United States
Environmental Protection -
Agency
Office of Water March 1975
Program Operations (WH-547) 430/9-74-001
Washington, DC 20460
Water
&EPA Wastewater Treatment Ponds
MCD-14
-------
Disclaimer Statement
This report has been reviewed by the Environmental Protection Agency and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
NOTES
To order this publication, MCD-14, "Wastewater Treatment Ponds," write
to:
General Services Administration (8BRG)
Centralized Mailing List Services
Building 41, Denver Federal Center
Denver, Colorado 80225
Please indicate the MCD number and title of publication.
-------
US ENVIRONMENTAL PROTECTION AGENCY
TECHNICAL BULLETIN
WASTEWATER TREATMENT PONDS
(Supplement to Federal Guidelines:
Design, Operation and Maintenance
of Wastewater Treatment Facilities)
1. PURPOSE: ...'-- '
This Bulletin presents technical information which will be used
by US EPA Regional Administrators to review grant applications involving
wastewater treatment ponds.
2. RELATED PUBLICATIONS:
This Bulletin supplements the Federal Guidelines Design, Operation,
and Maintenance of Municipal Wastewater Treatment Plants. Additional
design information can be found in EPA Technology Transfer publications:
1. Upgrading Lagoons, EPA-625/4-73-0016, Aug. 1973 (1)
2. Performance and Upgrading of Wastewater Stabilization Ponds,
US EPA Technology Transfer Design Seminars, 1977 (3)
3. Process Design Manual: Wastewater Treatment Facilities for
Sewered Small Communities, EPA-625/1-77-009, Oct. 1977 (42)
4. Process Design Manual: Design of Municipal Wastewater
Stabilization Ponds (in preparation, ERIC, US EPA,
Cincinnati, OH)
Operation and maintenance information can be found in:
5. Operations Manual - Stabilization Ponds, EPA-430/9-77-012,
August 1977
3. TERMINOLOGY:
A wide variety of often conflicting terms is used to describe
wastewater treatment ponds. .For the purpose of this Bulletin a waste-
water treatment (stabilization) pond is defined as a basin within
which natural stabilization processes occur. The oxygen necessary to
sustain some of these processes can come from photosynthetic and/or
mechanical sources. Ponds are also characterized by the hydraulic flow
pattern in use. The following terminology is used for the ponds
discussed in the Bulletin:
-------
A. Oxidation Pond - A pond which is aerobic throughout. The
depth is shallow to permit light penetration to support the
photosynthetic activity of contained algae. The oxygen
sources to support aerobic stabilization are from algae
activity and wind action at the liquid surface.
B. Facultative Pond - A pond having an aerobic zone near the
surface with a gradient to anaerobic conditions near the
bottom. Oxygen sources are the same as described for
oxidation ponds, but the oxygen provided cannot maintain total
aerobic conditions in the deeper facultative pond. These are
the most common types of domestic waste stabilization ponds in
the U.S.
C. Aerated/Partial Mix Pond - A pond designed for mechanical
aeration as the oxygen source. The mixing intensity is not
sufficient to keep all solids in suspension. As a result,
there will be some sludge deposition and related anaerobic
zones at or near the pond bottom. The incomplete mixing also
permits light penetration and can result in significant algae
growth at times. Algae and turbulence at the liquid surface
will provide some dissolved oxygen (DO), but the design is
usually based on mechanical aeration as the sole oxygen source.
D. Aerated/Complete Mix Pond - A pond designed for mechanical
aeration as the oxygen source, and also with sufficient mixing
intensity to keep solids in suspension. Algae will generally
not be a factor due to the turbulent conditions and lack of
light penetration.
Many complete mix ponds are actually designed as a variation
of the activated sludge process including clarification and
sludge recycle. Such complete mix systems must continue to
satisfy the basic secondary treatment requirements of 40 CFR,
Part 133. However, pond systems that might have a complete/
mix aeration cell (for odor control or partial oxidation of
strong wastes) followed by partial mix or facultative cells
could be subject to the suspended solids criteria presented in
this bulletin.
E. Continuous Discharge Pond - A pond designed without imposed
constraints on discharge. The actual discharge may be inter- •
mittent due to low seasonal flow or seasonal evaporation, etc.,
but the design would permit continuous unrestricted discharge.
All of the ponds described above (A, B, C, D) can be designed
for this mode of operation.
-------
F. Controlled Discharge Pond - A pond designed to retain the
wastewater without discharge for a significant period of time
(6 months to one year). Discharge is then planned for a
relatively short period (1-3 weeks) when pond characteristics
are compatible with receiving water conditions. It might be
possible to design any of the ponds defined above (A, B, C, D)
for this mode of operation. However, the long detention
period reduces the need for mechanical aeration so this mode
of operation is most commonly found with facultative ponds.
G. Complete Retention Pond - A pond designed for evaporation
and/or seepage as the hydraulic pathway so there is no
discharge to surface waters. The method may be acceptable in
locations having suitable climatic conditions and with proper
regard for ground water protection, odor control, and water
rights. These ponds would be similar in configuration to the
previously described oxidation type having a shallow depth and
large surface area to provide maximum potential for evapora-
tion. Another type of "no discharge" pond would be a component
in a land treatment system. These are discussed in a later
section of this Bulletin.
Typical design factors for these different types of ponds are
summarized in Table 2.
4. USE OF THE CRITERIA:
Projects involving waste treatment ponds proposed for Federal
financial assistance from EPA will be based on the criteria contained in
this Technical Bulletin. Approval can be given to different designs if
reasonable assurance can be given to the EPA Regional'Administrator that
satisfactory performance will be achieved.
The criteria in this Technical Bulletin are intended to provide a
typical baseline of engineering practice, and must be applied with
engineering judgment on a case-by-case basis. The EPA Regional Admini-
strator will review each project to identify and resolve additional .
factors important to the design of a specific project. Responsibility
for satisfactory performance, however, remains with the grant applicant.
It is the policy of EPA to encourage the use of innovative technol-
ogy. Such technology may be eligible for an increased percentage of
federal funding as defined by section 202(a)(2) of the Clean Water Act
of 1977 (P.L. 95-217). EPA Regional Administrators will give full
consideration to innovative technologies which may not be included in
this Bulletin.
-------
5. PERFORMANCE REQUIREMENTS:
The Federal Water Pollution Control Act Amendments of 1972 (PL 92-
500) established the minimum performance requirements for publicly
owned treatment works. Section 301(b)(l)(B) of that Act requires that
such treatment works must, as a minimum, meet effluent limitations based
on secondary treatment as defined by the EPA Administrator. The EPA
published information on secondary treatment in August 1973 in 40 CFR
Part 133.(4). This contained criteria for biochemical oxygen demand
(BOD), suspended solids (SS), fecal coliform bacteria and pH. Sub-
sequently, the requirements for fecal coliform were deleted from 40 CFR
Part 133 on July 25, 1976, leaving BOD, SS, and pH as originally defined.
Wastewater treatment ponds have historically been accepted as a
secondary treatment process and have been particularly advantageous for
smaller communities. Treatment performance with respect to BOD removal
has been generally acceptable if ponds were conservatively designed and
properly operated. Treatment performance with respect to suspended
solids is often complicated by the presence of algae cells in the pond
effluent. After considerable study and discussion the EPA published
revised suspended solids limitations for wastewater treatment ponds on
October 7, 1977.
The effluent criteria currently applicable to wastewater treatment
ponds are:
(a) BODs - The arithmetic mean for 30 consecutive days shall not
exceed 30 mg/1 or 85% removal, whichever results in the lesser
effluent concentration.
The arithmetic mean of the values for 7 consecutive days shall
not exceed 45 mg/1.
(b) Suspended Solids - Wastewater treatment ponds which are the
sole process for secondary treatment and with maximum facility
design capacity of 2 MGD or less and which meet the BOD
limitations as prescribed by 40 CFR 133.102(a), are required
to meet an effluent limitation for suspended solids in accord-
ance with values set by the state or appropriate EPA Regional
Office. The current values set by the States and Regional
Offices are listed below. These values correspond to a 30 day
consecutive average or an average over the period of discharge
when the duration of the discharge is less than 30 days. In
some cases States have developed additional values, such as
weekly averages or daily maximums for compliance monitoring
purposes. These additional values are not indicated in the
chart below.
-------
TABLE 1
Location
Alabama
Alaska ;
Arizona
Arkansas
California
Colorado
Aerated. Ponds
All others
Connecticut
Delaware
District of Columbia
Florida
Georgia
Guam
Hawaii
Idaho T
Illinois
Indiana .
Iowa •••".".
Controlled Discharge, 3 cell
All others
Kansas
Kentucky
Louisiana
Maine
Maryland.
Massachusetts
Michigan
Controlled Seasonal Discharge
Summer
Winter
Minnesota
Mississippi
Missouri. -. " .
Montana
Nebraska . -
Suspended Solids Limit
(mg/1)
90 :•••-.-'
70 •"
90
90 : ..
95
75
105
- NIC.
N.C. .
N.C.
N.C.
90 •.-•'•
N.C. .
N.C. ••.••-..
. N.C.
, 37
70
case-by-case but not greater
than, 80 .
80 '
80
N.C.
90 ••-..-.
45
"90
- N.C. ' ' :. •
70
40
N.C.
90
80
100
80
-------
River
River
North Carolina
North Dakota
North & East of Missouri
South & West of Missouri
Nevada
New Hampshire
New Jersey
New Mexico
New York
Ohio
Oklahoma
Oregon
East of Cascade Mts.
West of Cascade Mts.
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
East of Blue Ridge Mts.
West of Blue Ridge Mts.
Eastern slope counties
Loudoun, Fauquier, Rappahannock
Green, Albemarle, Nelson
Bedford, Frank!in.
Madison;
Amherst.
Virgin Islands
Washington
West Virginia
Wisconsin
Wyoming
Trust Territories
Notes:
Patrick
& N. Marianas
90
60
100
90
45
N.C.
90
70
65
90
85
50
N.C.
N.C.
45
90
110
100
90
N.C.
55
60
78
case-by-case
application of 60/78
limits
N.C.
75
80
60
100
N.C.
1. N.C. - no change from existing criteria
2. The values set for Iowa and Virginia incorporate a
specific case-by-case provision; however, in accordance
with 40 CFR 133.103(c), adjustments of the suspended
solids limitations for individual ponds in all states are
to be authorized on a case-by-case basis.
-------
3. The values tabulated above can be considered as interim.
:• Further revision and refinement will be possible as additional
data becomes available.
4. Wastewater treatment ponds with a maximum facility design
capacity in excess of 2 MGD will have to satisfy the basic
suspended solids requirements of 40 CFR Part 133 (i.e.: 30
mg/1 or 85% removal on a 30 day average and, 45 mg/1 on a
7 day average). Other ponds that are not eligible for an
adjustment in suspended solids limitations include: basins or
ponds used as a final polishing step for other secondary
. treatment systems and ponds which include complete-mix
aeration and sludge recycle since these systems are in essence
a variation of the activated sludge process.
(c) pH - The effluent values for pH shall remain within the range
of 6.0 to 9.0, unless variations are due to natural causes
(i.e.: natural pH of wastewater and/or phenomena resulting
from biological activity in the pond). Adjustment of pH is
only required where inorganic chemicals are added for treat-
ment or contributions from industrial sources cause the pH .'
to be outside the range of 6.0 to 9.0. •
More stringent performance requirements than defined above may be
necessary to meet other criteria such as State water quality standards,
including disinfection requirements. In such cases the criteria
contained in this Bulletin will have to be adjusted accordingly.
• " ~ - / . ' ' _. ..,..'.. •
6. BACKGROUND: ; '.
There are more than 5,000 publicly owned wastewater treatment ponds
in the United States. Generally, these ponds are located in small com-
munities and are designed for flows less than 2 MGD., Ponds have been
used where land is available because operation is simple and operating
costs are small. The low energy requirements of these systems are
particularly attractive. The great majority of the existing systems are
continuous flow facultative or oxidation ponds.
There is a wide variation in the design of these systems; and until
recently comprehensive performance data were lacking. An extensive
evaluation of four facultative and five aerated ponds supported by the
EPA has provided considerable information on the capabilities of these
studies and is available from the Municipal Environmental Research
Laboratory, US EPA, Cincinnati, Ohio 45268. A brief .summary of these
studies can be found in the reference (3) previously cited.
-------
Regarding the ability of continuous flow facultative and oxidation
ponds to meet secondary treatment requirements the data indicate that:
(a) The BOD level in general is satisfactory and could be achieved
in all cases by improved design. Natural oxygen sources (i.e.:
algae, surface turbulence) are reduced or eliminated during the
winter in ice covered ponds. The BOD levels would not be met
under these conditions for short detention time systems.
