United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-83-007 Mar. 1983
&EPA Project Summary
Advanced Biological
Treatment of Municipal
Wastewater Through
Aquaculture
Dempsey H. Hall and Joel E. Shelton
This research project was initiated
with the overall objectives of: (a) assess-
ing the potential of aquaculture as a
suitable means of treating municipal
sewage in a mid-temperate latitude on
an annual basis, (b) providing a set of
design criteria for implementation of
aquaculture as an advanced wastewater
treatment method, and (c) achieving an
effluent quality amenable to PL 92-500
and the 1977, 1983. and 1985 stan-
dards and goals.
Two four-celled raceways construc-
ted in a series adjacent to a primary
wastewater stabilization pond were
used in the studies. One raceway series
functioned as the experimental system,
while the other served as a control. The
first experimental phase used a source
of wastewater from the primary waste-
water stabilization pond. The second
experimental phase used a source of
wastewater from the primary clarif ier of
an activated sludge treatment plant.
The primary clarifier also provided the
source of wastewater to the primary
wastewater stabilization pond. Under
both experimental conditions the experi-
mental raceway was stocked with a
native Oklahoma fish, Pimephales
promelas Raf., at two stocking densi-
ties, one for each experimental phase.
An analysis of the wastewater quality
data assembled during the two experi-
mental phases revealed moderate re-
ductions in suspended solids during the
first experimental phase which could
have been attributed to the presence of
the fish. No distinguishable reductions
in five-day biochemical oxygen demand
(BOD5) were statistically supported that
could be attributed to the fish stock.
Analyses of nutrient parameters also
indicated no distinguishable reductions
due to fish populations. During the
second experimental phase, high mor-
tality due primarily to oxygen stress
revealed no observable impact on the
quality of wastewater that could be
attributed to the fish. Retention time of
the wastewater within each cell of the
raceway appeared to play a strong role
in the observed percentage reductions
in most of the regulatory and nutrient
parameters.
A marked reduction in fecal coliform
organisms was attributed to the reten-
tion time of the wastewater rather than
due to influences of the fish present in
the cells.
Biological studies of fish growth and
reproductive capabilities revealed mod-
erate successes with respect to repro-
duction, while the analysis of growth
revealed exceptional potentials for pro-
duction of biomass over a short period
of time.
The full project report covers the
period of March 1977 through August
1979 and describes the experiments
and results in detail.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada, OK, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
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Introduction
The current demand for advanced
wastewater treatment practices, arising
from the enactment of PL 92-500, the
Federal Water Pollution Control Act of
1972, coupled with a demand for energy
conservation and the underlying econom-
ic implications, is rapidly creating a
dilemma in the field of wastewater treat-
ment. In Oklahoma alone, approximately
80 percent of the communities are cur-
rently utilizing wastewater stabilization
ponds as a means of treating municipal
sewage. Such conventional treatment
practices have not adequately produced
effluents of a quality amenable to estab-
lished standards provided by PL 92-500.
The problem that currently exists in
finding an equitable solution arises not
from a lack of advanced waste treatment
technology but from a cost-effective
implementation of advanced physical-
chemical treatment processes in areas
where the serviced population is inade-
quate to finance and maintain such
facilities. Such a problem establishes a
strong premise for investigating the
potentials of utilizing existing conven-
tional treatment methods and supplement-
ing physico-chemical and biological treat-
ment processes with extended biological
activity in the form of aquaculture.
The primary objectives of this study
were to: (a) assess the potential of aqua-
culture as a suitable means of treating
municipal sewage in a mid-temperate
latitude on an annual basis, (b) provide a
set of design criteria for implementation
of aquaculture as a wastewate treatment
method, and (c) achieve an effluent quality
amenable to PL 92-500 and the 1977,
1983, and 1985 standards and goals.
Subordinate objectives included a quanti-
tative determination of the degree of
sewage treatment during major seasons,
and an evaluation of practical uses and
economic potentials of biological products
of the system.
The scope of this study was somewhat
broad in context, yet limited in application
due to the limited background information
available and the physico-chemical nature
of the wastewater environment. Such
limitations necessitated the use of certain
criteria in selecting a suitable test orga-
nism, namely: (a) a species of fish native
to Oklahoma waters, (b) a species known
to have a high tolerance for unstable
conditions which exist at various intervals
in wastewater stabilization ponds, primar-
ily dissolved oxygen (D.O.), and (c) a
species of fish readily available and easily
handled. For these reasons the fathead
minnow (Pimephales promelas Raf.),
although not the most efficient filter
feeder, was selected as the test organism.
