as may be deemed necessary.
(c) An ordinance adopted under par. (a) shall contain a schedule of
cash deposits which are to be required for the various ordinance viola-
tions for which a citation may be issued. The ordinance shall also
specify the court, clerk of court or other official to whom cash
deposits are to be made and shall require that receipts be given for
cash deposits.
(2) Issuance; filing, (a) Citations authorized under this section
may be issued by law enforcement officers of the county, city or village.
In addition, the governing body of a county, city or village may
designate by ordinance or resolution other county, city or village
officials who may issue citations with respect to ordinances which are
D-30
-------
directly related to the official responsibilities of the officials.
Officials granted the authority to issue citations may delegate,
with the approval of the governing body, the authority to employees.
Authority delegated to an official or employe shall be revoked in
the same manner by which it is conferred.
(b) The issuance of a citation by a person authorized to do so
under par. (a) shall be deemed adequate process to give the appropri-
ate court jurisdiction over the subject matter of the offense for the pur-
pose of receiving cash deposits, if directed to do so, and for the
purposes of sub. (3)(b) and (c). Issuance and filing of a citation
does not constitute commencement of an action. Issuance of a citation
does not violate s. 9^6.68.
(3) Violator's options; procedure on default, (a) The person
named as the alleged violator in a citation may appear in court at the
time specified in the citation or may mail or deliver personally a
cash deposit in the amount, within the time and to the court, clerk
of court or other official specified in the citation. If a person
makes a cash deposit, * * * the person may nevertheless appear in court
at the time specified in the citation, provided that the cash deposit
may be retained for application against any forfeiture which may be
imposed.
(b) If a person appears in court in response to a citation, the
citation may be used as the initial pleading unless the court directs
that a formal complaint be made, and such appearance confers personal
jurisdiction over the person. The person may plead guilty, no con-
test or not guilty. If the person pleads guilty or no contest, the
court shall accept the plea, enter a judgment of guilty and impose a
forfeiture. A plea of not guilty shall put all matters in such case
at issue, and the matter shall be set for trial.
(c) If the alleged violator makes a cash deposit and fails to
appear in court, the citation may serve as the initial pleading and
the violator shall be deemed to have tendered a plea of no contest
and submitted to a forfeiture not exceeding the amount of the deposit.
The court may either accept the plea of no contest and enter judg-
ment accordingly or reject the plea. If the court accepts the plea
of no contest, the defendant may move within 10 days after the date
set for * * * the appearance to withdraw the plea of no contest,
open the judgment and enter a plea of not guilty if * * * the defend-
ent shows to the satisfaction of the court that * * * the failure to
appear was due to mistake, inadvertence, surprise or excusable neg-
lect. If the plea of no contest is accepted and not subsequently
changed to a plea of not guilty, no costs or fees shall be taxed
against the violator. If the court rejects the plea of no contest
or if the alleged violator does not make a cash deposit and fails to
appear in court at the time specified in the citation, an action for
collection of the forfeiture may be commenced. A city or village may
commence action under s. 66.12(1) and a county may commence action
under s. 288.10. The citation may be used as the complaint in the
action for the collection of the forfeiture.
(U) Relationship to other laws. The adoption and authorization
for use of a citation under this section shall not preclude the govern-
ing body from adopting any other ordinance or providing for the
D-31
-------
enforcement of any other law or ordinance relating to the same or any
other matter. The issuance of a citation under this section shall
not preclude the proceeding under any other ordinance or law relating
to the same or any other matter. The proceeding under any other
ordinance or law relating to the same or any other matter shall not
preclude the issuance of a citation under this section.
It is likely that the use of the uniform citation and complaint will
result in an administrative cost savings since the amount of time spent by the
attorney involved should be less. Revenue should be generated by forfeited
money, as well.
Small claims courts—Most states have small claims courts for cases
involving less than 500 or 1000 dollars. Usually, these courts allow an
abbreviated, less formal procedure. Standardized forms are often used. When
seeking only fines or forfeitures, it is recommended that state and local
authorities consider using small claims courts to prosecute on-site system
ordinance and rule violations. Regardless of how the enforcement action was
commenced (e.g., uniform citation and complaint, summons, warrant), if the
regulatory agency is seeking a forfeiture less than the dollar limit set for
the court, usually it may be brought in the small claims court.
In addition to the simplified procedures and standardized forms, small
claims courts also have the advantage of typically having less of a case
backlog. Thus, enforcement of violations can be accelerated at less cost.
The only disadvantage is the unavailability of injuncture or equitable relief
in the courts.
Civil service status—Many local regulatory officials and some state
officials serve at the pleasure of those who appointed them to their jobs.
Stewart (197*0 noted that Wisconsin regulatory officials are sensitive to this
and have expressed a need for increased job security. These statements are
probably typical of those from officials of other states. In some cases, the
lack of job security probably has hindered vigorous application and enforce-
ment of on-site system regulations. To provide the necessary job security,
it is recommended that a civil service classification be established for
local and state officials responsible for the implementation and enforcement
of sanitary codes.
Operation and Maintenance—
This phase of on-site system regulation is often the most overlooked.
For the conventional septic tank system, it is recommended that the system
be inspected annually and the septic tank be pumped when necessary (USPHS,
1967). Many states make this recommendation in their codes. However, this
recommendation is seldom followed since there is typically no regulatory
enforcement of these provisions. For example, Wisconsin has requirements
in the state code which require the pumping of septic tanks whenever the
combined depth of sludge and scum equals one-third of the effective depth
of the tank (Wis. Admin Code Chap. 62.20). After surveying septic tank
systems serving homes around 8 lakes in Wisconsin, the state Division of
Health concluded there was "an almost complete lack of servicing of the
septic tanks." This survey concluded that this lack of maintenance likely
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resulted because few property owners knew the location of their systems (Wirth
and Hill, 196?).
From the homeowner's perspective, a regulatory program will be necessary,
because all too often, the system is approached with an out-of-sight-out-of-
mind attitude. Winneberger (l9?6) has isolated two reasons for this neglect:
1. The tolerance of many septic tank systems to function faithfully
without any maintenance, and
2. The system resists maintenance in that it is buried underground.
For systems other than conventional septic tank systems, maintenance
requirements may be more involved. It seems certain that a regulatory program
involving more than a recommendation for septic tank cleaning in a local
ordinance or state code will be needed to assure adequate maintenance.
There are two components necessary for a successful regulation of the
maintenance of any type of on-site system. One component must assure that
the location of the system is known. The location must be referenced to a
benchmark or other permanent fixture or marker to allow ease of location after
the system is underground. Also, a filing and retrieval system must be estab-
lished to provide information about the system's location whenever future
maintenance is to be performed.
The other component of a successful regulatory program should provide a
method of assuring that each system will be inspected and maintenance performed
when needed. This may be accomplished in one of several ways. The most
preferred method is the maintenance permit program, in the author's opinion.
Maintenance permit—It is recommended that regulatory agencies establish
maintenance programs to assure that systems are inspected regularly and ser-
viced when necessary. To guarantee this, the program would require periodic
inspection of the system as a prerequisite to issuing (or renewing ) a main-
tenance permit. The system owner would be mailed a maintenance permit application
reminding him to have his system inspected and have any necessary servicing
performed within a specified time period (e.g., 60 days). The person making
the inspection would sign and date one portion of the owner's permit, thereby
certifying that inspection and servicing was completed. Just prior to the
expiration of the permit period the process would be repeated.
Under this program it would be necessary that system inspections be per-
formed by individuals knowledgeable with the operation of such systems.
Wastewater pumpers or haulers could perform inspections of septic tank systems
in states where they are licensed. Systems with mechanical components could
be inspected by licensed plumbers, installers or public inspectors. Alter-
natively, special purpose districts could perform inspections and maintenance
as a service to system owners in the district. For example, the Santa Cruz
Septic Tank Maintenance District in California currently provides this service.
The administration of this permit program could be a simple routine
matter involving clerical staff time only. The clerk would mail out the
permit application forms and issue the permit upon receipt of a completed
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application and fee. The clerical staff would maintain the files vhich would
have a "tickler" system to retrieve those permits nearing expiration.
This program could be applied most easily to systems installed since the
date of the enabling ordinance or statute. Lack of knowledge about the
systems and the owner's address would usually make it difficult to impose the
permit program upon existing systems. Newly-installed systems would probably
not need maintenance and could be issued the first permit simply upon payment
of the fee.
The enabling ordinance or statutory language which establishes this permit
program must provide that it is unlawful to occupy a home served by an on-site
system unless a current maintenance permit has been issued for that system.
Thus, when the owner failed to renew a maintenance permit, he would be in vio-
lation of the ordinance or statute. From a legal viewpoint, enforcement of
this type of violation is straightforward since the only fact which has to be
proven is that the owner (or others) occupies a home served by an on-site
system which does not have a valid maintenance permit. It is not necessary to
prove the negative facts that the system was not inspected, was not maintained
or was not adequately functioning. The ease of the proof of facts should
encourage enforcement and prosecution by governmental legal officials (district
attorneys, etc.) and, depending upon the wording, the courts might give
equitable relief by ordering inspection of the system at the owner's expense,
as well as ordering the payment of a fine or forfeiture.
Stewart (1976) proposed the following model statutory language suitable
for any local or state regulatory authority which desires to establish a
septic tank maintenance permit program:
MODEL SECTION 1.0 SEPTIC TANK MAINTENANCE PERMIT
1.1 PERMIT REQUIRED. No owner may occupy, permit to be occupied,
rent, lease, live in or reside in, either seasonally or permanently,
any building, residence, or other structure serviced by an on-site
domestic sewage treatment and disposal system; unless the owner
has a valid septic tank maintenance permit for that system issued
in his name by the (sanitary inspector or zoning
administrator). Owner is defined to mean a natural person, partner-
ship, corporation, the state or any subdivision thereof.
1.2 FEE. A fee of $ shall accompany each application
for the septic tank maintenance permit.
1.3 PERMIT APPLICATION. Application for a septic tank mainten-
ance permit shall be made to the (sanitary inspector
or zoning administrator) on forms supplied by him. All applications
shall state the owner's name and address, the address or location
of the private sewage system, and shall contain the following
statement:
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"I certify that on day of , 19 , I inspected
the septic tank located at the address stated on this application,
and I (check one):
pumped all sludge and scum out of the septic tank, or
found that the volume of sludge and scum was less than
1/3 of the tank volume, and I did not pump the septic
tank.
Signature
Certification or license number
l.U ISSUANCE. The (sanitary inspector or zoning adminis-
trator) shall issue a permit to the applicant upon receipt of the fee
and a completed application, properly signed by a person licensed to ser-
vice septic tanks and stating his sanitary license number. The permit
shall include on its face all information contained in the application
and shall contain the date of issuance.
1.5 VALIDITY. The permit issued under this section shall be valid
for a period of two years from the date of issuance.
1.6 SALE OF PROPERTY. When property containing a private domestic
sewage system is sold, the new property owner, prior to occupying, renting,
leasing, or residing in the building, residence or structure served by
the system, shall make application for and receive a septic tank main-
tenance permit; however, the system may be used for a period not to ex-
ceed 30 days during pendency of his application for the permit.
Additional model language is suggested to require that information about
the location of all systems installed in the future. It is recognized that many
jurisdictions already have this requirement and the following model language
is suggested for those which lack such a requirement:
MODEL SECTION 2.0 PLAN VIEWS
2.1 Every application for a sanitary permit shall include a detailed
plan view of the proposed system prepared or drawn by a (state)
Registered Surveyor or a (state) Professional Engineer. The
plan view shall be signed by said surveyor or engineer and shall also
contain the license number of said surveyor or engineer.
2.2 This detailed plan view shall be dimensioned and drawn to
scale and shall show the location of the system and the dwelling served
by such system. The recommended scale is but in
any case the scale used shall be sufficient to show clearly all the
required dimensions and distances enumerated below.
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2.3 The following dimensions and distances shall be shown on
the plan view: the dimensions of the entire lot or a sufficient
portion such that all other required dimensions and distances may be
shown; the dimensions of the dwelling to be served by the system;
the location of the dwellings and all other buildings on the lot
with distances from lot lines to said dwellings and buildings; the
location of all septic tank and other treatment tank manholes and the
distance and direction of each manhole to the dwelling and to any
other nearby reference points; the location and dimensions of all
soil absorption fields and replacement areas; and the location and
distances from all wells, reservoirs, swimming pools or high water
marks of any lake, stream, pond or flowage located on the lot or on
adjacent properties within 100 feet of the septic tanks, treatment
tanks, sewage disposal systems or replacement disposal areas.
2.1* No on-site sewage treatment and disposal system shall be in-
stalled, modified, added to or replaced unless a plan view for that
system drawn by a registered surveyor or professional engineer has been
submitted.
To be useful, this information about location must be retrievable and the
following model language is offered to establish a filing system:
MODEL ORDINANCE SECTION 3.0 PLAN VIEW FILING SYSTEM 3.1 A fil-
ing system for plan views of on-site sewage treatment and disposal
systems is hereby established.
3.2 It shall be the duty of the (county zoning admin-
istrator, sanitarian or other designated person) to accept all
approved plan views and to file them by the address or the location
of the system. He shall further establish a cross-index which shall
list the original owner's name and shall cross list the address of
the system. Further, he may establish any additional files or other
cross-indexes which he determines advisable. In furtherance of this
filing system the (county zoning administrator, sanitarian
or other designated person) may require that additional information
shall be included on the plan view to aid in filing, indexing or
retrieving said plan view.
Conditional sanitary permit—As an alternative to the maintenance per-
mit program, sanitary permits for on-site systems could be made valid subject
to the condition that inspection and pumping (if necessary) be performed on a
specified regular basis. The enabling legislation or ordinances would have
to be worded to make it unlawful for a system owner to use his system unless
he had a valid sanitary permit.
Local filing requirement—The ability to locate the components of an
on-site system is an obvious prerequisite to any inspection and maintenance
program. Some state and local authorities currently require the filing of a
proposed (or as-built) plan of the system. Summit County Health Department
in Ohio has such a filing requirement and maintains an excellent retrieval
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system. If a septage pumper is having difficulty locating a septic tank,
the Department is able to give detailed location information over the phone.
Similarly, the State of Wisconsin requires that every county in the state
must file a plan for each system installed in its jurisdiction and "cross-
index" the plan to facilitate retrieval. Dane County, Wisconsin also requires
a copy of the plan with an adhesive back to be applied to the building's
electric fuse or circuit breaker box.
Thus, it is recommended that every regulatory authority require that each
system owner file an "as-built" plan of his system, clearly referencing tne
location of the system components. Such a plan is invaluable when it becomes
necessary to inspect or service the on-site system. Many owners do not know
the location of their systems and this makes maintenance difficult. In order
to improve this phase of regulation, it is recommended that states and/or
local authorities adopt this filing requirement and establish a file for these
plans indexed by street address, name of original owner, installer and, per-
haps, legal description.
Failing Systems—
Sanitary surveys—Detection of the failing system is one of the most
important aspects of this final regulatory phase. State and local authorities
should seek funding to perform sanitary surveys. Although a large staff and
budget may be necessary, these surveys are the most thorough method of deter-
mining which systems are failing.
Sanitary surveys may be conducted at one of several different levels of
sophistication as follows:
1. A visit to the location of each system to check for physical signs
of failure (i.e., odor or wetness).
2. The owners or users of the system might be questioned about the
operation of their system and a search of the regulatory agency's
records made to obtain information about the individual system
(age of the system, maintenance, location, etc.).
3. Each system is checked for failure by flushing an indicator
dye through the system (dye testing).
U. Attempts made to check on the adequacy of the site selection and
installation of the system (by analyzing the soil and digging
up a portion of the system) and on the effect of the system on the
groundwater (by taking well samples).
Sanitary surveys provide information which should permit an estimation of the
regulatory program effectiveness. Obviously, the greater the level of sophis-
tication used in performing the survey, the better this estimation.
The commitment of regulatory agency staff time to perform a sanitary
survey, even at lower levels of sophistication, is generally so great that it
tends to limit the number of sanitary surveys performed. In a 196? survey
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of the individual on-site sewerage systems around eight lakes, the Wisconsin
Department of Health and Social Services (DHSS) estimated that it expended
over four staff hours per system investigated to inspect, compile and write-
up the survey of klO systems (Wirth and Hill, 196?). Thus, a major limitation
on the use of sanitary surveys is the large expenditure of time required.
Although, it is possible that the agency could obtain part—time help to perform
these surveys (i.e., students or National Guard or Armed Forces Reservists).
An equally important limitation of sanitary surveys is the difficulty
of determining the actual cause of failure, since the system is buried.
The cause of failure is important because it tends to point out weaknesses
in the regulatory program itself. This type of information sometimes may only
be obtained by excavation of a portion of the failed system. The expense of
this type of survey is great.