(b) The suspended solids level is generally not achieved because
of the algae in the effluent.
(c) The pH of the effluent varies markedly depending on alkalinity
C02 relationships. The variation is, however, rarely sufficient
to require pH adjustment.
Aerated ponds with properly designed suspended solids separation can
meet the adjusted requirements. Since partial-mix systems permit some
algae growth, suspended solids can be high at times.
Controlled discharge ponds have been used in northern climates
and can meet the requirements if properly operated. Such ponds and
other long retention, multiple cell systems achieve significant reduc-
tions in fecal coliform levels. A fecal coliform concentration of
approximately 200/100 ml can be achieved without disinfection if ade-
quate hydraulic residence times are provided.
As indicated above, the responsible factor for suspended solids
performance in the general case was algae. Algae are naturally present
in wastewater treatment ponds and the non-aerated types are specifically
designed to rely on photosynthetic oxygenation. Algae cells, which are
an integral part of the treatment system, do not settle readily and may
be carried out of the pond as suspended solids in the effluent. Methods
for removing algae from pond effluents have been developed and are
described in a later section.
Each state had the options to retain current values, to determine
an adjusted value for the entire state, or to determine several values
for appropriate contiguous geographical areas. As shown in Table 1,
all three options were utilized by various states. The basic proce-
dures to determine these adjusted values were conducted by the states,
with the assistance of the applicable EPA Regional Office if needed.
Only those ponds meeting the BOD requirements were eligible for
inclusion in the statistical analysis. The new suspended solids value
was to be equal to the effluent concentration achieved 90% of the time.
-------
In some cases the data base for the analysis was quite limited and in .
all cases additional data are being collected. A periodic re-evaluation
of this expanding data base could result in further changes so the
values are considered "interim."
7. DESIGN FEATURES: • ..-.'.;.-....
Typical design parameters for continuous flow ponds are given in .
Table 2. 1 .
Most existing wastewater ponds were designed within the range of
parameters listed in Table 2. There are many local modifications ,
employed. It is not uncommon for state agencies and EPA regions to have
specific criteria for pond design. Several attempts have been made to
develop a more rational basis for facultative pond design and are
available in the engineering literature (31,29,38). None of these can
be used to consistently predict performance of actual ponds in a variety
of settings. The probable cause is the variations in hydraulic residence
times that occur in actual systems. Until methods are available to more
accurately define hydraulic residence time, pond design will probably
remain an empirical procedure based on successful past experience.
The unique features of controlled discharge ponds are long term
retention and periodic, controlled discharge usually once or twice a
year. Ponds of this type have operated satisfactorily in the north central
U.S. using the following design criteria:
Overall organic loading: 20-25 pounds BODs/acre.
Liquid depth: not more than 6 feet for the first cell, not more
than 8 feet for subsequent cells.
Hydraulic detention: At least 6 months above
level (including precipitation), but not less
ice cover.
the 2 foot liquid
than;the period of
Number of cells: At least 3 for reliability, with piping
flexibility for parallel or series operation.
The design of the controlled discharge pond must include an analysis
showing that receiving stream water quality standards will be maintained
during discharge intervals, and that the receiving watercourses can
accomodate the discharge rate from the pond. The design must also include
a recommended discharge schedule.
-------
O)
«=C Q.
O -P
•r- re
•p -P
re r—
5 3 "-
x re
o u.
u.
o
o
i-D
(U
o
jQ
E S- «C
O
O
IO
o
CM
CO
o
CM
CO
•o
O)
•p
re
-------
Selecting the optimum day and hour for release of the pond contents
is critical to the success of this method. The operation and main-
tenance manual must include instructions on how to correlate pond dis-
charge with effluent and stream quality. The pond contents and stream
must be carefully examined, before and during the release of the; pond
contents. •'••"' "' " '' ; . -•"•.••/.• .
In a typical program, discharge of effluents follows a consistent
pattern for all ponds. The following steps are usually taken:
(a) Isolate the cell to be discharged, usually the final one in
the series, by valving-off the inlet line from the preceding
. . • cell. . * • . • • .-.._ ... ,..•.;.-:• .., . ...
;(b) Arrange to analyze samples for BOD, suspended solids, volatile
suspended solids, pH, and other parameters which may be
required for a particular location.
(c) Plan to work so as to spend full time on control of the dis-
charge throughout the period.
(d) Sample contents of the cell to be discharged for dissolved
oxygen, noting turbidity, color, and any unusual conditions.
(e) Note conditions in the stream to receive the effluent.
(f) Notify the state regulatory agency of results of these obser-
vations and plans for discharge and obtain approval.
(g) If discharge is approved, commence discharge and continue so
• long as weather is favorable, dissolved oxygen is near or above
saturation values and turbidity is not excessive following the
prearranged discharge flow pattern among the cells. Usually
this consists of drawing down the last two cells in the series
(if there are three or more) to about 18-24 inches after isola-
tion; interrupting the discharge for a week or more to divert
raw waste to a cell which has been drawn down and resting the
initial cell before its discharge. When this first cell is
drawn down to about 24 inches depth, the usual series flow
pattern, without discharge, is resumed. During discharge to
the receiving waters samples are taken at least three times
each day near the discharge pipe for immediate dissolved oxygen
analysis. Additional testing may be required for suspended
solids. ••'--•- , ..'.'"•
11
-------
Experience with these ponds is limited to northern states with
seasonal and climatic influences on algae growth. The concept will be
quite effective for BOD removal in any location and, if suspended solids
are within the limits given in Table 1, it should be effective in warmer
climates. The process will also work with a more frequent discharge
cycle than semi-annually, depending on receiving water conditions and
requirements. Operating the isolation cell on a fill and draw batch
basis is similar to the "phase isolation" technique discussed in a later
section for pond upgrading.
The design of partial mix aerated ponds is commonly based on first
order reaction rate equations for completed mixed flow even though by
definition the ponds are not completely mixed. As indicated in Table 1
at least 3 cells are usually provided. The aeration is usually tapered
with higher intensity near the inlet of the first cell and a quiescent
zone near the end of the final cell.
The detention time or pond volume is based on the low temperature
winter time reaction rates. The oxygen requirements are based on the
higher temperature summer reaction rates. No allowance is made for
photosynthetic oxygenation even though algae will be present. An
allowance must be made for sludge accumulation and for winter ice forma-
tion in northern climates. In Alaska, which might represent the worst
case, an allowance of 5% is made for sludge storage and 15% for ice forma-
tion in calculating total pond volume. The total depth of the pond is
then based on the requirements for the type of aeration equipment
chosen. Special attention is required for design of surface aerators in
cold climates because of ice problems.
Partial-mix ponds may have high suspended solids on an infrequent
basis due to algae. If these values exceed the limits given in Table 1
it may be possible to operate the final cell in an intermittent discharge
mode during algae blooms.
Complete retention ponds may be feasible in locations with low cost
land and high evaporation rates. Many existing complete retention
systems probably depend to a greater degree than is desirable on seepage.
Many states are adopting increasingly stringent seepage requirements for
wastewater pond systems.
Design features common to most pond systems include earthen dikes
and inlet and outlet works. Designs can usually be based on a balanced
cut and fill so that most of the excavated material can be used in dike
construction. Outside slopes of dikes are usually 3:1 or flatter to
permit grass mowing. Inside slopes are steeper, ranging from 2:1 to
3:1. When the size of pond cells are much greater than 10 acres or if
12
-------
the system is in a particularly windy location the inside slopes of the :
dikes should be protected from wave erosion. Membrane liners are easily
punctured and some are sensitive to solar radiation so it is common •
practice to. overlay at least the above water portion with soil and rip
Tap. , - '"'''-: ' : ' -••'•''•. •..-'.-•••;•• ' .:".:.' ; ' -
The inlet structure for small ponds is generally at the center.
For large ponds the use of inlet diffusers with multiple outlet; ports is
desirable to distribute suspended solids over a larger area. Transfer
and outlet structures should permit lowering the .water/level at a rate
of less than 1 foot per week when the facility is receiving its normal
load. Manhole type structures are commonly used with either valved
piping or adjustable "stop log" type overflow gates used ,tp control
depth. " ;
8. GENERAL CONSIDERATIONS: ; .
The following criteria apply to the waste treatment ponds covered
in this Bulletin. ... .. ...... , ... ,
, (a) Pathogen Control . ' ' ; "
Natural die-off of pathogens is very effective in long
..retention time facultative and controlled discharge ponds.
.: Fecal col iform concentrations of approximately 20.0/100 ml can ..-
be achieved without disinfection if adequate hydraulic residence
times are provided. A positive disinfection technique may be
^ necessary for ponds to comply with site specific discharge
requirements. Chlorination can achieve the required : fecal
coli form reductions. A mathematical model designed to be
applicable to most pond systems, along with monographs which
can.be used to calculate chlorine dosages to yield adequate
residuals without lysing algae cells, is presented in reference
(b) Control of Short Circuiting
• Short circuiting of flow occurs to varying degrees in most
existing ponds. In a study of a multiple cell system, it was
found that the actual detention time in the cells varied from
25 to 89 percent of the theoretical design detention time, (27).
The use of multiple cells operated in series and multiple
:.. port inlet structures is effective in reducing short circuit-
ing. In-basin baffles can also ^be effective but special
attention is required. in northern climates to avoid problems
13
-------
with ice. Multiple cells are probably the most effective
approach. No less than 3 cells will be provided for ponds
covered by this Bulletin.
(c) Seepage Control
Lining of the pond bottom and inner dike surfaces may be
necessary if compaction of the in-situ soils does not produce
an acceptable level of impermeability. In general, all of the
states in the U.S. require protection of the beneficial use of
ground water beneath a pond. Only a few states define a specific
seepage limitation. Most states do not have a specific value
but decide on a case-by-case basis for protection of ground water.
Lining materials range from locally available clays, bentonite,
asphalt, concrete, soil cement, and various membranes. Some
of the low seepage rates required would be difficult to achieve
with soil stabilization techniques so constructed liners or
membranes might be necessary. Reference (28) describes in
complete detail techniques for pond lining.
(d) Sludge Accumulation
Sludge will accumulate to varying degrees on the bottom
of all of the ponds covered by this Bulletin. Most of the
accumulation will occur at or near the inlet structures.
Decomposition of these benthic sludge deposits is via anaero-
bic processes. This sludge can in time exert a significant
oxygen demand on the system. The problem is particularly
critical in northern temperate climates where a temperature
induced "turnover" of pond contents can occur in the spring
and fall of each year. This "turnover" can resuspend some of
the benthic material and result in odor as well as temporary
effluent quality problems.
Sludge will accumulate at faster rates in ponds in cold
climates since the low winter temperatures inhibit the anaero-
bic reactions. In Alaska, which is probably the worst case, it
is common practice to reserve up to 5% of the design volume
for sludge accumulation.
9. UPGRADING TECHNIQUES:
Algae removal may still be necessary for: ponds greater than 2 mgd
capacity, ponds not meeting the BOD requirements and ponds discharging
to water quality limiting stream segments. A number of techniques for
upgrading have been studied in recent years.
14
-------
(a) Land Application
Land application of pond effluents is an excellent
technique for final treatment. Reference (22) discusses in
detail the basic land treatment modes and variations.
Wastewater treatment ponds and/or treatment storage pond
combinations are often the most cost effective way to achieve
the preapplication treatment levels recommended by EPA prior
to the final land treatment step.
(b) Conversion to Controlled Discharge
An existing continuous discharge pond can be converted
to a controlled discharge pond if the previously outlined
conditions are met. Usually additional land area will be
required to obtain the volume required for controlled
discharge.
(c) Intermittent Sand Filtration
Experimental research and practical operation of full
scale facilities has demonstrated the effectiveness of inter-
mittent sand filtration for upgrading lagoon effluents. As
with all wastewater treatment systems, performance is dependent
on proper operation and maintenance. However, less operator
skill and manpower is required for operation of intermittent
sand filters than with most other upgrading systems. Experience
indicates that a high quality effluent may be achieved at a
relatively low cost. Intermittent sand filtration is not a
new technique. Rather, it is the application of an old
technique to the problem of upgrading lagoon effluents.
