Septage Management
Prepared by
Lombardo & Associates, Inc.
90 Canal St.
Boston, MA 02114
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Septage Management
I. Introduction
A. Quantity of Septage
B. Quality of Septage
II. Septage Management Alternatives
A. Biological Treatment
B. Land Application
C. Composting
0. Lime Stabilization
E. Chemical Oxidation
F. Electron Treatment/Land Application
G. Co-Disposal with Solid Waste
H. Conventional Waste Treatment
I. Co-Treatment at Wastewater Treatment Plant
III. Cost Effective Solutions for Septage Management
A. Pumping/Hauling
B. Lagoon Treatment
C. Land Application
0. Composting
E. Urae Stabilization
F. Chemical Oxidation
G. Conventional Treatment
IV. Septage Management Plan
A. Septage Treatment Facility
B. Septage Pumping and Hauling
V. References
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I. INTRODUCTION
The 1977 Clean Water Act and Its subsequent regulations gave renewed
recognition to onsite wastewater disposal as a viable technology for
use in many small communities, rural towns and suburban developments.
Properly designed and constructed, septic systems can provide an effec-
tive and Inexpensive alternative to the wastewater disposal problems
of such areas. However, the use of septic systems, both conventional
septic tank and soil absorption systems and alternative designs, requires
periodic maintenance. This includes the pumping of the accumulated sludge
and scum, called septage.
Pumping of septage creates the necessity to dispose of this highly offen-
sive sludge in a safe, cost-effective and convenient manner. Many technologi-
cal alternatives exist for the proper management of septage. This report
provides an introduction and comparative discussion of major septage
treatment and disposal alternatives. Following this general description
is * cost effective comparison of the alternatives available to the town
of Woodrock. Finally a more detailed description of one cost effective
solution, including capital and operation and maintenance cost estimates,
is presented.
A. Quantity of Septage
The quantity of septage generated is dependent upon the number of
septic systems In operation, the average size of septic tanks and the
frequency of pumping. Recommended pumping frequencies range from 2 to
5 years.
The standard approach to determining liquid septage volumes is to
use an equation which encompasses these factors:
(population] (*. unsewered population) «
Septage (gal/yr) - household size X
The town of Moodrock Is projected to have the following
characteristics.
Population (year 2000) 17680
% Unsewered 100S
Household Size (average) 3.8 persons/household
Tank Volume (average) 1200 gallons
Pumping Frequency Every 3 years
Under these conditions Woodrock will require 1550 household
systems to be pumped annually resulting in a yearly domestic septage
volume of 1.86 million gallons. Additional septage will be generated
by commercial and industrial activities which also rely on the use of
septic tanks for the disposal of their wastewater. In Woodrock these
amounts are 0.125 and 0.04 million gallons per year respectively. This
yields a total septage generation rate of 2.025 million gallons per
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year which must be disposed of by the town of Woodcock.
Left solely to the responsibility of Individual home owners contract-
ing with private pumper/haulers, the flow of septage exhibits a wide var-
iability. Lower pumpout frequency Is often exhibited In winter months,
especially 1n cold climate areas. A proper septage management program
can alleviate some of this variability, by initiating a year round pumping
schedule.
B. Quality of Septage
Septage 1s a highly variable anaerobic slurry, which may exhibit
various offensive characteristics such as the presence of pathogenic
organisms, odor, poor settleab1T1ty and dewaterablUty and a high foaming
capacity when aerated. The U.S. EPA-published characteristics of domestic
septage are shown In Table 1.
Bacteriologically, septage contains a wide variety of aerobes and
anaerobes. The presence of aerobic organisms is linked to either the
dissolved oxygen of the Incoming sewage being sufficient to support
limited aerobic growth or to their presence tn the Influent sewage which
provides a relatively constant number of such organisms. Pseudomonas
and similar aerobic bacteria are beneficial 1n that they are capable
of Hp1d and detergent degradation. Numerous obligate anaerobic micro-
organisms are also present, however there 1s difficulty In Isolating many
of them due to their high oxygen sensitivity and their exposure to oxygen
during pumping. Figure 1 shows a comparative enumeration of microorganisms
present 1n septage.
II. SEPTAGE MANAGEMENT ALTERNATIVES
Numerous combinations of technologies exist for the treatment and
disposal of septage. Many of these have derived from the treatment of
other sludges, primary municipal sludge from secondary treatment plants.
Many new technologies are still in relative Infancy. A complete compre-
hensive coverage of all of these Is beyond the scope of this report. The
purposes of this section are to identify and describe the major septage
treatment and disposal alternatives available for a town similar to
Uoodrock and to assess the key environmental and operational advantages
and disadvantages associated with each method. These alternatives are
listed In Table 2. The reader is referred to references at the back of
the text for further information.
A. Biological Treatment
Biological treatment systems, either aerobic, anaerobic or a com-
bination of the two, affect treatment by establishing conditions which
enhance the waste-decomposition capability of the mlcroblal populations
present in septage.
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TABLE 1 SEPTAGE CHARACTERISTICS (1)*
(AITvalues in mg/Texcept where noted)
Parameter
EPA Mean
Concentration
Minimum
Reported
Maximum
Reported
Variability**
TS
TVS
TSS
VSS
BOOs
COD
TOC
TKN
NH3-N
N02-N
N03-N
Total P
P04
Alkalinity
Grease
pH (units)
LAS
Al
AS
Cd
Cr
Cu
Fe
Hg
Mn
Hi
Pb
Se
Zn
38,800
25,300
13,300
8,700
5,000
42,900
9,900
680
160
— —
— -
250
— —
— —
9,100
6-9
160
48
0.16
0.71
1.1
6.4
200.0
0.28
5.0
0.9
8.4
0.1
49.0
1,132( 9)
4,500(96)
310(12)
3,660(96)
440 ( 9)
1,500(12)
1,316(14)
66(14)
6(14)
0.1(15)
0.1(15)
20(96)
10(96)
522(12)
604(14)
1.5(9)
110(14)
2.00d4)
0. 03C")
0.05d4)
0.3(14)
0.3(15)
3.0d4)
0.0002(14)
0.5(14)
0.2d4)
1.5d4)
0.02d4)
33.0d5)
130,475(11)
71,402(11)
93,378(11)
51,500(16)
78,600(12)
703,000(12)
96,000(15)
1,900(96)
380(15)
1.3(15)
11(17)
760(14)
170(96)
4,190(12)
23,368(14)
12.6(9)
200(14)
200.0(14)
0.05d4)
10.8d4)
3.0d5)
34.0d4)
750.0d4)
4.0(14)
32.0d4)
28.0(15)
31.0(14)
0.3d4)
153.0d4)
115
16
301
14
179
469
73
29
63
13
110
38
17
8
39
8
2
100
17
216
10
113
250
20,000
64
140
21
15
5
* Numbers in parentheses ( ) refer to references at back of report
**Values represent ratio of maximum to minimum
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OL
UJ
A-Septate
B- Septic Tank Sewogt*
o 8
1 6
2 5
a
S 4
2 3
«» -
9'
0*
*"l
5
jlj 95V. Confidence Limits
*
i«
^
(•^
,
^
••
n
••
mi
r
r-5
^
s
-
f"! "
•M L— » J
>w
IH
<*i
A B A B A3 A B A B AS
Aerobic Anaerobic Synthetic E.coli Lactose Non-Lactote
Fermented Ferment ert
*Taketi from inlet end of functioning septic tanks
Figure 1 Comparative enumeration of specific types of
microorganisms with 95% confidence limits. (1)
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Table 2
SEPTAGE MANAGEMENT ALTERNATIVES
A. Biological treatment via:
- aerobic lagoon
- anaerobic lagoon
B. Land applications via:
- surface application
- subsurface applicati-n
C. Composting
0. Lime stabilization
E. Chemical oxidation {— Purifax method)
F. Electron treatment/land application
G. Co-disposal with solid wastes
H. Conventional waste treatment
I. Co-treatment at a wastewater treatment plant
For alternatives A, 0, E and H it is assumed that dewatering follows treatment,
with liquid effluent discharged to the ground and dewatered sludge disposed of
via landfill.
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—Aerobic Lagoons
Aerobic lagoons are typically shallow (6 to 18 Inches deep) or
deep (1 to 4 feet deep) impoundments with large surface areas
formed by constructing earthen dams and dikes. Several basins
are often used 1n conjunction, to facilitate a rotation schedule
which allows for the drying and subsequent removal of sludge
material prior to the next loading. A1r can be provided to the
pond either through surface aerators or dlffuser pipes laid
at the bottom of the lagoon. With proper design and operation
up to 95 percent BOO reduction can be achieved. (See Figure 2).
The design of aerobic lagoons for the treatment of septage must
give consideration to sol Ids retention time (SRT), volatile
suspended sol Ids (VSS) loading, oxygen requirements and desired
waste reduction. The SRT reported for effective treatment of
septage has ranged from 5 to more than 30 days depending upon
the desired end result. Five days Is generally sufficient to
provide acclimatization to eliminate.odors, twenty days of aeration
has produced effluents of less than 20 mg/1 soluble BOD*, while
more than 30 days has been required to affect a VSS redaction of
more than 40%. (2,3)
A limited amount of laboratory data Is available on the solids
loadings for the aerobic digestion of septage. A range of 0.03
to 1.3 Ib VSS/cu.ft./day has been reported. (3) Air requirements
should be sufficient to keep sol Ids In suspension and maintain a
dissolved oxygen level of 1 to 2 mg/1. Flow rates between 0.25
and 0.50 scfm/ft^ have been tested at the EPA/Lebanon Pilot Plant
with the latter yielding significantly better VSS reductions (70%)
than the former (85X) and than those reported above. (2)
Advantages of aerobic lagoons Include simple operation, low costs,
and the ability to handle large loads on a fluctuating basis.
Disadvantages Include potential leachate contamination of ground-
water, need for frequent sludge removal and disposal, large land
requirements, foul odors, unsightly foaming and Insect breeding.
Care must be taken to locate lagoons away from geologically-unstable
areas.
—Anaerobic Lagoons
Anaerobic lagoons are Impoundments generally 8 to 12 feet deep,
but occasionally up to 20 feet deep, 1n which settleable and
Inert sol Ids are stabilized by active fermentation. The liquid
fraction 1s further treated and dissipated via accompanying
Infiltration/percolation beds.
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Figure 2
Schematic of Aerobic Lagoon Liquid Septage Treatment
Air
1
Raw
Septage
Aerobic
Lagoons
Solids
Disposal
Figure 3
Schematic of Anaerobic Lagoon Liquid Septage Treatment
Raw
Anaerobic
Lagoons
\
J
\
Infiltration/
Percolation
Beds
Solids
Disposal
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Some states Ce.g. Massachusetts) require anaerobic lagoons to be a
minimum of 6-foot deep, others (e.g. Connecticut) will allow a minimum
operating depth of 3 to 5 feet. The New England Interstate Water
Pollution Control Commission recommends that one of the following two
flow patterns be used:
a) A minimum of two lagoons in series, with control of discharge
to the second lagoon by release during quiescent periods to
minimize the carryover of suspended solids Into the second
lagoon. The bottom of each lagoon should be lined with at
least one foot of sand with good filtration characteristics.
Careful consideration should be given to adequate sizing of
lagoons in order to prevent hydraulic overload of the system
as the Infiltration rate decreases during use of the lagoons.
b) A minimum of two lagoons Installed in parallel, followed
by at least six percolation beds with a total effective area
of 1 sq. ft./gaT./day of design flow. The soil In the percolation
bed shall provide a percolation rate of not over 2 minutes per
Inch. The base of the percolation facilities shall be at
least 6 ft. above maximum groundwater.