Also, the use of surveys are limited because of difficulty in determining
when failure occurs. One type of failure (hydraulic) can be easily detected
while others (treatment efficiency) require a detailed survey of the ground-
water surrounding the failed system. In hydraulic failure, the sewage does not
infiltrate into the soil, but instead earlier backs up into the home or ground
surface, collects in depressions, runs off, or evaporates. This may pose
public health problems and the possibility for degradation of surface water
quality.
In treatment efficiency failure, the system fails to adequately treat the
sewage before it reaches the groundwater. While not as obvious, this inad-
equate treatment must be considered as a failure. Where individual water
supply systems are used, the threat to public health is apparent if pathogenic
material is permitted to reach the groundwater. Also, the groundwater is de-
graded by the addition of pathogenic and nutrients contained in domestic
sewage.
Other limitations arise due to fluctuations of rainfall and groundwater
levels. For example, a system may be adequately functioning during dry seasons
but fail when the rainfall and groundwater levels are high in the spring. Thus,
the time of the year that a survey is performed may affect the results of the
survey.
Violation as an encumbrance—Often, the effect of a sanitary code violation
on the property title is unclear. In an effort to give notice of sanitary
violations to potential buyers of land, it is recommended that state or local
governmental units adopt, either legislatively or administratively, the require-
ment that regulatory officials must file copies of all violations with the
register of deeds or similar official. Reported violations would have to con-
tain the legal description of the property on which the violation is occurring.
The effect of such a filing requirement would be to have the violation
appear in the chain of title whenever an abstract or title insurance policy
is prepared. If the owner of the violating system ever attempted to obtain an
additional mortgage on his property or to sell his property, the potential
mortgagee or buyer would be alerted to the violation. With the violation
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appearing as a possible cloud upon his title, the property values likely
would be depressed, providing the landowner with an incentive to correct the
violation.
As an alternative or adjunct to this filing requirement, notice of exist-
ing violations could be given to potential buyers by requiring an inspection of
the system prior to sale. However, due to constitutional limitations, it may
not be possible to legislatively bar the sale of property until any violations
are corrected. Despite this limitation, the pre-sale inspection would accomplish
its primary purpose of giving notice to buyers.
Centralized Management of On-Site Systems
The use of centralized management of on-site systems probably offers the
best regulatory technique available. Centralized management is the exercise
of administrative and/or regulatory control by a single authority over dis-
persed on-site systems. While this concept is quite simple, it does require
the existence of an entity which has the authority to perform certain functions.
Powers Needed by a Management Entity—
Any management entity which endeavors to administer on-site systems with
the same effectiveness as one which manages the conventional central system,
must have the power and authority to perform vital functions. First, the
public management entity should be empowered to own, purchase, lease and rent
both real and personal property; and to plan, design, construct, inspect,
operate and maintain all types of on-site systems located within the juris-
diction of the management entity, whether the system is a typical septic system
serving a single family residence or a much more involved, complex system
serving a group of residences. This does not imply that the entity should be
limited to providing services within its jurisdictional boundaries, only that
the entity should clearly have the above "ownership and operation" powers
within its boundaries. The entity may be given by state statute, by case law,
or as terms under a contract, extra-jurisdictional authority to operate, main-
tain and perhaps own such systems outside of the entities boundaries as well.
Secondly, it is highly desirable that the entity meet the eligibility
requirements for loans and grants in aid of construction of these systems from
both the federal and state governments. While it is obvious that a management
entity can function without being eligible for these loans and grants, the
viability of the centralized management is strengthened when grant money is used
to offset some or most of the costs to the families served by the entity.
This is especially true since low income rural families often cannot afford to
finance the entire cost of their system. Experience has shown that low-income
families cannot pay wastewater bills in excess of $7-00 per month or a combined
water-sewage bill of $1*1.00 per month (Commission on Rural Water, 1973). This
rate is difficult to reach without benefit of public subsidy. Non-rural
residents have typically paid considerably less than this amount.
Third, the mangement entity should be able to enter into contracts, to
undertake debt obligations either by borrowing and/or by issuing stock shares
or bonds, and to sue and be sued. These powers are more than mere legal niceties
because without them the entity would not be able to acquire the property,
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equipment and supplies and services necessary to construct or operate the
on-site systems.
Fourthly, the entity must be able to fix and collect charges for sewerage
usage, determine the benefit to all property in its jurisdiction, set the value
or cost of such benefit and assess or collect the cost from each property
owner so benefitted. Further, it has been argued that the entity should have
the power to levy taxes upon all owners within its jurisdiction for the purpose
of raising funds to administer the program. Obviously, this taxing power
is limited to various governmental or quasi-governmental management entities.
In lieu of taxing power, the non-government management entities must have the
authority implied or directly granted, to set and charge user fees to cover
administrative costs.
Fifth, and quite important, the entity must have the power to plan and
control how and at what time service will be extended to those within its juris-
diction.
Lastly, the entity would be much more effective in protecting the public
health and promoting good public sanitation if it were also empowered to make
rules and regulations regarding proper sanitation and the use of on-site
systems and to issue orders against violators of these rules or regulations.
As a desirable additional power, the entity should be empowered to require the
abatement of malfunctioning systems and to require the replacement of all such
systems, according to the plans of the entity. Again, several of these powers
would only be available to governmental or quasi-governmental management
entities.
Various Types of Public Central Management—
The entities which could provide central management of on-site systems
vary from state to state. State constitutions, state statutes, administrative
agency rules and regulations must be examined to determine which types of
entities are authorized to manage on-site systems on a state by state basis.
Further, the case law (essentially laws made by the courts) must be checked to
determine if the courts have construed the constitution, statutes or regulations
to give or remove the authority to manage such a system from a candidate entity.
The following discussion of various entities does not attempt to identify
which entities are permitted in each state. A sample of some of the possible
entities is as follows:
Municipalities—While this term has many and various legal definitions,
it is used here to include only incorporated cities and villages. In some states,
the municipal charter granted to the city or village authorizes the administration
of water and sewer services as a permissible governmental activity. Other states
provide this same authorization to cities and villages in the state statutes
dealing with municipal law. Generally, these statutory provisions detail
the procedures to be followed in supplying these services. Thus, both the
municipal charter and any and all applicable municipal law statutory language
must be checked to determine the extent of this entity's authority to own and
operate on-site systems. This entity typically has the authority to provide
centralized management.
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Counties and townships—While the general authority of counties in the
U.S. ranges from a boundary drawn on a map (New England States) to complete
home rule powers "bordering on that of a sovereign, the county may be empowered
to own and operate on-site systems. The authority of both counties and town-
ships is set out in each state's statutes and laws. It is necessary to check
the statutory language to determine whether either has been granted sufficient
authority.
Special purpose districts—There are many special purpose districts which
are given the requisite authority to properly perform as central management
entities. These districts are quasi-governmental in nature and their authority is
usually set out in the state's statutes or laws. Because the district is often
included in the statutory definition of "municipality", however, the authority
of such a district is expanded. Hence, it is necessary to examine the state's
statutes on municipal law to determine the real extent of the district's power.
Single purpose special districts, established to deal with public sani-
tation, will generally have sufficient authority. Also, multi-purpose districts
having a primary purpose other than public sanitation might also have sufficient
authority to satisfactorily own and operate on-site systems. While districts
may have many different names, e.g., sanitation district, service district,
sanitary district, etc., the authority of the district is determined by the
underlying statutory language.
Private non-profit corporations—These entities must be incorporated as
non-profit corporations in the state in which they seek to perform management
functions. Depending on the laws of the individual state and the services
to be provided, these corporations may be considered to be public utilities
and as such, would have to comply with the laws and regulations of the state's
public service or public utility commission. The authority of this type of
entity would be contained in its charter of incorporation and in the applicable
public utility law of that particular state.
Rural electric cooperatives—In some states the REA cooperatives are author-
ized to perform the functions necessary for proper administration of on-site
systems. The authority of these cooperatives is contained, in part, within the
state's statutes.
Private profit-making businesses—This type of entity may be either a sole
proprietorship or incorporated business formed to supply sanitation services.
Regardless of the type of business, the state public service or public utility
commission usually regulates this type of entity. The authority of the private
profit business is limited by any public utility laws or regulations of the
commission which apply to this type of entity.
Others—There are a few other types of entities which might be authorized
in some states to own and operate on-site systems. For example, systems
installed ton Native American reservations would probably not fall within any
of the first six types of entities but, instead, would be controlled by the
U.S. Public Health Service. Further, some states, such as Wisconsin, have a
strong history of cooperatives and may permit a co-op (other than a REA) to
function as a mangement entity.
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Examples of Central Management of On-Site Systems—
While new in concept, central management of on-site systems has been
tried in several places. The following discussion of examples is not exhaus-
tive, but is intended to be illustrative of the state of the art in central
management. In at least half of the following examples, the management entity
is public or quasi-public; however, few of these entities have gone the full
distance of both owning and operating the on-site systems.
Most of the case histories are drawn from California, Wisconsin and
those project areas affiliated with the National Demonstration Water Project
(NDWP). The reason that California is in the vanguard of the movement to
centrally managed on-site systems in rural areas is due, in part, to the efforts
of Winneberger, septic tank consultant. Winneberger has been an advocate
of the septic tank system as an alternative to central collection and treat-
ment systems. District or public management of the septic tank systems is
essential to this concept (Winneberger and Andermann, 1972).
The NDWP recognizes centrally managed on-site systems as the preferred
alternative to central collection and treatment systems in rural or sparsely
populated areas. The NDWP developmental activities were originally funded
by the Office of Economic Opportunities (OEO) and was founded to establish a
method of rural water development. The developed method consisted of central
management of on-site systems (individual wells and wells serving clusters of
residences) of water supply. Since the original development of rural water
systems, the NDWP has expanded its concern to the development of a method of
rural wastewater treatment and disposal. Essentially, the method consists of
the same central management of on-site systems. However, the NDWP has shown
some hesitancy to rely on public central management entities; instead, it
espouses the use of private entities, especially non-profit corporations.
To date, the experience in Wisconsin has been somewhat limited. Public
central management in the form of special purpose districts, has been used to
inspect and maintain septic tanks within the district's jurisdiction.
Currently, however, there is only one district which both, owns and operates
on-site systems (Otis, 1977).
A possible fourth category of experience in central management of on-
site systems has arisen due to the demonstration of low pressure or vacuum
sewers. While it can be argued that pressure sewers are really central systems,
there is an additional component which tends to put pressure/vacuum sewers
under the rubric of on-site systems. In the case of pressure sewers, this
component is the effluent or grinder pump. These components are installed
in individual residences or in some cases, a single pump may be used to serve
a cluster of homes. However, ownership, maintenance and operation of these
pumps is handled by a central management entity and the similarity to on-site
treatment and disposal systems is obvious.
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The examples of central management of non-central systems are as follows:
California—
Santa Cruz County septio tank maintenance district—As the name implies,
the primary function of this entity is the inspection and pumping of all septic
tanks within the district. The county board of supervisors is required to
contract out the inspection and pumping services. The district is empowered
to establish a monthly charge and to collect this charge by separate billing
or through taxes. Provision is made such that the system owner will bear the
cost of "exceptional" pimping (defined as more than one pumping in any
consecutive 3 year period) as well as the cost of repairing or replacing the
system.
This district is not given the authority to own systems and, as of 197^•>
it did not perform soil studies of individual sites nor did it design
systems. Without actual ownership of the systems, the district is ineligible
for most construction grants or loans and by not providing individual site
evaluation and system design, the district loses control over the effectiveness
and reliability of the systems it seeks to maintain. This burden falls upon
the county health department. Thus, this district is somewhat limited.
Georgetown Divide Public Utility Distviot (GDPUD)—This district is
located in El Dorado County, California, and employs one full time environ-
mentalist. By legal arrangements (formation of a special sewer improvement
district within the GDPUD) the Auburn Lake Trails subdivision is receiving
central management services from the GDPUD. The district's environmentalist
is authorized to:
1. Perform feasibility studies on lots within the subdivision
to evaluate the potential for the use of individual on-site
systems;
2. Design specific kinds of on-site systems to serve the individual
sites;
3. Monitor the installation of all systems within the subdivision;
U. Inspect and maintain the systems after installation; and
5. Monitor water quality to determine the effect of the individual
systems upon water leaving the subdivision.
This district also may require the installation of public sewers when and
where necessary. Currently, one area of the subdivision is already sewered.
More sewers may be required, but the build out rate of this recreational
subdivision is about 3 percent per year, thus the need for additional sewers
will be determined sometime in the future. The functions performed by this
district border on almost complete central management of on-site systems.
The only limitation appears to be the fact that the district does not own
the individual systems.
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Bolinas Community PubHe Utility District (BCPUD)—This district was
involved in several legal problems in 197^- At that time, the district was
in the process of constructing a central system to treat the wastewater from
the populous area of the district (Bolinas CBD). Individual on-site systems
were strongly favored by the BCPUD for use in the less densely populated areas.
The district had performed several management functions such as surveying all
existing systems within the district and establishing design requirements.
It proposed to monitor the construction of all systems, maintain the systems
and monitor water quality in the district's watershed. Further, in an effort
to preserve and protect the effectiveness of the area for individual soil
disposal systems, the district proposed to require permits for excavation,
filling, or grading within the district. However, there has been a legal ques-
tion involving the effect of overlapping county (Marin) and district juris-
diction in the area of individual on-site systems. Lack of resolution of this
question as well as the additional requirement of statisfying the State Water
Quality Control Board has impeded, to some degree, this district in the manage-
ment of individual on-site systems. However, it is anticipated that this
district will approach the GDPUD in the degree of central management of individ-
ual systems, lacking only ownership of the systems themselves.
National demonstration water projects—
Guyandotte Water and Sewer Development Association (GWSDA)—This program,
located in Logan County, West Virginia, will involve several discrete
individual projects. The first project planned is to supply both water and
sewer service to 250 families in Big Creek. The proposed wastewater treatment
system does not contemplate the use of individual systems, but the use of a
combination of gravity and pressure lines and a single central treatment
facility. The entity used to manage the systems is a public service district
as provided for by West Virginia law. Other public service districts have
been approved for additional projects in the Guyandotte area with the GWSDA
Association contracting to provide operation and maintenance services to
each of the public service districts. It is this central management pro-
vision for operation and maintenance that makes this program of such interest.
In effect, what is proposed is provision of central management services to
a group of discrete, separate central systems.
Lee County Cooperative Clinio—This program is administered by a rural
health facility.There are U development areas in the current plan. The
Poplar Grove area is a community which is experiencing a severe health
problem due to septic tank system failures. A sewer improvement district
has been formed to administer the Poplar Grove project. The improvement dis-
trict hopes to qualify for an EPA construction grant to construct a conven-
tional system. Again, despite the fact that the program proposes to use a
central system, it is of interest since the Lee County Co-op apparently
will provide central management services to several discrete, separate
(albeit conventional) central systems.
Cooperatives Water and Sewer Association (CWSA)—This association consists
of a partnership of k rural electric cooperatives which serve 18 counties
in the northwest Florida panhandle. A recent amendment to the Florida
-------
statutes permits these co-ops to own and operate "both water and sanitary
sewer systems. There are several advantages of extending the vast experi-
ence of the co-ops in the field of rural electrification to managing water
and sewer systems. For example, they already have the managerial expertise to
bill for services and supply operation and maintenance services. Also, in
most cases, the addition of other utilities (water and sewer) to their "basic
responsibility of supplying electricity would be the most cost effective
method of supplying these additional services to the rural areas.
As noted previously, rural electric cooperatives might not have the
authority to perform the necessary management functions. The state laws
must be examined. This C¥SA program certainly warrants further attention due
to the natural meld of sewer and water supply with the existing co-ops.
Wisconsin—
Town Sanitary Districts (TSD)—Wisconsin has given sufficient
authority to various public districts and has empowered them to
own, operate and maintain various systems of sewage treatment
and disposal including on-site systems serving individual residences.
One such type of district is the Town Sanitary District (TSD). In a thorough
survey of Wisconsin's Town Sanitary Districts, performed in 197^, no districts
reported that they owned any individual systems; however, the survey did
disclose that some do perform management functions such as monitoring the
installation of new septic systems (13% of those responding to the question-
naire); inspecting the systems (1.6%) and maintaining-pumping the systems (h%)
(Klessig and Yanggen, 197^)- Since the survey, one town sanitary district
Sanitary District No. 1 of the Town of Westboro, Taylor County, Wisconsin,
has acquired ownership of septic tanks located on private property. The tanks
serve as pretreatment to the wastewater collection in small diameter gravity
sewers. This system has been in service since June 1977 and is functioning
well.