Intermittent sand filtration is similar to the practice of
slow sand filtration in potable water treatment or the slow
sand filtration of raw sewage which was practiced during the
early 1900's. Intermittent sand filtration of lagoon effluents
is the application of lagoon effluent on a periodic or inter-
mittent basis to a sand filter bed. As the wastewater passes
through the sand filter bed, suspended solids and organic
matter are removed through a combination of physical straining
and biological degradation processes. The particulate matter
collects in the top 5 to 7.5 cm (2 to 3 inches) of the sand
filter bed. This buildup of organic matter eventually clogs
the top 5 to 7.5 cm (2 to. 3 inches) of the sand filter bed and
prevents the passage of the effluent through the sand filter.
The sand filter is then taken out of service and the top layer
of clogged sand is removed. The sand filter is then put back
into service and the spent sand is either discarded or washed .
and used as replacement sand for the sand filter.
15
-------
The development of intermittent sand filtration to
upgrade lagoon effluents has been demonstrated with pilot
scale and full scale systems treating effluents from facul-
tative, aerated, and anaerobic ponds. Typical design criteria
for full scale systems are given in Table 3. References (3),
(14) should be consulted for details.
Table 3. Design Criteria for Full
Systems at Mount Shasta,
and Ailey, Georgia
Scale Intermittent Sand Filter
California; Moriarty, New Mexico;
Parameter
Design Q (mgd)
Lagoon Type
Filter Area (acre)
No. Filters
Hydraulic Loading (mgad)
Effective Size (mm)
Uniformity Coeff.
Mount
Shasta
1.2
Aerated
0.5
6
0.7
0.37
5.1
Mori arty
0.4
Partial mix aerated
0.082
8
0.6
0.20
4.1
Ai 1 ey
0.08
Facultative
0.14
2
0.4
0.50
4.0
(d) Rock Filter
The rock filter is essentially a porous rock embankment
at the end of a pond system through which the pond effluent is
allowed to flow. Suspended solids settle out on the rock
surfaces and in the void spaces and then are biologically
degraded. Typical filter construction uses rocks greater than
1 inch and less than 5 inches in diameter with most of the
rocks approximately a 2 inch size. Recommended hydraulic
loadings range from 9 gallons/ft3/day in warm weather to 3
gallon/ft3/day in cold weather. Reference (3) should be
consulted for details.
(e) Chemical Treatments
Chemical treatments for coagulation-flocculation and
settling of suspended solids have been tried with pond systems
with success. Both external mechanical treatments and in-pond
treatments have been demonstrated.
16
-------
Coagulation followed by sedimentation, and possibly
filtration, has been used extensively for the removal of
. suspended and colloidal material from water. In the case of
the chemical treatment of wastewater treatment pond effluents
the data are not comprehensive (12). Lime, alum, and ferric
salts are the most commonly used/coagulating agents. Because
of the many variables, a pilot testing program will usually be
necessary to ensure proper operation of the system. There
must be a satisfactory method of ultimate disposition of . .•
resultant sludges. Unless designed for constant flow, close
control of the process is required to obtain satisfactory :
performance. Depending on the alkalinity of .the wastewater,
the operating cost of the chemicals for this method can be
relatively high. Additional information is contained in
references; (1), (2), (18), (12), (24), and (25). • "
In-pond chemical treatment in a controlled discharge pond
has been sucessfully demonstrated in Canada. Techniques using '
high concentrations of chlorine with a long contact time
followed by settling and filtration have also been shown to
reduce algae suspended solids.
(f) Natural In-Pond Removal :
A technique called "phase isolation" for algae removal
has been studied. It was developed in the pond system serving
the city of Woodland, CA., and consists of a batch fill,and
draw operation with a detention time of two to three weeks.
The results of studies on the Woodland system indicated that
the process was not consistent. Wind action resuspended
bottom deposits at\times and in late summer and early.fall
different types of algae developed that would not settle.
Suspended solids in the effluents ranged from less than 30
mg/1 to over 60 mg/1. , •
Other natural approaches include the use of filter-feeding
fish for algae removal and other techniques in the emerging
aquaculture technology. The use of aquatic plants such as >
hyacinths and duckweed has been shown to control algae deve-
lopment. The mechanism is the shading effect of these floating
plants which restricts the light transmission needed for algae
growth. Supplemental aeration is then usually required to
maintain desired oxygen levels in the pond. '-•": V
17
-------
(g) Mechanical Removal
Techniques in this category would include centrifugation,
microstraining with a 1 micron polyester fabric, dissolved air
flotation and granular media filtration. All have been
successfully demonstrated. References (3), (27) contain specific
details.
10. FUTURE ACTION:
The information contained in this Bulletin will be modified as
additional field experience becomes available. Those having such
information are encouraged to submit it to the Director, Municipal
Construction Division (WH-547), Office of Water Program Operations,
Environmental Protection Agency, Washington, D.C. 20460.
11. BIBLIOGRAPHY:
(1) Upgrading Lagoons, by D. H. Caldwell, S. D. Parker, and W.R. Uhte.
Prepared for the EPA Technology Transfer Program. August 1973.
(2) Upgrading Existing Lagoons, by R. F. Lewis and J. M. Smith.
Prepared for the EPA Technology Transfer Program. October 1973.
(3) Performance and Upgrading of Wastewater Stabilization Ponds by
E. J. Middlebrooks, J. H. Reynolds, and C. H. Middlebrooks.
Prepared for the EPA Technology Transfer Program. January 1977.
(4) Secondary Treatment Information, 40 CFR Part 133, 38 FR 22298
August 17, 1973; amended 41 FR 30786, July 26, 1976; amended
42 FR 54664, October 7, 1977.
(5) Waste Treatment Lagoons - State of the Art, by Missouri Basin
Engineering Health Council. EPA Research Report 17090 EHX 07/71
July 1971.
(6) Wastewater Engineering, by Metcalf and Eddy, Inc.
Book Company. 1972.
McGraw-Hill
(7) Technical Bulletin: Design Criteria for Mechanical, Electric, and
Fluid System and Component Reliability, Office of Water Program
Operations. EPA Publication 430-99-74-001. 1973.
(8) Echelberger, W. F., J. L. Pavoni, P. C. Singer, and M. W. Tenney,
Disinfection of Algae Laden Waters," Journal of the Sanitary
Engineering Division, ASCE, Vol. 97, No. SA 5. October 1971
18
-------
(9) Horn, L., "Ch1 orination of Waste Pond Effluent," 2nd International
Symposium for Waste Treatment Lagoons, edited by Ross E. McKinney
for Missouri Basin Engineering Health Council. 1970.
'(10) Waste Stabilization Lagoon Micro-organism Removal Efficiency and
Effluent Disinfection With Chlorine, by B. A. Johnson, J: L.
Wright, D. S. Bowles, J. H. Reynolds, and E.J.* Middlebrooks.
Contract Number 68-03-2151, Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, Cincinnati,
Ohio 45268.
(11) Removal of Algae from Waste Stabilization:Pond Effluents - A State
of the Art, by V. Kothandaraman and R. L. Evans. Illinois State
Water Survey Circular 108, Urbana, Illinois. 1972.
(12) Evaluation of Techniques for Algae Removal from Wastewater
Stabilization Ponds by E. J. Middlebrooks, D. B. Porcells, R. A.
Gearheart, G. R. Marshall, J. H. Reynolds, and W. J, Grenny. Utah
Water Research Laboratory, Utah State University, Logan, Utah.
January 1974. :
(13) Intermittent Sand Filtration to Upgrade Existing Wastewater Treat-
ment Facilities, by G. R. Marshall and E. J. Middlebrooks. Utah
Water Research Laboratory, Utah State University, Logan, Utah.
February 1974.
(14) Separation of Algae Cells from Wastewater Lagoon Effluenting
Volume I, Intermittent Land Filtration to Upgrade Waste Stabili-
zation Lagoon Effluent, by S. E. Harris, D. S. Filip, J. H.
Reynolds and E. J. Middlebrooks. Contract Number 68-03-0281,
Municipal Environmental Research Laboratory, US Environmental
Protection Agency, Cincinnati, Ohio 45268.
(15)
Separation of Algae Cells From Wastewater Lagoon Effluents, Volume
II, Effect of Sand Size on the Performance of Intermittent Sand
Filters, by B. Tupyi, D. S. Filip, J. H. Reynolds,,and E. J.
Middlebrooks. , Contract Number 68-03-0281.Municipal Environmental
Environmental Protection Agency, Cincinnati
Research Laboratory,
Ohio 45268.
US
(16) Sewage Treatment Plant Design, ASCE Manual of Engineering Practice
No. 36/WPCF Manual of Practice No. 8. 1959.
(17) Survey of Facilities Using Land Application of Wastewater, by R. H.%
Sullivan, M. M. Cohn, and S. S. Baxter. Prepared for Office of
Water Program Operations. EPA Publication 430-9-73-006a. July 1973.
19
-------
(18) Wastewater Treatment and Reuse by Land Application, by C. E. Pound
and R. W. Crites. EPA Research Report 660/2-73-006A. August 1973.
f
(19) Land Treatment of Municipal Wastewater Effluents: Design Factors -
I, by C. E. Pound, R. W. Crites, and D. A. Griffes. Prepared for
the EPA Technology Transfer Program. January 1976.
(20) Land Treatment of Municipal Wastewater Effluents: Design Factors -
II, by 6. M. Powell. Prepared for the EPA Technology Transfer
Program. January 1976.
(21) Land Treatment of Municipal Wastewater Effluents: Case Histories.
Prepared for the EPA Technology Transfer Program. January 1976.
(22) Process Design Manual for Land Treatment of Municipal Wastewater,
by Metcalf & Eddy, Inc., Prepared for Environmental Research
Information Center, Technology Transfer, Office of Water Program
Operations, U.S. Environmental Protection Agency; U.S. Army Corps
of Engineers, U.S. Department of Agriculture. EPA Publication 625/
1-77-008. October 1977.
(23) Al-Layla, M.A. and E. J. Middlebrooks, "Effect of Temperature on
Algae Removal from Wastewater Stabilization Ponds By Alum
Coagulation," Water Research, 9,, 10, 1975.
(24) Shindala, A. and J. W. Stewart, "Chemical Coagulation of Effluents
from Municipal Waste Stabilization Ponds," Water and Sewage Works,
118, 4, 100-103, 1971.
(25) Reed, S. C., A. B. Hais Cost Effective Use of Municipal Waste-
water Treatment Ponds, Proceedings ASCE Annual Convention, 1978.
(26) Christiansen, C. D., H. J. Coutts, Performance of Aerated Lagoons
in Northern Climates, EPA-600/3-79-003, 1979.
(27) Middlebrooks, E. J. et al, Performance and Upgrading of Waste-
water Stabilization Ponds, Proceedings of a Conference at Utah
State University, EPA-600/9-79-011, 1979.
(28) Middlebrooks, E. J., et. al, Wastewater Stabilization Pond
Linings, USA CRREL Special Report 18-3, Reprint by US EPA OWPO,
#MCD-54, 1979.
(29) Benjes, H. H. Small Communities Wastewater Treatment Facilities -
Biological Treatment Systems. Section II, Design Seminar Handout,
Small Wastewater Treatment Facilities, ERIC, US EPA. Jan. 1978.
20
-------
(30) Bowles, D. S., E. 0. Middlebrooks, J. H. Reynolds.^ Coliform
Decay Rates in Waste Stabilization Ponds. Presented at WPCF
annual conference, October 1977. .
(31) Bowen, S. P. Performance Evaluation of Existing Lagoons,
Peterborough, N.H. EPA 600/2-77-085, MERL, US EPA Aug. 1977.
(32) Gloyna, E. F. Facultative Waste Stabilization Pond Design. Ponds
as a Wastewater Treatment Alternative. Univ. Texas, Austin.
' June 1975. ..,.".'. t -....' \ • :
(33) Hill, D. 0., A. Shindala. Performance Evaluation of Kilmichael
Lagoon. EPA 600/2-77-T09. MERL, US EPA Aug. 1977.
(34) Marais, 6. V. R. Dynamic Behavior of Oxidation Ponds, 2nd
International Symposium for Waste Treatment Lagoons. June 1970.
(35) McKinney, R. E. Performance Evaluation of An Existing Lagoon
System at Eudora, Kansas. EPA 600/2-77-167, MERL, US EPA. Sept.
. 1977. •'••-',;, '•-.-: :
(36) MetcaTf & Eddy, Inc. Wastewater Engineering, McGraw Hill, N.Y.,
N.Y. 1977.
(37) Middlebrooks, E. J., H. H. Reynolds, C. H. Middlebrooks.
Performance and Upgrading of Wastewater Stabilization Ponds.
Section I, Design Seminar Handout, Small Wastewater Treatment
'Facilities. ERIC, US EPA, Jan. 1978.