In addition a minimum of 20 days detention at average flow Is
recommended. (4)
Advantages of this system include the ability to handle shock
loads, low operation and maintenance costs, and relatively short detention
time (15-30 days). Disadvantages Include poor nitrate removal with
consequent potential groundwater contamination, and the need for ultimate
sludge disposal. (See Figure 3).
B. Land Application
The use of the land as a final receiver of wastewater, sludges and
septage has been the subject of intense research and development for the
past 10 years. These wastes are useful as either a low grade fertilizer
when applied to agricultural land (used for the production of crops), or
as a soil conditioner when they are applied to unproductive areas such
as strip-mined lands. The application of these wastes can be in either
a liquid or solid form (dewatered sludge or septage), and can be applied
to the top of the soil or Incorporated Into It 1n a variety of ways.
—Surface Application
There are basically two methods of applying liquid wastes to the
surface of the land: Irrigation or overland flow. The Irrigation
method 1s most applicable to flat lands where little or no
runoff occurs. In both methods, liquid septage can be applied
onto the land with spray guns, liquid-spreading trucks or the more
common farm liquid manure spreader. A number of potential problems
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are associated with surface disposal techniques Including possible
human or animal contact with pathogenic organisms, offensive odors,
and nitrogen and heavy metals contamination of groundwater and
of surface waters from runoff. EPA requires septage stabilization
prior to surface application; other regulations relative to land
application and other septage disposal practices are summarized
1n reference (5).
—Subsurface Appl Icatlon
Subsurface application of septage Is another land application method.
Three subsurface application techniques are used: 1) The plow-
furrow-cover method; In which septage 1s applied In a narrow furrow
and covered with earth by a following plow, 2) The sub-sod
Injection method, In which septage 1s Injected 1n either a wide
band or several narrow bands Into cavities six to eight Inches
deep, and 3) The terreator method, In which a machine with an
oscillating chisel potnt plows open a hole and dispenses the
septage. Subsurface application provides better odor and pest
control and reduces the likelihood of human or animal contact
with pathogenic organisms.
Many states will give consideration to the application of septage
by subsurface techniques subject to nitrogen and heavy metals
limitations. Nitrogen 1s'of concern because of the potential of
leachate from the septage to contaminate drinking water supplies.
It 1s generally recognized that concentrations of nitrate-nitrogen
1n excess of 10 mg/1 may cause health problems, specifically
Infant methemoglob1nem1a. The state of Maine has reported that
a loading criteria of 62,500 gal/acre/yr on moderately drained
soils should not result In pollution caused by excess nitrogen.
These loadings result In nitrogen application rates of 500 lb/acre/
yr and 300 Ib/acre/yr respectively. (6)
The retention of heavy metals In the soil Is a complex and poorly
understood process. However, workable estimates of application
limits based on the cation exchange capacity of the soil have been
proposed by the Wisconsin Department of Natural Resources. (7)
This has led to a proposed limit for Cadmium loading of 2 lb/acre/
year with a total lifetime loading of 20 Ib/year. It Is Interesting
to note that for a sample of septage taken from an EPA pilot
facility, using these criteria, nitrogen Is by far the limiting
factor. Yearly loadings based on Cadmium was 33.1 times the
application rate based on the limiting nitrogen loading. (1)
Sludge or septage can also be dewatered and applied to the land 1n
a solid form. As with liquid systems the dewatered septage can be
applied on top.of the land or mixed Into the top soil layer.
Specifically designed trucks can spread the dewatered sludge or
solid manure spreaders can be used. The sludge can be plowed
Into the land or left on top.
10
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With those methods that require the use of heavy equipment for
application, crops may be damaged during the growing season,
particularly such crops as corn, wheat, barley, etc. Damage
from heavy equipment is less with more frequently harvested
crops such as hay or grasses.
There are several important considerations in site selection for
land application of septage. The soils, geology and hydrology
at each of the prospective sites must be carefully examined to
determine soil type, permeability, drainage, slope of the land,
depth to groundwater, seasonal groundwater fluctuations, direction
and rate of groundwater flow, location of surface water bodies,
depth to bedrock, and proximity of the site to homes, commercial
establishments, etc. A summary of siting considerations for land
application of septage is presented in Table 3.
Climate also plays a significant role in determining when septage
can not be applied, and sufficient septage holding facilities must
be provided to account for these periods. Sizing of storage
facilities should be based on historical weather records. Defini-
tion of acceptable weather conditions for application must take
Into consideration septage characteristics and soil conditions as
well as the climatic variables of temperature and precipitation.
As with siting, general guidelines are difficult to specify;
consultation with hydrologlsts, geologists, soil scientists and
other specialists 1s highly recommended.
Land application techniques have the advantages of utilizing
septage for Its fertilizer value rather than simple disposing of
it. Disadvantages Include potential groundwater contamination by
all forms of nitrogen, high costs for injection equipment and
equipment storage facilities, climatic limitations, a large land
requirement, and the necessity of a one-to-two week waiting
period between applications. An obvious problem with land appli-
cation techniques is the unpredictability of favorable weather
conditions and the necessity of providing septage storage facilities
for unfavorable weather periods.
C. Composting
Composting 1s the stabilization of organic material through the process
of aerobic, thermophllic decomposition. Oewatered septage can be composed
and a humus like product will result. In addition the high temperatures
produced during composting results In substantial pachogen distinction.
In the septage treatment alternative described below composting will be
the key component for stabilizing septage solids. (See Figure 4)
The composting system is composed of three separate processes:
1) Preliminary treatment Including screening and chemical conditioning
of the septage to facilitate liquid/solid separation, 2) A solids
handling phase, including the composting step, and 3) The liquid handling
and disposal phase.
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Table 3: Land Application of Septage - Siting Considerations
Siting Factor
1. Soil Conditions
2. Slope
3. Depth to Groundwater
4. Direction/rate of Groundwater
How
Location of Surface Water
Proximity to homes, commercial
house establishments, etc.
Desired Characteristics*
• Restrictive permeability
minimal ponding, freedom
from boulders
• High Moderate to high cation
exchange capacity if metal con-
tamination is a potential problem
(8)
• Between 0.3 and 1.0 percent for
ridge-furrow cover depending
on solids concentration and soil
conditions. (8)
• Maximum of 8% for other methods
to prevent surface erosion by
storm water (1)
• At least 4 feet of soil between
point of application and seasonal
high groundwater**
• Groundwater patterns must be well
defined and isolated with no inter-
mediate domestic source wells bet-
ween the application point and
discharge to river or ocean (8).
• An adequate subsurface buffer
strip between site and receiving
waters to provide pollutant atten-
uation, uptake or dilution (8).
• Most states have recommended set
back criteria. Massachusetts,
for example, recommends 1000
feet from places of human habitation.
*0ue to the complex nature of leachete migration from septage disposal
sites, design criteria are not recommended. Each potential site
must be subjected to a detailed hydro-geological evaluation by professional
soil scientist and geologists in order to assess its suitability.
**8ased on recommendati6ns of Massachusetts, Connecticut and the New England
Interstate Water Pollution Control Commission.
12
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F1gure. 4
Schematic of a Composting System for Septage Treatment
Pretreatment/
Chemical
Conditioning
-> LI quid Treatment
Composting
Compost
Product
Land Application
Conventional Treatment
Aquaculture
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Ravi septage should be Initially passed through a rough bar screen
Into an aerated holding tank or basin. This unit changes the septage
from an anaerobic to an aerobic state. It also provides equalization,
allowing septage to enter the rest of the system at a controlled rate.
From the equalization unit the septage should be further screened
to facilitate effective chemical conditioning. A 40 mesh vibrating screen
has proved an effective means of accomplishing this. The screened solids
are Incorporated Into the composting operation while the liquid fraction
1s processed further.
After screening, the liquid portion of the septage 1s chemically
conditioned to affect further solid-liquid separation. A number of
different chemicals have been tested singly and 1n combinations. Including:
Ferric chloride, Hme and ferric chloride, aluminum sulfate (alum),
sulfurlc add and lime, and polymers.
Regardless of the chemical(s) used, the basic process 1s the same.
First the chemical Is added and mixed with the septage providing the
necessary dispersal of the chemical through the septage. Following this
the mixture Is allowed to settle providing the desired solids-liquid
separation.
In some of the two chemical schemes, such as the add/lime process,
the two processes are conducted sequentially. First the septage 1s acidi-
fied to a pH of 2, mixed and allowed to settle. After the settled sludge
and supernatant have been separated, the pH 1s readjusted to 11 by the
addition of Hme, mixed and again settled.
Design and performance criteria based primarily on pilot scale
Investigations are presented 1n Table 4.
Solids resulting from the conditioning are further dewatered to a
20-30 percent solids content. Various mechanical filtration methods or
sand drying beds can be used for this purpose.
A combination of these dewatered sol Ids. the previously screened
solids and an added bulking agent comprises the raw material for the
compost phase of the process. Bulking agents typically used for composting
are woodchlps, bark chips, sawdust, rice hulls, etc. Generally, one part
of septage solids Is combined with two to three parts of bulking agents,
to attain a moisture content of 40 to 60 percent solids, the desired range
for composting.
Composting 1s usually accomplished through one of three methods:
windrow, mechanical or forced aeration composting. The windrow method
consists of constructing elongated triangular piles of septage and bulking
agent. In order to Introduce, or expose all portions of the pile to
oxygen, 1t must be turned on a regular basis, varying from a few times
each day to once every few days. This method Is highly equipment and
labor Intensive.
14
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Table 4: SUMMARY OF CHEMICAL CONDITIONING DESIGN PARAMETERS ANQ
PERFORMANCE (9)
Chemical(s)
Fed,
Design Parameters
Dosage: 400-600 mg/1*
Rapid Mix Time - 30 min
Slow Mix Time - 90 min
Settling Time - 22 hrs.
Fed -/ Li me
(Processed run
sequentially)
Dosage: Fed, - as above*
L1me - 2,500-4,000
mg/1*
Mix Time (Lime) - 1 hr.
Settling Time (lime) 22 hrs.
Fed,/Lime Dosage Fed, - 400 mg/1*
3 LimeJ - 4,000 mg/1*
Performance
1. Sludge volumes
approximately 40%
2. Difficult to define phase
separation
3. Removals of SSt VSS, Total
BOD5 and COD and Total P04 >90'
4. Organic N removal > 70% and
NH3-N removal> 45%
1. Sludge volumes approximately
1058 **
2. Moderate levels of TSS, BOD5
and nitrogeneous compounds
remain in effluent.
1. Good phase separation.
2. Sludge volumes approximately
32.52.
3. Removals of SS, VSS,-Total
4.
5.
BOD5> 9056
Removal of NH3~N>37.5X
Removal Organic N and COD
> 67.4%
Phosphorus removal> 77?
Alum
Dosage 2,250 - 8,250 mg/1*
Mix Time - 2 hrs.
Settling Time - 22 hrs.
1. Good phase seperation only
at optimum dosage.
2. Sludge volumes approximately
322.
3. Removal of SS, VSS, COD and
Total BOD5 > 962
4. Removal of NH3-N>47%.
5. Removal of organic N and
phosphous.) 90%
15
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Table 4 (Continued)
Chemical (si
Acid/Lime
Design Parameters
Dosage: acid 3000-4000 mg/1
(to pH 2)
Lime 3500-4500 mg/1
(to pH 11)
Mix Time
acid - 2 hrs.