REGULATION OF ALTERNATIVE SYSTEMS
The scope of this discussion is limited to on-site treatment and/or
disposal systems which handle only small wastewater flows. Unfortunately,
there is no common terminology used in the field of on-site treatment and dis-
posal, hence, definitions are necessary. The following are offered to aid
in this discussion.
Definitions
Conventional Treatment—
"Conventional treatment" is that which is obtained by using the septic
tank as it is generally used to treat wastewater. Although there is a wide
variance in state septic tank design parameters, this variance is not of
concern here as it is not necessary to examine the specific design parameters
in consideration of regulatory programs.
-------
Alternative Treatment—
"Alternative treatment" is defined as any treatment method other than
"conventional" septic tank treatment. No value judgment is intended by the
choice of these two vords, i.e., alternative treatment methods are not in-
herently better (or worse) than the conventional treatment method.
Conventional Disposal—
"Conventional disposal" means the method of disposal which relies on
subsurface soil infiltration of the treated wastewater. Typical disposal
methods are soil absorption trenches, beds, seepage pits, etc. Henceforth,
these will be simply referred to as subsurface soil absorption fields. Again,
it is noted that there is a wide variance in the design and site evaluation
criteria for these fields but this variance has no direct impact in this
discussion.
Alternative Disposal—
The easiest wasy to define "alternative disposal" methods as used here
is simply to say that it includes all disposal methods other than conventional
disposal. As with alternative treatment, no judgment value is intended by
this bifurcation of disposal methods into conventional (subsurface soil ab-
sorption) and alternative (all other methods of disposal).
Surface Discharge—
"Surface discharge" is defined as the discharge of effluent from a
wastewater treatment system into a receiving body of water. Although PL 92-500
does not specifically define "surface discharge", section 502 (12) of the act
defines discharge of pollutants to have a meaning quite similar to "surface
discharge" as defined here, since "pollutant" is defined by section 502 (6)
of the act to mean sewage, sewage sludge, chemical wastes, biological materials,
etc. discharged into the water.
Point Source—
"Point source" as defined "by section 502 (lU) of PL 92-500 is any dis-
cernible, confined and discrete conveyance from which pollutants are or may
be discharged.
Publically Owned Treatment Works—
"Publicaliy owned treatment works" are any device or system used in
the storage, treatment of municipal sewage which is owned and operated by a
public entity. This is the same meaning as provided in Section 212 (2) of
PL 92-500. If publically owned, a system serving more than two residences
would be included within this classification.
Central Management of Non-Central Systems—
A number of on-site treatment and disposal systems serving individual
residences and/or small clusters of homes and non-residential structures
is referred to as a "non-central system." "Central management" of this non-
central system is defined to mean a single governmental or quasi-governmental
unit having the authority to manage these dispersed systems. Thus, "central
management of non-central systems" is simply a regulatory management technique
D-U6
-------
as discussed previously. The use of central management will be suggested as
a regulatory technique for most of the alternative treatment-disposal systems
analyzed in this Appendix.
Matrix of Permissible Treatment-Disposal Combinations
A matrix of possible treatment and disposal combinations of on-site
sewerage is presented in Table D-8. Any system may be thought of as having a
treatment and a disposal aspect. Essentially, any system, whether available
today or yet to be developed and/or proven , will have either a conventional
innovative or no treatment method coupled with conventional, innovative or no
disposal (containment). However, a further breakdown of alternative disposal
methods is necessary to adequately set out all of the possible alternative
disposal methods. The three additional subheadings: (l) soil, (2) surface
water discharge and (3} evapotranspiration (E-T).
An attempt was made to include, in the appropriate locations in this
matrix, descriptions of a few of the known on-site treatment and/or disposal
combinations. It is believed, however, that any other combinations can be
added. The only function served by this matrix is to aid in the creation and
ciLscussion of regulatory programs to control various types of on-site systems
which have been or could be developed.
Elimination of Certain Treatment - Disposal Combinations—
For the purpose of this discussion, certain combinations of treatment-
disposal combinations have been dismissed as being either highly improbable
and/or undesirable. The conventional treatment - containment and off-site
disposal is considered to be unlikely because it is doubtful that any purpose
would be served by conventional (septic tank) treatment of wastewater prior to
discharge into a holding tank. The only possible justification for treatment
of the wastewater would be to increase the likelihood that municipal waste-
water treatment plants would accept the pumpage from the holding tanks. All of
the combinations providing no treatment prior to disposal were dismissed
because they are either highly undesirable or unlawful.
Regulation of Alternative Soil Disposal Systems
Since many alternative on-site systems are more complex than the septic
tank-soil absorption system (e.g., mounds, evapotranspiration systems, etc.)
there are increased possibilities for error in their design and installation.
Thus, the regulatory program must be capable of adequate plan review and in-
stallation inspection.
Suggested Regulatory Techniques—
Pre-approval functions—The regulatory process should be initiated either
by the submission of plans for review and approval or by application for a
permit to install an alternate system. Generally, every on-site regulatory
program would impose either the requirement of obtaining plan approval or permit
prior to commencing construction of any of these systems.
-------
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Inspection—Due to the sensitive nature of the locations for on-site
disposal systems, a mandatory on-site inspection is strongly recommended. This
inspection would be the basis upon which the administrative agent would deter-
mine whether such a system is to be permitted for use at that location. Since
the agent relies upon this inspection, it is further urged that the agent,
himself, make all the inspections.
Licensing or certification of inspectors—As an alternative to the regu-
latory agency staff making all inspections, inspections could be made by
agents, licensed or certified by the administrative authority. This licensure
or certification is necessary to assure the quality of inspections. Such
assurances can only be had if the inspectors license or certification is subject
to suspension or revocation.
Education and/or licensing of installers—Due to the complex nature of some
of these alternative disposal systems, a program to instruct the installers
in the proper methods and techniques as well as the general design bases and
characteristics of the alternative systems, is strongly recommended. Consider-
ation should be given to licensing or certifying these installers to gain more
assurance that the systems will be correctly installed.
Inspection checklists—A program to inspect the construction of these
systems at each critical point during construction is strongly recommended.
It is further recommended that this inspection be performed by the regulatory
authority itself and that a thorough checklist be developed and used for
all such inspections.
Inspection certification—If the regulatory authority cannot perform the
inspection, it is recommended that the delegated agent chosen to perform such
inspections be required to follow the same checklist and certify that the
inspection was properly made. If this approval is selected in lieu of actual
inspection by the regulatory authority, the regulatory authority must then
provide a program to educate the inspectors in the proper design, construction
and installation techniques of the alternate systems.
Suggestions Regarding Choice of Regulatory Authorities—
As stated earlier, it is believed that in many situations, the state is
the best unit of government to administer a regulatory program to control
on-site systems. Briefly, the bases for this conclusion are that: l) the state
government is less subject to pressure by individual citizens to issue or
approve an on-site system for their particular property, 2) the state either
has more expertise or has the resources to hire staff with specialized expertise
in on-site systems, and 3) most states generally have the ultimate power to
regulate any issue of state wide concern, i.e., proper application of on-site
systems in order to protect public health and water quality.
The discussion regarding the choice of regulatory authorities which
follows, suggests various levels of potential involvement by the state.
In addition to regulation by the state, central management (and possibly owner-
ship) by a local unit of government is also considered.
-------
State review of all local government programs regulating alternative
disposal systems—It is recommended that states adopt a mandatory plan
review of all the alternative disposal systems approved "by local units of
government. This state review process conducted by the appropriate state
authority prior to construction, would prevent the use of systems on improper
sites by countermanding local approval whenever required. This could be
accomplished by making the local unit of government's permit or plan approval
subject to state level reversal within a given number of days.
To insure proper and timely inspections are performed, the state could
require proof from the local governmental units that each alternative disposal
system was inspected. This proof could be in the form of a statement certi-
fying that the system was inspected during construction. The same type of
state level review could be imposed upon a monitoring program to assure that
the local unit of government was properly monitoring the systems after in-
stallation.
As an alternative to individual state review of each system, it is
suggested that the state enact a mandatory review of the local regulatory
programs. When a local program is found to be deficient, the state should
impose a state program until the locality brings its program up to standards.
The state would have to establish minimum standards for local programs,
including enforcement practices, staff requirements, employment practices,
siting and installation inspection requirements, etc. These standards could
include design and siting requirements for on-site systems.
State regulatory program for all alternative disposal systems—If state
level plan review is not desired, the state agency could seek complete res-
ponsibility for regulating these alternative systems. The basis for a state
regulatory program would be the critical health and water quality problems
which could result if the alternative systems were improperly regulated.
Public health and water quality are both areas of state wide concern and would
justify the pre-emption of local governmental control, even in states having
strong local governments.
The appropriate state agency could perform some or all of the suggested
regulatory techniques discussed above. Recognizing the importance of
assuring proper evaluation of the sites where these alternative systems are
to be located, the state agency, at a minimum, would want to perform the
on-site inspection prior to approving the installation of a system. In
addition, the plan review or permit process also would be performed by the
state, since it is this process which supplies information which would be
needed by the state to perform the on-site inspection. Other functions such
as inspection of the installation could be performed by this same state
agency. Clearly, the education and/or licensing of installers should be per-
formed by the state.
Central management of non-central systems—A central management entity,
such as special purpose district or other quasi-governmental unit, might be
used to perform many of the regulatory functions described above. The
ability of such districts to administer a regulatory program would depend
D-50
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both upon the enabling statutory language of the district and whether the
local governmental units and state administrative authorities could delegate
to or rely upon the districts to perform regulatory functions.
Briefly, better regulation of these alternative disposal systems might
be obtained because the central management entity would be able to work
closely with those persons within its jurisdiction and could perform some or
all of the following functions:
1. Control the siting of each alternative system;
2. Control the design of each system;
3. Supervise and inspect the construction of each system;
U. Inspect and maintain each alternative system after installation;
5. Fund and staff a program to monitor the water quality within the
district; and
6. Repair or replace the failing systems (charging the system owner
the cost).
Alternative soil disposal system ownership—Finally, regarding regulatory
authority, it is suggested that a unit of local government or centralized
management entity could own all alternative soil disposal systems within its
jurisdiction. Ownership would provide the regulatory authority with almost
total control. The system would usually be located on the property of the
individual served by the alternative system. Therefore, an easement would be
required to give the governmental unit permission to install, maintain, remove
and/or replace the system. The individual so served would be assessed the
costs of providing these systems typically through a special assessment or
user charge.
Important regulatory advantages would be achieved because the governmental
unit could handle the design, installation, maintenance and operation of these
alternative systems. As the owner, the governmental unit would have an
incentive to assure that the systems were properly designed and installed.
The individual, contrary to the typical situation today, would clearly have
an incentive to report any malfunction or failure of the system since the
system is owned by the governmental unit. This would especially be true if
the costs of repair or replacement were not directly assessed against the
homeowner at the time of failure but amortized through user charges. This
would require that the unit of government would have the authority to own and
operate such alternative on-site wastewater disposal systems or else enabling
legislation would have to be sought.
Case History - Wisconsin's Program to Regulate Alternative Disposal Systems—
Description of the program—In June of 1975, the state agency responsible
for the administration of on-site systems, the Wisconsin Department of Health
D-51
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and Social Services, Bureau of Environmental Health (hereinafter DHSS or
department) "began a two-year trial of a regulatory program which had been
developed to control three types of alternative disposal systems—mound
systems. Each county was given the option of determining whether it would
participate in this trial of the regulatory program. Most counties
chose to participate.
The regulatory program employed many (but not all) of the regulatory
techniques discussed above. Most of the pre-approval control functions were
performed by the state (DHSS) and the post-approval control functions were
performed by the county authority responsible for regulation of on-site sys-
tems. These pre-approval regulatory techniques were as follows:
1. An individual application was required from the individual land-
owner for each proposed use requiring a mound system (Figure D-l),
2. The state reviewed each application,
3. An on-site inspection of the proposed location was conducted by
either: a) state personnel (DHSS) or, b) a soil tester certified
by the state (DHSS), and
IK A letter of approval was sent by the state (DHSS) to the applicant
and the county regulatory official if the proposed site was found
to be suitable (Figure D-2).
Most of the post-approval regulatory functions used were as follows:
1. County regulatory official was required to attend a state (DHSS)
sponsored program for training regarding the inspection of the
alternative systems,
2. The trained county official was required to inspect each alter-
native system during construction pursuant to a checklist provided
by the state (DHSS) (Figure D-3),
3. The county official was required to certify that the inspection
was properly performed,
U. This same official was required to return each checklist and the
statement certifying that inspection was made to the state (DHSS),
5. The state (DHSS) issued a letter to the system owner authorizing
use of the system if the checklist and certifying statement
appeared to be in order (Figure D-U), and
6. The county government was required to have an appropriate official
monitor each alternative system and file with the state (DHSS) a
status report after one year's operation.
Thus, the state performed most of the pre-approval regulatory functions
and the county and state split the post-approval regulatory functions.
D-52
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Figure D-l. Application for Use of an Alternate System.
Plb. 108
WISCONSIN DEPARTMENT OF HEALTH & SOCIAL SERVICES
DIVISION OF HEALTH, BUREAU OF ENVIRONMENTAL HEALTH
P. 0. BOX 309
MADISON, WISCONSIN 53701
APPLICATION FOR THE USE OF AN ALTERNATE SYSTEM
ft*********************************
Location lA lA T _, H, R E (or) W
Town or Municipality Street Address
Lot No. , Block , Subdivision County_
Landowner' s Name: _____________________________________________
Mailing Address:
I (We), the undersigned, hereby make application for permission to install an
alternate system on the above-described premises. I recognize that the above
premises are not suited for the conventional septic tank-soil absorption field
and recognize that the alternate system applied for is to be used on my proper
ty which fails to meet the soil and site requirements of a conventional sys-
tem. If permission is granted, I agree to have the system installed in con-
formance with the Division's approved plans and specifications. If the system
is improperly installed, I agree to modify, repair or replace it if so ordered.
I further understand that the alternate system is more complex in nature than
a conventional septic tank system and as such will require detailed inspection
during construction and monitoring after the system is put into use. I agree
to permit both county officials charged with administering county sanitary
ordinances and Division employees or other authorized persons to have access
to the above described premises at any reasonable time for the purpose of in-
specting the construction or monitoring of the system. I further agree to
either personally or by my agent contact the proper county official to arrange
the time and date to begin construction of the system.
I understand that this application does not permit me (the applicant) or my
agent (the contractor) to begin the installation of any alternate system.
The Division or other authorized representative will perform an onsite
inspection of the above-described premises. If the system is approved, the
Division will send the applicant a Letter Authorizing the Construction of an
Alternate System. I agree to permit Division employees or other authorized
persons to have access to the premises at any reasonable time for the purpose
of making such onsite evaluation and I further agree not to begin construction
prior to the receipt of such a letter.
(continued)
D-53
-------
Figure D-l (continued)
-2-
I understand that this application does not permit me or any other person to
discharge sewage into the alternate system, sought by this application, until
I receive a Letter Approving the Use of an Alternate System from the Division.
This letter will be sent by the Division after it receives, from the proper
county officials, a checklist and statement certifying that the alternate
system was properly constructed. I agree not to use or permit the use of the
alternate system prior to receiving such a letter.
I recognize the limitations of the above-described premises and in consider-
ation for the use of the alternate system applied for by this application,
I agree to repair, modify or replace, at my expense, the alternate system if
the county officials or the Division find the system to be malfunctioning.
Further, I understand that the county or the Division may require that the
alternate system be replaced with a holding tank or with a system of a more
suitable design. I understand and agree that if a holding tank is required, I
will have to make arrangements satisfactory to the Division for the disposal
of the effluent.
I agree to give notice to any subsequent buyer that an application for an
alternate system has been made and if installed, that the premises are served
by an alternate system and further agree to give that buyer a copy of this
application.
I understand that the Division and the county do not guarantee and do not pro-
vide a warranty (either implied or express) that the alternate system sought
by this application will properly function. The Division receives this
application subject to this understanding and subject to all the conditions
and obligations set out in this application.
Date Signature of Applicant
STATE OF WISCONSIN)
) ss.
COUNTY OF )
Subscribed and sworn to before me
this day of , 19 •
Notary Public, State of Wisconsin
Ify Commission expires:
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Figure D-2. Alternative System Approval Letter
To: Property Owner
The Bureau of Environmental Health has reviewed plans, site survey information
and installation details covering the construction of a (new or replacement)
private sewage disposal system on your property located
(location)
County, Wisconsin. The plans and installation details were prepared by
name title
and received for approval on date .
The site evaluation was conducted by name title
The soil is name and/or description . The soil percolation
rate is . The premises meets the soil and
site requirements specificed for the use of Alternate System no. which
was developed by the University of Wisconsin Small Scale Waste Management
Project.