(38) Oswald, W. J.etal. Designing Ponds to Meet Water Quality
Criteria Second International Symposium for Waste Treatment
Lagoons. June 1970. \
(39) Pierce, D. M.- Performance of Raw Waste Stabilization Lagoons in
Michigan With Long Period Storage Before Discharge. Proceedings
Symposium Upgrading Wastewater Stabilization Ponds Meet New
Discharge Standards Utah State University PRM 6159-1, Nov. 1974..
(40) Reynolds. J. H., et al. Performance Evaluation of an Existing
Seven Cell Lagoon System, EPA 600/2-77-086, MERL, US EPA, Aug. 1977.
(41) Thirumurthi, D. Design Criteria for Waste Stabilization Ponds.
J.W.P.C.F. 46 (9) 2094-2106 (1974)
(42) US EPA Process Design Manual - Wastewater Treatment Facilities
for Sewered Small Communities. EPA-625/1^77-009, ERIC, US EPA.
October 1977. " '" •'••'
21
-------
-------
•APPENDIX"
-------
-------
FRIDAY, AUGUST 17, 1973
WASHINGTON, D.C.
Volume 38 « Number 159
PART II
ENVIRONMENTAL
PROTECTION
AGENCY
WATER PROGRAMS
Secondary Treatment
Information
No. 159—Ft. II 1
-------
£2298
RULES AND REGULATIONS
Title 40—Protection of Environment
CHAPTER t—ENVIRONMENTAL
PROTECTION AGENCY
SUBCHAPTER D—WATER PROGRAMS
PART 133—SECONDARY TREATMENT
INFORMATION
On April 30,1973, notice was published
in the FEDERAL REGISTER that the En-
vironmental Protection Agency was pro-
posing information on secondary treat-
ment pursuant to section 304(d) (1) of
the Federal Water Pollution Control
Act Amendments of 1972 (the Act).
Reference should be made to the .pre-
amble of the proposed rulemaking for a
description of the purposes and intended
use of the regulation.
Written comments on the proposed
rulemaking were Invited and received
from Interested parties. The Environ-
mental Protection Agency has care-
fully considered all comments received.
All written comments are on file with the
Agency.
The regulation has been reorganized
and rewritten to improve clarity.
Major changes that were made as a re-
sult of comments received are sum-
marized below:
(a) The terms "1-week" . and "1-
montti" as used In § 133.102 (a) and
(b) of the proposed rulemaking have
been changed to 7 consecutive days and
30 consecutive days respectively (See
§ 133.102 (a), (b), and (c) ).
(b) Some comments indicated that the
proposed rulemaking appeared to re-
quire 85 percent removal of biochemical
oxygen demand and suspended solids
only In cases when a treatment works
•would treat a substantial portion of ex-
tremely high strength industrial waste
(See § 133.102(g) of the proposed rule-
making) . The intent was that in no case
should the percentage removal of bio-
chemical oxygen demand and suspended
solids in a 30 day period be less than 85
percent. This has been clarified in the
regulation. In addition, it has been ex-
pressed as percent remaining rather than
percent removal calculated using the
arithmetic means of the values for in-
fluent and effluent samples collected in
a 30 day period (See § 133.102 (a) and
(b)).
(c) Comments were made as to the
difficulty of achieving 85 percent removal
of biochemical oxygen demand and sus-
pended solids during wet weather for
treatment works receiving flows from
combined sewer systems. Recognizing
this, a paragraph was added which
will allow waiver or adjustment of that
requirement on a case-by-case basis
(See 1133.103 (a)).
(d) The definition of a 24-hour com-
posite sample (See § 133.102 (o) of the
proposed rulemaking) was deleted from
the regulation. The sampling require-
ments for publicly owned treatment
works will be established in guidelines
issued pursuant to sections 304 (g) and
402 of the Act.
(e) In § 133.103 of the proposed rule-
making, it was recognized that secondary
treatment processes are subject to upsets
over which little or no control may be
exercised. This provision has been de-
leted. It is no longer considered necessary
in this regulation since procedures for
notice and review of upset incidents will
be included in discharge permits issued
pursuant to section 402 of the Act.
(f) Paragraph (f) of § 133.102 of the
proposed rulemaking, wl?ich relates to
treatment works which receive substan-
tial portions of high strength industrial
wastes, has been rewritten for clarity. In
addition, a provision has been added
which limits the use of the upwards ad-
justment provision to only those cases in
which the flow or loading from an indus-
try category exceeds 10 percent of the
design flow or loading of the treatment
works. This intended to reduce or elimi-
nate the administrative burden which
would be involved in making insignifi-
cant adjustments in the biochemical
oxygen demand and suspended solids
criteria (See § 133.103 (b)).
The major comments for which
changes were not made are discussed
below:
(a) Comments were received which
recommended that the regulation be
written to allow effluent limitations to be
based on the treatment necessary to meet
water quality standards. No change has
been made in the regulations because the
Act and its legislative history clearly
show that the regulation is to be based
on the capabilities of secondary treat-
ment technology and not ambient water
quality effects.
(b) A number of comments were re-
ceived which pointed out that waste sta-
bilization ponds alone are not generally
capable of achieving the proposed efflu-
ent quality in terms of suspended solids
and fecal conform bacteria. A few com-
menters expressed the opposite view. The
Agency is of the opinion that with proper
design (including solids separation proc-
esses and disinfection in some cases) and
operation, the level of effluent quality
specified can be achieved with waste
stabilization ponds. A technical bulletin
will be published in the near future which
will provide guidance on the design and
operation of waste stabilization ponds.
(c) Disinfection must be employed in
order to achieve the fecal coliform bac-
teria levels specified. A few commenters
argued that disinfectant is not a second-
ary treatment process and therefore the
fecal coliform bacteria requirements
should be deleted. No changes were made
because disinfection is considered by the
Agency to be an important element of
secondary treatment which is necessary
for protection of public health (See
1133.102 (c)).
Effective date. These regulations shall
become effective on August 17,1973.
JOHN QTTARLES,
Acting Administrator
AUGUST 14,1973.
Chapter I of title 40 of the Code of
Federal Regulations Is amended by add-
ing a new Part 133 as follows:
Sac.
133.100
133.101
133.102
133.103
133.104
Purpose.
Authority.
Secondary treatment.
Special considerations.
Sampling and test procedures.
AUTHOSITY: Sees. 304()(1), S01(t>) (1) (B),
Federal Water Pollution Control Act Amend-
ments, 1D72, Pi. 92-500.
§ 133.100 Purpose.
This part provides information on the
level of effluent quality attainable
through the application of secondary
treatment.
§ 133.101 Authority.
The information contained in this
Part is provided pursuant to sections
304(d) (1) and 301 (b) (1) (B) of the Fed-
eral Water Pollution Control Act
Amendments of 1972, PL 92-500 (the
Act).
§ 133.102 Secondary treatment.
The following paragraphs describe the
minimum level of effluent quality attain-
able by secondary treatment in terms of
the parameters biochemical oxygen de-
mand, suspended solids, fecal coliform
bacteria and pH. All requirements for
each parameter shall be achieved except
as provided for in § 133.103.
(a) Biochemical oxygen demand (.five-
day). (1) The arithmetic mean of the
values for effluent samples collected In a
period of 30 consecutive days shall not
exceed 30 milligrams per liter.
(2) The arithmetic mean of the val-
ues for effluent samples collected in a
period of seven consecutive days shall
•not exceed 45 milligrams per liter.
(3) The arithmetic mean of the val-
ues for effluent samples collected in a
period of 30 consecutive days shall not
exceed 15 percent of the arithmetic mean
of the values for influent samples col-
lected at approximately the same times
during the same period (85 percent re-
moval) .
(b) Suspended solids. (1) The arith-
metic mean of the values for effluent
samples collected In a period of 30 con-
secutive days shall not exceed 30 milli-
grams per liter.
(2) The arithmetic mean of the val-
ues for effluent samples collected in a
period of seven consecutive days shall
not exceed 45 milligrams per liter.
(3) The arithmetic mean of the val-
ues for effluent samples collected in a
period of 30 consecutive days shall not
exceed 15 percent of the arithmetic mean
of the values for influent samples col-
lected at approximately the same times
during the same period (85 percent re-
moval).
(c) Fecal caliform-bacteria. (1) The
geometric mean of the value for effluent
camples collected in a period of 30 con-
secutive days shall not exceed 200 per
100 milliliters.
FEDERAL REGISTER, VOL. 38,'NO. 159—FRIDAY, AUGUST 17, 1973
-------
RULES AND REGULATIONS
22299
(2) The geometric mean of the values
for effluent samples collected in a period
of seven consecutive days shall not ex-
ceed 400 per 100 milliliters.
(d) pH. The effluent values for pH shall
remain within the limits of 6.0 to 9.0.
§ 133.103 Special considerations.
(a) Combined sewers, Secondary
treatment may not be capable of meet-
ing the percentage removal requirements
of paragraphs (a) (3) and (b) (3) of
§ 133.102 during wet weather in treat-
ment works which receive flows from
combined sewers (sewers which are de-
signed to transport both storm water
and sanitary sewage). For such treat-
ment works,.the decision must be made
on a case-by-case basis' as to whether
any attainable percentage removal level
can be denned, and if so, what that level
should be.
(b) Industrial wastes. For certain in-
dustrial categories, the discharge to nav-
igable waters of biochemical oxygen de-
mand and suspended solids permitted
under sections 30 Kb) (1) (A) (i) or 306 of
the Act may be less stringent than the
values given in paragraphs (a) (1). and
(b) (1) of § 133.102. In cases when wastes
would be introduced from such an indus-
trial category into a publicly owned
treatment works, the values for biochemi-
cal oxygen demand and suspended solids
in paragraphs (a) (1) and (b) (1) of
§ 133.102 may be adjusted upwards pro-
vided that: (1) the permitted discharge
of such pollutants, attributable to the
industrial category, would not be greater
than that which would be permitted
under sections 301 (b) (1) (a) (i) or 306
of the Act if such industrial category
were to discharge directly into the navi-
gable waters, and (2) the flow or loading
of such pollutants introduced by the in-
dustrial category exceeds 10 percent of
the design flow or loading of the publicly
owned treatment works. When such ari
adjustment is made, the values for bio-
chemical oxygen demand or suspended
solids in paragraphs (a) (2) and (b) (2)
of § 133.102 should be adjusted propor-
tionally. '..'.:'.
§ 133.104 Sampling and test procedures.
(a) Sampling and test procedures for
pollutants listed in § 133.102 shall be in
accordance with guidelines promulgated
by the Administrator pursuant to sec-
tions 304(g) and 402 of the Act.
(b) Chemical oxygen demand (COD)
or total organic carbon (TOO may be
substituted for biochemical oxygen -de-
mand (BOD) when a long-term BOD:
COD or BOD:TOG correlation has been
demonstrated.
[FR Doc.73-17194 Piled &-10-73;8:45 am]
FEDERAL REGISTER, VOL. 38, NO. 159—FRIDAY, AUGUST 17, 1973
-------
-------
WEDNESDAY, NOVEMBER 15, 1978
ENVIRONMENTAL
PROTECTION
AGENCY
WASTEWATER
TREATMENT PONDS
Suspended Solids Limitations
-------
NOTICES
[6560-01-M]
FNVIRONMENTAL PROTECTION
AGENCY
[FRL-1008O
SECONDARY TREATMENT INFORMATION
REGULATION
Suspended Solidi limitations for Waitewater
Treatment Pondt
On October 7, 1977, the Environ-
mental Protection Agency (EPA) pub-
lished in the FEDERAL REGISTER (42 PR
54666) a final amendment to the sec-
ondary treatment information regula-
tion applicable to the suspended solids
limitations for certain municipal
wastewater treatment ponds. The sec-
ondary treatment information regula-
tion, 40 CPR 133, contains effluent
limitations in terms of biochemical
oxygen demand, suspended solids and
pH which must be achieved by munici-
pal wastewater treatment plants.
The amendment added a new para-
graph (c) to § 133.103 of 40 CFR 133.
This allows a case-by-case adjustment
in suspended solids limitations for
publicly owned waste stabilization
ponds, if: The pond has a design ca-
pacity of 2 million gallons per day or
less; ponds are the sole process for sec-
ondary treatment; and, the pond
meets the biochemical oxygen demand
limitations as prescribed by 40 CFR
133.102(a). Ponds that are not eligible
for this adjustment include: Basins or
ponds used as a final polishing step for
other secondary treatment systems,
and ponds, which include complete-mix
aeration and sludge recycle or return
since these systems are in essence a
variation of the activated sludge proc-
ess. Aerated ponds without sludge re-
cycle, however, are eligible for adjust-
ments provided the other specific re-
quirements are met.