Lime - *s hr.
Settling Time:
acid - 6-8 hrs.
lime - 2 hrs.
Performance
1. Very good phase
separation.
2. Combined sludge
Volume about 31%.
3. Removals of SS, VSS,
total B00e and COO
> 95X. 5
4. Removal of organic N
approximately 80Z
5. Removal of phosphorus
about 702
* Jar tests required on each batch of septage to determine optimum dosage
levels.
**10t of FeCl3 supernatant.
16
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Mechanical composting can be achieved through a number of patented
processes. In general, these are operated on a continuous basis with
the mixture of septage sludge and bulking agent introduced into the front
end of a "reactor". Augers (or other nixing devices) keep the compost
In continuous motion through the unit. Blowers provide the air required
in the process. Composting can be accomplished In these systems In 7-14
days. (8)
A more Innovative method Is the static, 'forced-air compost pile,
shown In Figure 5. With this method, the pile 1s constructed 1n one spot
and 1s not moved during composting. The piles are constructed by first
laying perforated pipe (generally 4" plastic) on a paved composting pad
and covering then with a layer of unscreened compost or the bulking
material. Unscreened compost 1s the material resulting from this process
prior to screening to remove the reusable bulking material. This material
provides an adequately stable base on which to pile the septage and facilitates
the forcing of air through the pile and into the perforated pipe. It also
absorbs excess moisture that may leach from the compost.
Conditioned septage, mixed with the bulking material is then placed
on this base 1n triangular piles. This 1s 1n turn covered using screened
compost (separated from the bulking material} or the bulking material '
Itself. This cover provides insulation, prevents odors from escaping the
pile and allows the forced air through.
For efficient composting, these piles are aerated for 3 to 4 weeks.
by which time, a stable product results. The piles are then dismantled
and the compost Is screened to remove the bulking agent and allowed to
cure for at least one more month prior to use (marketing, spreading on
municipal parkland, free distribution, etc.). The bulking agent is returned
to storage for reuse 1n the next batch of compost.
Area requirements for forced aeration composting 1s dependent on a
number of factors including amount of sludge composted, amount of bulking
material used and stored and amount of storage area required as dictated
by weather conditions. The following area guidelines are recommended for
an area with a climate similar to Washington., O.C. (10):
. p , (1.1) (vol. of 4 weeks sludge production) R » 1
i. raa area. Average height of sludge layer
h P volume of bulking agent
wnere * volume of sludge
2. Processing Area • Pad Area
3. Curtng and Storage Area • 2 x Pad Area
Oxygen 1s Introduced througn the use of a blower which draws air in
through the pile, into perforated pipe, and out through the blower. An
aeration rate of about 500 cubic feet (14 nr) per hour per ton of sludge
(dry weight basis) should maintain the oxygen level In the p1l« between
5 and 155 and provide for rapid decomposition of the sludge and extended
17
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Figure 5
The Forced Air Compost Pile (10)
Compost
Pile
(a) Schematic of Forced Air Compost Pile
Blower
Water
Trap
Screened
Compost
Deodorizing
Pile
Screened Compost
or Bulking Acan
Perforated
Pipe
ulking Agent and Septage
Unscreened Compost or
ulking Agent
(b) Cross Section of Forced Air Compost Pile
18
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thermophlHc activity. Continuous aeration results In rather large tempera-
ture gradients within the pile. Cycles of 20 to 30 minutes, with the fan
operating 1/10 to 1/2 of the cycle, have given more uniform temperature
distribution.
After the air passes through the pile, it may contain objectionable
odors. To eliminate these odors, the emitted air 1s filtered through
a small pile of previously composted material, before venting. (10)
While composting treats the solids portion of the dewatered septage,
the liquid effluent must also be treated. The filtrate generated during
the dewaterlng step 1s blended with the liquid fraction leaving the chemical
conditioning step. Depending on the resultant pH this liquid may need to
be neutralized to a pH of 7.0. At this stage, the liquid 1s not amenable
to surface discharge and must be treated further. This can be accomplished
through either land application, conventional waste treatment, or other
Innovative methods such as aquaculture.
Land application of the liquid effluent can be accomplished In a similar
manner to land application of septage. However, the characteristics of
this liquid effluent are substantially different from that of raw septage
as It has less fertilizer value. Therefore, the land requirements to
dispose of this material will be only 25 to 50 percent of what 1s required
for raw septage. Pathogens are reduced 1n the conditioning step of the
composting process, especially where very low or very high pH levels are
attained, and thus, the liquid effluent may be amenable to spray Irrigation
or overland flow techniques as well as sub-sod Injection. As with raw
septage, lagoon storage must be provided for the effluent since It cannot
be applied during unfavorable weather conditions. Crops grown on the spray-
Irrigated land can either be sold after harvesting or composted with the
septage solids.
A second method for treating the liquid effluent 1s through conventional
secondary waste treatment technology, 1.e activated sludge, trickling filter,
or rotating biological contactors. Since this liquid has been pretreated,
and sol Ids settled from 1t, no primary treatment will be required 1n this
facility. The liquid can be passed directly Into one of the biological
treatment processes mentioned above where It will be stabilized. The
effluent resulting from the process will be of sufficient quality for direct
discharge. Through the biological treatment process, sludge will be produced.
This sludge can be dewatered and returned to the composting operation to
be composted along with the septage. Biological treatment processes must
be operated continuously. These treatment processes are more complicated
than aquaculture and require more operator attention, not only throughout
the week but also on weekends and holidays.
Aquaculture, another method of treating the liquid effluent from the
composting process, Is a relatively new waste treatment process which Is
currently receiving Increased attention. Aquaculture Is defined In this
report as a treatment process where wastes are stabilized using aquatic
plants In a confined, controlled environment.
19
-------
The majority of the research conducted in this area has utilized water
hyacinths to accomplish treatment. However, hyacinths do not grow well
in northern climates and other aquatic plants such as duckweeds or bull
rushes have been found to be a suitable replacement. In an aquaculture
facility, channels are constructed in which plants are grown. The liquid
Is introduced Into one end of the channel, and allowed to flow by gravity
through the system. As the wastes pass by the plants, nutrients are taken
up and the waste 1s purified by the time it leaves the facility.
To enhance Its effectiveness in cold climates the entire aquaculture
facility can be housed In a solar greenhouse. This will promote growth
of the plants by providing a year-round warm environment, although addition-
al heating may also be required. No aquaculture facilities have yet been
constructed to treat either municipal wastewater or conditioned septage
effluent in cold climate areas. The state of the art has advanced to the
point that such systems have been encouraged at both the pilot and full
scale demonstration levels (11) and projects have been proposed utilizing
this technology. Because this Is a biological system, it must be operated
on a continuous basts (i.e. seven days per week). However, due to the
simplicity of the process, operator attention on weekends and holidays
should be minimal.
In a composting operation, the "off-gases" from the compost pile can
be utilized to enhance the aquaculture operation since these off-gases are
rich in carbon dioxide (CC^). Studies have shown that Improvements in
aquatic plant yields can be realized if these plants are grown in a CO?
rich environment. Piping the compost pile off-gases into the greenhouse
may, therefore, hold some potential benefit to the process.
Biomass produced by Inherent plant growth must be periodically
harvested. This material can be added to the composting process for
disposal. The advantages to composting are the effective kill of pathogens,
attractively-competitive capital and operations and maintenance costs,
production of a valuable, salable commodity and maintenance of groundwater
quality. Disadvantages Include land requirements for the composting site
and the fact that composting is a relatively new process for the treatment
of septage. Also required Is a system for treatment and disposal of the
liquid portion separated from the septage.
0. Lime Stabilization
The addition of lime 1n sufficient quantities will stabilize septage
and destroy pathogenic organisms. Unlike other stabilization processes,
such as aerobic or anaerobic digestion, no destruction of organic matter
or solids reduction occurs during the lime stabilization process. (See
Figure 6).
In this process, raw septage and lime are mixed together for a specific
period of time until a pH 1n excess of 12.0 1s reached and then held at that
pH for 30 minutes. Lime dosage requirements have been reported to range
from 0.09-0.51 pounds peV pound of dry solids over a corresponding total
solids content range of 1-4.E percent. (12) Mixing can be accomplished
through diffused air mixing or mechanical mixers. The next step in the
20
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Figure 6
Schematic for a Lime Stabilization Process for Septage Treatment
line.
Addition
Raw
Septage
Mix
Tank
Clarification
Thickening
L
Dewatering
^.Solids
Disposal
_^_ Liquid
Disposal
-------
process 1s "thickening". This can be accomplished in the mixing tank
(by shutting off the uiixtng mechanism) or in a separate vessel. The
thickened septage sludge is then dewatered using mechanical means (vacuum
filter, filter press) or sand drying beds, to a consistency of 20-30
percent solids. TMs sludge can then be landfllled directly. The liquid
from these processes-supernatant from the thickening step and filtrate
from the dewaterlng step - can be disposed of through Infiltration/
percolation beds, land application, aquaculture, or In a conventional
treatment plant.
Advantages of this technique include a high degree of bacterial
removal and low levels of chemical pollution In the liquid effluent.
Disadvantages Include the unknown long-term effects of stabilized sludge
disposal in landfills. Disadvantages associated with the chosen liquid
effluent disposal technique must also be considered.
E. 'Chemical Oxidation (BIF Purifax Method)
The Purl fax process utilizes the chemical oxidizing power of chlorine
gas for the stabilization of septage. This process, Hke Hue stabilization,
does not achieve organic matter or solids destruction during the treatment
of septage. It does however, produce a stable, Inert end-product. The
process does provide the added benefits of odor control and it conditions
the sludge sol Ids to promote better dewaterablllty.
The first step in the process is to screen the septage to remove large
particles, pebbles, sand and grit. This material can be disposed of in
a landfill. Next, the septage is transferred to a holding/blending tank
where ft is kept completely mixed either by diffused air or mechanical means.
The purpose of this tank is two-fold: 1) It holds the septage until a
sufficient quantity is stored and ready for processing in the Purl fax
unit and 2) it evens out the characteristics of the septage from many
different loads. Next, the septage is transferred to the Purifax unit,
of only a few minutes. (See Figure 7). However, 1t is necessary to store
the treated septage for 48 hours to allow the chlorine residual to drop to
0. The septage can then be dewatered with mechanical devices but some
additional conditioning is generally required. The dewatered sludge is
then landfilled while the liquid can be neutralized through aeration or
direct caustic addition to raise the pH, before treatment. Since the
effluent 1s not amenable to direct discharge into a surface water, Infil-
tration/percolation beds are most appropriate.
The Purl fax unit Is available over a wide range of flow capabilities,
from 10 gallons per minute to a theoretically unlimited maximum. Septage
treatment facilities in operation include a 400,000 gpd facility at
Babylon, New York and a 65,000 gpd facility at Ventura, California. Sizing
information is available^from BIF, the manufacturer of the Purl fax system.
Chlorine requirements for septage with a 1.2% suspended solids content is
0.0059 pounds per gallon of septage (13).