The proposed system will serve a single family residence containing no.
bedrooms. The system has been sized in accord with the requirements set
forth in the alternate system design criteria. Wastes from the home will
discharge to a gallon capacity septic tank which will discharge to a
gallon capacity pump chamber from which a pump having a capacity of
gallons per minute against a total dynamic head of feet will discharge
through inch diameter pipe to the soil absorption system.
The proposed system is not in strict keeping with design criteria for private
sewage disposal systems as established in the Wisconsin Administrative Code.
However, certain features not specifically referred to in the "alternate designs"
must be in accord with the regulations. Due to the existence of site soil
limitations it is of utmost importance that the system be installed in com-
plete accord with the plans and installation details and the conditions of
approval contained herein; that the appropriate vil, COA twn, city official
conduct thorough inspections at specified times, reporting his findings to
this Division and that the contractor not deviate from this formal approval
and follow directions or orders issued by the appropriate local or state
authorities.
In accordance with Chapter 1^5, Wisconsin Statutes and Section H 62.2k (l),
Wisconsin Administrative Code, approval to construct the alternate design
private sewage disposal system is granted subject to the following conditions.
If construction commences the Department will imply acceptance of the
conditions.
(continued)
D-55
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Figure D-2 (continued)
1. That the vil, co, twn, city authority administering the local sanitary
ordinance permit the installation as proposed.
2. That a state septic tank permit be obtained.
3- That a copy of the plans and installation details covering the proposed
system be supplied to the appropriate local officials.
k. That construction of the system not commence until the appropriate
local official is notified and that construction proceed on a schedule
dictated by that official.
5. That the owner of the system not commence its use nor permit any other
person or persons to use it until a letter approving use is received from
the Division.
6. That the appropriate local official be notified of the day when use of the
system is to commence.
7- That a copy of this approval and the approved plans and installation
details be kept on the premises during and after installation.
8. That appropriate local officials, employees of this Division and/or
representatives of the University of Wisconsin Small Scale Waste Manage-
ment Project be permitted to have access to the premises at any reasonable
time for the purpose of inspecting and monitoring the system, including
the conducting of any necessary bore holes or other physical examinations
and the collection of samples of soil or liquids.
9. That in event the alternate design system or any of its component parts
malfunction so as to create a health hazard by discharge of partially
treated or untreated liquid wastes onto the ground surface or into the
waters of the state the owner will repair, modify or replace at his
expense (including the possibility of installation of a holding tank with
proper disposal) the alternate design system with such action approved
by the Division and the appropriate local official.
10. That any subsequent buyer of the premises be given notice that an alternate
design system is installed and a copy of this letter of approval be given
such buyer.
11. That the alternate design system installation be made in complete accord
with the plans and installation details; appropriate sections of
Chapter H 62, Wisconsin Administrative Code, that are not varied from in
the alternate design; and the conditions of approval contained herein.
In granting this approval, the Division does not hold itself liable for any
defects in construction; does not guarantee and further does not give warranty,
(continued)
D-56
-------
Figure D-2 (continued)
either implied or express, that the system will function adequately or indef-
initely; nor does it hold itself liable for any damages that may result from
the installation of the system and reserves the right, after consultation with
the University of Wisconsin Small Scale Waste Management Project and local
personnel, to order changes or additions should conditions arise making such
action necessary.
In case installation of the system has not actually commenced within two
years from date, this approval is void. After two years, therefore, new
application must be made for approval of these or other plans and installation
details before any construction is undertaken.
By order of George H. Handy, M.D., State Health Officer.
H.E. Wirth, P.E., Director
Bureau of Environmental Health
Skk
cc: University of Wisconsin P & S to File
Designer Owner
County Designer
District
Contractor if known and not designer
File
D-57
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Figure D-3. Construction Checklist for the Inspection of Alternate
Sewage Disposal Systems.
Construction Inspection of Alternate Design Sewage Disposal Systems
Wisconsin Department of Health & Social Services
Section of Plumbing & Fire Protection Systems
Plan Identification No.
Installed for
A. Site Investigation at onset of construction
1. Name of Installer
2. County Inspector Date
3. Package #
k. Preliminary onsite made by Date
5. Depth to limiting factor (50% unconsolidated rock or estimated ground
water level)
6. Percolation rate
7- County installation permit number
8. Are percolation and soil boring holes evident? Yes No
9. Is system located in area of soil tests? Yes No
10. Is system located in area shown on state approved plans? Yes
No
11. Ground slope in area of system
12. Site data is correct as presented by C.S.T. and system designer?
Yes No
Inspection of Construction
1. Disposal site plowed and properly prepared? Yes __
2. Disposal site conditions wet or damp? Wet Damp
3. Type of fill material
U. Depth of fill (lf Minimum)
5. Is a crawler type tractor used? Yes No
a. Blade Bucket
6. Has site been driven on by any vehicles? Yes No
(continued)
D-58
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Figure D-3 (continued)
7. Trench width as indicated on approved plans? Yes
8. Trench spacing as indicated on approved plans? Yes
9. Have trench bottoms been properly leveled? Yes
10. Trench length and number as shown on approved plans? Yes No
11. Distribution piping proper diameter? Yes No
12. Holes in distribution piping properly sized? Yes
13. Holes in distribution piping properly spaced? Yes
1^. Holes in distribution piping in a straight line? Yes
15. Distribution holes drilled straight into piping? Yes
16. Depth of gravel below distribution piping
17. Depth of gravel above distribution piping
18. Thickness of marsh hay covering
19- Permanent marker at end of each trench
20. Depth of fill over center of system _
21. Depth of fill over outer trenches
22. Side slopes
23. Type of fill used above trenches
2 It. Depth of top soil
25. Seeded? Yes No
C. Pumping Chamber
1. Diameter of inlet
2. Diameter of outlet
3. Head
IK Size of pump tank gallons
5. Draw down of gallons pumped per cycle
6. Manufacturer and type of pump same as that indicated on approved
plans? Yes No
7. Quick disconnect provided? Yes No
8. Diameter of manhole
9. Height of manhole above finished grade _________________
10. Diameter of vent
11. Height of vent above finished grade
12. Pump tank located as shown on approved plans? Yes No
(continued)
D-59
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Figure D-3 (continued)
D. Septic Tank
1. Properly installed? Yes No
COMMENTS
I, the undersigned, hereby certify that the questions were answered
on the basis of my personal inspection or knowledge of the construction
of this alternate system and further that all data and answers recorded
on this form are correct and to the best of my knowledge and belief.
Name : Signature :
Title:
WE HAVE INCLUDED WO COPIES OF THIS FORM FOR COMPLETION BY YOUR OFFICE.
WHEN INSPECTION OF CONSTRUCTION IS COMPLETE, ONE COMPLETED FORM SHALL
BE RETURNED TO THIS OFFICE WITHIN TEN (10) DAYS AFTER YOUR FINAL
INSPECTION OF THIS ALTERNATE SYSTEM.
Date received by Section of Plumbing & Fire Protection Systems
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Figure D-U. Letter of Approval for System Use
To: owner
Re: Approval for use of an alternate system
The Division has received from the county official responsible for enforcement
of the sanitary ordinances in your county both a checklist and a statement
certifying that the above described alternate system was inspected during con-
struction. The Division has reviewed both documents and is satisfied that the
above described alternate system was properly constructed.
The alternate system owner is reminded that this alternate system was necessary
because of the unsuitability of the above described premises for a conventional
septic tank-soil absorption field system. Due to the soil and site limitations
of land like yours, alternate systems were developed to provide adequate treat-
ment and safe disposal of wastewater. However, the Division does not guarantee
and further, does not give a warranty (either implied or express) that your
alternate system will function properly for any given period of time. Both when
you applied for an alternate system and when you received a letter authorizing
the construction of an alternate system, you agreed to accept the responsibility
to repair or replace the above described alternate system if county officials
or the Division find it to be malfunctioning. As the owner of this alternate
system, you have further agreed that any repairs or replacement will be
totally at your own expense with no recourse to the county or the Division for
any part of the costs.
The alternate system may be used if the owner agrees to the following conditions:
1. That the system owner must permit both the county officials entrusted with
the enforcement of county sanitary ordinances and employees of the Division
or other authorized persons to have access to the above described premises
at any reasonable time for the purpose of monitoring the alternate system;
2. That the system owner agrees to repair, modify or replace at his expense
the above described alternate system if the county official or the Division
finds the system to be malfunctioning. Any modification to or replacement
of the alternate system must be acceptable to the Division;
3. That the owner agrees to give notice to the proper county officials and
to the Division prior to beginning use of this alternate system;
it. That the owner agrees to inform any subsequent buyer that an alternate
system has been installed by giving the buyer a copy of this letter, and
a copy of the plans and specifications of the alternate system.
(continued)
D-6l
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Figure D-l* (continued)
By beginning to use this alternate system, the owner agrees to accept and
to comply with all of the conditions set forth above. The Division will
imply acceptance of these conditions if the owner begins use of this alternate
system.
Sincerely,
James A. Sargent
Chief
JAS:skk
cc: District
County ZA
University of Wisconsin
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Regulation of Surface Disposal Systems
The systems under consideration in this section are classified as alter-
native treatment - alternative disposal systems. While a vide range of alter-
native treatment methods are envisioned, only one type of alternative disposal
is considered - surface discharge. It is both the alternative treatment
methods as well as surface discharge which mandate a regulatory program more
stringent than that used for conventional systems. This type of system
differs from the other alternative disposal systems because of the discharge
to a watercourse. Systems which rely on the soil for final disposal are seen
as posing much less of an immediate threat if their respective treatment com-
ponents fail. The lack of soil disposal, however, requires total reliance
upon a properly functioning treatment component. Increased regulatory demands
also are imposed because the treatment componentsrequire relatively more fre-
quent maintenance when compared to the conventional septic tank. Thus the
regulatory mechanism must be capable of meeting this increased responsibility.
In addition, an institutional/regulatory mechanism must be available to monitor
the discharge to assure that the on-site system is providing treatment suffi-
cient to protect public health and water quality.
Unique Regulatory Aspects—
Of all the on-site systems, there are certain regulatory aspects which
are unique to surface water discharge systems. Tliese aspects are briefly
noted below.
Applicable federal requirements—Unlike the other methods of on-site
treatment and/or disposal, this method is regulated by federal law (PL 92-500).
Any discharge to surface waters will have to comply with the federal require-
ments and state water quality standards adopted pursuant to PL 92-500. With
perhaps some modification, an existing federal-state regulatory program would
be used to control these systems.
Different state agencies involved—In many states there exists a dicho-
tomy in regulation of sewerage. On-site systems are traditionally regulated
by one state agency (typically that agency responsible for public health)
while a different agency is responsible for water quality protection. However,
since surface water discharging systems pose such a potential threat to water
quality and public health, both state agencies may regulate these systems.
The regulatory programs of two state agencies may pose some difficulties if
their requirements may conflict. In any event, coordination between the two
regulatory agencies will be necessary.
Federal Requirements Regulating Discharges to Water—
Off-lot discharging systems are regulated by the Federal Water Pollution
Control Act Amendments of 1972, Section ^02. Under this act the discharge
of any pollutant into the nation's waters without a permit is unlawful.
The permitting process (National Pollutant Discharge Elimination System -
NPDES) is the keystone of the strategy for improving the quality of the nation's
waters. A permit cannot be issued by the state water quality agency if the
proposed discharge will violate any other provisions of the Act. Via this
regulatory technique, the Act imposes upon all dischargers the requirement to
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meet effluent limitations, attain water quality related effluent limitations,
meet water quality standards of the receiving waters, and meet total maximum
daily load restrictions, if any.
The impact of this Act upon off-lot discharging systems for small flows
is the same as upon any other discharger with the exception that some of the
administrative requirements might be more burdensome to individual system
owners.
To obtain a discharge permit, the proposed system would have to comply
with all the provisions of the Act. Of primary importance is the effluent
limitations. Other water quality requirements are all related to the water
quality of the receiving waters. Therefore, until the receiving waters are
identified, it is quite difficult to discuss the impact that these requirements
would have.
The permit system and effluent limitations are discussed below. For
illustrative purposes, a discussion of the Wisconsin NPDES permits and efflu-
ent limitations program is provided.
Pollutant discharge elimination permits—While this act granted the USEPA
administrator the authority to issue discharge permits, it was clearly the
intention of Congress that each state would be delegated authority to adopt
and administer a permit program. Most states have undertaken such a permit
program and, in most instances, additional state enabling legislation was
required. For example, in Wisconsin, the state legislature enacted ch. 1^7,
Wis. Stats, since the Department of Natural Resources lacked the necessary
authority.
Regardless of whether the permit program is administered by a regulatory
agency of the state or by the USEPA, the permit program imposes the same
minimum requirements on point source dischargers of pollutants. Prior to
approval of any state program, the appropriate USEPA regional administrator
must determine that the designated state agency has adequate authority to
administer a permit program which meets minimum standards.
A permit is required for the point source discharge of any pollutant
or combination of pollutants, and can only be issued if the discharge will
not violate the other provisions of the act. This means that surface water
discharging systems would have to meet effluent limitations. If these
systems are classified as publicly owned treatment works, they would have
to meet effluent limitations based upon secondary treatment by July 1, 1977
(or any more stringent limitations necessary to meet water quality standards
or other state and federal requirements). By July 1, 1983, publically owned
treatment works are required to apply the best practicable waste treatment
technology in order to obtain a discharge permit. The federal construction
grant program is aimed at assisting publically owned treatment works to meet
these objectives. If these systems are not publically owned treatment works,
however, they must meet the effluent limitations of best available control
technology by July 1, 1983 (Section 301, P.L. 92-500).
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Both the discharges from publically owned treatment works and all other
point source discharges may be further limited if the discharge would inter-
fere with the attainment of specific water quality goals. In addition, permits
may only be issued if the discharge will meet all the applicable standards
of performance including maximum daily loads and toxic or pre-treatment efflu-
ent limitations.
The discharge permit program outlined in P.L. 92-500 specifies that a
permit is required for on-site systems with surface water discharge and
indicates that effluent limitations and other standards to be applied should
not vary from state to state. Thus, the effect of the discharge permit pro-
gram upon the development and regulation of on-site systems with surface
water discharge should be uniform throughout the nation. Since P.L. 92-500
imposes only minimum requirements, a state could impose either more stringent
effluent limitations or extend the scope of the discharges to cover land
disposal.
The discharge permit program of a particular state should be examined
to determine if it contains requirements in addition to those imposed by
P.L. 92-500. In the discussion of Wisconsin's discharge permit program, it
will be noted that groundwater quality protection is included within the
permit program jurisdiction.
Wisconsin's jpollutant discharge elimination system—Pursuant to P.L.
92-500, the Wisconsin legislature enacted ch.lU7, Wis. Stats, to grant the
DWR the needed authority to establish an approved pollutant discharge permit
program (Sec. lVf.01 (2), 1973).
Sec. 1^7-02 made the discharge of any pollutant into any waters of
the state (surface and ground waters) unlawful unless such discharge is
done under a permit issued by the department. No permits may be issued unless
all applicable standards and effluent limitations are met. Sec. 1^7.025
mandated that within 180 days after enactment, every owner of any existing
point source discharging pollutante into the waters of the state must apply
for a permit. Also, every owner of a new point source wishing to commence
discharging must apply for a permit at least l80 days prior to the date on
which discharge is to commence.
On-site wastewater systems which propose to discharge any effluent into
the surface waters of the state, therefore, would require a discharge permit.
Further, due to the all encompassing definition of water, any on-site system
discharging to a land disposal system could also be required to obtain a
permit. However, the department has chosen not to exercise its statutory
authority over on-site systems using land disposal. According to the rules
adopted by the department, the discharge of domestic sewage to disposal
system such as to septic tanks and drain fields is exempted.
By necessity, Wisconsin's discharge permit program parallels the under-
lying federal program since it separates publically owned treatment works
from all other categories of point source discharges. The same effluent
limitations are imposed upon each category by the Wisconsin programs as does
the federal program. Similarly, the Wisconsin program prohibits the
D-65
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issuance of a permit unless the discharger meets all applicable performance,
effluent, and water quality related standards, as well as
total maximum daily loads (Sec. 1U7.02 (3) Wis. Stats., 1973). In summary,
the Wisconsin program requires a permit for the lawful surface discharge
of effluent from an on-site system which is issued only for surface discharg-
ing systems meeting the effluent limitations and other applicable standards.
Additional Possible State Regulatory Techniques—
Some regulatory techniques exist in other states which might apply
to off-lot discharging systems. Two commonly used regulatory techniques
are discussed below in regard to their impact or applicability to individual
off-lot discharging systems. While not every state currently employs each
of these, the techniques have been basic to the regulation of publically
owned treatment works and may apply to small wastewater flow systems, as well.