The fathead minnow has been classified
as an opportunistic feeder, utilizing small
invertebrate organisms as well as algae,
and its long intestinal tract suggests an
ability to function efficiently as a herbi-
vore.
Conclusions
The analysis of the regulatory param-
eter suspended solids, under the waste-
water and stocking conditions employed
in the first experimental phase, revealed
an apparent contribution of the fish
present within the test cells. Such a
contribution was reflected in a compar-
ison between the concentration of sus-
pended solids within the effluent in the
final cell of the experimental versus
control series raceways. Unlike the
suspended solids parameter, another
regulatory parameter, BOD5, showed no
statistically significant contrast between
experimental and control cells, with re-
spect to concentrations monitored. Such
results suggest that the direct reduction
in suspended solids was insignificant to
indirectly stimulate a reduction in BOD5.
The observed percentage reduction in
BOD5 from influent to effluent of each
raceway (control and experimental) was
apparently related directly to the retention
time of wastewater rather than the
presence of the fish within the waste-
water.
The analyses of regulatory parameters
(BOD5and suspended solids), and nutrient
parameters, under wastewater and stock-
ing conditions in the second experimental
phase revealed no apparent contribution
of the fish to a reduction in concentra-
tions.
Considering the nature of the waste-
water tested under the second experi-
mental phase (wastewater of primary
treatment quality), it is apparent that if
cultures of fathead minnows are to be
implemented as a cost-effective means of
supplemental wastewater treatment, they
should be considered as an adjunct to the
wastewater stabilization pond and not as
a substitute for secondary treatment
afforded by the wastewater stabilization
pond processes.
Under the wastewater conditions pro-
vided in the first experimental phase,
wastewater from a primary wastewater
stabilization pond, the fathead minnow
exhibited the ability to live and reproduce
successfully with only limited threat from
disease.
Under the wastewater conditions pro-
vided in the second experimental phase,
wastewater from primary treatment qual-
ity, the fathead minnow was able to
survive. However, under extreme stresses
initiated by wastewater with a high oxy-
gen demand, such an existence was extremely
limited and prohibited reproductive rigor
and success.
In summary, the wastewater community
provides an extremely opportunistic envi-
ronment which, if managed and moni-
tored closely, may provide a very cost-
effective approach to the utilization of
nutrients that conventionally are carried
away by receiving stream waters and very
often end up overloading and upsetting
the balance of nutrients provided for m
the natural stream environment. Finfish
within the wastewater environment pro-
vide an opportunity for recycling nutrients,
capturing fundamental elements within
protein-rich products usable in numerous
ways by man. Such an approach can be
feasibly implemented as a valuable water
reuse technique.
Recommendations
A definite potential exists for the inte-
gration of aquaculture techniques and
wastewater treatment. If such a goal is to
be implemented, further studies are
necessary to more clearly define the intri-
cate food web that exists within the waste
stabilization pond. Such a definition
would provide a stronger basis for selec-
ting the appropriate species of fish to be
cultured.
The unstable nature of raw and even
primarily treated municipal wastewater
limits the potential of introducing a
population of finfish due to the high level
of competition for oxygen; therefore, if
finfish culture in the wastewater environ-
ment is to be a successful integration of
productivity and wastewater treatment,
such operations should focus on supple-
menting the secondary treatment mode.
Due to the-wide range of diurnal fluctu-
ations in oxygen and temperature within
the wastewater stabilization pond, finfish
culture practices should include: (1) a
source of emergency aeration to provide a
means of quickly stabilizing septic con-
ditions often experienced during the
year-round operation of the lagoon, partic-
ularly during late summer and early spring
seasons, (2) adequate manpower and
equipment for handling fish stock to limit
the stresses imposed on the fish during
handling, (3) disease control protocol to
ensure minimal stock loss, and (4) alter-
native planning for wastewater flows,
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including multiple raceway designs,
which allow the operator a means of
alternating flow and thus eliminate prob-
lems with overloading.
The successful implementation of aqua-
culture practices with wastewater treat-
ment will rely heavily on interdisciplinary
skills of biologists and wastewater treat-
ment specialists particularly in organiza-
tion and establishment of such an
operation. Proper initial organization will
ensure a smooth operation which should
require only minimal skills to maintain
after installation.