22
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Figure 1
Schematic of Chlorine Oxidation (Purifax Process) for Septage Treatment
Raw
Septage
Screening
Blending
Tank
Purifax
Process
Disposal
t
Liquid
Aeration
Dewatering
Solids
Disposal
-------
Advantages to this system include the production of a biologically
stable, odorless, inert material, dewatering of sludge to 30 percent
solids in 1-3 days, better than 95 percent removal of BOD, COO, phosphorus,
iron and zinc, and better than 80 percent removal of nitrogen. Disadvantages
include pretreatment requirements for grit removal and equalization, large
chlorine requirements, potential hazards of handling and using chlorine
gas, high chemical and power costs, and low pH and high chlorine concentration
in the process effluent. The potential of carcinogenic compounds being
produced by the chlorine oxidation process has been a major concern with
the use of this process, since these compounds may leach into the ground
or surface waters from the sludge or liquid effluent.
F. Electron Treatment/Land Application
The use of electron treatment of septage is a relatively new technology.
In this method, septage is pasteurized as it moves, in a wide, thin stream
through a "curtain" of downward-directed electrons.
The first step In the process is to screen and degrit the septage. These
solids can be disposed of directly Into a sanitary landfill. Next, the
septage Is held in an equalization tank where it is aerated and mixed. At
a controlled rate, the septage 1s fed from the holding tank to the electron
treatment unit. The system is designed to disinfect septage in a fraction
of a second by subjecting it to a "beam of energized electrons. This unit
can treat septage containing up to 8 percent solids. No radioactivity
results from this process and the temperature of the septage rises less than
3 degrees centigrade. Along with the destruction of biological organisms,
the destruction of certain pesticides and herbicides as well as PCB's may
occur. After electron treatment, the liquid septage can be disposed of
through sub-sod injection on agricultural land. (See Figure 8).
Major design parameters include flow, sludge characteristics primarily
solids content, and intended end use of processed septage. Only one electron
beam system is now operating in this country, that being at the Deer Island
Facility serving Boston, Massachusetts where sewage sludge is being irradiat-
ed (8). A second facility which is betng proposed for the Miami, Florida
area will be handling septage (14).
Advantages of this process are that septage can be disinfected
rapidly making it more suitable for land application. There also appears
to be destruction of certain toxic chemicals. Disadvantages include the
fact that this is a relatively new process and as such, no long-term
performance or operating cost data exists for a full-scale facility.
G. Co-disposal with Solid Waste
"Co-disposal" is a generalized term which, in this report, refers to
the stabilization of saptage solids (sludge) and municipal refuse through
either thermal or biological means. "Thermal stabilization" is the incinera-
tion of sludge and refuse producing ash, which is disposed of in a landfill,
and steam, which can be sold as an energy source. Biological stabilization
can be accomplished through composting, producing an end-product that is
useful as a soil conditioner and fertilizer.
24
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Figure 8
Schematic of an Electron Treatment/Land Application System
Raw Septage
Screening
Degriting
Aeration/
Holding
Tank
Electron
Treatment
Land
Application
ro
ui
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For a town the size of Woodrock, municipal solid waste generation
will be approximately 12,000 tons per year in the design year of 2000,
assuming between 3.0 and 3.5 pounds of solid waste are generated per
person per day. In addition approximately 300-350 tons of dewatered
septage solids will be generated annually. This represents a substantial
quantity of material available for co-disposal through Incineration or
composting.
1. Incineration
The technology for burning dewatered sludge solids and municipal
solid wastes to produce steam has Improved 1n recent years to a
point where there are facilities handling as little as 25 tons per
day. Sludge, either septage or treated wastewater sludge, is
dewatered to 25-30 percent solids and nixed with municipal solid
wastes. No classification of the municipal solid wastes 1s
required, (I.e. removal of metals (cans, etc.) or glass). The
incinerators are designed to accept these materials, which sub-
stantially reduces pretreatment costs. Septage must be dewatered,
however, so that little or no auxiliary fuel will be required
for combustion. The solid waste and dewatered septage 1s intro-
duced into the incinerator where the materials are burned under
"starved air" conditions. This produces an inert ash (less than
1 percent organic material) and combustible gases. The gases
enter Into a second burning chamber where the air to fuel ratio is
maintained at a proper level to Insure complete combustion. The
heat produced 1n this chamber is used In a heat exchanger where
steam is produced. Steam can be used Internally for heating or
sold externally for heating or process steam.
2. Composting
The second method of co-disposal of municipal solid wastes and
septage is through composting. Composting of municipal refuse
has been in practice for nany years and the concept of co-disposal
wtth sludge has also received constderable attention in past years.
The basic description of the composting process has been explained
previously in this section and will not be repeated here.
H. Conventional Waste Treatment
Conventional waste treatment involves the use of sewage treatment tech-
nology, specifically secondary treatment, for the stabilization and purifica-
tion of septage. One such conventional waste treatment utilizing screening
aerated flow equalization (since the process will require 7 day-per-weefc-
operation), primary clarification, rotating biological contactors (RBC's)
for secondary clarification, and chlorination is described below.
s
The liquid effluent should be disposed of through infiltration/percolation
beds, since it will probably not meet the water quality criteria for direct
discharge to a surface water. One operating RBC facility has demonstrated
the ability to remove 88-90* and 68-71% suspended solids. However, with
-------
high Influent loading, the effluent quality of 32-48 mg/1 for BODg and
42 mg/1 for suspended solfds still exceeds discharge requirements (15).
It should be noted that this liquid is suitable for use In land appli-
cation or other wastewater treatment systems. Solids generated in the pro-
cess through primary sedimentation and secondary treatment are dewatered,
combined with the screenings and disposed of In a landfill.
In the primary treatment phase of the process, solids are allowed to
settle and thicken In the bottom of a clarifier. This process will remove
approximately 50 percent of the suspended solIds and BOD from the waste
stream. The solids are removed from the clarifier and mixed with solids
from the secondary treatment process.
The secondary treatment step involves the use of an RBC and a secondary
clarifier. RBC's are made of a series of lightweight disks immersed in a
cylindrical vat containing the septage. As the disks rotate, the waste
organics are absorbed by or diffused into the layer of bacteria living on
the disks. As the portion of the dtsk emerges from the liquid, organics
are .bio-degraded. Usually several RBC units-are placed In series for waste
treatment.
As bacterial growth proceeds, sloughing off of portions of the micro-
bial slime occurs. This sludge 1s then removed from the waste stream through
sedimentation In the secondary clarifier. Although It Is difficult to pre-
dict exact quantities of sludge from this operation without pilot scale
testing, the literature Indicates that an average sludge production will be
0.45 kg per kg of BOO degraded. This conventional treatment process is
shown In Figure 9.
The advantages of this type of system are that it 1s a standard waste
treatment process, it 1s capable of handling shock loads, and able to treat
high-strength wastes. Disadvantages Include the need for further effluent
treatment, high capital costs, high energy demands and the need for sludge
removal.
I. Co-Treatment at Mastewater Treatment Plant
The hauling of septage to existing conventional wastewater treatment
facilities Is a very common means of septage disposal. Septage is generally
added to the liquid stream either directly via the headworks, or into a
holding/blending tank from which it can be bled Into the system at a con-
trolled rate. Addition directly to the solids stream is also possible.
Although a practical method of disposal in many areas, the practice
poses potential operational problems. These problems include:
- Shock overloading of existing plants producing effluent discharge
violations. This 1s especially true where adequate control Is not
exercised over receipt and addition of septage treatment works.
27
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Figure 9
Schematic of a Conventional Treatment System for Septage
w* ••
tew ... ., /
Septage r—
Primary RBC Sec
Equalization ' Clarif ier -* Unit • Cle
o 1 • t
Screenings
air
Dewatering
1
P. Solids Disposal
(landfill)
»ndary Liquid
irif ier ^ Chlorination — * Disposal
ro
oa
-------
• Organic overloading caused by the high strength wastes (50 times
that of sewage) Imposing too great an oxygen demand for the existing
aeratton equipment.
- Sol Ids overloading of existing solids handling equipment (chemical
conditioning units, filters, etc.)
Numerous factors Including hauling distance, existing excess capacity
and operational control contribute to the feasibility of treating septage
at existing facilities. A study recently completed at the University of
Lowell (15) addressing this Issue has yielded the recommendations summarized
in Table 5.
The design of new sewage treatment facilities should address the likeli-
hood and amount of septage which can be expected. Design of the facility
should be based on an average waste loading of combined sewage and septage.
Advantages of co-treatment. Include maximum use of a wastewater treat-
ment facility, Its equipment, personnel, and the existing regulatory frame-
work. The process also produces a stabtltzed sludge. Disadvantages Include
possible costly pretreatment requirements, potential for plant disruption
from sol Ids overloading and oxygen depletion, and Increased likelihood of
exceeding permitted effluent quality criteria.
In the case of Uoodrock 1t has been proposed that co-treatment at a
Pollution Control District (PCD) facility In Stlllwater Is a viable alter-
native. StUlwater Is a neighboring community slightly more than five miles
south of Woodrock. At present the PCD facility accepts septage on a fixed
user cost basis.
Summary
This section has discussed the major alternatives for the treatment and
disposal of septage available to the town of Uoodrock. Obviously many
modifications and variations are possible In other situations. A summary
of the advantages and disadvantages of each of the treatment options Is
presented 1n Table 6.
29
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TABLE 5 RECOMMENDATIONS FOR TREATING SEPTAGE AT
EXISTING WASTEWATER TREATMENT FACILITIES (15)
Hauling Distance
10 miles - reasonable
10-20 miles - marginal
20 miles - excessive
Septage Loading Rate (based on an extended aeration facility)
Existing Loading Recommended Septage Loading*
(As percentage of capacity (As percentage of wastewater How)
25i 3*
SOX 2%
75% 12
* Loading up to and exceeding SX of sewage flow is possible if adequate
aeration capacity exists or if excess capacity 1s added specifically
for this purpose.
Solids Handling
- Septage can generally not be dewatered without chemical addition.
• Secondary sludge derived fnom co-treatment of sewage and septage
dewaters well (using vacuum filtration) with the addition of
either polymers or lime.
30
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Table 6
Summary of Advantages and Disadvantages of Alternative
Septage Treatment and Disposal Methods
Treatment
System
Lagoon
Land application
Composting
Line
stabilization
Chemical
oxidation
(Purifax)
Advantages
•major sludge dewaterlng
facilities not required
•low operation cost
-simplicity of operation
•accommodates large loads
fluctuation
•low energy use
•no chemical additions
•no chemicals needed to
kill pathogenic
organisms
-competitive capital and
operation & maintenance
costs
•potentially reusable
end-product with
fertilizer value
•no groundwater pollution
•high degree of bacteria
removal
-low amounts of chemical
pollutants in liquid
effluent
-production of biologically
stable, odorless material
-rapid debatering of sludge
to 301 solids
•95% removal of BCD, COD
^phosphorous, iron, & zinc
-80% removal of nitrogen
Disadvantages
-frequent solids collection
and disposal required
-foul odors
-foaming problems (aerobic)
-large land requirement
-insect breeding
-potential groundwater
contamination
-potential groundwater
contamination by nitrogen
and heavy metals
-large land requirements
-need for holding facility
during periods of frozen
or saturated soil
•inconsistent effluent
quality
-relatively high costs
-relatively new process
-land requirements
-relatively nigh costs
-pretreatmem: required
for grit removal and
equalization
-large chlorine requirement
-potential hazard of using
chlorine gas
31
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Table 6 (Continued)
Treatment
System
Chemical
Oxidation
(Purl fax)
(Cont'd)
Advantages
Electron
Treatment
Co-Disposal
Incineration
Composting
Conventional Waste
Treatment
Cc-treatment at VIWTP
-pathogen destruction
-possible toxic chemical
destruction
-complete destruction of
organic material,
pathogens and viruses
-production of steam as
a saleable product
-increased production of
a saleable product
-proven waste treatment
process
-stable, can handle stock
loads
-can treat high strength
wastes
-maximum use of facility
equipment, and personnel
-existence of regulatory
framework
•Stabilized slude
produced
Disadvantages
•high chemical and
power costs
-low pH and high chlorine
concentration in the
process effluent
-concern over the carcinogenic
characteristics of
chlorinated compounds
-new process
-no long-term performance
data
-no long-term cost data
for operation and
maintenance
-expensive Initial costs
-ash still has to be
disposed
-logistical problems
associated with hauling
solid wastes to a central
facility
-need to find a use or
market for increased
compost volume
-increased costs for
expansion to accommodate
solid wastes
-expensive process
-high energy demand
-sludge dewatering and
disposal Is needed
-costly pretreatment
requirements
-potential for plant upset
by high solids and
SOD loadings
-potential violation of
effluent standards
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Ill COST EFFECTIVE SOLUTIONS FOR SEPTAGE MANAGEMENT
The costs of different septage treatment methods are a major consider-
ation in the decision-making process and must be evaluated along with
environmental and operational factors. This section will examine the
economics of each treatment alternative as they relate specifically to the
town of Woodrock.