The amended suspended solids limi-
tations were determined by statistical
analysis of available data. The accept-
able limit was defined as that concen-
tration achieved 90 percent of the
time by waste stabilization ponds that
are achieving the biochemical oxygen
demand limitations of 40 CFR
133.102(a). Each State was considered
separately as well as appropriate con-
tiguous geographic areas .within a
State or group of States. The analysis
was done by the States or the applica-
ble EPA regional office in cooperation
with the States.
A considerable amount of latitude
was allowed in developing these values
to account for varying conditions af-
fecting pond use and performance
across the country. Categorizations
within States based on factors such as
geographic location, seasonal variation
and the type of pond were permitted.
In some instances, the values present-
ed below reflect these factors.
In accordance with the amended reg-
ulation, a single value corresponding
to the concentration achievable 90
percent of the time may be used to es-
tablish the suspended solids limita-
tions for ponds within a State. The
concentration achievable 90 percent of
the time has been generally accepted
as corresponding to a 30 consecutive
day average (or an average value over
the period of discharge when entire
duration of the discharge is less than
30 days). This interpretation is consist-
ent with the analysis which was used
as the basis for the other suspended
solids and biochemical oxygen demand
limitations contained in 40 CFR 133.
For this reason, a single suspended
solid concentration has been listed
below for ponds (or subcategory of
ponds) within a State. In some cases,
however, the States and EPA regional
offices have agreed upon additional
values, such as weekly averages or
daily maximums, which will be used
for compliance monitoring purposes
within those States.
In some cases the data base for the
analysis was quite limited and in all
cases additional data are being collect-
ed. A periodic reevaluation of this ex-
panding data base will be conducted
and could result in further changes in
the suspended solids limitations listed
below. Several EPA regional offices
have already indicated their intent to
conduct a reevaluation within 2 years
or less. Even though publication of
these values is not a formal rulemak-
ing procedure, public comments are
welcome and will be considered in any
revisions. Comments should be submit-
ted to Director, Municipal Construc-
tion Division (WH-547),' Environmen-
tal Protection Agency, Washington,
D.C. 20460.
FOR FURTHER INFORMATION
CONTACT:
Sherwood Reed.or Alan Hals, Munic-
ipal Construction Division (WH-
547), Office of Water Program Oper-
ations, Environmental Protection
Agency, Washington, D.C. 20460,
202-426-8976.
Dated October 27, 1978.
THOMAS C. JORLING,
Assistant Administrator for
Water and Waste Management.
FEDERAL REGISTER, VOL. 43, NO. 721—WEDNESDAY, NOVEMBER 15, 1978
-------
55280
[I505-01-C]
N(
[NVIROWltSTAL PROT.tCTlOtj AGt.'lCY
Suspended Solids Limitations for
Location
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Aerated Ponds
All others
Connecticut
Delaware
District of Columbia
Florida
Georgia
fiuan
Hawaii
Idaho '_
Illinois
Ind-iana
Iowa
Controlled Discharge, 3 cell
All others
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Controlled'Seasonal Discharge
Suimer
Winter
Minnesota
Mississippi
Missouri
Montana
Nebraska
North Carolina
North Dakota
North 4 East of Missouri River
South 8 West of/Missouri River
Wastewater Treatment Ponds**
Suspended Solids Limit*
90
70
90 '
90
95
75 .'-..'.
105
N.C.
N.C.
N.C.
N.C.
90 . .
N.C.
N.C.
N.C.
37
70 _ . .. ,__._ _ ...... ..
case-by-case but 'not greater
than 80
80- '
80
N.C.
90
45 .
90.- ..'. .
N.C.
70
• 40
N.C.
: 90
80
100
80
90 •
60
100 •
NQTJCES
Suii-fndcd Solids LimitJl)or.< "for W.i>trw.iU'r Iri-atmciit
(tontlnufd)
Location ....
Nevada
New Hampshire -'.
New Jersey
New Mexico
New York
Ohio
Oklahoma
Orogori
fast of Cascade Mts.
West of Cascade Hts.
Pennsylvania .
Puerto Rico
P.hode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Verrant '
Virginia ' ' '
East of Blue Ridge Mts.
West of Blue Ridge Hts.
Eastern slope counties
Loudoun, Fauquier, Rappahannock
Madison, Green, Albemarle, Nelson
Amherst, Bedford, franklin, Patrick
Virgin Islands
Washington :- . . - "
West Virginia ' ' ,
Wisconsin .
Wyoming
Trust Territories 8 N. Marianas
NOTCS: ' -• • ;.. :'••'.
N.C. - no change from existing criteria
* thirty consecutive day average or average over the period
of discharge when the duration of the discharge is less than
30 days
** The values set for Iowa and Virginia incorporate a specific case-
by-case provision; however, in accordance with 40 CfR 133.103{c).
adjustments of the suspended solids limitations for individual
ponds in all states are to be authorized on a case-by-case basis.
Suspt-mlcd Solids Limit*
(mg/1)
90
45
N.C.
90
70
65
90
85
50
N.C.
N.C.
45
90 -
110
100
90
N.C.
- 55 •' '. .
60
78
case-by-case
application of 60/78
limits
N.C.
75
80
60
100
N.C.
FEDERAL REGISTER, VOL. 43. NO. 228—MONDAY, NOVEMBER 27, 1978
-------
-------
MONDAY, JULY 26, 1976
PART II:
ENVIRONMENTAL
PROTECTION
AGENCY
WATER PROGRAMS
Secondary Treatment Information
-------
30786
RULES AND REGULATIONS
Title 40—Protection of Environment
CHAPTER I—ENVIRONMENTAL
PROTECTION AGENCY
SUBCHAPTER D—WATER PROGRAMS
[ERIi 510-7]
PART 133—SECONDARY TREATMENT
INFORMATION
Biochemical Oxygen Demand, Suspended
Solids and pH
On. August 15, 1975, notice was pub-
lished, in the FEDERAL REGISTER that the
Environmental Protection Agency was
proposing the amendment of the Second-
ary Treatment Information regulation
contained in 40 CFR Part 133 and pro-
mulgated on August 17, 1973 pursuant to
sections 301 and 304 of the Federal Water
Pollution Control Act Amendments of
1972 (Pub. L. 92-500, the Act). The pro-
posed amendment was for the deletion of
1133.102(c) (limitations for fecal coli-
form bacteria) and the addition of § 133.-
103 (c) ("Special Consideration" for clar-
ification of the pH limitations contained
in § 133.102 (d)). Published in the FED-
ERAL REGISTER concurrently with the pro-
posed amendment of 40 CFR Part 133
was a supplementary statement of EPA
policy on the disinfection of municipal
wastewater.
Written comments on the proposed
rulemaking and statement of policy were
invited and received from interested par-
ties. The Environmental Protection
Agency has carefully considered all com-
ments received. All written comments are
on file with the Agency.
Virtually all of the comments on the
proposed rule changes concerned the in-
tent and effect of the deletion of the
fecal collform bacteria limitations from
40 CFR Part 133 and the limiting of the
pH requirements to processes using inor-
ganic chemicals and/or those receiving
significant industrial contributions.
The majority of the responses received
Indicated support for either one or both
of the proposed amendments. The pro-
posed amendment for deletion of the
fecal coliform limitations from 40 CFR
Part 133 specified reliance on State water
quality standards for establishment of
minimum disinfection requirements for
publicly owned treatment works
(POTW's). A significant majority of the
responding State agencies (i.e., the agen-
cies responsible for setting and imple-
menting water quality standards) sup-
ported the amendment for deletion of the
fecal coliform limits from 40 CFR Part
133.
The other principal comments received
and. the responses to them are summa-
rized below:
(a) Several comments indicated sup-
port of an amendment to 40 CFR Part
133 to achieve flexibility in establishment
of disinfection requirements but advo-
cated alternatives other than the one
proposed (i.e., deletion of the fecal coli-
form bacteria limitations from the Sec-
ondary Treatment Regulations). The al-
ternatives suggested were: (1) Retaining
the limits on fecal coliform bacteria in
40 CFR Part 133 but allowing a variance
procedure to permit case-by-case excep-
tions, (2) raising the numerical limits on
fecal coliform bacteria in 40 CFR Part
133, and (3) adopting a control param-
eter other than fecal coliform bacteria
(e.g., total coliform bacteria or minimum
chlorine residual).
Reliance on water quality standards
for establishment of disinfection require-
ments for POTW's in lieu of limitations
in 40 CFR Part 133 was selected by the
Agency because the regulatory scheme
established by the Act specifies the use
of water quality standards for control of
those pollutants which are not limited
by uniformly applied effluent standards
or for which more stringent limitations
than those required by minimum effluent
standards are required to achieve specific
water quality needs. Development and
implementation of water quality stand-
ards pursuant to the requirements of
Pub. L. 92-500 are currently being car-
ried out by the States so that transition
to reliance on water quality standards
for establishment of disinfection require-
ments for POTW's can be handled with
a minimum amount of disruption.
The Agency also believes that because
of the potential problems associated with
the unnecessary use of disinfectants and
the variable need for disinfection from
one area of the country to another or one
season to another, it is best to set disin-
fection requirements for POTW's on a
case-by-case basis. By deleting the fecal
coliform bacteria limitations from 40
CFR Part 133, the States will have the
flexibility to establish disinfection re-
quirements for POTW's in accordance
with local needs. Accordingly, one of the
alternate regulatory schemes suggested
for control of disinfection practices, such
use of total coliform bacteria as an in-
dicator or less stringent limits on fecal
coliform bacteria, may be appropriate for
specific water quality needs and imple-
mented locally. In other areas where dis-
infection of municipal wastewater dis-
charges will be widely required in accord-
ance with local water quality and public
health needs, a general provision for dis-
infection with specific case-by-case ex-
ceptions may be appropriate.
(b) A number of comments disagreed
with the proposed amendment for dele-
tion of the fecal coliform bacteria limi-
tations from 40 CFR Part 133 because it
would shift the responsibility for imple-
mentation of disinfection requirements
to the States and because the Agency had
not supplied sufficient guidance to the
States in the area of wastewater disinfec-
tion.
As indicated in the FEDERAL REGISTER
notice of August 15, 1975, virtually every
State and territory has water quality re-
lated standards pertaining to wastewater
disinfection. Because the requirements of
Pub. L. 92-500 are in the process of being
implemented and control of municipal
wastewater disinfection is in a transi-
tional stage, State standards continue to
dominate disinfection practices in most
areas. Protection of public health from
disease has been and continues to be a
primary objective under the present sys-
tem of control of disinfection of munici-
pal wastewater by means of State stand-
ards. As nofed previously, the majority
of the State agencies responsible for
establishment and implementation of dis-
infection requirements which responded
with comments supported the proposed
amendment. Several States submitted
proposals for State disinfection require-
ments which were being considered for
implementation in anticipation of the
final amendment of 40 CFR Part 133 for
deletion of the fecal coliform bacteria
limitations.
Disinfection requirements for POTW's
are and will continue to be enforceable
conditions of permits issued under the
authority of the National Pollutant Dis-
charge Elimination System (NPDES).
The Agency has prepared guidance for
implementing the change in disinfection
requirements for POTW's in NPDES
permits. This guidance was prepared with
the intent of simplifying the procedure
for assigning effluent limitations for in-
dicator organisms for municipal waste-
water discharges so that the transition
from effluent based disinfection require-
ments to water quality based require-
ments will be both efficient and effective.
The Agency has recently published in
draft form, "Quality Criteria for
Water" with the stated objective of pro-
viding the basis of judgment in several
EPA and State programs that are as-
sociated with water quality considera-
tions. Included in "Quality Criteria for
Water" are chapters which provide
guidance on standards for coliform
bacteria and chlorine.
Also available to provide background
guidance on municipal wastewater dis-
infection practices is the final "Task
Force Report—Disinfection of Waste-
water." The report is available from the
General Services Administration (8FY),
Centralized Mailing Lists Services, Build-
ing 41, Denver Federal Center, Denver,
Colorado 80225. The title and number of
the report are: "Disinfection of Waste-
water—Task Force Report," MCD-21:
No. EPA-430/9-75-012.