Facilities,
Operation, and Results
The study was conducted at the
Bethany-Warr Acres sewage treatment
facility which serves a portion of the
northwest Oklahoma City municipal com-
plex. The treatment phases of the facility
consisted of: (a) screening, (b) grinding
(comminutor), (c) aeration, (d) primary
and secondary clarification, and (e) sludge
digestion. Following these treatment
phases the effluent was discharged to
primary and secondary wastewater stabil-
ization ponds, where the wastewater
underwent biological oxidation processes
before being discharged into the adjacent
receiving stream (Bluff Creek, a first-
order stream location on the Cottonwood
Creek drainage basin).
In order to obtain the necessary con-
trols, with respect to flow and retention of
wastewater, a separate small-scaled
series of wastewater stabilization ponds
were constructed adjacent to the existing
primary wastewater stabilization pond.
This facility, as shown in Figure 1,
consisted of eight earthen cells, arranged
in two series with four cells in each
series. Each cell had a surface area of
approximately 0.1 hectare (0.25 acres).
The two series of cells were constructed
in parallel, with each individual cell within
one series corresponding to the same
numbered cell within the adjacent series,
with respect to sequence, flow, and
retention time. This design allowed for
one series to serve as an experimental
control for the other series. All cells
within a single series were constructed
as identically as possible to its correspond-
ing cell of the adjacent series, and all
ponds were designed with the same
general specifications with respect to
depth, area, and distribution receptacles.
At the end of the two series of treatment
cells, one large cell was constructed to
receive flows from both series of cells.
The contents of this cell was periodically
used for irrigation purposes or was
pumped back into the secondary waste-
water stabilization pond of the permanent
treatment facility.
The experimental facilities were de-
signed to maintain maximum achieveable
control on flow of wastewater through
use of distribution receptacles equipped
with 30° V-notch weirs. The arrangement
of these receptacles was designed to
allow the investigator an alternate means
of distributing flow of wastewate through-
out the entire series of experimental cells.
Due to the nature of the wastewater
received by the experimental system, the
serial flow pattern was selected as the
most appropriate design for experimenta-
tion, as it allowed for optimum retention
time which in turn produced a quality of
wastewater suitable for fish culture.
During the course of the study, the
existing treatmentfacility was reconstruc-
ted and modified. This necessitated the
utilization of two experimental phases
with two separate sets of conditions. The
two sets of conditions differed primarily
with respect to wastewater characteris-
tics and stocking density of fish. The
physical characteristics of flow and reten-
tion were the same for both experimental
phases.
During the first experimental phase,
from October 19, 1977 through May 17,
1978, primary lagoon effluent was pro-
vided as the source of wastewater for
experimentation. Each of the four cells
within the test series were stocked with
Pimephales promelas Raf. at a density of
approximately 38 kilograms (kg)/0.1
hectare (83 pounds (lb)/0.25 acres).
During the second experimental phase,
from August 2, 1978 through May 9,
1979, the wastewater source was sup-
plied directly from the primary clarifier of
the existing treatment facility, by means
of a submersible pump transmitting waste-
water to the centrally located collection
point and distributing the wastewater to
the two series raceways. Due to the high
suspended solids and low D.O. content of
the wastewater received from the pri mary
clarifier, it was necessary to retain the
wastewater, allowing time for stabiliza-
tion and production of phytoplankton.
This was accomplished by eliminating
fish stock from the first cell in the
experimental series, which provided a
more stable environment for the f inf ish in
the remaining cells of this series. The
remaining three cells were stocked at a
density of 151 kg/0.1 hectare (334
lb/0.25 acres).
Under both experimental phases, waste-
water was received by a centrally located
distribution receptable (Figure 1) and was
distributed to each of the two series
raceways at an average flow of 0.95
liters/second (I/sec) (15 gallons per
minute [gprn]). The flow rate varied from
0.63 I/sec (10 gpm) to 1.26 I/sec (20
gpm) depending on several uncontrollable
factors inherent to gravitational distribu-
tion. This variation in flow necessitated
daily monitoring and correction by adjust-
ment of the V-notch weirs in the distri-
bution receptacles of the first cell in each
series. The flow between each cell within
each series varied somewhat from the
flow to the first cell in each series,
depending on the evaporation rate and
the amount of rainfall. Without compen-
sating for input from rainfall or loss from
evaporation, the retention time of waste-
water in each cell was approximately 15-
20 days.
For purposes of identifying sample
locations, each of the cells in the two
series was assigned numbers sequenti-
ally through the series. Along with the
numbered location, subscripts were as-
signed to designate the control series and
thetest series; A- designating the control
series with no fish and B -designating the
experimental series which contained fish
(Figure 1).