Wisconsin1s program is used as an illustration to aid in determining whether
these regulatory techniques should be applied to small wastewater flow systems.
Plan approval—Most states and some local units of government require
the owner of a wastewater facility to submit plans prior to construction of
the proposed system. Typically, this plan review is performed by the state
agency having responsibility for water quality protection. Publically owned
treatment works usually receive 75 percent federally of the costs of con-
struction through federal construction grants. Therefore, the state's plan
review is done in compliance with federal regulations followed by a review by
the appropriate EPA regional office. Plan review and approval by the state
agency and EPA regional office is certain to be a requirement to be imposed
on on-site systems where federal construction assistance is sought.
Depending on ownership, on-site systems proposing surface water discharge
may be eligible for federal construction grants and thus, be reviewed under
the federal grants procedure. For those facilities not eligible for federal
assistance, the state or local governmental unit may or may not have a plan
review and approval process which would apply to these systems. The "non-
federal grants" portion of any state's plan review and approval requirements
must be examined to determine whether on-site systems are included within the
definition of the systems which are required to obtain plan approval. Typi-
cally, these state statutes or department rules may require review and
approval of the plans for a proposed "wastewater treatment works or facility."
There is no uniform state approach to consideration of proposed individual
on-site systems with surface water discharge as a "works or facility"
requiring plan review.
A potential problem may arise in states where individual on-site-surface
water discharging systems have not been used previously. This occurs because
they are very similar to the conventional wastewater treatment facility in
that they discharge to the surface waters. Thus, the state agency which has
the responsibility for regulation of sewerage facilities must determine whether
on-site-surface water discharging systems are to be regulated as conventional
sewerage facilities. If the agency determines that the systems are under
its jurisdiction, then the agency must impose its requirements upon the
on-site systems. However, the outcome of this decision may not be critical
D-66
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because individual surface discharging systems not characterized as treatment
works (and, thus not regulated "by the agency responsible for sewerage systems)
are probably regulated by the state and/or local agency which regulates
individual on-site systems. With regulation practically assured, the only
question is what form the regulation will take.
Wisconsin statutes and administrative rules are examined as an illus-
tration of on-site-surfacing discharge systems characterized as sewerage
facilities subject to the plan review and approval. State statutes (Sec.
lUk.Oh Wis. Stats., 1973) require that every owner file a certified copy of
the complete plans of the proposed "system or plant" or extension thereof
and other information concerning maintenance, operation and other details as
may be required by the Department of Natural Resources (DNR), the state agency
primarily responsible for water quality. The DNR has 90 days to approve,
conditionally approve or reject the plans. An owner who fails to comply with
this requirement before installing a system or plant would be subject to a
fine of from $10 to $5,000. Each day of continuing violation constitutes a
separate offense (Sec. lMt.57 Wis. Stats., 1973).
The phrase "system or plant" is defined by statute to include "water
and sewerage systems and sewerage and refuse disposal plants" (Sec. 1^.01 (6)
Wis. Stats., 1973). The term "sewerage system" is also defined by statute
to mean (Sec. lUf.Ol (5) Wis. Stats.., 1973):
". . .all structures, conduits and pipe lines by which
sewage is collected and disposed of, except plumbing
inside and in connection with buildings served, and
service pipes from building to street main."
It is clear that any type of on-site treatment and disposal wastewater
system could be included within the definition of "system or plant." Thus,
the requirements of plan submission and department review and approval would
apply to these surface discharging on-site systems. Current practice at the
department, however, does not require the submission of plans, departmental
review or approval for a single on-site system using soil disposal of the
effluent, regardless of the number of persons served by the system, although
the department has just recently imposed the plan review and approval require-
ment upon a community system consisting of individual septic tanks - small
diameter gravity sewer pipe discharging into common soil disposal fields.
It may be inferred that if an on-site system were proposed to serve a single
family by treating and then discharging effluent to the surface waters of
the state, the department might impose the plan review and approval require-
ment.
The requirement that owners of each on-site-surface water discharging
system submit plans and delay construction of the system until receiving
departmental approval may impose increased costs upon the owner. First,
the direct cost of plan preparation may increase. In Wisconsin, conventional
on-site systems serving one or two family residences must comply only with
a minimum state standard and are not required to obtain any plan approval
from the state agency (Department of Health and Social Services - DHSS)
which regulates all conventional on-site systems.
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Other less direct costs may be incurred during the plan review process,
which may take as long as 90 days. Thus, the owner would either have to
submit plans well in advance of his construction date or subject himself to
the risks of construction delays with all of the attendant costs.
In conclusion, surface water discharging systems in Wisconsin easily
could be characterized as a "sewerage system" and thereby be subject to plan
review and approval by the state water quality agency. Regardless of this
characterization, the owner of the proposed system would still be required to
comply with all local regulatory procedures as well as any that might be
imposed by the Wisconsin Department of Health and Social Services.
Certification of sewerage treatment plant operators—Most states and
some local units of government have a program to examine and certify sewerage
treatment plant operators. Typically, those states which have such a program
require that only certified operators may be employed to operate certain
types of treatment facilities. This requirement is just as important as the
certification program since, without this requirement, many owners of treat-
ment facilities probably would not employ state certified operators because a
premium might have to be paid to obtain them. Therefore, to assure trained
certified operators are employed, a state program should consist of both the
certification process and the requirement that only certified operators may
operate sewerage facilities within the state.
The desired goal of any certification program is to have qualified oper-
ators operating all of the treatment facilities within each state. This
certification procedure is to assure the capability of the wastewater facility
operators. Although other devices or techniques could be used to'assure the
availability of qualified operators, this certification program is perhaps
the easiest to administer.
The certification program, or other techniques or devices to accomplish
this goal, can be effectively implemented by including the use of a certi-
fied operator as a condition of the discharge permit. This approach may
require enabling legislation in some states. Further, those states which
require plan approval may also make their approval conditional upon the
assurance that only certified operators will operate the treatment facility.
While it is clear that the treatment works serving large metropolitan
areas should be operated only by qualified operators, the issue becomes
less clear as the communities served decrease in size. That is, will the
state agency responsible for administering the certification program deter-
mine that on-site systems employing surface water discharge, but serving only
small populations, such as a single family, require a certified operator.
This determination should depend on a thoughtful consideration of the
characteristics of each on-site system. After review, the appropriate state
agency could determine whether a certified operator would be required.
This requirement would be imposed for one or more of the following reasons:
1. The system is sensitive and easily upset requiring close
monitoring.
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2. The system is complex, or
3. The system is likely to pose a threat to public health or vater
quality.
While this list of reasons is by no means complete, it is offered to aid
in the judgement of whether a state will require a certified operator for
various types of on-site systems. This is a question of how the on-site sys-
tem will be viewed. If viewed as being analogous to a municipal treatment
facility, the state will likely require a certified operator. Because of
public health and water quality concerns, it is anticipated that on-site
systems which propose surface water discharge also will be required to have
a certified operator. It is necessary to examine the relevant statutes,
rules and guidelines in the state of interest to determine whether that state
has a certified operator program and whether the requirement includes on-site
systems.
Because of the varying complexity of treatment facilities, it would be
expected that states would classify the facilities in order of complexity.
Certification of operators should reflect these classes. For example, it
would be unnecessary for the operator of a small stabilization lagoon to be
qualified to operate a large metropolitan activated sludge treatment plant.
It is anticipated that most states which have a certification program have
also defined classes of treatment facilities with appropriate minimum levels
of training, education (degree) and operating experience for the operators of
each treatment facility class.
If included under a state operator certification program, on-site systems
including those with surface discharge, probably would be classified in the
least complex class of treatment facilities. The amount of training, edu-
cation and operating experiences which the opeartor would be required to
have therefore, would be the least demanding of the levels required for certi-
fication. However, it is not known whether the requirement for a certified
operator of on-site systems will pose an unreasonable burden for the system
owner. Of course, the owner could become certified to operate his own
on-site system, assuming that he could meet the basic minimum requirements
for certification.
Wisconsin Statutes require that all treatment facilities be operated
by certified operators. Pursuant to this requirement, administrative rules
were adopted to classify both treatment facilities and corresponding opera-
tors . The statutes provide that the Department of Natural Resources shall
establish an examination program for the certification of sewage ^treatment
plant operators and impose a deadline after which no person shall operate
a sewage treatment plant unless he is certified (Sec. l^U.025 (2)(l) Wis.
Stats., 1973). According to the administrative rules adopted pursuant to
this statute, a sewage treatment plant is defined as (Sec. NR llU.02 (3),
Wis. Admin. Code, 1971):
"... any facility or group of units provided for the treat-
ment of sanitary sewage and/or industrial waste."
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The definition specifically excludes septic tank and soil disposal systems:
By implication, other on-site systems, especially those with surface water
discharge, are included and are subject to the certified operator requirement.
A further examination of these rules shows that the Department has
classified sewage treatment plants based on one of two criteria: flow or
complexity of the process employed by the plant. Individual domestic on-site
systems are not included either under the lowest flow (.1 MGD) criterion nor
the complexity criterion. However, an additional classification, Class IV
which includes "All other plants which treat sanitary sewage," would include
on-site systems (Sec. NR lllt.08 (l)(d) Wis. Admin. Code, 1973). These rules
establish 5 grades of sewage treatment plant operators and require that an
individual to become certified in any grade must meet one of the combination
of educational and experience requirements and pass the appropriate examination
(Sec. NR lilt.09 (l) Wis. Admin. Code, 1973). The rules also provide that
anyone holding a grade I, II, III or IV certificate may operate a class IV
sewage treatment plant (the probable class for on-site-surface discharge
systems). Thus, a grade IV operator would be able to operate on-site systems.
The rules define grade IV experience requirements to be (Sec. NR 11^.09 (d)
Wis. Admin. Code, 1973):
"Completion of special course of training in sewage treatment
and demonstration of aptitude in operation of sewage treatment
works."
These special courses are offered one or more times per year and might be one
to two weeks in length.
Suggested Regulatory Techniques—
Since each on-site surface water discharge probably will have to comply
with federal (PL 92-500) and state water quality standards, the regulation
of these systems should be assured. As discussed previously, each discharge
will be required to obtain a pollutant discharge permit (NPDES) and meet
federally set discharge standards (currently secondary treatment requirements).
Also, the federal requirements include monitoring and reporting minimums
which must be met by each permittee. Therefore, the regulatory program for
this category of treatment-disposal will be largely determined by the federal
requirements under P.L. 92-500. However, the state or local regulatory
agency may employ additional regulatory techniques as suggested below.
Certified treatment plant operators—The requirement that certified
operators be employed to operate and maintain on-site surface water discharg-
ing wastewater systems already may be imposed by state law or local government
ordinance. If not, it is recommended that consideration be given to imposing
such a requirement. It is felt that certification of treatment plant opera-
tors would provide a regulatory technique which could significantly strengthen
the existing federal-state regulatory program.
Typically, one or more agencies of state government will have the
responsibility for regulating these surface discharge systems. Therefore, it
is recommended that certification be imposed at the state level. The exact
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mechanisms and the designation of the appropriate state agency are not
considered here. However, the program must be rigorous enough to guarantee
that only properly trained operators would be certified. If certified
operators are required, the state agency which regulates on-site systems
should gain increased assurance that the systems will be adequately operated.
While it might appear that requiring a certified operator would be burden-
some for the system owner, there are several methods which could reduce this
burden.
In those states which require a certified operator for some or all types
of on-site systems (especially surface water discharge), some certified
operators will contract their services to system owners. Since the operation
of these individual systems is not time intensive, the certified operator
could service many systems. Depending upon the size of the market in any
given locale, one or more certified operators might be able to earn an ade-
quate income by supplying such services.
Alternatively, it is possible for several system owners to hire a single
certified operator to operate all of their systems. This approach could
be undertaken either through an informal agreement between owners, or through
the special district approach.
Plan review by state or local government—The extensive plan review
required for public treatment works may be applicable to on-site systems using
surface water discharge. However, most regulatory programs which control
the conventional on-site system contain a plan review requirement, albeit
somewhat rudimentary when compared to the requirements of public treatment
works. It is recommended that the regulatory program contain adequate author-
ity to require the potential on-site system owner to submit detailed plans
for review. In most Jurisdictions, this requirement already exists or the
rules and regulations can be easily modified to require expanded reviey when
surface water discharge is sought.
Note that adequate plan review will be obtained via the facilities
planning or procedures imposed by P.L. 92-500 whenever the proposed treatment
work is to receive a federal construction grant. Although on-site systems
are grant eligible, it is recognized that state funding lists generally
assign low priority to small projects. Rather than waiting several years
until funds are available, some owners may decide to proceed without federal
assistance. In such cases, relying on the grant review process alone will
be an insufficient control.
Central management of non-central systems—Adequate operation and main-
tenance of these alternative treatment-surface discharge systems could be
provided by a central management entity such as a general or special purpose
unit of government. It is strongly recommended that states and/or local
units of government, impose, before granting approval to the use of on-site
surface water discharging systems, the requirement that the systems are to
be operated and maintained (and perhaps also owned) by a central management
entity.
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Governmental ownership—Where permitted by state constitution or
statutes, ownership by the state or local units of government provides the
best assurance of proper operation and maintenance of these alternative
treatment-surface discharge systems. Other advantages were discussed prev-
iously and will not be repeated here.
LAND USE IMPLICATIONS OF ALTERNATIVE ON-SITE WASTEWATER DISPOSAL SYSTEMS
In many areas of the country, planners have relied upon two related facts
concerning wastewater service in planning ex-urban and other low density
areas. The first of these is the unsuitability of some soils within their
jurisdiction for conventional septic tank systems. The second fact is that
public sewerage systems are too expensive, in many cases, for less densely
populated areas. Unfortunately, in areas unsuitable for septic tank systems,
the only other alternative usually considered is a public central sewer system.
However, expense frequently rules out its use, discouraging development of the
area. New technology, either in the form of alternative disposal systems or
more cost effective methods of public sewerage could make development of
these areas more practical. Communities which previously discouraged develop-
ment in areas where septic tank systems were not feasible, may want to
reevaluate their land use plans and regulations.
Alternative Disposal Systems — Case Studies of Potential Impact
The alternative disposal systems discussed in the body of this report
provide methods for safe treatment and disposal of small wastewater flows on
sites previously considered unsuitable. Specifically, mound disposal systems
for very slowly permeable soils and for permeable soils over shallow creviced
or porous bedrock have already been developed. Work continues on the develop-
ment of alternative disposal systems which are not dependent on soil or site
conditions, i.e., surface water discharging systems.
The implications of these existing and potential alternatives pose for
land use is obvious, especially when one considers that an estimated 68 per-
cent of the United States has been judged to be unsuitable for the conven-
tional septic tank system (Wenk, 1971).
Of course, the unstated premise here is that sanitary ordinances and
subdivision regulations are sufficiently enforced to curtail or prohibit
the installation of conventional septic tank systems on unsuitable sites.
Strict enforcement of septic tank system siting requirements is often the
exception rather than the rule in many areas, however.
Two case studies suggest that the development of alternate systems could
have considerable impact, especially in those areas where development with
septic tank systems is prevented because of unsuitable soils (Amato and
Goehring, 197^; Water Resources Management Workshop, 1973). The alternate
systems are designed to provide safe, effective disposal of domestic
wastewater for certain areas that had been unsuited for septic tank systems.
Thus, such systems are available for use in any area which meets the reduced
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site and soil requirements imposed by the alternatives. With this environ-
mental limitation removed, only other land use controls, if any, will limit
the developability of that area.
Obviously, the potential impact on a given governmental unit increases
as the amount of previously unsuitable land becomes developable through the
use of alternate systems. Those governmental units relying on septic system
siting criteria should be aware of the development of new alternate methods
of wastewater disposal. Those areas which have restricted development based
on the unsuitability of lands for conventional systems may need to adopt more
sophisticated land use plan and control systems. The development of environ-
mental resource data should be a top priority assignment of planning commissions
so they will be in a better position to advise local officials concerning land
use decisions.
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APPENDIX E
GLOSSARY
A horizon: An horizon formed at or near the surface, but within the
mineral soil, having properties that reflect the influence of
accumulating organic matter or eluviation, alone or in combination.