(c) Several comments were received
which questioned: (1) The impact of
the deletion of the fecal coliform bac-
teria limitations from 40 CFR Part 133
on the use of chlorine and alternative
disinfectants; (2) the potential inconsist-
ency of the proposed rule change with
section 101 (a) (2) of the Act which speci-
fies as an interim a national goal, wher-
ever attainable, fishable and swimmable
waters by 1983; and (3) the effect of the
proposed deletion of the fecal coliform
bacteria limits from 40 CFR Part 133 on
reducing the potential hazard associated
with the formation of carcinogenic
compounds as a result of municipal
wastewater disinfection. Similarly, other
responses were received which com-
mented that the FEDERAL REGISTER no-
tices may jeopardize the protection of
public health from disease because the
notices appear to de-emphasize the im-
portance of municipal wastewater dis-
infection.
FEDERAL REGISTER, VOL. 41, NO. 144—MONDAY, JULY 26, 1976
-------
RULES AND REGULATIONS
30787 .
The position of the Environmental
Protection Agency has been and con-
tinues to be that the overriding criterion,
with respect to decisions concerning the
practice of municipal wastewater disin-
fection, is protection of public health
from infectious disease. The Agency,
however, also recognizes that protection
of public health from disease can be
maintained without continuous disinfec^
tion of all municipal wastewater dis-
charges. Because chlorination is the
wastewater disinfection process which is
presently available for widespread ap-
plication, retention of the fecal coliform
bacteria limitations in 40 CFR Part 133
as originally promulgated would signifi-
cantly increase the use of chlorine for
wastewater disinfection in this country.
The potential for problems such as tox-
icity to human and aquatic environments
and excessive expenditure of valuable
energy and monetary resources is in-
creased unnecessarily as a result of a
regulation which requires disinfection hi
certain instances where it is not neces-
sary for the protection of public health
from disease. It is the finding of the
Agency that public health can be main-
tained in the future without inadver-
tently contributing to these problems.
The increase in the use of chlorine
for sanitation purposes (including mu-
nicipal wastewater disinfection) in this
country prior to the implementation of
Pub. L. 92-500 has been approximately
the same as the annual rate of increase
in the amount of wastewater discharged
from POTW's—four percent. It is pro-
jected that the use of chlorine for mu-
nicipal wastewater disinfection would
increase by an average of approximately
10 percent per year during the period
that Pub. L. 92-500 is being implemented
(1973-1983) if continuous disinfection
of municipal wastewater discharges re-
mains as a.requirement of 40 CFR Part
133. The difference in the amount of
chlorine used for municipal wastewater
disinfection, assuming an annual in-
crease of 10 percent as opposed to 4 per-
cent, wo_uld be 184,000 tons per year by
1983 which is greater than the estimated
total use of chlorine for municipal waste-
water disinfection in 1974. Furthermore,
it is likely that the annual increase in
the use of chlorine will be less than 4
percent per year as the effluent quality
of discharges from POTW's improve (i.e.,
less disinfectant is generally required to
achieve the same level of disinfection
as effluent quality increases), as opera-
tional procedures for control of disinfec-
tion processes improve, and as the use
.of alternate.disinfectants increases.
Concerning the use of alternate dis-
infection processes, the Agency has an
extensive, on-going research and devel-
opment program for the development and
demonstration of alternate disinfection
processes and improved control of chlori-
nation processes. The "Task Force Re-
port—Disinfection of Wastewater" sum-
marizes the pertinent information con-
cerning alternative processes for disin-
fection (including reliability, safety and
cost) and describes the Agency's research
and development program in the area
of wastewater disinfection.
With regard to the use of chlorine for
wastewater disinfection, the Agency rec-
ognizes the continuing need for the pro-
tection of public health from disease and
does not believe there is .conclusive evi-
dence to warrant the prohibition of the
use of chlorine for wastewater disinfec-
tion at the present time. The cost of
chlorination/dechlorination should be
compared to that of alternative disin-
fection processes when the need for dis-
' infection, and protection of aquatic life
co^exist. Comparison of the costs for
alternative disinfection processes to de-
termine cost-effectiveness is required by
law for projects involving the construc-
tion of disinfection facilities funded with
construction grants under Title if-of
Pub. L. 92-500. Serious consideration
should be given to use of: alternate dis-
infection processes in those areas where
organic compounds which can react with
chlorine to form potentially toxic cbm^
pounds are known to exist in the waste-
water. However, it is recognized that
chlorination processes will generally be
the most cost effective at the present
time. It is for this reason, in part, that
establishment of disinfection require-
ments for POTW's on a case-by-case-
basis in' accordance with specific water
quality criteria is important.
Other responses commented that the
deletion of the fecal coliform limitations
from 40 CFR Part 133, is inconsistent
with the goal of Pub. L. 92-500 for at-
tainment of fishable and swimmable
waters by 1983 and may jeopardize the
integrity of that requirement of the Act.
Water quality standards define condi-
tions necessary to' meet the 1983 goal
uses of Pub. L. 92-500. Deleting the ef-
fluent limitations from 40 CFR Part 133
does not preclude the achievement of the
1983 goal because water quality stand-
ards are established, in part, to protect
public health and allow recreation in and
on the water. In cases where water qual-
ity standards do not describe conditions..
necessary for fishable/swimmable water,
the EPA Regional Administrator, in ac-
cordance with section 302 of the Act, can
establish effluent limitations on a case-,
by-case basis after a public hearing on
the costs and benefits of achieving those
limits. As achievement of nshable/swim-
mable waters becomes imminent, we will
be in a better position to re-evaluate the
disinfection requirements for municipal
wastewater discharges in consideration
of the improved water quality at that
time. In the interim, time will be avail-
able for investigation of cost-effective
alternate disinfection processes and
analysis of more conclusive data on the
potential hazards associated with waste-
water disinfection.
(d) Several comments were received
which indicated .opposition to the pro-
posed amendment for deletion of the
fecal Coliform bacteria limitations'from
40 CFR Part 133 because bacteriological
monitoring is important for protection
of public health. Other comments ex-
pressed either support for or opposition
to the continued use of fecal coliform
bacteria as an indicator of the pathogenic
contamination of water or wastewater.
Comments were also received which
questioned the retaining of disinfection
requirements for POTW's as enforce-
able conditions of NPDES permits.
Opposition to the deletion of the fecal
coliform bacteria limitations from 40
CFR Part 133 on the basis of discontinu-
ance of bacteriological monitoring or
retention of disinfection requirements
in permits is apparently based on a mis-
understanding of the purpose of the Sec-
ondary Treatment Regulation. In ac-
cordance with the provisions of Pub. 3j.
92-500, secondary treatment is the
minimum level of treatment required
for POTW's; 40 CFR Part 133 defines
that level of treatment hi "terms of
effluent quality. The fecal coliform"
bacteria limitations in 40 CFR Part 133
were, in essence, a requirement for "con-
tinuous disinfection of wastewater ef-
fluents from POTW's and fecal coliform
bacteria were the measure of the effec-
tiveness of the disinfection process. As
such, the limitations on fecal coliform
bacteria in 40 CFR Part 133 are not ac-
tual- permit conditions for .monitoring
and effluent quality, although they will
obviously affect the permit requirements
for POTW's.
Monitoring requirements and effluent
limitations for municipal wastewater ef-
fluents are set in accordance with the
pollutant parameters for-which control
is necessary. Iii those instances where
disinfection .is required 'and coliform
limitations are established, obviously
bacteriological monitoring and effluent
limitations pertaining to disinfection will
be necessary and shall be required as
NPDES permit .conditions.' Iri those in-
stances where bacteriological monitor-
ing is hot required as a permit condi-
tion, it shall have been previously de-
termined that ^disinfection and effluent
limitations for coliform bacteria are'
not necessary at that particular time
for that particular discharge.
Concerning the "use of fecal coliform
bacteria as an indicator of pathogenic
contamination, it is recognized that just
as there is not an ideal disinfection proc-.
ess presently available, there .also is
not an ideal indicator of pathogenic
contamination at the present, time. The
EPA is presently conducting several
studies for the development of new mi-
crobiological indicators for water and
wastewater examination. However, the
.use of coliform bacteria has historically
proven to be a valuable and practical
indicator of the relative disease causing
potential of water and wastewater. The
Agency believes the continued use of the
available microbiological indicators (in-
cluding total and fecal Cpliform bac-
teria) is essential for the protection of
the public from disease.
(e) Comments were received which
recommended limits on residual chlorine
either for protection of aquatic life
(maximum chlorine residual) or to en-
sure adequate disinfection (minimum
chlorine residual). The comment was
also received that maintenance of a mini-
mum chlorine residual is not an accurate
indication of the effectiveness of the dis-
infection process, l
Limits on the maximum chlorine
residual in wastewater effluents are. con-
FEDERAL REGISTER, VOl. 41, NO, 144—MONDAY, JULY 26, 1976
-------
30788
RULES AND REGULATIONS
sidered necessary in some areas where
protection of aquatic life from toxicity is
Important. Several States have estab-
lished standards limiting the amount of
chlorine allowable in wastewater dis-
charges to certain types of waters. Also,
as indicated previously, "Quality Criteria
for Water" has a chapter which suggests
criteria for total chlorine residual for
protection of salmonid fish and other
freshwater and marine organisms. Limi-
tations on residual chlorine in municipal
wastewater effluents obviously must be
an integral part of water quality con-
siderations and such limitations will be
established on a case-by-case basis in ac-
cordance with the degree of protection
necessary.
Specification of a minimum chlorine
residual in wastewater effluents to ensure
adequate disinfection has not been the
approach used by the Agency because it
is process related and precludes the use
of alternative disinfection processes. Al-
though the Agency does not intend to
dictate the effluent parameter used to
measure the effectiveness of disinfection
processes for FOTW's after deletion of
the fecal coliform bacteria limitations
from 40 CFR Part 133, support of non-
process related indicators, such as coli-
form bacteria, is maintained for the same
reasons that fecal coliform bacteria were
originally selected as a measure of
effluent quality for 40 CFR Part 133. The
use of a minimum chlorine residual is,
however, recognized as a valuable pa-
rameter for process control of well de-
signed chlorination facilities. If chlorine
residual is considered for use as a process
control for chlorination facilities, it is
recommended that a range of chlorine
concentrations (maximum and mini-
mum) be specified to not only ensure
effective disinfection, but also to limit
the amount of chlorine used and remain-
ing at the time of discharge.
(f) Some commenters expressed the
opinion that deletion of the fecal coli-
form limitations from 40 CFR Part 133
and reliance on State water quality
standards will jeopardize water quality
and the protection of public health in
Interstate waters. 40 CPU 130.17 (c) (4)
(Policies and Procedures for Continuing
Planning Process-Water Quality Stand-
ards) requires that "The State shall take
Into consideration the water quality
standards of downstream waters and
shall assure that Its water quality stand-
ards provide for attainment of the water
standards of downstream waters." The
Administrator must approve or disap-
prove any State water quality standards
In accordance with section 303 of Pub. L.
92-500, and thus has the authority to rule
In cases where State water quality stand-
ards for interstate water are in conflict.
(g) A number of comments were re-
ceived which recommended that both the
amendments for deletion of the fecal
coliform bacteria limitations from 40
CFR Part 133 and the clarification of the
pH limitations be extended to apply to
Industrial effluent limitations. Section
304(d) (1) of Pub. L. 92-500 requires that
the EPA "publish information * * * on
the degree of effluent reduction attainable
through the application of secondary
treatment." The basis which is to be con-
sidered as a minimum for effluent limita-
tions for industrial dischargers (Section
304(b) of Pub. L. 92-500) is, in part, the
limits of available technology. In con-
sideration of these statutory differences,
effluent limitations for municipal and in-
dustrial discharges will logically vary
with regard to the control of one or more
pollutant parameters.
(h) A number of commenters disagreed
with the amendment concerning the pH
limitations because they believed that
acidic or basic discharges from biological
treatment processes can be harmful to
receiving waters in the same way that
discharges from chemical treatment
processes or processes with significant in-
dustrial contributions can. Similarly,
other comments indicated that, even if
the pll of the effluent falls within the
range of 6-9, discharges from any type
of municipal wastewater treatment plant
can adversely affect receiving waters de-
pending on the characteristics of the wa-
ter body. Still other comments cited in-
formation which indicates that the pH of
wastewater effluents generally has no sig-
nificant effect on receiving waters be-
cause of the natural buffering capacity
of most waters. For this reason, these
comments recommended that the pH
limitations be entirely deleted from 40
CFR Part 133.
No changes in the amendment for pH
limitation have been made in response to
these comments. Pub. L. 92-500 and its
legislative history clearly shows that the
Secondary Treatment Regulation is to be
based on the capabilities of secondary
treatment technology and not ambient
water quality effects (S. Rep. 92-12361
Leg. Hist. 309; S. Rep. 92-414, Leg. Hist.