The costing analysis in this section presents the costs of pumping/
hauling and six treatment alternatives for the town of Woodrock. These
costs are presented in the following order:
a) Pumping/Hauling
b) Lagoon Treatment
c) Land Application
d) Composting
e) Lime Stabilization
f) Chemical Oxidation, and
g) Conventional Treatment
h) Co-treatment with Still water
These are based upon a design flow for the town of Woodrock of 2,025,000
gallons per year in the year 2000. Each alternative system was designed to
accomodate this flow. The sources of cost information are shown In Table 7.
Costs for specific pieces of equipment such as mixers, aerators, dewatering
equipment, pumps, trucks, etc. were obtained directly from manufacturers.
Other cost components such as tanks, pavement, fencing, conveyors, earthwork
and buildings are based on building and construction cost manuals. Land costs
in this analysis reflect the prices currently applicable to the town of Woodrock.
Nonetheless 1t must be emphasized that these costs have been developed for
illustrative purposes only and should not be construed to use as general cost
estimates to be applied to a specific situation.
The alternatives are compared on the basis of a cost effectiveness
analysis as required by the EPA Municiapl Wastewater Treatment Works, Construc-
tion Grants Program (43 FR 44087-44090). Details and procedures on cost esti-
mation and cost effective analysis are not presented. The reader Is referred
to an accompanying report entitled "Cost Effective Analysis" for this infor-
mation.
In line with the above requirements, for most major components in
these alternatives, a 20-year useful life is assumed. However, costs of such
items as pumps, blowers, and mixers are calculated on the basis of a five-
year life while all vehicles (trucks and front-end loaders) were assumed to
have a ten-year life, If properly maintained. Amortization of these capital
costs was made on the basis of the useful life of each piece of oquipment
and an Interest (discount) rate of 7-1/8 percent, as specified by the
Federal Water Resource Council. Lastly, it should be noted that these
alternatives are compared on a present worth basis.
33
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TABLE 7
Sources of Cost Information For
Septage Management Alternatives
Source
Equipment - Manufacturers
e.g. mixers
aerators
dewatered equipment
pumps
trucks
Other Components Building and Construction
tanks Cost Manuals
pavement
fencing
conveyors
earthwork
buildings
LatKj Local prices for town
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A. Pumper/Hauler Costs
Pumping and hauling of septage Is required for all treatment options
as a method for gathering septage and bringing it to one central location.
In general, there are three approaches to the development of a septage
pumping and hauling program for the town of Woodrock. The objectives of
such a maintenance program will be to insure that septic tanks are pumped
out on a regular basis and brought to a municipal facility for treatment.
The three options are:
1) The municipality provides the pumping and hauling service,
2} One or more licensed pumpers enters Into a contract with the
municipality to provide the pumping and hauling service,
3} The Individual homeowner contracts with an individual pumper
who operates freely In a competitive market.
Of these three options, the first is analyzed in detail since 1t
represents the maximum municipal Involvement for the community, and
provides representative data on what pumping and hauling costs should be.
The management arrangements required of the other two options are also
examined briefly. It should be noted that, under the 1977 amendments
to the federal Clean Hater Act, septage pumping equipment costs are grant-
eligible.
Option 1: Town-Owned Pumping Service
In this approach, a specified town agency ts responsible for actual
pumping and hauling of septage. Septic tanks, throughout the town, are
pumped at regular three-year Intervals. With a projected population of
17,679 In the town of Woodrock by the year 2000 and an assumed residential
density of 3.a persons/household, there will be an estimated 4650 households.
Thus by the year 2000, 1550 household would require pumping each year;
an average of 6 to 7 households would be pumped daily (250 working day/year),
It is reasonable to assume that two men, working full-time, with two trucks,
could provide this service, however, three trucks would provide flexibility
If one breaks down. A summary of costs for pumping/hauling is presented
below; a more detailed breakdown 1s presented in Section IV.B.
Costs for Pumping/Haul ing of Seotaqe
Capital Costs $ 180,000
Annual Q 4 M - Present Worth 630,000
Salvage Value
TOTAL - PRESENT WORTH $ 810,000
35
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Option 2: Municipal/Private Hauler Contract
Under this alternative, the town contracts with one or more pumpers/
haulers to operate a regular maintenance program throughout the town. The
contract(s) would be released on a bid-basis which would assure a competitive
price. This system does not require hiring any additional town employees,
but the town would be responsible for collecting a uniform pumping fee from
the homeowner.
Option 3: Homeowner/Private Pumper
Under this system, private pumper/hauler contractors operate within the
community on a competitive basis. The town notifies the homeowner when the
pumping Is needed and the homeowner contracts with one of the licensed
pumpers In town. The homeowner 1s responsible for notifying the town that
the.pumping has been done. The town would be responsible for administrative
record keeping, sending reminder notices and .following up on homeowners who
fall to respond to the reminder.
B. Treatment and Disposal Costs
The treatment and disposal options considered feasible for the town of
Woodrock were analyzed on the basis of their cost summaries of these costs
and presented 1n Tables 8-14. Table IS presents a summary of the cost-
effective analysis for these alternatives. These costs are presented In
the following order:
a) Lagoon Treatment - Table 8
b) Land Application - Table 9
c) Composting • Table 10
d) Lime Stabilization - Table 11
e) Chemical Oxidation, and - Table 12
f) Conventional Treatment - Table 13
g) Co-treatment with Still water - Table »
One alternative which was not analyzed for Woodrock which warrants
additional mention Is the surface land application of septage. Although
it was not considered for Hoodrock due to an assumed prohibition, It may
not be the case elsewhere. The cost of this option, as with the subsurface
option, Is highly dependent on the local land costs. Other component
costs, such as application and operation and maintenance costs will be
slightly less than for subsurface application. Surface land application
Is perhaps the most common method of septage disposal. Where local conditions
allow this technique and sufficient land exists, and with proper management,
It can be a viable treatment alternative.
36
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TABLE 8: COSTS FOR LAGOON TREATMENT OF SEPTAGE
1. CAPITAL COSTS
"A. Equipment
Holding Tank/Piping $46,200
Aeration Equipment/ Pumps 18,900
B. Buildings 17,300
C. Site Work & Monitoring 24,900
D. Lagoon 22,800
E. Land (2.25 Acres @ $10,000) 22,500
F. Development Costs 61,000
TOTAL CONSTRUCTION COSTS $213,600
2. ANNUAL OPERATION AND MAINTENANCE
A. Labor $11.500
B. Chemicals (Lime) 6,000
C. Sludge Disposal 13,300
0. Electricity 3,500
E. Site Maintenance 1.°°°
F. Lab Analysis 1.500
TOTAL ANNUAL 0 4 M $ 36,800
37
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TABLE 9: COSTS FOR SUBSURFACE LAND APPLICATION OF SEPTAGE
1. Capital Cost
A. Application Equipment $ 97,200
B. Buildings 17,300
C. Site Work & Monitoring 14,700
0. Lagoon 65,300
E. Land (32 acres @ 10,000) 320,000
F. Development Costs 205,800
TOTAL CONSTRUCTION COSTS $720,200
2. Annual Operation and Maintenance
A. Labor $13,000
B. Chemicals (Lime} 6,800
C. Septage Application 5,400
D. Site Maintenance 2,500
E. Lab Analysis 1,500
TOTAL ANNUAL 0 & M $ 26,700
38
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TABLE 10: COSTS FOR COMPOSTING OF SEPTAGE
1. Capital Costs
A. Equipment
Holding Tank $ 2,500
Screens 25,000
Acid/Lime Conditioning 68,500
Dewatering 80,000
Composting 95,000
Anaerobic Upflow Filter 40,000
Aquaculture 75,000
B. Buildings 50,000
C. Site Work 17,500
-D. Piping and Electricity 40,000
E. Land (2.5 acres 0 10,000) 25,000
F. Development Costs 207,400
TOTAL CONSTRUCTION COST $725,900
2. Annual Operation and Maintenance
A. Labor $13.000
B. Chemicals 3,000
C. Electricity 4,500
D. Vehicle 0 & M 9,000
E. Wood Chips 3,000
F. Site Maintenance 1,000
G. Lab Analysis 1,500
H. Resource Recovery -4,000
TOTAL 0 & M $32,000
39
-------
TABLE 11: COSTS FOR LIME STABILIZATION OF SEPTAGE
1. Capital Costs
A. Equi pment
-Tanks 122,500
-Screens 19,000
-Lime Feed 22,800
-Dewatering 100,800
-Aeration Equip/Pumps 20,200
-Conveyor 4,300
B. Building 50,000
C. Site Work & Monitoring 28,500
P. Piping and Electricity 33,400
{. Land (1.5 acres 9 $10,000) 15,000
F. Development Costs 166,600
TOTAL $583,100
2. Annual Operation and Maintenance Costs
A. Labor 14,500
B. Chemicals 9,700
C. Sludge Disposal 13,300
D. Electricity 8,000
E. Site Maintenance 1,000
F. Lab Analysis 1.500
$48,000
40
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TABLE 12: COSTS FOR CHEMICAL OXIDATION OF SEPTAGE
1. Capital Costs
A. Equipment
-Tanks
-Screens
-Lime Feed
-Oewateri ng
-Aeration Equip/Pumps
-Conveyor
B. Building
C. Site Work & Monitoring
0. Piping and Electrical
E. Land (1.5 acres 9 $10,000}
F. Development Costs
2. Annual Operation and Maintenance Costs
A. Labor
B. Chemicals (Chlorine)
C. Sludge Disposal
D. Electricity
E. Site Maintenance
F. Lab Analysis
lOOjOOO
16,800
261,200
100,800
14,400
4,300
50,000
28,500
33,400
15,000
249.800
TOTAL CONSTRUCTION COSTS' $874,200
17,000
5,800
13,300
10,200
1,000
1.500
TOTAL ANNUAL 0 & M
$ 48,800
41
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TABLE 13: COSTS FOR CONVENTIONAL TREATMENT OF SEPTAGE
1. Capital Costs
A. Equi pment
•Tanks
-Rotating Biological Contractor
-Dewatering Equipment
- Chiorination Equipment
• Pumps
B. Building
C. Site Work & Monitoring
0. Piping and Electrical
E. Land (1.5 acres 9 $10,000)
F. Development Costs
2. Annual Operation and Maintenance Costs
A. Labor
B. Chemicals
C. Sludge Removal
D. Electricity
E. Site Maintenance
F. Lab Analysis
41,000
40,900
100,800
5,000
21,600
50,000
28,500
33,400
15,000
134,500
TOTAL CONSTRUCTION COSTS 470,700
28,500
2,500
13,300
14,300
1,000
1,500
TOTAL ANNUAL 0 & M 59,300
42
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Table 14: Cost of Cotreatment at PCD Facility in Stillwater
1. Annual Operation and Maintenance Costs
A. Fixed Fee ($33/1000 Gals*) = $66,800
B. Excess 0 & M** 5,100
Total Annual 0 & M $7:1,900
* Estimated Fee as of 1984
** Accounts for additional hauling distance
43
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IV. SEPTAGE MANAGEMENT PLAN
A. Septage Treatment Facility
The-selected alternative for the treatment and disposal of septage for
the town of Woodrock Is the composting system described in Section II.C.