AB horizon: A transitional horizon between the A and B horizons, having
features of the A horizon in its upper part and features of the B
horizon in its lower part, but without a clearly defined point to
indicate where these features separate.
absorption: The process by which one substance is taken into and included
within another substance, as the absorption of water by soil or
nutrients by plants.
activated sludge: Sludge floe produced in raw or settled wastewater by
the growth of zoogleal bacteria and other organisms in the presence
of dissolved oxygen and accumulated in sufficient concentration by
returning floe previously formed.
activated sludge process: A biological wastewater treatment process in
which a mixture of wastewater and activated sludge is agitated and
aerated. The activated sludge is subsequently separated from the
treated wastewater (mixed liquor) by sedimentation and wasted or
returned to the process as needed.
adsorption: The increased concentration of molecules or ions at a surface,
including exchangeable cations and anions on soil particles.
aeration: The bringing about of intimate contact between air and a liquid
by one of the following methods: spraying the liquid in the air; or
by agitation of the liquid to promote absorption of air.
aeration tank: A tank in which sludge, wastewater, or other liquid is
aerated.
aerobic: (1) Having molecular oxygen as a part of the environment.
(2) Growing or occurring only in the presence of molecular oxygen, as
aerobic organisms.
aerobic bacteria: Bacteria that require free elemental oxygen for their
growth.
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agar: A polysaccharide obtained from various species of seaweeds, used
to gel materials (especially microbiological media). It cannot be
broken down by most bacteria.
aggregate, soil: A group of soil particles cohering so as to behave
mechanically as a unit.
aggregation: The act or process of forming aggregates, or the state of
being aggregated.
air-dry: The state of dryness of a soil at equilibrium with the moisture
contained in the surrounding atmosphere.
Alfisol: An order of soils having a B2 horizon high in crystalline clay
and a moderately high level of exchangeable bases. These soils
usually occur in the climatic range associated with scrub to well-
developed deciduous forests.
Alluvial soil: (1) A soil developing from recently deposited alluvium
and exhibiting essentially no horizon development. (2) A great soil
group of the azonal order.
alluvium: Sediment deposited on land from streams.
alternative disposal: Any disposal method other than conventional subsurface
soil disposal.
alternative treatment: Any treatment method other than conventional
septic tank treatment.
ameba, p. amebae: A unicellular organism with an indefinite changeable form.
Also spelled amoeba.
amino acid: An organic compound containing both a carboxyl (COOH) and an
amino £—NH2) group, bonded to the same carbon atom. The 20 amino acids
which are the subunits of proteins vary in the structure of their side
chains.
ammonification: The biochemical process whereby ammoniacal nitrogen is
released from nitrogen-containing organic compounds.
anaerobic: (1) The absence of molecular oxygen. (2) Growing in the absence
of molecular oxygen (such as anaerobic bacteria).
anaerobic bacteria: Bacteria that grow only in the absence of free
elemental oxygen.
anaerobic contact process: An anaerobic waste treatment process in which
the microorganisms responsible for waste stabilization are removed
from the treated effluent stream by sedimentation or other means and
held in or returned to the process to enhance the rate of treatment.
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anaerobic digestion: the degradation of organic matter brought about
through the action of microorganisms in the absence of element oxygen.
anaerobic respiration: The metabolic process in which electrons are trans-
ferred from one compound to an inorganic acceptor molecule other than
oxygen. The most common acceptor molecules are carbonate, sulfate,
and nitrate.
anaerobic waste treatment: waste stabilization brought about through the
action of microorganisms in the absence of air or elemental oxygen.
Usually refers to waste treatment by methane fermentation.
antibiotic: A chemical substance produced by certain molds and bacteria
which inhibits the growth or kills other microorganisms. Some
antibiotics can now be synthesized chemically and others can be altered
by chemical methods so as to enhance their usefulness.
antibody: Protein produced by the body in response to the presence of an
antigen; can combine specifically with that antigen.
antigen: A substance that can incite the production of specific antibodies
and can combine with those antibodies.
attenuated: Modified so as to be incapable of causing disease under ordin-
ary circumstances.
autoclave: A device employing steam under pressure and used for sterilizing
materials stable to heat and moisture.
autotroph: An organism that can utilize CC^ as its main source of carbon.
autotrophic: Capable of utilizing carbon dioxide or carbonates as the sole
source of carbon and obtaining energy for the reduction of carbon and
biosynthetic processes from radiant energy (photoautotroph) or oxida-
tion of inorganic substances (chemoautotroph).
B horizon: An horizon immediately beneath the A horizon characterized by
a higher colloid (clay or humus) content, or by a darker or brighter
color than the soil immediately above or below, the color usually
being associated with the colloidal materials. The colloids may be
of illuvial origin, as clay or humus, they may have been formed in
place (clays, including sesquioxides), or they may have been derived
from a texturally layered parent material.
backwashing: the operation of cleaning a filter by reversing the flow of
liquid through it and washing out matter previously captured in it.
Filters would include true filters such as sand and diatomaceous-earth
types but not other treatment units such as trickling filters.
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bacteria: Primitive plants, generally free of pigment, which reproduce
by dividing in one, two or three planes. They occur as single cells,
groups, chains or filaments, and do not require light for their life
processes. They may be grown by special culturing out of their
native habitat.
aerobic: Bacteria which require free (elementary) oxygen for
their growth.
anaerobic: Bacteria which grow in the absence of free oxygen
and derive oxygen from breaking down complex substances.
bacteriophage: A virus that infects bacteria; often abbreviated "phage."
bar: A unit of pressure equal to one million dynes per square centimeter,
which is nearly equal to the standard atmosphere.
base-saturation percentage: The extent to which the adsorption complex of
a soil is saturated with exchangeable cations other than hydrogen
or aluminum. It is expressed as a percentage of the total cation-
exchange capacity.
bedrock: The solid rock underlying soils and the regolith at depths
ranging from zero (where exposed by erosion) to several hundred feet.
biochemical oxygen demand (BOD): The amount of oxygen required to maintain
aerobic conditions during decomposition.
biomass: The total mass of living organisms in a given volume (for
example, in seawater it is the total mass of living organisms per
liter). The total weight of all organisms in any particular environ-
ment .
black water: Liquid and solid human body waste and the carriage waters
generated through toilet usage.
bulk density, soil: The mass of dry soil per unit bulk volume. The bulk
volume is determined before drying to constant weight at 105° C.
C horizon: Horizon that normally lies beneath the B horizon but may lie
beneath the A horizon where the only significant change caused by soil
development is an increase in organic matter, which produces an A
horizon. In concept, the C horizon is unaltered or slightly altered
parent material.
calcareous soil: Soil containing sufficient calcium carbonate (often with
magnesium carbonate) to effervesce visibly when treated with cold
C.1N hydrochloric acid.
capillary attraction: A liquid's movement over or retention by a solid
surface due to the interaction of adhesive and cohesive forces.
-------
capillary fringe: A zone just above the water table that is maintained in
an essentially saturated state by capillary forces of lift.
carbohydrate: An organic compound consisting of many hydroxyl (—OH) groups
and containing either a ketone 0 or aldehyde 0 group.
il ) II
(—C—' (—C—H)
Examples include sugars, cellulose, glycogen, starch.
carrier: An individual who has pathogenic microbes in or on his or her body
without showing any signs of illness. The carrier state occurs during
incubation and convalescence of infectious disease and with asymptomatic
infection, colonization, or contamination. As usually used, the term
implies that the microbes have access to the exterior of the body and
thus potentially to other people.
catalase: An enzyme, found in human beings and many microorganisms, which
degrades hydrogen peroxide to oxygen and water.
cation exchange: The interchange between a cation in solution and another
cation on the surface of any surface-active material such as clay or
organic colloids.
cation-exchange capacity: The sum total of exchangeable cations that a soil
can adsorb. Sometimes called total-exchange capacity, base-exchange
capacity, or cation-adsorption capacity. Expressed in milliequivalents
per 100 grams or per gram of soil (or of other exchanges such as clay).
cellulose: A polysaccharide, composed of glucose subunits. The most abun-
dant organic compound in the world.
chemical oxygen demand (COD): A measure of the oxygen equivalent of that
portion of organic matter that is susceptible to oxidization by a strong
chemical oxidizing agent.
chemical precipitation: The addition to sewage of such chemicals as will,
by reaction with one another and the constituents of the sewage,
produce a floccul
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clay: (1) A soil separate consisting of particles < 0.002 mm in equivalent
diameter. (2) A textural class.
clay mineral: (1) Naturally occurring inorganic crystalline or amorphous
material found in soils and other earthy deposits, the particles being
predominantly < 0.002 mm in diameter. Largely of secondary origin.
cleavage: Tendency to break in the same direction, thus yielding fragments
of predictable shape.
clod: An artificially produced, compact, coherent mass of soil ranging in
size from 5 or 10 mm to as much as 8 or 10 inches.
columnar structure: A soil structural type with a vertical axis much
longer than the horizontal axes and a distinctly rounded upper surface.
See prismatic structure.
coagulation: In water and wastewater treatment, the destabilization and
initial aggregation of colloidal and finely divided suspended matter
by the addition of a floe-forming chemical or by biological processes.
coarse texture: The texture exhibited by sands, loamy sands, and sandy
loams except very fine sandy loam.
coliform-group bacteria: A group of bacteria predominantly inhabiting the
intestines of man or animal, but also occasionally found elsewhere.
It includes all aerobic and facultative anaerobic, Gram-negative,
non-spore-forming bacilli that ferment lactose with production of gas.
Also included are all bacteria that produce a dark, purplish-green colony
with metallic sheen by the membrane-filter technique used for coliform
identification. The two groups are not always identical, but they are
generally of equal sanitary significance.
colloids: The finely divided suspended matter which will not settle and
the apparently dissolved matter which may be transformed into suspended
matter by contact with solid surfaces or precipitated by chemical treat-
ment. Substances which are soluble as judged by ordinary physical tests,
but will not pass through a parchment membrane.
concentration: The relative content of a substance. Example: The strength
of a solution.
conductivity, hydraulic: As applied to soils—the ability of the soil to
transmit water in liquid form through pores.
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consistence: (1) The resistance of a material to deformation or rupture.
(2) The degree of cohesion or adhesion of the soil mass. Terms used
for describing consistence at various soil moisture contents are:
wet soil: Non sticky, slightly sticky, sticky, very sticky,
nonplastic, slightly plastic, plastic, and very plastic.
moist soil: Loose, very friable, friable, firm, very firm, and
extremely firm.
dry soil: Loose, soft, slightly hard, hard, very hard, and
extremely hard.
cementation: weakly cemented, strongly cemented, and indurated.
conventional disposal: The method of disposal which relies on subsurface
soil infiltration of the treated wastewater.
conventional treatment: Treatment which is effected by using a septic tank
as it is generally used to treat wastewater.
crumb: A soft, porous, more or less rounded ped from 1 to 5 mm in diameter.
crust: A surface layer on soils, ranging in thickness from a few millimeters
to perhaps as much as an inch, that is much more compact, hard, and
brittle, when dry, than the material immediately beneath it.
cytopathic effects (CPE): Observable changes in cells in vitro produced
by viral action; for example, lysis of cells or fusion of cells.
deflocculate: To separate the individual components of compound particles
by chemical and/or physical means. See disperse.
degradation: The breakdown of substances by biological action.
denitrification: The biochemical reduction of nitrate or nitrite to gaseous
molecular nitrogen or an oxide of nitrogen.
digestion: (1) The biological decomposition of organic matter in sludge,
resulting in partial gasification, liquefaction and mineralization.
(2) The process carried out in a digester.
disease: A process resulting in tissue damage or alteration of function,
producing symptoms, or noticeable by laboratory or physical examination.
disinfection: Killing pathogenic microbes on or in a material without necessarily
sterilizing it. Use of this term usually implies that a liquid or gaseous
chemical agent is employed for the microbial killing.
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disperse: (1) To break up compound particles, such as aggregates, into the
individual component particles. (2) To distribute or suspend fine
particles, such as clay, in or throughout a dispersion medium, such
as water.
dissolved oxygen: The oxygen dissolved in water, wastewater or other
liquid, usually expressed in milligrams per liter (mg/L), parts per
million (ppm) or percent of saturation. Abbreviated DO.
dissolved solids: Theoretically, the anhydrous residues of the dissolved
constituents in water. Actually, the term is defined by the method
used in determination. In water and wastewater treatment the standard
methods tests are used.
double layer: In colloid chemistry, a double layer of electrical charges,
one consisting of the charges provided by the solid phase (usually
negative) and the second by adsorbed ions of opposite charge.
E. coli: Abbreviation of Escherichia coli.
effluent: Sewage, water or other liquid, partially or completely treated
or in its natural state, as the case may be, flowing out of a
reservoir, basin, treatment plant or part thereof.
effluent weir: A weir at the outflow end of a sedimentation basin or other
hydraulic structure.
electron: A subatomic particle of negative electrical charge that orbits
the positively charged nucleus of an atom. For maximum stability an
atom must have a certain number of electrons in its outermost orbit.
eluviation: The removal of soil material in suspension from a layer or
layers of a soil. (Usually, the loss of material in solution is
described by the term leaching).
enzyme: An organic catalyst. A protein molecule which lowers the activation
energy of substrates allowing them to react at temperatures compatible
with life.
epidermis: The outermost skin layers.
Escherichia coli (E. coli): One of the species of bacteria in the coliform
group. Its presence is considered indicative of fresh fecal contamin-
ation.
eutrophic: A term applied to water that has a concentration of nutrients
optimal, or nearly so, for plant or animal growth.
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evapotranspiration: The combined loss of water from a given area, and
during a specified period of time, by evaporation from the soil
surface and by transpiration from plants.
extended aeration: A modification of the activated sludge process which
provides for aerobic sludge digestion within the aeration system.
The concept envisages the stabilization of organic matter under aerobic
conditions and disposal of the end products into the air as gases and
with the plant effluent as finely divided suspended matter and soluble
matter.
facultative anaerobic bacteria: Bacteria which can adapt themselves to
growth in the presence, as well as in the absence, of oxygen. May be
referred to as facultative bacteria.
fats: Simple lipids consisting of esters of glycerol with fatty acids.
fermentation: The metabolic process in which the final electron acceptor
is an organic compound.
field capacity: The water remaining in a field soil that has been thoroughly
wetted and drained until free drainage has practically ceased.
filter: A device or structure for removing solid or colloidal material,
usually of a type that cannot be removed by sedimentation, from water,
wastewater or other liquid. The liquid is passed through a filtering
medium, usually a granular material but sometimes finely woven cloth,
unglazed porcelain, or specially prepared paper. There are many types
of filters used in water or wastewater treatment.
filtering medium: Any material through which water, wastewater or other
liquid is passed for the purpose of purification, treatment or
conditioning.
filter clogging: The effect occurring when fine particles fill the voids
of a sand filter or biological bed or when growths form surface mats
that retard the normal passage of liquid through the filter.
filtrate: The liquid which has passed through a filter.
final effluent: The effluent from the final treatment unit of a wastewater
treatment plant.
final sedimentation: The separation of solids from wastewater in a final
settling tank.
final settling tank: A tank through which the effluent from a trickling
filter or an aeration or contact-aeration tank is passed to remove
the settleable solids. Also called final settling basin.
fine texture: The texture exhibited by soils having clay as a part of
their textural class name.
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first-stage biochemical oxygen demand: That part of oxygen demand associated
with biochemical oxidation of carbonaceous, as distinct from nitrogenous,
material. Usually, the greater part, if not all, of the carbonaceous
material is oxidized before the second stage, or substantial oxidation
of the nitrogenous material, takes place. Nearly always, at least a
portion of the carbonaceous material is oxidized before oxidation of
nitrogenous material even starts.
five-day BOD: That part of oxygen demand associated with biochemical
oxidation of carbonaceous, as distinct from nitrogeneous, material.
It is determined by allowing biochemical oxidation to proceed, under
conditions specified in Standard Methods, for 5 days.
floe: Small gelatinous masses formed in a liquid by the reaction of a
coagulant added thereto, through biochemical processes or by agglomera-
tion.
flood plain: Flat or nearly flat land on the floor of a river valley that
is covered by water during floods.
fragipan: A natural subsurface horizon with high bulk density relative to
the solum above, seemingly cemented when dry, but when moist showing
a moderate to weak brittleness. The layer is low in organic matter,
mottled, slowly or very slowly permeable to water, and usually shows
occasional or frequent bleached cracks forming polygons. It may be
found in profiles of either cultivated or virgin soils but not in
calcareous material.
gravitational potential: See potential, soil water.
grease trap: A device by means of which the grease content of sewage is
cooled and congealed so that it may be skimmed from the surface.
«
grey water: Liquid and solid wastes generated through usage of water-using
fixtures and appliances excluding the toilet and possibly the garbage
disposal.
groundwater: That portion of the total precipitation which at any particu-
lar time is either passing through or standing in the soil and the under-
lying strata and is free to move under the influence of gravity.
hardpan: A hardened soil layer, in the lower A or in the B horizon, caused
by cementation of soil particles with organic matter or with materials
such as silica, sesquioxides, or calcium carbonate. The hardness does
not change appreciably with changes in moisture content and pieces of
the hard layer do not slake in water. See caliche and claypan.