1461). In accordance with this principle,
neutralization has historically been con-
sidered a component part of those sec-
ondary treatment processes which use in-
organic chemicals for the treatment of
wastewater (e.g., lime precipitation or
mineral addition processes) and those
processes which receive significant in-
dustrial flows that have not been pre-
treated for neutralization of acidic or
basic wastes. Neutralization prior to dis-
charge, however, has generally not been
considered an integral part of the process
in secondary treatment facilities which
incorporate strictly physical and biologi-
cal treatment methods.
In cases where control of pH within
the range of 6-9 is not sufficient to pro-
tect receiving waters or where dis-
charges not subject to the pH limitations
of 40 CFR Part 133 will adversely affect
receiving water quality, effluent limita-
tions for pH based on water quality re-
quirements will apply on a case-by-case
basis. "Quality Criteria for Water" con-
tains information and possible criteria
for establishment of water quality stand-
ards for pH. As is the case with all-water
quality based standards, effluent limita-
tions for pH which are established to
achieve specific water quality objectives
may be more stringent than or require
limits on pollutant parameters not con-
trolled by effluent limited (technology-
based) standards such as 40 CFR Part
133.
(i) Comments were made that the pro-
posed amendment for the pH limitations
was unclear with respect to its appli-
cability in situations where inorganic
chemicals, such as disinfectants and floc-
culants, are added to supplement
physical/biological secondary treatment
processes. The amendment for the pH
limitations has been reorganized as in-
dicated below. The provisions pertaining
to pH are now set forth in their entirety
in § 133.102(c).
In consideration of the foregoing, Part
133 of Chapter I of Title 40 of the Code
of Federal Regulations is amended as set
forth below.
(Sec. 304(d)(l) and 301(b)(l)(B) of the
Federal Water Pollution Control Act Amend-
ments of 1972 (33 TT.S.C. 1342, 1345 & 1361) )
Dated: July 16,1976.
RUSSELL E. TRAIN,
Administrator.
1. Section 133.102 is revised to read as
follows:
§ 133.102 Secondary treatment.
The following paragraphs describe the
minimum level of effluent quality attain-
able by secondary treatment in terms of
the parameters—biochemical oxygen de-
mand, suspended solids and pH. All re-
quirements for each parameter shall be
achieved except as provided for in
§ 133.103.
(a) Biochemical Oxygen Demand (.five-
day). (1) The arithmetic mean of the
values for effluent samples collected in a
period of 30 consecutive days shall not
exceed 30 milligrams per liter.
(2) The arithmetic mean of the values
for effluent samples collected in a period
of 7 consecutive days shall not exceed 45
milligrams per liter.
(3) The arithmetic mean of the values
for effluent samples collected in a period
of 30 consecutive days shall not exceed
15 percent of the arithmetic mean of the
values for influent samples collected at
approximately the same times during the
same period (85 percent removal).
(b) Suspended solids. (1) The arith-
metic mean of the values for effluent
samples collected in a period of 30 con-
secutive days shall not exceed 30 milli-
grams per liter.
(2) The arithmetic mean of the values
for effluent samples collected in a period
of 7 consecutive days shall not exceed
45 milligrams per liter.
(3) The arithmetic mean of the values
for effluent samples collected in a period
of 30 consecutive days shall not exceed
15 percent of the arithmetic mean of the
values for influent samples collected at
approximately the same times during the
same period (85 percent removal).
(c) pH. The effluent values for pH
shall be maintained within the limits of
6.0 to 9.0 unless the publicly owned treat-
ment works demonstrates that:
(1) Inorganic chemicals are not added
to the waste stream as part of the treat-
ment process; and
(2) Contributions from industrial
sources do not cause the pH of the
effluent to be less than 6.0 or greater
than 9.0.
[PR Doc.76-21249 Piled 7-23-76;8:46 am]
FEDERAL REGISTER, VOL. 41, NO. 144—MONDAY, JULY 26, 1976
-------
NOTICES
30789
ENVIRONMENTAL PROTECTION
AGENCY
[FRL 510-8]
MUNICIPAL WASTEWATER DISINFECTION
Secondary Treatment
The Environmental Protection Agency
has amended the Secondary Treatment
Information regulation contained in 40
CFR Part 133 and promulgated pursuant
to section 304(d) (1) of the Federal Water
Pollution Control Act Amendments of
1972 (the Act). Section 301 (b) (1) (B) of
the Act requires the effluent limitations
based on secondary treatment, be
achieved for all publicly owned treat-
ment works in existence on July 1, 1977,
or approved for a construction grant
prior to June 30, 1974 (for which con-
struction must be completed within four
years of approval). The amendment, pub-
lished concurrently with this notific^-
tion, deletes the fecal colifprm bacteria
limitations from the definition of sec-
ondary treatment.
At the time that 40 CFR Part 133 was
first promulgated, limitations on fecal
coliform bacteria were included in the
definition of secondary treatment on the
basis that disinfection is necessary for
the protection of public health. In recog-
nition of more recent information, it is
now felt that it is environmentally sound
to establish disinfection requirements for
domestic.wastewater discharges in ac-
cordance with water quality standards
promulgated pursuant to section 302 and
303 of the Act and associated public
health needs. In this manner, the neces-
sary protection of public health can be
assured, while achieving adequate safe-
guards against the adverse effects which
could result from the excessive use of dis-
infectants. ,
In January 1974, an Environmental
Protection Agency Task Force was
formed to review EPA policy on waste-
water disinfection and the use of chlo-
rine. The Task Force recognized that
chlorine and chlorine-based compounds
are presently receiving essentially exclu-
sive use for the disinfection of waste-
water. While chlorine is an effective dis-
infectant with respect to meeting bac-
teriological standards and is adequately
protecting public health, there are po-
tential dangers associated with the use
of chlorine. Disinfection of wastewater
with chlorine can result in the formation
of halogenated organic compounds which
have been identified as potential carcino-
gens. Considerable data also exist to in-
dicate that chlorination of wastewater
can result in a residual chlorine level
that is toxic to aquatic life. The Task
Force concluded that in view of the fact
that present policy inadvertently en-
courages the use of chlorine, a regulation
which in certain instances requires dis-
infection unnecessarily further com-
pounds the potential problems associated
with the chlorinatipn of wastewater.
Prior to the enactment of Pub. L. 92-
500, domestic wastewater disinfection
practice was, for the most part, con-
trolled locally by the States. In proposing
the deletion of the .disinfection require-
ments from 40 CFR Part 133 and recom-
mending reliance on water quality stand-
ards, the EPA made an assessment of the
State standards relating to wastewater
disinfection. It was determined that vir7
tually all of the States and Territories
have water quality related regulations
pertaining to the disinfection of waste-
water and that public health was ade-
quately being maintained. In many in-
stances, other than continuous disin-
fection was being practiced where the
possibility of human contact with the
receiving waters was remote.
Disinfection requirements have been
and must continue to be directed at pro-
tecting the public health. Water quality
standards which establish the need for
disinfection must, as a minimum, include
the following:
(1) Protection of public water sup-
plies.
(2) Protection of fisheries and shell-
fish, waters. ,
(3) Protection of irrigation and agri-
cultural waters.
(4) Protection of waters where human
contact is likely.
(5) Protection of interstate waters to
which the above criteria apply.
The Agency published in draft form
on October 10, 1975, Quality Criteria for
Waters which is intended to be used as
the basis for State water quality stand-
ards. Criteria for fecal coliform bacteria
and chlorine are included. These criteria
are available for use by the States in the
development of water quality standards
and the related disinfection requirements
for publicly owned treatment works.
The benefits, achieved by disinfection
should be weighed against the environ-
mental risks and costs. It is intended that
the use of chlorine disinfection would be
considered only when there are public
health hazards to be controlled. The ex-
clusive use of chlorine for disinfection
should not be continued where protection
of aquatic life is of primary considera-
tion. Alternate means of disinfection and
disinfectant control (dechlorination)
must be considered where public health
hazards and potential adverse impact on
the aquatic and human environments
co-exist. Disinfection should not be re-
quired in those instances where benefits
are not present.
The final Task Force Report provides
a compilation of the existing technical
and scientific data related to the issues
raised by wastewater disinfection. The
report is divided into four main parts—
Summary, Conclusions and Recom-
mendations; Public Health Effects and
Considerations; Toxic Effects on the
Aquatic Environment; and Disinfection
Process Alternatives. Also included in the
report is a summary of the Agency's on-
going research and development pro-
gram iri the area of wastewater disinfec-
tion and alternate means of "disinfection.
The report is available from the Cen-
tralized failing Lists Services, Building
41, Denver Federal Center, Denver, Colo-
rado 80225. The title and number of the
report are "Disinfection of Wastewater—
Task Force Report;" MCD-21; No. EPA-
430/9-75-012. -
RUSSELL E. TRAIN,
Administrator.
JtTLY 16,1976.
[FB Doo.76-21250 Piled 7-23-76;8:4S am]
FEDERAL REGISTER, VOL. 41, NO. 144—MONDAY, JULY 26, 1976
-------
-------
FRIDAY, OCTOBER 7, 1977
PART III
ENVIRONMENTAL
PROTECTION
AGENCY
WASTEWATER
TREATMENT PONDS
Suspended Solids Limitations
-------
54664
RULES AND REGULATIONS
[ 6560-01 ]
Title 40—Protection of Environment
CHAPTER I—ENVIRONMENTAL
PROTECTION AGENCY
SUBCHAPTER D—WATER PROGRAMS
[FBL 769-4]
PART 133—SECONDARY TREATMENT
INFORMATION
Suspended Solids Limitations for
Waste water Treatment Ponds
AGENCY: Environmental Protection
Agency.
ACTION: Final rule.
SUMMARY: This rule amends the Sec-
ondary Treatment Information regula-
tion to allow less stringent suspended
solids limitations for .wastewater treat-
ment ponds. The amendment is based on
the fact that properly designed and oper-
ated wastewater treatment ponds are a
form of secondary treatment which may
not be capable of achieving the sus-
pended solids limitations contained in
the Secondary Treatment Information
regulation without supplemental treat-
ment processes for removal of suspended
solids (primarily algae).
EFFECTIVE DATE: November 7, 1977.
FOR FURTHER INFORMATION CON-
TACT:
Alan Hais, Municipal Construction Di-
vision (WH-547), Office of Water Pro-
gram Operations, Environmental Pro-
tection Agency, Washington, D.C.
20460 (202-426-8976).
SUPPLEMENTARY INFORMATION:
On September 2, 1976, notice was pub-
lished in the FEDERAL REGISTER that the
Environmental Protection Agency was
proposing the amendment of the Second-
ary Treatment Information regulation
(41 FR 37222). The Secondary Treat-
ment Information regulation contains
effluent limitations in terms of biochemi-
cal oxygen demand, suspended solids and
pH which must be achieved by municipal
wastewater treatment plants (publicly
owned treatment works) in accordance
with section 301(b) (1) (B) of the Federal
Water Pollution Control Act Amend-
ments of 1972 (FWPCA). The Secondary
Treatment Information regulation was
promulgated pursuant to section 304 (d)
(1) of the FWPXJA on August 17, 1973
(38 FR 22298), and amended for deletion
of the fecal colifonn bacteria limitations
and clarification of the pH requirement
on July 26,1976 (41 FR 30786).
Fifty-five (55) of the sixty (60) com-
ments received in response to the pro-
posed amendment supported adjusting
the suspended solids limitations for
wastewater treatment ponds. The final
amendment is substantially the same as
proposed, with the only significant
change noted below. A number of the
commenters, while agreeing in principle
with the proposal, requested clarifica-
tion on certain points. The responses to
these and the other major comments are
also discussed below.
DISCUSSION OP MAJOR COMMENTS
MAXIMUM FACILITY DESIGN CAPACITY
The proposed amendment (§ 133.103
(c) (special considerations) indicated,
in part, that the suspended solids limita-
tions could be adjusted for wastewater
treatment ponds with a maximum facil-
ity design capacity of one million gallons
per day (mgd) or less.' This provision
was included because the Agency believes
that the supplemental treatment meth-
ods, which are often needed to achieve
the suspended solids limitations of
§ 103.102 (b) with wastewater treatment
ponds, unavoidably add to the complexity
of designs and may strain the operational
capabilities of small communities where
the vast majority of wastewater treat-
ment ponds are used. The one million
gallons per day maximum facility design
capacity was based on a population of
10,000 and an average wastewater flow
of 100 gallons per capita per day. A
number of comments were received
which indicated specific instances where
wastewater flows to. wastewater treat-
ment ponds in communities of 10,000
population or less exceed one mgd. In
recognition of the fact that there may
be valid reasons for wastewater flows to
exceed 100 gallons per capita per day,
the final rule has been changed to in-
dicate that the suspended limitations
may be adjusted for wastewater treat-
ment ponds with a maximum facility
design capacity of two mgd or less.