During this study, under both phases,
wastewater samples were collected
weekly from the discharge point at each
cell within the two series and a sample
was collected from the initial wastewater
supplied to the system. All samples were
collected on the same weekday at approxi-
mately the same time of day (1100-1200
hour). Along with the wastewater sam-
ples, temperature and dissolved oxygen
data were collected at each sampling
location. Several water quality param-
eters were analyzed including BOD5,
suspended solids, and nutrients.
The performance of the system under
two operational modes was evaluated by
determining the mean effluent levels from
each cell for each of the selected param-
eters and by comparing changes in the
character of the flow as it moved through
the experimental series of cells with the
character of the flow at the corresponding
points in the control series. In addition,
overall performance of each series was
determined by comparing the effluent
concentration from the last cell in each
series with the level of that parameter in
the influent to the series.
In order to minimize the variability due
to the day-to-day changes in the character
of the influent and variability due to
seasonal influences on temperature, sta-
tistical comparison of each cell in the
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experimental series with the correspond-
ing cell in the control series was con-
ducted utilizing a t-test of observations
paired according to sample date. This
permitted the use of an alpha level of
0.05.
Due to the observed critical periods of
low oxygen concentrations encountered
during the study, a means of supple-
menting photosynthetic oxygen produc-
tion was provided using forced air blowers
and perforated distribution lines for dif-
f users. The supplemental aeration supply
was designed to provide aeration to
experimental and control cells concur-
rently to minimize bias to the experi-
mentation. Most of the supplemental
aeration was necessaryduring the winter
months when extended periods of ice
cover jeopardized the existence of suf-
ficient dissolved oxygen concentrations.
In addition to the monitoring of physico-
chemical parameters, biological activity
of fish was monitored visually and through
analysis of growth patterns. Factors moni-
tored visually included reproductive activ-
ity, movement and congregation of fish
due to oxygen stress, mortality, disease
and periodic inventory of fish stock.
During the first experimental phase,
the statistical analysis of BOD5 data
(Table 1) indicated a significantly lower
concentration in the first experimental
cell than in the first control cell, at both
the 0.1 and 0.05 alpha levels. The only
other cells that maintained any significant
differences were the second cells of the
raceway series, which displayed signifi-
cant differences at the 0.1 level only.
Considering the real differences in mean
effluent concentrations and the relatively
narrow range of percent reduction values,
it was assumed that no real differences
existed between the control cell effluent
BOD5 levels and the experimental cell
BOD5 levels.
Under the second experimental phase,
the results of the BOD5 analyses indicated
no statistically significant differences in
effluent concentrations for each of the
experimental and control cells of the first
three stages in the raceway series. The
last experimental cell containing fish,
displayed significantly higher effluent
BOD5 than its corresponding control cell.
Also, the observed percentage reduction
was much higher for the control series
than for the experimental series contain-
ing fish.
Statistical analysis of the suspended
solids data during the first experimental
phase revealed a somewhat different
trend from that of BODs concentration
within the first two experimental cells
Return Effluent —Secondary Lagoon f f
Holding
Cell
I .
Pt/mp-llj
™" * "* ™" 1
.;,«, j-{fa, H
i
i *
4 4B j-i i 3B j-H
N X \
\ X ^
. x x
Surface Irrigation * j— -
\ \ \
\ \ \
\ \ \
\ \ \
T 2A FT T 1A I
1 ' - 1 ^ f
1
i i
El IT1 1
* 2B J-| * !B j
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30°V-Notch Weir
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Primary
Lagoon
Figure 1. Diagram of Oklahoma State Department of Health, Aquaculture research
facilities located at the Bethany-Warr Acres Municipal Wastewater Treatment Plant.
Table 1.
Analytical Results for Regulatory Parameter. BODs. Sampled During First and
Second Experimental Phases
First Phase
Effluent
Stat.
Para,
x mg/l
S
N
x mg/l
S
N
Infl. Cell
57.8
34.0 Contr
Exp.
t (paired observations)
x mg/l
S
N
x mg/l
S
N
60.9
41.7 Contr.
31
Exp.
1
24.6
12.6
250
19.9
11.6
24.0
a.b
428
23.8
33.0
47.2
28.3
33.0
2
27.0
17.2
25.0
21.5
14.1
25.0
b
Second Phase
32.5
17.8
33.0
31.7
21.3
32 O
3
27.5
15.9
24.0
24.6
14.7
24.0
30.3
20.4
33.Q
28.4
15.7
32.0
t (paired observations)
4 Red.
22.4 61
13.2
24.0
21.5 63
11 1
22.0
26.7 41C
14.6
33.0
30. 1 33C
14.0
33.0
a.b
"Indicates statistical significance at X = 0.05.