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head: The energy, either kinetic or potential, possessed by each unit weight
of a liquid, expressed as the vertical height through which a unit weight
would have to fall to release the average energy possessed. It is used
in various compound terms such as pressure head, velocity head and loss
of head.
heavy soil: (Obsolete in scientific use). A soil with a high content of
the fine separates, particularly clay, or one with a high drawbar pull
and hence difficult to cultivate. See fine texture.
heterotroph (organotroph); heterotrophic organism: An organism that obtains
energy from organic compounds. An organism that utilizes an organic
compound as its main source of carbon.
heterotrophic: Capable of deriving energy for life processes only from the
decomposition of organic compounds and incapable of using inorganic
compounds as sole sources of energy or for organic synthesis. Contrast
with autotrophic.
horizon: See soil horizon.
host: An organism on or in which smaller organisms or viruses live, feed,
or reproduce. When dealing with parasites having complex life cycles,
the host in which the adult lives, or the one in which sexual reproduc-
tion takes place, is called the definitive host. A host harboring larval
or asexually reproducing forms is called an intermediate host.
hydration: The physical binding of water molecules to ions, molecules,
particles, or other matter.
hydraulic conductivity: See conductivity, hydraulic.
hydraulic gradient: The slope of the hydraulic grade line; the rate of
change of pressure head; the ratio of the loss in the sum of the pressure
head and a position head to the flow distance. For open channels, it
is the slope of the water surface and is frequently considered parallel
to the invert. For closed conduits under pressure, it is the slope
of the line joining the elevations to which water would rise in pipes
freely vented and under atmospheric pressure. A positive slope is
usually one which drops in the direction of flow.
hydrolysis: The chemical reaction of a compound with water, whereupon the
anion from the compound combines with the hydrogen and the cation
from the compound combines with the hydroxyl from the water to form
an acid and a base.
E-ll
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illuviation: The process of deposition of colloidal soil material, removed
from one horizon to another in the soil; usually from an upper to a
lower horizon in the soil profile. See eluviation.
immunity: State of protection; for example, state of protection against
the mumps virus. Natural or innate immunity—protection that results
from the genetic make up of the host; for example, domestic animals
have an innate immunity to mumps virus. Acquired immunity—immunity
gained as a result of exposure to an agent; for example, immunity to
mumps virus is usually acquired (actively) by response to infection
with the virus, but it may also be acquired (passively) by the adminis-
tration of specific antibodies formed by another host.
immobilization: The conversion of an element from the inorganic to the
organic form in microbial or plant tissue, thus rendering the element
not readily available to other organisms or plants.
impervious: Resistant to penetration by fluids or by roots.
infection: Invasion of tissues (including skin or mucous membranes) by
microbes with or without the production of disease.
infiltration: The downward entry of water into the soil.
influent: Water, wastewater or other liquid flowing into a reservoir,
basin or treatment plant or any unit thereof.
inorganic matter: Chemical substances of mineral origin, or more correctly,
not of basically carbon structure.
intermittent filter: A natural or artificial bed of sand or other fine-
grained material to the surface of which wastewater is applied
intermittently in flooding doses and through which it passes; opportunity
is given for filtration and the maintenance of an aerobic condition.
ion: A charged atom, molecule or radical, the migration of which affects
the transport of electricity through an electrolyte or, to a certain
extent, through a gas. An atom or molecule that has lost or gained
one or more electrons. By such ionization it becomes electrically
charged. An example is the alpha particle.
ion exchange: A chemical process involving reversible interchange of Jons
between a liquid and a solid but no radical change in structure of the
solid.
ions: Atoms that are positively charged (cations) because of the loss of
one or more electrons, or that are negatively charged (anions) because
of a gain in electrons.
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isomorphous substitution: The replacement of an ion considered normal to
a mineral structure by another during the formation of a mineral.
landscape: All the natural features, such as fields, hills, forests, water,
etc., which distinguish one part of the earth's surface from another
part. Usually that portion of land or territory which the eye can
comprehend in a single view, including all its natural characteristics.
leach: To cause water or other liquid to percolate through something.
leaching: The removal of materials in solution from the soil.
lift, air: A device for raising liquid by injecting air in and near the
bottom of a riser pipe submerged in the liquid to be raised.
lipid: Any of a diverse group of organic substances which are relatively
insoluble in water but soluble in alcohol, ether, chloroform, or other
fat solvents.
liquefaction: Act or process of liquefying or of rendering or becoming
liquid; reduction to a liquid state.
liquor: Water, wastewater, or any combination; commonly used to designate
liquid phase when other phases are present.
loading: The time rate at which material is applied to a treatment device
involving length, area, or volume or other design factor.
loess: Material transported and deposited by wind and consisting of
predominantly silt-sized particles.
lysimeter: A device for measuring percolation and leaching losses from a
column of soil under controlled conditions.
manifold: A pipe fitting with numerous branches to convey fluids between
a large pipe and several smaller pipes or to permit choice of diverting
flow from one of several sources or to one of several discharge points.
manometer: An instrument for measuring pressure. It usually consists of
a U-shaped tube containing a liquid, the surface of which in one end
of the tube moves proportionally with changes in pressure on the liquid
in the other end. Also, a tube type of differential pressure gage.
mapping unit: A soil or combination of soils delineated on a map and,where
possible, named to show the taxonomic unit or units included. Principally,
mapping units on maps of soils depict soil types, phases, associations,
or complexes.
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matric potential: See potential, soil water.
mechanical aeration: The mixing, by mechanical means, of wastewater
and activated sludge in the aeration tank of the activated sludge
process to bring fresh surfaces of liquid into contact with the atmosphere.
medium texture: The texture exhibited by very fine sandy loams, loams,
silt loams, and silts.
membrane filter: A filter made of plastic with a known pore diameter.
It is used in bacteriological examination of water.
mesh: One of the openings or spaces in a screen. The value of the mesh is
usually given as the number of openings per linear inch. This gives
no recognition to the diameter of the wire and thus the mesh number
does not always have a definite relation to the size of the hole.
microorganism: Minute organism, either plant or animal, invisible or barely
visible to the naked eye.
milligrams per liter: A unit of the concentration of water or wastewater
constituent. It is 0.001 g of the constituent in 1,000 ml of water.
It has replaced the unit formerly used commonly, parts per million, to
which it is approximately equivalent, in reporting the results of water
and wastewater analysis.
mineral: Any of a class of substances occurring in nature, usually comprising
inorganic substances, such as quartz and feldspar, of definite chemical
composition and usually of definite crystal structure, but sometimes also
including rocks formed by these substances as well as certain natural
products of organic origin, such as asphalt and coal.
mineralization: The conversion of an element from an organic form to
an inorganic state as a result of microbial decomposition.
mineralogy, soil: In practical use, the kinds and proportions of minerals
present in a soil.
mineral soil: A soil consisting predominantly of, and having its properties
determined by, mineral matter. Usually contains < 20% organic matter,
but may contain an organic surface layer up to 30 cm thick.
mixed liquor: A mixture of activated sludge and organic matter undergoing
activated sludge treatment in the aeration tank.
Mollisol: Soil order consisting of soils having a thick A horizon with
more than one percent organic matter and a base-saturation percentage
above 50. Normally, they are formed under grass vegetation.
Distinguished from Vertisols in that they are not self-inverting.
-------
monosaccharide: A sugar, a simple carbohydrate, generally having the formula
C H 0 where n can vary from 3 to 8. The most common are 5 and 6.
n 2n n
montmorillonite: An aluminosilicate clay mineral with a 2:1 expanding
structure; that is, with two silicon tetrahedral layers enclosing an
aluminum octahedral layer. Considerable expansion may be caused by
water moving between silica layers of contiguous units.
morphology: See soil morphology.
mottling: Spots or blotches of different color or shades of color interspersed
with the dominant color.
negative pressure: A pressure less than the local atmospheric pressure at a
given point.
nitrification: The biochemical oxidation of ammonium to nitrate.
nonsettleable solids: Wastewater matter that will stay in suspension for an
extended period of time. Such period may be arbitrarily taken for test-
ing purposes as one hour.
organic matter: Chemical substances of animal or vegetable origin, or
more correctly, of basically carbon structure, comprising compounds
consisting of hydrocarbons and their derivatives.
organic nitrogen: Nitrogen combined in organic molecules such as proteins,
amino acids.
organic soil: A soil which contains a high percentage (> 15% or 20%) of
organic matter throughout the solum.
osmotic potential: See potential, soil water.
osmotic pressure: In concept, the force per unit area required to equal
the attractive (hydration) force for water exerted by ions dissolved
in a solution.
oven-dry soil: Soil which has been dried at 105° C until it reaches an
essentially constant weight.
oxidation: (l) The burning or other conversion of an element to an oxide-
(2) An increase in positive valence of an element or ion cauSPrf hv '
electron loss. LdUSeQ £>y
-------
oxidation process: Any method of wastewater treatment for the oxidation
of the putresclble organic matter. The usual methods are biological
filtration and the activated sludge process.
oxidation-reduction potential: The potential required to transfer electrons
from the oxidant to the reductant and used as a qualitative measure
of the state of oxidation in wastewater treatment systems.
oxygen demand: The quantity of oxygen utilized in the biochemical oxidation
of organic matter in a specified time, at a specified temperature and
under specified conditions. See BOD.
Ozone: Oxygen in molecular form with three atoms of oxygen forming each
molecule (0 ).
o
parasite: An organism that lives in or on another organism (the host) and
gains benefit at the expense of the host.
parent material: The unconsolidated mineral or organic matter from which
soils are developed.
particle density: The mass per unit volume of individual particles;
usually expressed as grams per cubic centimeter.
particle size: The effective diameter of a particle usually measured by
sedimentation or sieving.
particle-size distribution: The amounts of the various soil separates in
a soil sample, usually expressed as weight percentages.
parts per million (ppm): Measure of proportion by weight; equivalent to
a unit of solute per million unit weights of solution. Milligrams
per liter expressing the concentration of a specified component in a
dilute sewage.
pasteurization: The processes of heating food or other substances under-
controlled conditions of time and temperature (for example, 63°C for
30 min) to kill pathogens and reduce the numbers of other microbes.
P«i*o8.nlc: Causing disease. "Pathogenic" is also used to designate microbes
Which commonly cause infectious diseases, as opposed to those which
do so uncommonly or never.
edt
crumb, prism, block,
"ith a
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monosaccharide: A sugar, a simple carbohydrate, generally having the formula
C H» 0 where n can vary from 3 to 8. The most common are 5 and 6.
montmorillonite: An aluminosilicate clay mineral with a 2:1 expanding
structure; that is, with two silicon tetrahedral layers enclosing an
aluminum octahedral layer. Considerable expansion may be caused by
water moving between silica layers of contiguous units.
morphology: See soil morphology.
mottling: Spots or blotches of different color or shades of color interspersed
with the dominant color.
negative pressure: A pressure less than the local atmospheric pressure at a
given point.
nitrification: The biochemical oxidation of ammonium to nitrate.
nonsettleable solids: Wastewater matter that will stay in suspension for an
extended period of time. Such period may be arbitrarily taken for test-
ing purposes as one hour.
organic matter: Chemical substances of animal or vegetable origin, or
more correctly, of basically carbon structure, comprising compounds
consisting of hydrocarbons and their derivatives.
organic nitrogen: Nitrogen combined in organic molecules such as proteins,
amino acids.
organic soil: A soil which contains a high percentage (> 15% or 20%) of
organic matter throughout the solum.
osmotic potential: See potential, soil water.
osmotic pressure: In concept, the force per unit area required to equal
the attractive (hydration) force for water exerted by ions dissolved
in a solution.
oven-dry soil: Soil which has been dried at 105° C until it reaches an
essentially constant weight.
oxidation: (1) The burning or other conversion of an element to an oxide;
(2) An increase in positive valence of an element or ion caused by
electron loss.
E-15
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oxidation process: Any method of wastewater treatment for the oxidation
of the putrescjuble organic matter. The usual methods are biological
filtration and the activated sludge process.
oxidation-reduction potential: The potential required to transfer electrons
from the oxidant to the reductant and used as a qualitative measure
of the state of oxidation in wastewater treatment systems.
oxygen demand: The quantity of oxygen utilized in the biochemical oxidation
of organic matter in a specified time, at a specified temperature and
under specified conditions. See BOD.
Ozone: Oxygen in molecular form with three atoms of oxygen forming each
molecule (0,.).
o
parasite: An organism that lives in or on another organism (the host) and
gains benefit at the expense of the host.
parent material: The unconsolidated mineral or organic matter from which
soils are developed.
particle density: The mass per unit volume of individual particles;
usually expressed as grams per cubic centimeter.
particle size: The effective diameter of a particle usually measured by
sedimentation or sieving.
particle-size distribution: The amounts of the various soil separates in
a soil sample, usually expressed as weight percentages.
parts per million (ppm): Measure of proportion by weight; equivalent to
a unit of solute per million unit weights of solution. Milligrams
per liter expressing the concentration of a specified component in a
dilute sewage.
pasteurization: The processes of heating food or other substances under
controlled conditions of time and temperature (for example, 63°C for
30 min) to kill pathogens and reduce the numbers of other microbes.
pathogenic: Causing disease. "Pathogenic" is also used to designate microbes
which commonly cause infectious diseases, as opposed to those which
do so uncommonly or never.
ped: A unit of soil structure such as an aggregate, crumb, prism, block,
or granule, formed by natural processes (in contrast with a clod, which
is formed artificially).
E-16
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isomorphous substitution: The replacement of an ion considered normal to
a mineral structure by another during the formation of a mineral.
landscape: All the natural features, such as fields, hills, forests, water,
etc., which distinguish one part of the earth's surface from another
part. Usually that portion of land or territory which the eye can
comprehend in a single view, including all its natural characteristics.
leach: To cause water or other liquid to percolate through something.
leaching: The removal of materials in solution from the soil.
lift, air: A device for raising liquid by injecting air in and near the
bottom of a riser pipe submerged in the liquid to be raised.
lipid: Any of a diverse group of organic substances which are relatively
insoluble in water but soluble in alcohol, ether, chloroform, or other
fat solvents.
liquefaction: Act or process of liquefying or of rendering or becoming
liquid; reduction to a liquid state.
liquor: Water, wastewater, or any combination; commonly used to designate
liquid phase when other phases are present.
loading: The time rate at which material is applied to a treatment device
involving length, area, or volume or other design factor.
loess: Material transported and deposited by wind and consisting of
predominantly silt-sized particles.
lysimeter: A device for measuring percolation and leaching losses from a
column of soil under controlled conditions.
manifold: A pipe fitting with numerous branches to convey fluids between
a large pipe and several smaller pipes or to permit choice of diverting
flow from one of several sources or to one of several discharge points.
manometer: An instrument for measuring pressure. It usually consists of
a U-shaped tube containing a liquid, the surface of which in one end
of the tube moves proportionally with changes in pressure on the liquid
in the other end. Also, a tube type of differential pressure gage.
mapping unit: A soil or combination of soils delineated on a map and,where
possible, named to show the taxonomic unit or units included. Principally,
mapping units on maps of soils depict soil types, phases, associations,
or complexes.
E-13
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matric potential: See potential, soil water.
mechanical aeration: The mixing, by mechanical means, of wastewater
and activated sludge in the aeration tank of the activated sludge
process to bring fresh surfaces of liquid into contact with the atmosphere,
medium texture: The texture exhibited by very fine sandy loams, loams,
silt loams, and silts.
membrane filter: A filter made of plastic with a known pore diameter.
It is used in bacteriological examination of water.
mesh: One of the openings or spaces in a screen. The value of the mesh is
usually given as the number of openings per linear inch. This gives
no recognition to the diameter of the wire and thus the mesh number
does not always have a definite relation to the size of the hole.
microorganism: Minute organism, either plant or animal, invisible or barely
visible to the naked eye.
milligrams per liter: A unit of the concentration of water or wastewater
constituent. It is 0.001 g of the constituent in 1,000 ml of water.
It has replaced the unit formerly used commonly, parts per million, to
which it is approximately equivalent, in reporting the results of water
and wastewater analysis.
mineral: Any of a class of substances occurring in nature, usually comprising
inorganic substances, such as quartz and feldspar, of definite chemical
composition and usually of definite crystal structure, but sometimes also
including rocks formed by these substances as well as certain natural
products of organic origin, such as asphalt and coal.
mineralization: The conversion of an element from an organic form to
an inorganic state as a result of microbial decomposition.
mineralogy, soil: In practical use, the kinds and proportions of minerals
present in a soil.
mineral soil: A soil consisting predominantly of, and having its properties
determined by, mineral matter. Usually contains < 20% organic matter,
but may contain an organic surface layer up to 30 cm thick.
mixed liquor: A mixture of activated sludge and organic matter undergoing
activated sludge treatment in the aeration tank.
