United States
Environmental Protection
Agency
Robert S. Kerr Environmental Research'
Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-83-015 May 1983
Project Summary
Overland Flow Treatment of
Municipal Sewage at Easley, SC
A. Ray Abernathy
A full-scale overland flow facility was
constructed in the piedmont region of
South Carolina where precipitation
averages 127 cm (50 inches) per year.
Both comminuted raw sewage and
facultative lagoon effluent were applied
to overland flow slopes. Effective
treatment of comminuted raw sewage
was achieved along with polishing of
the lagoon effluent. Algal cells in the
lagoon effluent were difficult to remove
by overland flow and frequently resulted
in greater than 30 mg/l suspended solids
concentration in the final effluent from
lagoon plots.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada, OK, to
announce 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).
Introduction
This project sought to demonstrate the
feasibility of treating either comminuted
raw sewage or effluent from a facultative
lagoon in piedmont South Carolina where
mild winters prevail in a region of high
rainfall. The major objective was to
demonstrate the effective treatment of
the two waste streams in a rather simple,
easily operated overland flow facility.
Treatment System
The facility consisted of separate
pumping systems for each wastewater.
The systems were designed to apply 95
cubic meters per day (25,000 gpd) of
comminuted raw sewage and 284 cubic
meters per day (75,000 gpd) of lagoon
effluent to overland flow slopes. Fourteen
separate plots were designed with a flow
distance of 46 meters (150 feet) to treat
lagoon effluent, and three plots 50
meters (165 feet) long were designed to
receive raw wastewater. A V-notch weir
was included at the foot of each plot for
gaging runoff.
Grassed channels received the plot
runoff, and the channels joined to form
one main channel to convey the treated
wastewater to a chlorine contact cham-
ber for disinfection. After disinfection and
metering through a Parshall flume the
effluent was discharged to a receiving
stream.
Conclusions
The facility was in operation for three
years at several application rates and
schedules. Influent and effluent
measurements of BOD5, organic carbon,
suspended solids, and nitrogen and
phosphorus compounds were made to
evaluate system performance. Samples
were also collected at intervals down
individual plots to determine profiles of
removal of the different parameters.
Both systems produced effluents
which equalled or exceeded the quality of
effluent from typical secondary sewage
treatment systems. The major problem
with treating lagoon effluent by overland
flow was the persistence of small algae
capable of moving along with the applied
wastewater and exiting with the treated
effluent. As a result, the effluent
frequently exceeded 30 mg/l suspended
solids and was typically higher in sus-
pended solids than effluent from plots
treating raw sewage.
The systems were relatively simple to
operate. Maintaining the pumps, clearing
occasional plugged spray nozzles, and
cutting the grass cover crop were the
major operational tasks required to main-
tain the treatment system.
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Raw Sewage Treatment
for the raw sewage application system
total BOD5 (87% reduction) and suspended
solids (85% reduction) were readily
removed. Nitrogen and phosphorus re-
movals averaged 62% and 50%, respect-
ively. Table 1 shows a summary of the
performance of the raw sewage system.
Figure 1 shows the profile of BOD5
removal relative to travel distance for the
raw sewage plots.
160
140
120
^ 100
1 80
§
0]
60
40
20
0
Figure 1.
15 30 41 50
Downslope Distance (m)
BODsprofile—raw sewage
application.
Lagoon Effluent Treatment
As mentioned earlier, algal cells were
difficult to remove from facultative lagoon
effluent. Table 2 shows the mean
performance of the lagoon effluent
system. As can be seen the lagoon
effluent plots removed 55% BOD5, 45%
suspended solids, 67%total nitrogen, and
34% total phosphorus from the lagoon
effluent. Table 2 contains a summary of
the performance of the lagoon effluent
system, and Figure 2 shows the profile of
BOD5 removal relative to travel distance
for the lagoon effluent plots.
Table 2. Summary of Performance of Lagoon Effluent Plots from
January 1979 through September 1981
Lagoon Effluent Lagoon Plot Effluent
Mean Number Mean Number Cone.
Cone. Range of Cone. Range of Removal
Parameter (mg/lj (mg/l) Samples (mg/l) (mg/l) Samples (%)
1
BOD
Suspended Solids
Total Organic Carbon
Total Phosphorus fas P)
Total Nitrogen (as N)
Ammonia Nitrogen (as N)
31
74
60
35
13
0.48
16-80
26-143
37-84
2.1 -5.5
9.7-17.3
0.02-3.6
45
50
33
32
10
42
14
41
46
2.3
4.3
0.16
9-30
5-152
20-61
0.6-4.2
3.2-14.0
0.01-0.49
63
99
56
66
48
69
55
45
23
34
67
67
700
80
: eo
?
' 40
20
0 7.6 15 23
Downslope Distance (mj
Figure 2. Suspended solids profile—lagoon effluent.
30
38
46
Costs
The facility cost $184,538 to construct
and $10,684 to operate for one year.
Without research costs the construction
and operating costs would have been
approximately $173,000 and $6,425,
respectively. These costs were for a
nominal capacity of 380 cubic meters
(100,000 gallons) per day, and the lagoon
was already in operation.
Table 1.
Summary of Performance of Raw Sewage Plots from
January 1979 through August 1980
Raw Sewage
Raw Sewage Plot Effluent
Parameter
BOD
Suspended So/ids
Total Organic Carbon
Total Phosphorus (as P)
Total Nitrogen (as N)
Ammonia Nitrogen fas N)
Mean
Cone.
(mg/l)
157
161
95
8.0
32
18
Number Mean
Range of Cone.
(mg/l) Samples (mg/l)
62-270
40-464
44-204
1.0-1.7
28-33
3.6-136
37
38
26
26
6
38
21
24
36
4.0
12
3.0
Number
Range of
(mg/l) Samples
3-50
2-122
20-54
0.1-8.0
2.7-43.7
0.04-13
36
53
44
36
31
53
Cone.
Removal
r/o)
86.9
85.1
61.8
50.0
62.5
83.3
Recommendations
Overland flow should be considered as
a wastewater treatment alternative for
small municipalities where land is
available at reasonable cost. Overland
flow is capable of achieving secondary
treatment of comminuted raw sewage
and polishing effluent from facultative
lagoons.
Research should be done to define the
upper limits of hydraulic loading rate. It
may be possible to apply wastewater at a
higher rate and thus reduce land costs.
Investigations are needed to improve
the removal of algal cells from facultative
lagoon effluent by overland flow. With
this one exception, overland flow did a
good job of polishing lagoon effluent.
Storage is needed even in mild climates
for emergency periods, mowing and
harvesting of grass, and short periods of
severe weather. Sufficient excess
overland flow treatment area could be
provided in lieu of this storage.
Although the research described in this
article has been funded wholly or in par
by the U. S. Environmental Protectior.
Agency through cooperative agreement
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number R803929 to the South Carolina
Department of Health and Environmental
Control, it has not been subject 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.
A. Ray Abernathy is with Clemson University, Clemson, SC 29631.
Bert E. Bledsoe is the EPA Project Officer (see below).
The complete report, entitled "Overland Flow Treatment of Municipal Sewage at
Easley, South Carolina," (Order No. PB 83-170 985; Cost: $14.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 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
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Agency
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