A number of comments were also re-
ceived which requested a clarification of
the term "maximum facilities design
capacity." As the term implies, it is the
flow rate which is used as the design
basis for sizing wastewater treatment
facilities. In most instances design ca-
pacities are expressed in terms of annual
average'flows, even though there may be
seasonal variations in flow rates which
obviously must be accounted for in the
sizing of treatment facilities.
APPLICABILITY OP THE REGULATION
A number of comments questioned
whether the suspended solids require-
ments for privately or Federally owned
ponds treating sanitary wastewater could
be adjusted as a result of the change
to 40 CFR 133. It is clear that section
304(d) (1) of the FWPCA requires pro-
mulgation of standards directly appli-
cable to publicly owned treatment works
only and therefore 40 CFR 133 is not
directly applicable to private or Federal
wastewater treatment ponds. However,
EPA has authority under section 402 of
the Act to issue permits where no
effluent limitation standards have been
promulgated and to fashion conditions
on a case-by-case basis premised on
EPA's best technical judgment. In fash-
ioning such conditions, EPA may con-
sider any available information. Accord-
ingly, the provisions of § 133.103(c) may
be considered as guidance in conjunction
with other information in determining
individual NPDES permit requirements
for privately and Federally owned
sewage treatment plants which are not
subject to effluent limitation guidelines
proposed or promulgated under sections
30.1, 304, and 306 of the FWPCA.
COMMENTS WHICH DID NOT SUPPORT
THE RULE CHANGE
One commenter stated that the
amendment is. not consistent with the
FWPCA because section 304 (d) contem-
plates secondary treatment limitations
that do not vary for different treatment
processes. Two of the comments which
objected to the rule change indicated
that the amendment is not needed be-
cause technology is available to enable
small communities to comply with the
existing requirements of 40 CFR 133.
Two comments also stated an objection
to. the amendment on the grounds that
some small communities already comply
or are in the process of complying with
the original requirements.
The legislative history of the FWPCA
indicates that secondary treatment may
be considered to represent a range of re-
movals (H. Rep. 92-911, p. 101, Leg.
Hist. p. 788). Based on this concept of
range, there are different subcategories
of treatment technologies within the
broad category of secondary treatment.
In this instance which is clearly sup-
ported by historical, technical and
economic data; EPA is exercising its au-
thority to define secondary treatment
through categorization. Wastewater
treatment ponds, without supplementary
suspended solids removal processes, have
traditionally been considered a form of
secondary treatment for small com-
munities. Moreover, wastewater treat-
ment ponds have been extensively used
by small communities in such applica-
tions primarily because of their low cost
and operational simplicity.
As stated in the preamble to the pro-
posed rulemaking, methods for remov-
ing excessive suspended solids (algae)
from wastewater treatment pond efflu-
ents have been developed but have not
been widely demonstrated in all climatic
regions of the country. The Agency was
faced with the fact that there was a
lack of confidence both in the capabilities
of conventional pond systems and in the
use of supplementary devices which
would effectively rule out the continued
use of wastewater treatment ponds to
achieve the secondary treatment re-
quirements in many sections of the
country. The Environmental Protection
Agency believes that wastewater treat-
ment ponds play a vital role in the
Nation's water pollution control strategy
and that, because of their advantages
of simplicity, low cost and minimal ener-
gy requirements, ponds should be re-
tained as an option for smaller com-
munities. The Agency also recognizes
that suspended solids due to live algae
in pond effluents have fundamentally and
substantially different characteristics
than sewage solids or solids from other
treatment processes. It is for these rea-
sons the final rulemaking is being
adopted substantially as proposed.
Viewed in other terms, adoption of the
amendment for ponds will result in
FEDERAL REGISTER, VOL. 42, NO. 195—FRIDAY, OCTOBER 7, 1977
-------
RULES AND REGULATIONS
54665
significant economic benefits, particu-
larly for small communities. It is esti-
mated that the projected savings in
capital construction costs alone will be
in excess of one billion dollars nation-
wide. .
In promulgating this amendment to
40 CPR 133 for small wastewater treat-
ment ponds, however, the Environmen-
tal Protection Agency does not intend
to imply that supplemental treatment
devices such as rock filters or intermit-
tent sand filters are not acceptable
methods for upgrading pond perform-
ance. In many instances where ponds
presently do not meet discharge require-
ments pursuant to specific quality stand-
ards, upgrading can be economically ac-
complished while generally preserving
the basic concept of simplified operation.
The Agency strongly believes that any
large scale approach to replace ponds
with mechanical plants would be ill-
advised because the previously men-
tioned advantages of ponds for small
communities must be sacrificed.
RELATIONSHIP TO INDUSTRIAL EFFLUENT
LIMITATIONS
Comments were received which sup-
ported the position that less stringent
suspended-solids limitations should also
be applied to industrial .wastewater
treatment ponds. Section 304(d) (1) of
the FWPCA requires that EPA "pub-
lish information * * * on the degree of
effluent reduction attainable through
application of secondary treatment." The
factors to be considered in setting efflu-
ent limitations for industrial discharges
pursuant to section 304(b) of the PWPCA
are distinct from the section 304Cd) (1)
criteria. In consideration of these stat-
utory differences, EPA clearly has au-
thority to establish different effluent lim-
itations for municipal and industrial
discharges with regard to the control
of one or more pollutant parameters.
ADJUSTMENT OF THE BIOCHEMICAL OXYGEN
DEMAND (BOD) LIMITATIONS FOR PONDS
A number of comments suggested
that an adjustment of the BOD limita-
tions of 40 CPB 133 should also be al-
lowed for wastewater treatment ponds.
An. equal number of commenters sup-
ported the position that the suspended
solids limitation of 40 CFB 133 is the only
parameter that properly designed and
operated ponds cannot meet.
While there is. not an extensive
amount of routine monitoring data
available to precisely define wastewater
treatment pond performance, the ma-
jority of the State Agencies with re-
sponsibilities in this area expressed the
belief during the development of the
amendment that wastewater treatment
ponds are generally capable of meeting
the BOD requirements of 40 CPR 133.102.
The Agency believes that adoption of
the amendment, as proposed, will effec-
tively ensure the continued acceptabil-
ity of wastewater treatment as a sec-
ondary treatment process. It is impor-
tant to recognize, however, that many
of these facilities will .still have to be
upgraded to meet the BOD limitations
of 40 CPB 133, which remain unchanged.
THE USE OF SUSPENDED SOLIDS AS A
REGULATORY PARAMETER FOR WASTEWATER
TREATMENT PONDS
Comments received from four State
Agencies' indicated that suspended sol-
ids limitations should be eliminated en-.
tirely as a regulatory parameter for
wastewater treatment ponds. The Envi-
ronmental Protection Agency recognizes
that, because suspended solids limita-
tions set in accordance with § 133.103
(c) are to be based on a sampling of
ponds which meet the BOD require-
ments of 40 CFB 133, BOD removal
capability will be the major factor used
in determining the adequacy of waste-
water treatment pond designs. How-
ever, the statutory history of the FWPCA
has been interpreted to require that
standards for publicly owned treatment
works include limitations on both BOD
and suspended solids. Furthermore, EPA
considers suspended solids to be a pol-
lutant parameter for which regulatory
control is important.
AVAILABILITY OF SUSPENDED SOLIDS
MONITORING DATA
Several comments were received
which supported the view that there is
insufficient suspended solids monitoring
data available to reliably establish al-
ternative limitations for ponds in ac-
cordance with § 133.103(c). A number of
other commenters provided actual
monitoring data or indicated that such
data is currently available. During the
period of time since the amendment was
proposed, the EPA Regional Offices have
been requested to begin compiling data
which could be used to establish sus-
pended solids limitations for ponds in
accordance with § 133.103(c). Efforts to
date have indicated that sufficient data
is available. Furthermore, preliminary
determinations have demonstrated a
reasonable degree of consistency nation-
wide.
REQUESTS FOR CLARIFICATION
Comments were received which re-
quested clarification of the following as-
pects of the rule change:
(1) What types of wastewater treat-
ment ppnds are covered by § 133.102 (c) ?
As indicated in § 133.102(c), adjustment
of the suspended solids limitations may
be made in cases where waste stabiliza-
tion ponds are the sole process.used for
secondary treatment. Determination of
the types of facilities to which § 133.103
(c) can be applied will be in accordance
with the terminology section of the EPA
technical bulletin, "Wastewater Treat-
ment Ponds" (EPA 430/9-74-011).
Specifically included are photosynthetic
and aerated ponds. The amendment is
not applicable to polishing or holding;
ponds which are preceded by other bio-
logical or physical/chemical treatment
processes capable .of secondary treat-
ment.
(2) Do the provisions of § 133.103(c)
apply to new facilities? Yes, the sus-
pended solids limitations for new waste-
water treatment ponds can be set in ac-
cordance with the provisions of § 133.-
103(c). It must be recognized, however,
design standards for new wastewater
treatment ponds may be more stringent
than those used in the determination
of "best waste stabilization pond tech-
nology" in cases where the States or the
EPA Regional Offices determine that
such design standards are important for
the overall reliability of new pond sys-
tems in that area.
(3) Does the amendment apply to the
criteria for best practicable waste treat-
ment technology? Yes, the criteria for
best practicable waste treatment tech-
nology contained in Alternative Waste
Management Techniques for Best Prac-
ticable Waste Treatment (EPA 430/9-
75-013, October 1975), states that "pub-
licly owned treatment works employing
treatment and discharge into navigable
waters shall, as a minimum, achieve the
degree of treatment attainable by the
application of secondary treatment as
defined in 40 CPB 133." Unless specific
revisions to the best practicable waste
treatment criteria are published-, or
other applicable, regulations are promul-
gated, the standards contained in 40
CFB 133, including the provisions of this
amendment, will continue as the mini-
mum requirements for treatment and
discharge alternatives.
(4) Will specific guidance on imple-
mentation of the rule change be issued?
As indicated previously, the EPA Be-
gional Offices have been working on pre-
liminary determinations for establish-
ment of suspended solids limitations for
wastewater treatment ponds in accord-
ance with the proposed provisions of
§ 133.103(c). In most cases these efforts
have been coordinated with the appro-
priate State Agencies. Draft guidance
on procedures for actual implementa-
tion of the rule change has been circu-
lated to the Begional Offices and will be
finalized upon adoption of the amend-
ment.
In consideration of the foregoing, Part
133 of Chapter I of Title 40 of the Code
of Federal Regulations is amended as set
forth below (section 304 (d) (1) and 301
(b) (1) OB) of the Federal Water Pollu-
tion Control Act Amendments of 1972
(33 U.S.C. 1342, 1345 and 1361)).
Dated: September 28, 1977.
DOUGLAS M. COSTLE,
Administrator.
1. Section 133.103 is amended by add-
ing paragraph (c) as follows:
§ 133.103 Special considerations.
(c) The Regional Administrator (or, if
appropriate, the State subject to EPA
approval) is authorized to adjust the
minimum levels of effluent quality set
forth in paragraphs (b) (1), (b) (2), and
(b) (3) of § 133.102 for treatment works
subject to this part, to conform to the
suspended solids cpncentrations achiev-
able with best waste stabilization pond
technology, providedTthat: (1) waste sta-
bilization ponds are the sole process used
FEDERAL REGISTER, VOL. 42, NO. 195—FRIDAY, OCTOBER 7, 1977
-------
54666
RULES AND REGULATIONS
for secondary treatment; (2) the maxi-
mum facility design capacity is two mil-
lion gallons per day or less; and (3) op-
eration and maintenance data indicate
that the requirements of paragraphs (b)
(1), (b) (2), and (b) (3) of § 133.102 can-
not be achieved. The term "best waste
stabilization pond technology" means a
suspended solids value, determined by
the Regional Administrator (or, if ap-
propriate, the State Director subject to
EPA approval), which is equal to the
effluent concentration achieved 90 per-
cent of the time within a State or ap-
propriate contiguous geographical area
by waste stabilization ponds that are
achieving the levels of effluent quality
established for biochemical oxygen de-
mand in § 133.102(a).
[PR Doc.77-29316 Piled 10-6-77:8:45 amj
FEDERAL REGISTER, VOL. 42, NO. 195—FRIDAY, OCTOBER 7, 1977
U.S. GOVERNMENT PRINTING OFFICE: 1980 — 677-094/U05
-------
-------
n
03 O
T3
5
'U
-
P
.
o
------- |