The overall treatment system Incorporates add/Hrne conditioning and aqua-
culture treatment of the liquid effluent. The facility will be located 1n
the southwestern portion of the town; a minimum 4.5 acre site will be required.
This alternative was selected over more cost-effective alternatives
(See Table 15) for two primary reasons:
- The composting process produces a useful end product and the treated
liquid effluent 1s well suited for land disposal. This results in
less potential for adverse environmental impact than can result from
either direct land treatment or lagoon treatment. The town rejected
these two alternatives for this reason.
- The operation and maintenance cost ($32,000/year) is less than for
co-treatment with Stmwater ($71,900/year) or lagoon treatment
($36,300/year). This makes this alternative much more acceptable to
the town since they have to-bear the totality of operation and main-
tenance costs while capital costs are eligible for sizable (up to
85%) federal grants.
A schematic process diagram of the selected alternative 1s presented in
Figure 10. Details of the design are presented 1n Table 16; cost estimates
were previously presented 1n Table 10.
The septage 1s collected from individual septic tanks by large capacity
pump trucks. It Is transported to the septage treatment site and pumped
through a bar screen and Into a large holding/aeration tank. This tank has
the capacity to hold (for later treatment) the contents of 20 Individual
septic tanks. The large sire of the tank is provided so that collection
of septage from problem systems can continue for several days even if the
septage plant Is closed for repairs. The tank also serves as an aeration
basin, providing oxygen to the previously anaerobic septage. Finally, this
tank allows an equalization of the flow of septage from the collection
process to the treatment process.
The next step in the septage treatment process Is screening. Bulk
sol Ids are removed from the waste stream using a vibrating screen and sent
to the composting process. Most of the septage solids are separated in this
step, while the filtrate goes on to further treatment.
The screen filtrate 1s then chemically treated to Improve Its dewaterlng
properties. The particular chemical treatment is an acid/lime process. First,
the septage is acidified to a pH of 2.0 through the addition of sulfuric
acid. After acidification, the septage enters a clarlfler where the majority
of solids settle out. The acidified supernatant 1s next treated with Hrne,
until a pH of 11.0 is reached. As with the acidification step, the liquid
is then Introduced Into a clarifler where the remaining solids, mostly
inorganic precipitates, are settled.
44
-------
Table 15: Summary of Present Worth Analysis of Sept-age
Treatment Alternatives
Initial
Capital Future Capital Operation and Salvage
Costs Costs .Maintenance Value Total
Present Worth
Factor
5 yr. 0.7077
10 yr. 0.5024
15 yr. 0.3561
Non-Energy 10.49 0.2524
Electricity 11.67
ALTERNATIVES
1.
2.
3.
4.
5.
6.
Pumping/
Hauling
Lagoon
Treatment
Land
Treatment
Composting
L1me
Stabilization
Chemical
Oxidation
180,000
213,600 29,600
720.200 48,800
725,900 90,900
583,100 38,400
874,200 29,300
390,200 -16.300 617,100
280,100 -158.000 1,091,100
330,500 -31,100 1,116,200
513,000 -14,400 1,120,100
410,600 -14,400 1,306,000
7. Conventional
Treatment
8. Cotreatment
with Stillwater
470,700 33,900
636,000
754,200
•14,400 1,129,300
754,200
45
-------
TABLE 16
Septage Treatment Facility - Design Specifications
Design Year; 2000
Design Population: 17,680
Septage Generation Rates (based on 3 year pumping frequency for domestic
systems and 1200 gallon average domestic septic
tank size).
Domestic: 1.86 million gallons per year (MGY)
Commercial: 0.125 million gallons per year
Industrial: 0.04 million gallons per year
Total: 2.025 (MGY)
Daily Load (based on 250 day year) - 8100 gpd
Total SolIds Loading 2700*/day
Total Suspended Solids Loading l,038#/day
Organic Loading 338#'s BOO/day
Septage Treatment System for Hoodrock
Process Design Data and Sizing
Collection 2000 gallon capacity pump truck (2 required; 3 desirable)
Holding/Aeration Dentention Time - 3 days.
Volume • 24.300 gallons (3249 cu ft)
Dimensions - 30' X 18' X 6' deep
Type of Aerator - Mechanical
Horse Power - 1.25 HP
Screening Loading - 135 - gpd/sq ft
Number of Screens - 6
Total Screen Area - 60
Screen Mesh Size - 20 Mesh
Type -Sweco 1 deck separator (48" diameter)
46
-------
Process
Acid/Lime Conditioning
TSS Loading - 275.3 #/day
Acid Dosage - 3000 mg/L (202.7 #/day)
Acid Storage (60 days) - 106.3 ft3 •
Tank dimensions - 5 foot diara. X 6' deep (118 ft3)
Mixing Time - 2 hours
Mixing Tank - 91 cu ft ,
Tank dimensions - 5 ft. diam. X 4-3/4 ft. depth (93 ft3]
•Mixer Type - Mechanical
Horsepower Requirements - 2.0
Settling Tank - 995 ft3
Tank Dimensions - 12 ft. diam. X 9 ft deep (1018 ft3)
Detention Time - 22 hours
Lime Dosage - 4000 mg/L ,
Tank Dimensions - 3 ft diam. X 3k ft depth (23 ft3)
Mixing Time - 30 minutes
Mixing Tank - 22.6 ft3
Mixer Type - Mechanical
Horsepower Requirements - 2.0
Settling Tank - 91 ft3
Settling Tank Dimensions - 5 ft diam. X 4-3/4 ft depth
Detention Time - 2 hours (93 ft3)
Dewatering
Composting
Septage Holding Tank (2 day capacity) - 647 cu ft
(23 ft diam X 5-3/4' depth)
TSS Loading - 263.4 #Day
Unit Type - Belt Filter Press
Belt Loading - 541 solid/ft - hr.
Belt Width - 3 feet
Operation Time: 2 hrs/day
Volume He Loading: 1620/gal/day
X Solids: 201
Solids Loading: 2702 Ib/day
Septage: Bulk Ratio: 1:3
Number of Blowers: 2
Front End Loader: 1.5 cu yd bucket
95 horsepower
Septage Holding Time: 30 days
Septage Holding Tank: 6500 cu ft
Septage Holding Tank
Dimensions 6* x 32' x 35'
47
-------
FIGURE 10 FLOW DIAGRAM-SEPTAGE TREATMENT FACILITY
RAW SEPTAGE
SCREENING
ACID/LIME
SOLIDS
V
LIQUID
NEUTRALIZATION
V
AQUACULTURE
V
SUB-SURFACE
DISCHARGE
SOLIDS
DEWATERING
SOLIDS
SOLIDS
\|
COMPOSTING
43
-------
The add/lime process was selected over other available processes because
of the good results obtained In pilot scale tests utilizing it. (See Table
and Reference 9). The solids resulting from the acid/lime treatment steps
are blended together 1n a large holding tank for final dewatering. This
holding tank provides some excess capacity 1n case of problems with the
dewatering apparatus. Dewatering 1s by a belt filter press, which essentially
squeezes water out of the settled sol Ids yielding a final solids content
of about 202.
The final step In septage solids treatment 1s composting. The solids
from the belt filter press are combined with those from the septage screening
operation and aquatic plants harvested from the sewage treatment process
(described below) In a large holding tank at the compost site. The composting
process Is a batch process, and storage must be provided for septage solids
generated during the composting cycle time. The compost process to be used
1s forced-air composting.
The supernatant from the septage 1s to be collected and treated. The
first treatment step 1s an anaerobic up flow filter which, by the mechanisms
of straining and anaerobic digestion, remove organic pollutants and suspended
sol Ids from the liquid. Next, the septage supernatant 1s sent to an aerated
lagpon/aquaculture system, similar to the one described 1n Section II.C.
Final effluent disposal 1s through a soil absorption system.
B. Septage Pumping/Hauling
In conjunction with the septage treatment facility there Is also a need
to provide for pumping and hauling- of the septage from the septic tanks to
the treatment facility. Option 1 whereby the municipality will purchase
septage pumping and hauling equipment (with grant assistance) and provide
this service was selected primarily because of the greater degree of control
It provides. Septic systems will be pumped out once every three years.
Septic systems which are repaired or replaced with federal funds will have
their septic tanks pumped by the town as part of their user costs. Other
system owners will be sent reminder cards every three years Indicating that
their septic tank should be pumped; they will be responsible for arranging
and paying for this service.
-------
The Town will own three septage pumping vehicles with vehicle costs
at $180,000 (local share 524,000).
Operating costs for septage pumping (per system) are:
Labor (3 hours @ $15.00/hour) $45.00
Travel (10 miles 9 $.50/mile) 5.00
Local Share Payment/Equipment 20.00
Replacement
Contingency 5.00
$75.00/system
The costs for operations/maintenance are:
Federally Funded Systems
Septage Pumping $25/year
-$75 pumping/three years
Non-Federally Funded (Continuing Systems)
Reminder Cards (one every three years) $0.25/year
-50-
-------
V. References
1. Rezek, J.U. and I.A. Cooper, August, 1980, "Septage Management", EPA-
600/8-80-032.
2. Bowker, R.P.6., May, 1977, Treatment and Disposal of Septic Tank
Sludges: A Status Report, USEPA, Municipal Environmental Research
Laboratory, Cincinnati, Ohio.
3. Jewell, W.J., et. al., 1975, "TreatablHty of Septic Tank Sludge
In Water Pollution Control In Low Density Areas", Proceedings of
a Rural Environmental Engineering Conference, W.J. Jewell and
Rita Swan, eds.; University of New Hampshire Press of New England,
Hanover, NH.
4. New England Interstate Water Pollution Control Commission, August,
1976 "Guidelines for Septage Handling and Disposal", TGM-1.
5. EPA, September, 1980, A Guide to Regulations and Guidance for the
.Utilization and Disposal of Municipal Sewage Sludge, EPA 430/9-80-015.
6. Maine Department of Environmental Protection, July, 1974, "Regulations
for Septic Tank Sludge Disposal on Land.
7. Dept. of Natural Resources, 1975, Guidelines for the Application of
Wastewater Sludge to Agricultural Land 1n Wisconsin, Technical
Bulletin No. 88, Madison. WI.
8. USEPA, September, 1979, Sludge Treatment and Disposal, Process
Design Manual, EPA 625/1-79-011.
9. Condren, A.J., September, 1978, "Pilot Scale Evaluations of Septage
Treatment Alternatives", EPA 600/2-78-164.