'"Indicates statistical significance at X = 0.10.
cComposite of cell 1 (x = 15.0, S - 26.1. N = 66) was used to calculate % reduction.
4
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(Table 2). No significant difference exists
for effluent suspended solids concentra-
tion between test cells and corresponding
control cells. The third experimental cell
showed a significantly lower concentra-
tion of suspended solids at an alpha level
of 0.1 than its corresponding control and
the fourth experimental cell showed a
significantly lower concentration at the
0.1 and the .05 alpha levels. Comparison
of the overall 20 percent reduction in
suspended solids from the point of intro-
duction of influent into the raceway to the
effluentfrom the numberfour experimen-
tal cell, and the 11 percent increase in
suspended solids observed across the
control cells indicates that a real differ-
ence exists. This difference can be attrib-
uted to the high finfish population present
in the third and fourth experimental cells
and their role in reducing suspended
solids. Also, the absence of significant
reductions in the first two cells of the
series likely resulted from the low finfish
population levels.
Concentrations of suspended solids
during the second experimental phase
tend to reflect the same pattern. Experi-
mental cells three and four were found to
contain significantly higher concentra-
tions of suspended solids than the corre-
sponding control cells. In fact, a 94
percent increase in suspended solids was
observed from the influent into the race-
way series to the effluent of the fourth
experimental cell, and a four percent
increase was observed over the control
series. Such results support the view that
a large proportion of the suspended solids
present in the primary clarifier waste
stream were not suitable for consumption
by the finfish and their population levels
contributed to the suspended solids load.
Experimental results for nutrient par-
ameters revealed a somewhat contradic-
tory pattern. Observed differences in
concentrations between experimental
cells and corresponding controls failed to
reveal any significance on which to base
a sound conclusion about a reduction in
nutrients due to fish living within the
cells.
During the course of study, visual
inspection of the general condition of the
fish within the wastewater environment
revealed a healthy and reproductively
viable population with only a moderate
amount of disease, apparently initiated by
handling during seining operations. Al-
though spawning was observed during
the study, the apparent success of such
reproductive activity was low as reflected
by standing crop harvested during the
second experimental phase. Low oxygen
Table 2.
Analytical Results for Regulatory Parameter, Suspended Solids. Sampled During
First and Second Experimental Phases.
First Phase
Effluent
Stat.
Para.
x mg/l
S
N
x mg/l
S
N
Infl.
32.8
19.2
25
Cell
Contr.
Exp.
1
24.2
21.7
24.0
22.5
17.0
26.0
2
34.3
20.8
26.0
30.3
23.8
25.0
3
34.1
20.5
25.0
26.3
11.7
25.0
4
36.5
23.4
26.0
26.4
8.5
25.0
%
Red.
-11
20
t (paired observations)
x mg/l 45.1
S 31.3
N 32
x mg/l
S
N
t (paired observations)
Contr.
Exp.
30.1
21.2
32.0
20.3
14.2
34.0
Second Phase
26.5
15.5
34.0
28.6
19.2
33.0
29.6
23.1
34.0
37.8
20.8
34.0
a.b
a,b
28.6
13.0
34.0
57.5
28.4
34.0
a.b
-94
"Indicates statistical significance atX- 0.05.
^Indicates statistical significance at X = 0.10.
"Composite of cell 1 (x = 29.7, S = 17.9, N = 66) was used to calculate % reduction.
concentrations experienced - throughout
the course of the study probably contri-
buted the single most detrimental impact
on the ability of the young minnows to
survive the embryonic stages of develop-
ment.
Although the research described in this
article has been funded wholly or in part
by the U.S. Environmental Protection
Agency through grant number R803703
to Oklahoma State Department of Health,
it has not been subjected to the Agency's
required peer and policy review and
therefore does not necessarily reflect the
views of the Agency and no official
endorsement should be inferred.
Dempsey H. Hall and Joel £. She/ton are with the Oklahoma State Department of
Health. Oklahoma City. OK 73152.
William R. Duffer is the EPA Project Officer (see below).
The complete report, entitled "Advanced Biological Treatment of Municipal Waste-
water ThroughAquaculture."(OrderNo. PB83-159319;Cost:$11.50. subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, MA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
U. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1914
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