Mollisol: Soil order consisting of soils having a thick A horizon with
more than one percent organic matter and a base-saturation percentage
above 50. Normally, they are formed under grass vegetation.
Distinguished from Vertisols in that they are not self-inverting.
-------
pedon: The smallest volume Csoil body) which displays the normal range of
variation in properties of a soil. Where properties such as horizon
thickness vary little along a lateral dimension, the pedon may occupy
an area of a square yard or less. Where such a property varies substanti-
ally along a lateral dimension, a large pedon several square yards in
area may be required to show the full range in variation.
percolation: The flow or trickling of a liquid downward through a contact
or filtering medium. The liquid may or may not fill the pores of the
medium.
percolation, soil water: The downward movement of excess water through soil.
permeability, soil: The ease with which gases, liquids, or plant roots
penetrate or pass through soil.
pH: A measure of acidity and alkalinity, neutrality being at pH 7; pH under
7 indicates an acid solution and pH over 7 an alkaline solution; the
nearer the pH to 7 the weaker the acid or alkali. The reciprocal of
the logarithm of the hydrogen-ion concentration. The concentration is
the weight of hydrogen ions, in grams, per liter of solution. Neutral
water, for example, has a pH value of 7 and a hydrogen ion concentration
of 10-7-
pH, soil: The degree of acidity or alkalinity expressed by the negative
logarithm of the hydrogen-ion activity of a soil.
phosphate: A salt or ester of phosphoric acid.
photooxidation: A chemical reaction occurring as a result of absorption of
light energy in the presence of oxygen. It is sometimes responsible
for the death of microbes.
photosynthesis: The sum total of the metabolic processes by which light
energy is utilized to convert C02 and a reduced inorganic compound
to cytoplasm. 6H2X + 6CC>2 -»• C H^Og + 6X.
plaque (plack): A clear area in a lawn or a monolayer of cells. Viral
plaques are created by viral lysis of infected cells within the clear
area.
plastic soil: A soil capable of being molded or deformed continuously
and permanently, by relatively moderate pressure, into various shapes.
See consistence.
platy structure: Soil aggregates that are developed predominately along
the horizontal axes; laminated; flaky.
plow pan: A compacted layer beneath the plow layer produced by pressure
exerted on the soil during plowing.
E-17
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polypeptide; A chain of amino acids bonded together by peptide bonds.
The length varies from several amino acids to the length coded for by
one gene.
polysaccharide: Long chains, branched or unbranched, of monosaccharide
subunits.
point source: Any discernible confined and discrete conveyance from which
pollutants are or may be discharged.
potential, soil water: The potential energy of a unit quantity of water
produced by the interaction of the water with such forces as capillary
(matric), ion hydration (osmotic), and gravity, expressed relative to
an arbitrarily selected reference potential. In practical application,
potentials are used to predict the direction and rate of water flow
through soils, or between the soil and some other system, such as plants
or the outer atmosphere. Flow occurs spontaneously between points of
different water potential, the direction of flow being toward the site
of lower potential.
pore-size distribution: The volume of the various sizes of pores in a soil.
Expressed as percentages of the bulk volume (soil plus pore space).
pore space: Space in the soil not occupied by solid particles.
porosity: The total volume of pore space; usually expressed as a percentage
of the total soil volume.
prismatic structure: A soil structural type with a vertical axis much longer
than the horizontal axes and a flat or indistinct upper surface.
See columnar structure.
profile, soil: A vertical section of the soil through all its horizons
and extending into the parent material.
protein: A macromolecule containing one or more polypeptide chains.
publicly owned treatment works: Any devices and systems used in the storage
and treatment of minicipal sewage which are owned and operated by a
public entity.
puddled soil: A soil in which structure has been mechanically destroyed,
which allows the soil to run together when saturated with water.
A soil that has been puddled occurs in a massive nonstructural state.
purification: The removal of objectionable matter from water by natural
or artificial methods.
E-18
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raw wastewater: Wastewater before it receives any treatment.
recalculation: In the wastewater field, the refiltration of all or a
portion of the effluent in a trickling filter to maintain a uniform
high rate through the filter. Return of a portion of the effluent
to maintain minimum flow is sometimes called recycling.
reduce: The opposite of oxidize. The action of a substance to decrease
the positive valence of an ion.
reduction: The decrease in positive valence, or increase in negative
valence, caused by a gain in electrons by an ion or atom.
returned sludge: Settled activated sludge returned to mix with incoming
raw or primary settled wastewater.
roughing filter: A wastewater filter of relatively coarse material operated
at a high rate to afford preliminary treatment.
runoff: That portion of the precipitation of an area which is discharged
from the area through stream channels.
sand: (1) A soil separate consisting of particles between 0.05 and 2.0 mm
in diameter. (2) A soil textural class.
sand filter: A filter in which sand is used as a filtering medium.
saturate: (1) To fill all the voids between soil particles with a liquid.
(2) To form the most concentrated solution possible under a given
set of physical conditions in the presence of an excess of the solute.
(3) To fill to capacity, as the adsorption complex with a cation species;
e.g., H-saturated, etc.
saturation: A condition reached by a material, whether it be in solid,
gaseous or liquid state, that holds another material within itself
in a given state in an amount such that no more of such material can
be held within it in the same state. The material is then said to be
saturated or in a condition of saturation.
scum: The layer or film of extraneous or foreign matter that rises to the
surface of a liquid and is formed there.
secondary settling tank: A tank through which effluent from some prior
treatment process flows for the purpose of removing settleable solids.
See sedimentation tank.
secondary wastewater treatment: The treatment of wastewater by biological
methods after primary treatment by sedimentation.
E-19
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sedimentation: The process of subsidence and deposition of suspended matter
carried by water, wastewater, or other liquids, by gravity. It is
usually accomplished by reducing the velocity of the liquid below the
point at which it can transport the suspended material.
sedimentation tank: A basin or tank in which water or wastewater containing
settleable solids is retained to remove by gravity a part of the sus-
pended matter. Also called sedimentation basin, settling basin,
settling tank.
selective medium: A medium that has components which restrict growth to
organisms of a particular type.
separate: See soil separates.
settleable solids: That matter in wastewater which will not stay in suspen-
sion during a preselected settling period, such as one hour, but either
settles to the bottom or floats to the top.
sewerage: A comprehensive term which includes facilities for collecting,
pumping, treating and disposing of sewage; the sewer system and the
sewage treatment works.
silt: (1) A soil separate consisting of particles between 0.05 and 0.002 mm
in diameter. (2) A soil textural class.
single-grained state: A nonstructural state normally observed in soils con-
taining a preponderance of large particles such as sand. Because
of a lack of cohesion, the sand grains tend not to assemble in aggre-
gate form.
siphon: A closed conduit a portion of which lies above the hydraulic grade
line, resulting in a pressure less than atmospheric and requiring a
vacuum within the conduit to start flow. A siphon utilizes atmospheric
pressure to effect or increase the flow of water through the conduit.
slope: Deviation of a plane surface from the horizontal. Slope is conven-
tionally expressed in degrees, which are units of vertical distance for
each 100 units of horizontal distance.
slow sand filter: A filter for the purification of water in which water.
without previous treatment is passed downward through a filtering
medium consisting of a layer of sand or other suitable material,
usually finer than for a rapid sand filter and for 24 to 40 inches
in depth.
E-20
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sludge blanket: Accumulation of sludge hydrodynamically suspended within
an enclosed body of water or wastewater.
soil: (1) The unconsolidated mineral material on the immediate surface of
the earth that serves as a natural medium for the growth of land plants.
(2) The unconsolidated mineral matter on the surface of the earth that
has been subjected to and influenced by genetic and environmental
factors of parent material, climate (including moisture and temperature),
macro- and microorganisms, and topography, all acting over a period of
time and producing a product-soil-that differs from the material from
which it is derived in many physical, chemical, biological, and
morphological properties.
soil classification: The systematic arrangement of soils into groups or
categories on the basis of their characteristics. Broad groupings are
made on the basis of general characteristics and subdivisions on the
basis of more detailed differences in specific properties. The three
higher categories, which are broadly defined, are orders, suborders,
and great groups. The lowest category is the soil series, with each
series consisting of many individual occurrences or bodies of soil that
are very similar in most respects.
soil genesis: The formation of soils; the creation of new characteristics
by soil-development processes.
soil horizon: A layer of soil or soil material approximately parallel to
the land surface and differing from adjacent genetically related layers
in physical, chemical, and biological properties or characteristics
such as color, structure, texture, consistence, pH, etc.
soil morphology: The physical constitution, particularly the structural
properties, of a soil profile as exhibited by the kinds, thickness,
and arrangement of the horizons in the profile, and by the texture,
structure, consistence, and porosity of each horizon.
soil map: A map showing the distribution of soil types or other soil
mapping units in relation to the prominent physical and cultural
features of the earth's surface.
soil moisture: Water contained in the soil.
soil separates: Groups of mineral particles separated on the basis of a
range in size. The principal separates are sand, silt, and clay.
soil series: The basic unit of soil classification and consisting of soils
which are essentially alike in all major profile characteristics
although the texture of the A horizon may vary somewhat. See soil type.
soil solution: The aqueous liquid phase of the soil and its solutes con-
sisting of ions dissociated from the surfaces of the soil particles and
of other soluble materials.
E-21
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soil structure: The combination or arrangement of individual soil particles
into definable aggregates, or peds, which are characterized and classified
on the basis of size, shape, and degree of distinctness.
soil suction: A measure of the force of water retention in unsaturated soil.
Soil suction is equal to a force per unit area that must be exceeded by
an externally applied suction to initiate water flow from the soil.
Soil suction is expressed in standard pressure terms.
soil survey: The systematic examination, description, classification,
and mapping of soils in an area.
soil texture: The relative proportions of the various soil separates in
a soil.
soil type: In mapping soils, a subdivision of a soil series based on differ-
ences in the texture of the A horizon.
soil water: A general term emphasizing the physical rather than the chemical
properties and behavior of the soil solution.
solids: Material in the solid state.
total: The solids in water, sewage or other liquids; includes
suspended and dissolved solids; all material remaining as residue
after water has been evaporated.
dissolved: Solids which are present in solution.
suspended: Solids which are physically suspended in water, sewage
or other liquids. The quantity of material deposited when a
quantity of water, sewage, otr other liquid is filtered through an
asbestos mat in a Gootch crucible.
volatile: The quantity of solids in water, sewage or other liquid
lost on ignition of total solids.
solids-retention time: The average residence time of suspended soils in
a biological waste treatment system, equal to the total weight of
suspended solids in the system divided by the total weight of suspended
solids leaving the system per unit of time (usually per day).
solum (plural: sola): The upper and most weathered part of the soil profile;
the A and B horizons.
solution feeder: A feeder for dispensing a chemical or other material in
the liquid or dissolved state to water or wastewater at a rate con-
trolled manually or automatically by the quantity of flow. The con-
stant rate is usually volumetric.
E-22
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Standards Methods: Methods or analysis of water, sewage, sludge and
industrial wastes approved by a Joint Committee of the American
Public Health Association, American Water Works Association and the
Federation of Sewage and Industrial Wastes Association.
sterilization: Rendering an object or substance free of all viable microbes.
Practically speaking, to sterilize an object is to make it extremely
improbable that a single living organism or virus remains.
structure, soil: See soil structure.
subsoil: In general concept, that part of the soil below the depth of
plowing.
substrate: The substance on which an enzyme acts to form the product.
suction: See soil suction.
surface discharge: The disposal of wastewater (before or after treatment)
to the land surface or into a receiving water body.
surface soil: The uppermost part of the soil, ordinarily moved in tillage,
or its equivalent in uncultivated soils and ranging in depth from
3-4- inches to 8-10 inches. Frequently designated as the plow layer
or the Ap horizon.
tensiometer: A device for measuring the negative hydraulic pressure
(or tension) of water in soil in situ; a porous, permeable ceramic
cup connected through a tube to a manometer or vacuum gauge.
tension, soil water: The expression, in positive terms, of the negative
hydraulic pressure of soil water.
texture: See soil texture.
textural class, soil: Soils grouped on the basis of a specified range in
texture. In the United States 12 textural classes are recognized.
tight soil: A compact, relatively impervious and tenacious soil (or
subsoil) which may or may not be plastic.
till: (1) Unstratified glacial drift deposited directly by the ice and
consisting of clay, sand, gravel, and boulders intermingled in any
proportion. (2) To plow and prepare for seeding; to seed or cultivate
the soil.
E-23
-------
titer: The concentration of a substance in solution; for example, the amount
of a specific antibody in serum, usually measured as the highest dilution
of serum which will give a positive test for that antibody. The titer
is often expressed as the reciprocal of dilution; thus a serum which
gives a positive test when diluted 1:256, but not at 1:512, is said to
have a titer of 256.
trickling filter: A filter consisting of an artificial bed or coarse
material, such as broken stone, clinkers, slate, slats, brush or
plastic materials, over which wastewater is distributed or applied in
drops, fi1ms or spray from troughs, drippers, moving distributors or
fixed nozzles and through which it trickles to the underdrains, giving
opportunity for the formation of zoogleal slimes which clarify and
oxidize the wastewater.
topography: The physical features of a landscape, especially its relief
and slope.
topsoil: (1) The layer of soil moved in cultivation. See surface soil.
(2) The A horizon. (3) The Al horizon. (4) Presumably fertile soil
material used to topdress roadbanks, gardens, and lawns.
total solids: The sum of dissolved and undissolved constituents in
water and wastewater, usually stated in milligrams per liter.
ultraviolet (UV) light: Electromagnetic radiation with a wavelength
between 175 and 350 nm (shorter than visible light). Certain wavelengths,
absorbed by nucleic acids result in mutation and death.
unsaturated flow: The movement of water in a soil which is not filled to
capacity with water.
vapor pressure: (1) the pressure exerted by a vapor in a confined space.
It is a function of the temperature. (2) The partial pressure of water
vapor in the atmosphere. Also see humidity. (3) Partial pressure of
any liquid.
vector: An animal, often an insect, which carries an infectious agent from
one host to another.
vehicle: An inanimate carrier of an infectious agent from one host to
another.
virus: An obligate intracellular parasite consisting of a bit of nucleic
acid, surrounded by a protein coat and sometimes enclosed by an
envelope. Different viruses are capable of infecting animals,
plants, and bacteria.
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-173
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
MANAGEMENT OF SMALL WASTE FLOWS
5. REPORT DATE
September 1978 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Small Scale Waste Management Project
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of Wisconsin - Madison
University of Wisconsin - Extension
Madison, Wisconsin 53706
10. PROGRAM ELEMENT NO.
C611B
11. CONTRACT/GRANT NO.
R802874
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Municipal Enginronmental Research Laboratory—Gin, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Final (7/71 - 6/77)
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: James Kreissl (513) 684-7614
16. ABSTRACT
This report is a compilation of laboratory and field investigations
conducted at the University of Wisconsin since 1971. As its primary objec-
tive, the research program was to conceive, evaluate and develop satisfactory
methods for the on-site treatment and disposal of wastewaters, regardless
of the site constraints. The studies were subdivided into several categories
including characterization of household and commercial wastewaters, assess-
ment of wastewater treatment alternatives, evaluation of soils for treatment
and disposal of wastewater, estimation of infiltrative capacities of soils,
design and operation of alternative systems dependent upon soil design and
operation of alternative systems not dependent upon soil, management of on-site
disposal systems and institutional and regulatory control of on-site systems.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Sewage
Water analysis
Sewage disposal
Sewage treatment
Soil science
Microbiology
Law (Juris prudence)
Sanitation
b.IDENTIFIERS/OPEN ENDED TERMS
On-site sewage disposal
wastewater characterizatic
alternative treatment sysl
subsurface soil systems
surface discharge
community-wide management
COS AT I Field/Group
>n
ems
13B, 061,
48E, 06M
89B
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
810
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
E-26
U. 5. GOVERNMENT PRINTING OFFICE: 1978-757-140/1423 Region No. 5-11
-------
viscosity: The cohesive force existing between particles of a fluid which
causes the fluid to offer resistance to a relative sliding motion
between particles.
water content: As applied to soils work: the amount of water held in
a soil expressed on a weight or volume basis. Conventionally, water
contents are expressed relative to the oven-dry weight or volume of
soil.
water table: That level in saturated soil where the hydraulic pressure
is zero.
water table, perched: The water table of a discontinuous saturated zone
in a soil.
wastewater: The spent water of a community. From the standpoint of source,
it may be a combination of the liquid and water-carried wastes from
residences, commercial buildings, industrial plants and institutions,
together with any groundwater, surface water and storm water that may
be present. In recent years, the word wastewater has taken precidence
over the word sewage.
E-25
-------
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