10. unison, G.B., et. al., May, 1980, Manual for Composting Sewage
Sludge by the Beltsvllle Aerated - Pile Method, EPA 600/8-80-022.
11. Persche, E.R., June, 1980, "Combined Aquaculture Systems for Wastewater
Treatment 1n Cold Climates - An Engineering Assessment 1n Aquaculture
Systems for Wastewater Treatment", an Engineering Assessment,
EPA 430/9-80-007.
12. Noland, R.F., et. al., September, 1978, Full Scale Demonstration of
Lime Stabilization. EPA 600/2-78-171.
13. BIF, "PuMfax. Sludge Treatment System", West Warwick, RI.
14. High Voltage Engineering, 1979-80, Application for the Treatment
of Septage for Safe Soil Improvements", High Voltage Engineering
Corporation, Burlington, Massachusetts.
15. Segal!, A.B., et. &., November, 1979, August, 1980, "Monitoring
Septage Addition to Wastewater Treatment Plants; Volume 1: Addition
to the Liquid Stream", EPA 600/2-79-132; Volume 2: Vacuum Filtration
of Septage, EPA 600/2-80-112.
51
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Work Session : Residuals Management- Exercise I
This work session is designed to illustrate the decisions faced
by a community with regard to sending its septage to an existing wastewater
treatment facility or constructing a separate septage facility. Using
the schematized map of the problem area and the cost curves on the following
pages, address the following questions:
1. What is the annual flow rate of septage to be handled by the
facility?
2. Determine the present worth of construciton and 0 & M costs for
the separate septage facility.
3. Determine the present worth of construction and 0 & M costs for
using the wastewater treatment facility under the following
conditions. (Note: the construction cost curve is for expansion
of the facility i-f necessary to accomodate the increased septage
flow).
a. if the facility is now operating at full capacity
b. if the facility is now operating well under capacity and
likely will remain that way over the next 20 years, (i.e.
capable of handling entire septage flow without modificaiton).
c. if the facility is now capable of handling the septage but is
planning additional users in 10 years which will bring it up to full
capacity. (The present worth factor for a single payment at year
10 with a 7 1/8% discount rate = 0.502)
4. Calculate the present worth of septage hauling for disposal at the
wastewater treatment plant. Assume hauling costs of $.50, S1..00, $2.00,
$3.00/mile and a present worth factor of 10.49.
5. For each of the conditions in 3 a, b, c, within what hauling distances
is it most cost effective to build a seperate septage facility.
6'. Discuss the potential advantages and disadvantages for a community
to construct a septage facility now versus in the future given the
availability of existing treatment plant capacity.
-------
5IMPLIFIEP
-------
Ul
i
Ul
TKEATMEIWT PUNT
I
M
u.
^
Ul
Ul
^
Ul
Q£
Q.
FACILITY
MAUUN6
-------
PROCESS DIAGRAM
LEOENO
A 20,000 gal r*cii*ina lank
8 60* ^ *i bra ling tcrttn
C 10,000 gal acid addition tank
0 B 000 gal Km* addition tank
C IO,OOa ooI ntvlHllnilon taitk
F 2-7000 tq ft hilwmltinl tend filttft
6 4000 gal ittviialltatfen lank
H Flhtf prtti
IOO Ib CafOHl,
G }-•-
AGIO SLUMS
NEUTRALIZED SLU06E
0 > 30«0ool
80C9< 460 la
TSS • 809 Ib
90O, '4 SOU
TSS >696lo
LIME SLUDGE
OEWATCRCD SUUOGE
BOO,' 44810
TSS * 19Jlb
CONVERSION MCTOES
gal. X 0.00379 » n3
In. X 2.94 • em
10.. ft. X 0.0929 « »2
en. )L X O.OZ83 i m5
0 >
800, '018
TSS : 15916
FILTRATE
0 • 2780gal\
BOO, < I2lb
TSS • « 116
RAW SEPTAGC
0'IO,OCOqal
SCREENINGS
0 > 80 f ol
SCREENED SEPTACE
0 • 9920fol
BOOj • 484 Ib
TSS < 73010
3001 b HaS04
AGIO SUPERNATANT
0 < 7<80gol
BOO, i 24 Ib
TSS » 24lb
2 3010 C4(OMI.
LIME SUPERNATANT
0 ' 6840 gal
8OO, ' 24 46
TSS « 4»
90 Ib H, SO*
NEUTRALIZED SUPERNATANT-FILTRATE
0 i 962Otal
BOO,' 36 ID
TSS
AOUEOUS EFFLUENT
0 t 9620«al
BOO,
TSS
Jib
lib
66o;2Cin^n^IP1i0t.ScalfftSaluations of Septa9fi Treatment Alternatives.'
ooo/z-78-164, September,, 1978.
EPA -
-------
Work Session: Residuals Management - Exercise II
This work session illustrates the principles involved in the design of a
septage treatment facility for the town of Uoodrock. The process flow diagram
on the next page illustrates the results of a pilot scale septage treatment
facility almost identical to that being proposed for Woodrock. The only
differences are the aqueous treatment (unit F) process and the quantity of
raw septage. In Woodrock the dewatered slude is being composted.
1) What is the daily septage generation rate for the town of •
Woodrock?
2) Based on the process flow diagram provided, how much acid and lime
will be requied to operate the Woodrock facility?
3) Based on the process flow diagram and the area requirements presented
on page 17 of the Septage Management Module, how much area is
required for the composting facility? 'Assume the following shape for
the septage layer.
4) What aeration rate is required? (See p. 17).
-------
Work Session: Residuals Management - Exercise III
This work session Illustrates some of the design considerations for
land application of septage.
1) Septage Storage Requirements: a) If has been decided that septage will
be applied to the land in 4 equal applications staged as follows: April 15,
June 15, August 15 and October 15. It is necessary to figure out the maximum
volume between applications so that the storage pond can be adequately'designed.
Using the following inflows determine necessary storage requirements.
Period Inflow
Oct. 15 - Apr. 15 836,850
. Apr. 15 - June 15 325,800
June 15 - Aug. 15 392,900
Aug. 15 - Oct. 15 469,450
b) How would storage requirements change if septage management practices
allowed for constant pumping throughout the year?
c) What might be in "optimal" septage pumping schedule given the application
schedule?
2} Septage Application Rates: The metholdology for determining application
rates is described in the accompanying manuscript. Use this methodology.and the
following assumptions to answer the following questions.
Assumptions:
Septage Characteristics as shown in Table 1, p. 4 of Septage
Management Module.
Crop to be grown: Reed Canary grass
Soil Cation Exchange Capacity: 10 meg/1 OOg.
Application Method: Sub-sod injection.
Amount of septage disposed of: 2.025 MGY
a) What is the annual nitrogen requirement for the selected crop?
b) How much ammonia nitrogen (in Ibs. per ton of dry solids) is pre-
sent in the septage? Considering the application method, how much of this
is available for plant us*?
-1-
-------
c) How much organic nitrogen (in Ibs. per ton of dry solids) is pre-
sent in the septage? . Us.ing the mineralization rates in the attached
methodology, how much organic nitrogen is available for plant usage? Perform
this calculation for the first four years of application.
d) Calculate the total amount of nitrogen available once the system
stabilizes at a constant availability.
e) Based on the results of 2.a and 2.d,what is the allowable septage
application rate?
f) How much cadmium (in Ibs. per ton of dry solids) is present in the
septage?
g) Using the 2 Ibs./acre/yr. allowable cadmium limit, what is the
allowable application rate?
h) Based on the results of 2.a and 2.g, what is the allowable application
rate?
1) How many tons of septage dry solids are produced annually in
Woodrock?
j) Based on the results of 2.h and 2.i, how much land is required for
septage disposal in Woodrock?
k) How much of each of the metals of concern (Pb, Zn, Cu, N1, Cd in
Ibs. per ton of dry solids is present in the septage?
1) Using'the maximum amount of metals allowed, as shown in Table 2, what
is the total allowable lifetime septage application for each metal.
m) Using the results of 2.1 and the application rate determined in 2.h,
what is the expected lifespan of the Woodrock septage disposal system?
-2-
-------
WORK SESSION: RESIDUALS MANAGEMENT - EXERCISE I - SOLUTIONS
1. Annual Septage Rate: 5,000 gals/day x 250 days/yr = 1.25 MGY
2. Construction: $650,000 Separate Treatment Facility
0 & M: $200.000
Total $850,000
3. a. Construction: $120,000 Wastewater Treatment Plant
0 & M: $580.000
Total $700,000
b. Construction: $ 0
0 & M: '$580.000
Total $580,000
c. Construction: $120,000 x .50 = $ 60,000
0 & M: $580.000
Total $640,000
4. Unit Hauling Costs Annual Cost* Present Worth
$ .50 $11,625 $122,000
$1.00 $23,250 $244,000
$2.00 $46,500 $488,000
$3.00 $69,750 $732,000
'Based on 93 miles/day or 23,250 miles/yr.
-1-
-------
5. a.
Unit Hauling Cost
$ .50
$1.00
$2.00
$3.00
Total PW for Treatment
at Wastewater Facility
$ 822,000
$ 944,000
$1,188,000
$1.432,000
Hauling Distance/Day
for which Separate
Facility is Cost
Effective
36 miles*
64 miles.
74 miles
^Present Worth of available hauling costs at which alternatives are
equal:
$944,000 - $850,000 = $94,000
Annual cost equivalency » $94,000/10.49 = $8960
Annual hauling distance = $8960/ $1.00/mi. = 8960
Daily hualing distance = 8960/250 = 36 mi/day
b.
Unit Hauling Cost
$ .50
SI. 00
$2.00
$3.00
Total PW for Treatment
at Wastewater Facility
$ 702,000
$ 824,000
$1,068,000
$1,312,000
Hauling Distance/Day
for which Separate
Facility is Cost
Effective
42 mi/day
74 mi/day
c.
Unit Hauling Cost
$ .50
$1.00
$2.00
$3.00
Total PW for Treatment
at Wastewater Facility
$ 762,000
$ 884,000
$1,128,000
$1,372,000
Hauling Distance/Day
for which Separate
Facility is Cost
Effective
6.5
35
66
-------
WORK SESSION: RESIDUALS MANAGEMENT - EXERCISE II - SOLUTION
1. 2,025,000 GPD/250 = 8100
2. Acid:
Chemical Conditioning j£§SL x 300 Ib = 243 Ib
Neutralization
8100
10,000
8100
10,000
x 50 Ib = 40.5 Ib
Total
283.5 Ib
Line:
Chemical Conditioning .81 x 250 = 202.5
Sludge Neutralization .81 x 100 • 81
Total 283.5
3. Average height of sludge layer: 2.5 feet
Assume R = 3
Sludge Production: .81 (44.5) = 36 cu. ft./day
or 36 x 20 = 720 cu. ft./4 weeks
Screenings: .81 (80)/748 = 8.7 cu. ft./day
or 8.7 x 20 = 174 cu. ft./4 weeks
Total Sludge = 900 cu. ft./4 weeks
Pad Area = (1.1) (900) (4) = 160Q sq ft>
£ »0
Processing Area = 1600 sq. ft.
Curing and Storage Area = 3200 sq. ft.
Total area required = 6400 square feet
-1-
-------
4. Aeration requirement is 500 ft /hr/ton of sludge (dry wt. basis).
Assuming a solids content of 20% or 20,000 mg/1.
The total dry solids being composted is
900 cu. ft. x 20,000 mg/1 x 28.3 1/cu. ft. x 2.2 x 106 Ib/mg
11,200 Ibs or 5.6 tons
Aeration requirements = 2800.ft3/hr
-2-
-------
WORK SESSION: RESIDUALS MANAGEMENT - EXERCISE III - SOLUTION
la.
Period Inflow Storage
Oct. 15 • Apr. 15 836,850 836,850
Apr. 15 application - 506,250 330,600
Apr. 15 - June 15 325,800 656,400
June 15 application • 506,250 150,150
June 15 - Aug. 15 392,900 543,050
Aug. 15 application - 506,250 36,800
Aug. 15 - Oct. 15 469,450 506,250
Oct. 15 application - 506,250 0
Storage requirements = 836,850 gallons or 111,900 ft '
Ib. Assuming constant pumping, J of the total annual septage would be
collected from Oct. 15-Apr. 15 resulting in a storage requirement
of 1,012,500 gallons or 135,400 ft3.
c. Apr. 15 Oct. 15 = 1,518,750 gallons
1,518,750/125 = 12,146 gpd
or about 10 tanks/day
Oct. 15 Apr. 15 = 506,250 gallons
4050 gpd
or about 3-4 tanks/day
Note: Such a schedule presents obvious managerial problems.
2a. From Table 1, for reed canary grass, the annual nitrogen
utilization rate - 226 Ib/acre.
2b. -Available Ammonia Nitrogen:
From Septage Management, Table 1:
Concentration (Nth-N) = 160 mg/1 .
Concentration (TS) = 38,800 mg/1
There is M""* NH3:"
Tnere 1S 38,600 mg TS
_ 160 Ibs NH3-N
or 38.800 Ibs TS x 2000 Ibs/ton =
825 Ibs NH3-N/ton of dry solids.
Since sub-sodsinjection is used, all of this is available.
-1-
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2c. Amount of Organic Nitrogen present:
Concentration (Org.N) = TKN-NH3-N = 680-160 = 520 mg/1
Concentration (TS) = 38,800 mg/1
There is 36 800 X 200° = *6*8 lbs Or9an1c N/ton of djy soll"ds-
The available amount is determined by the mineralization rate.
Year 1: 0.15 x 26.8 = 4.02 lbs Organic N/ton of dry solids.
The mineralization for subsequent years is 6%, 42 and 2% for
years 2, 3 and 4 respectively.
2d.
Year
1
2
3
4
NH3-N
8.25
8.24
8.24
8.24
Org-N
from
that .year
4.02
4.02
4.02
4.02
Org-N
from
previous
year
1.61
1.61
1.61
Org-N
from 2
years
previous
1.07
1.07
Org-N
from 3
years
previous
0.54
Total
lb- N/ton
of dry
solids
12.27
13.87
14.94
15.48
After year 4 the total amount available stabilizes at 15.5 Ibs/ton
of sludge: use this amount to determine the allowable application
.rate for full nitrogen utilization.
2e. Apportion R,te
226 IbN/acre
15.5 ibN/ton of dry solids
14.6 tons of dry solids/acre
2f. From Septage Management Table 1
Concentration (Cd) =0.71 mg/1
Concentration" (TS) » 38,800 mg/1
Amount of Cd
.71 Ib Cd • f
38,800 lb solids x 2000 Ibs/ton = 0.037 Ibs/ton of dry solids
-2-
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» ,. .. „ . Annual loading limit
2g. Application Rate ? ^^ Of cd
a 2 Ibs-Cd/acre
0.037 lbs-Cd/ton of dry solids
= 54.1 tons of dry solids/yr.
2h. Nitrogen is the limiting factor and the limiting application
rate is:
14.6 tons of dry solids/acre/yr
2i. 38,800 mg/1 x 2.025 x 106 gal/yr x 2.2 x 10"6 Ibs/mg x 3.78 1/gal
= 6.53 x 105 Ibs/yr
» 327 tons dry solids/yr
2j. Area requirement:
327 tons dry solids/yr-r 14.6 tons of dry solids/acre/yr
* 22.4 acres
2k. total Concentration Amount 21. Total allowable
(mg/1) (per ton of dry solids)* tons of sludge/
acre**
2326
198
758
5435
270
or lb pb/lb SQl1ds
.00022 Ib-Pb/lb solids x 2000 lb solids/ton solids
0.43 lb-Pb/ton of solids
**e.g for Pb: at a CEC of 10 the maximum allowable amount of
PB is 1000 Ib/acre
total application allowed over lifetime
• IQOOclb-Pb/acre 4-0.43 lb-Pb/ton of solids
= 2326 tons
-3-
Pb
Zn-
Cu
N1
Cd
*e.g.
8.4
49.0
6.4
0.9
0.71
for Pb: 8.4 mg Pb/1
38,800 mg solii
0.43
2.53
0.33
0.046
0.037
.. = 0 00022
ds/1 U*UUU"
nw i
lb
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2m. Step 1: Determine the limiting factor
From the above table the limiting constituent is Zn and the limiting
lifetime sludge application is 198 tons of dry solids/acre.
Step 2: Determine the lifespan of the site
lifespan = allowable total application 4. application rate
» 198 tons/acre -r 14.6 tons/acre/yr
* 13.6 years
-4-
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Methodology Used In Determining Annual Application Rates and System Life
A. Application Rates
The methodology used in determining sludge application rates recom-
mended for crop production are the same as for commercial fertilizer
application rates. Table IV-1 lists a varity of crops commonly grown
on land application systems and their respective nutrient requirements.
These nutrients (N, P and K) are needed for determining desired crop
yields and are the basis for fertilizer recommendations.
The application of sludges introduces nitrogen in two different forms.
Inorganic nitrogen (ammonia, nitrite and nitrate) is assumed available
for plant uptake immediately upon application. Organic nitrogen is con-
verted into plant-available inorganic forms at the rate of 152 the first
year, 62 the second year, 42 the third year and 22 the fourth year and there-
after. Therefore application rates are determined in accordance with the
nitrogen utilization rate of the specific crop grown in order to minimize
nitrogen groundwater contamination.
The amount of pi ant-avail able nitrogen added to soils by sludge is in-
fluenced by the application method used. When sludges are disposed of by
land spreading it has been reported that 50 percent of the applied inorganic
ammonia nitrogen (NH4-N) is lost to the atmosphere through ammonia volitiza-
tion. The sub-sod injection method injects the sludge into the soil, thus
losing little of the inorganic ammonia nitrogen to the atmosphere.
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Table IV-1
Annual Nitrogen, Phosphorus, and Potassium
Utilization by Selected Crops
Cropr
Yield Nitrogen
Phosphorus
. Potassium
Lb. per Acre
Corn
Corn silage
Soybeans
.
Grain sorghum
Wheat
Oats
Barl ey
Alfalfa
Orchard grass
Brome grass
Tall fescue
81 uegrass
Reed canarv crass
150 bu.
180 bu.
32 tons
50 bu.
60 bu.
8,000 Ib.
60 bu.
80 bu.
100 bu.
•100 bu.
8' tons
6 tons
5 tons
3.5 tons
"3 tons
7 tons
185
240
200
257t
336t
250
125
186
150
150
450+
300
166
135
200
226
35
44
315
21
29
40
22
24
24
24
35
44
29
29
24
30
178
199
203
100
120
166
91
134
125
125
398
311
211
154
149
AMI
282
Values reported above are from reports by the Potash Institute of America and
are for the total above-ground portion of the plants. Where only grain is re-
moved from the field, a significant proportion of the nutrients is left in the
residues. However, since most of these nutrients are temporarily tied up in the
residues, they are not readily available for crop use. Therefore, for the purpose
of estimating nutrient requirements for any particular crop year, complete crop
removal can be assumed.
^Legumes get most of their nitrogen from the air, so additional nitrogen sources
.are not normally needed.
Source: Knezek,Bernard D., and Sobert H. Killer, "Application of
Sludges *nd Wastewaters on Agricultural Land: A Planning and
Educational Guide," MCO-35, Denver, CO (March 1978).
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Annual sludge application rates are also governed by the amount of
cadmium applied. Load rates for cadmium on soils are set at 2 Ibs/acre
•year for food chain crops . This annual limit for cadmium Is based on
cadmium uptake by crops and the potential adverse effects on human
health.
8. Annual Application Rate Criteria
Annual septage application rates for the proposed Town of Woodrock land
application systems were determined by criteria set forth by the Organic
Recycling Waste Commission . The following outlines the guidelines for
the application of municipal sewage sludges on agricultural lands
Guidelines - Nitrogen
1. Obtain N fertilizer recommendation of N requirement of crop
A Ibs/acre
2. Calculate the available organic N and NH^-N in the sludge
using the following formulas:
- Available NK4*-N « X MH4*-H x 20 x f - B Ibs/ton of sludge
f » fraction of NH4*-N retained after application
Surface Application f 3 0.5
Sub-sod Injection f « 1.0
- Available organic-N = f organic-N x 20 x mineralized rate
« C Ibs/ton of sludge
(nineralized rate for first s 0.15)
-------
3. Calculate residual sludge N in soil a 0 Ibs/acre if
soil has received previous sludge applications.
- Mineralization rate » 0.06 first year
- Mineralization rate • 0.04 second year
- Mineralization rate * 0.02 third year
4. Calculate sludge application rate in tons of dry solids
per acre as:
N Required A - Residual N D
Tons of sludge/acre
Available organic-N C +
Available NH4+-N B
Guidelines - Cadmium
1. Obtained cadmium concentration In sludge
A mg/kg of dry solids
2. Calculate the amount of cadmium in sludge by the following
formula:
B cadmium 1n septage Ibs/ton of dry solids = A /SCO
3. Annual cadmium loading limit 2 Ibs/acre
4. Calculate sludge application rate in tons of dry solids per
acre as:
2 Ibs/Cd/acre
Tons of sludge/acre s
B Ibs/ton of dry solids
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C. System Lifespan
The lifespan of an application system is based upon the cumulative
amounts of lead (Pb), copper (Cu), nickel (N1), zinc (Zn) and cadmium
(Cd) applied to the soil. Maximum application loadings suggested by
the Environmental Protection Agency are listed in Table IV-2. It
should be noted that those loadings are cumulative loadings and are
a function of the soil's cation exchange capacity. When one of the
trace elements is loaded to its maximum allowable limit, septage
disposal at the site should be terminated.
D. System Lifespan Criteria
The following section contains the-criteria used in determining the
useful lifespans of both the land spreading and sub-sod injection sys-
tems using the EPA guidelines.
Criteria set forth by EPA
Zn-Cu-NI-Pb-Cd
1. Obtain Zn, N1, Cu, Pb, and Cd concentrations in sludge
expressed In mg/Vg of dry solids
2. Calculate total tons of sludge that can be applied without
exceeding loading limits presented in Table IV-2, by
the following formula:
loading limit
To±al tons of sludge/acre »
metal concentration x 0.002
The lowest value from above equation is the sludge appli-
cation limit.
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Table IV-2
Total Amount of Sludge Metals
Allowed on Agricultural Land
Soil Cation Exchange Capacity (meg/1OOg)
Trace Element Maximum Amount of Metal (Ib/Acre)
Pb
Zn
Cu
N1
Cd
0-5
500
250
125
125
5
5-15
1000
500
250
250
10
15
2000
1000
500
500
20
* Determined by the pH 7 Ammonium Acetate Procedure
Source: Xnezek, Bernard 0., and Robert H. Miller, "Application
of Sludges and Uastewaters on Agricultural Land: A
Planning and Educational Guide", MCD-35, Denver, CO
(March 1978).
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