United States
Environmental Protection
Agency
Municipal Environmental Research ^
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-039 Jan. 1983
v>EPA
Project Summary
Operation and Maintenance
Considerations for Land
Treatment Systems
Denis J. Lussier
Land treatment of municipal waste-
water has been practiced since 1840.
The use of land to treat domestic waste-
water has received major impetus re-
cently with the passage of the 1972
Amendments (PL 92-500) and the
1977 Amendments (PL-217) to the
Federal Water Pollution Control Act.
The 1977 Amendments (the Clean
Water Act) provide certain incentives
for funding land treatment systems
through the U.S. Environmental Protec-
tion Agency (EPA) Construction Grants
Program. This program encourages the
use of innovative and alternative tech-
nology for the treatment of municipal
wastewater. Major emphasis is placed
on the planning, design, and construc-
tion of cost-effective municipal treat-
ment works that maximize recycling
and reclamation of water, nutrients,
and energy, and minimize adverse envi-
ronmental and public health impacts.
These developments have made the
land treatment of wastewater a viable
alternative.
Previous EPA research has focused
on two aspects of the land treatment of
wastewater—its long-term environ-
mental effects, and the design consid-
erations for land treatment systems.
EPA has recently produced a series of 10
documents that present the effects of
long-term wastewater application at se-
lected slow-rate and rapid infiltration
sites. These studies are intended to pro-
vide new insights into the long-term ef-
fects of land treatment of municipal
wastewater. In the area of land treatment
system design, EPA (in cooperation with
the U.S. Army Corps of Engineers and
the U.S. Department of Agriculture) has
produced the Process Design Manual
for Land Treatment of Municipal Waste-
water (EPA-625/1-77-008). This man-
ual, which is currently undergoing revi-
sion, is the major data source for the
design of land treatment systems.
Results reported in this publication
related to design will be incorporated in-
to the revised manual when it is reissued.
None of the above documents ade-
quately addresses the issues of opera-
tion and maintenance of land treatment
systems, however. The purpose of this
study was to provide information on
operation and maintenance, staffing,
and costs. The study was also intended
to describe problems currently being ex-
perienced at land treatment sites because
of operator and/or design limitations.
This Project Summary was developed
by EPA's Municipal Environmental Re-
search Laboratory, Cincinnati, OH, 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
The study was broken into two phases.
In the first phase, a project team visited
28 sites using land treatment systems
-------
to collect information on current prac-
tices. The second phase involved defin-
ing procedures to improve the operation
and maintenance of land treatment
systems.
Phase 1
During the first phase, data were
collected for several general areas. One
area was facility staffing. The data col-
lected included numbers and functions
of personnel engaged in operating and
maintaining the land treatment system
and other treatment systems at the site.
This information was collected so that
recommendations on staff size and
qualifications could be tabulated and
proposed.
Another type of data collected during
the site visits was process control and
operational information. These data in-
cluded the operational strategy used by
the operator to decide where, when,
and how much wastewater should be
applied. In addition, the preapplication
treatment was reviewed in terms of its
impact on the land treatment system.
A third area in which data were gath-
ered during the site visits was operation
and maintenance costs. This information
was collected and categorized if possible
—salaries, energy, chemicals, materials,
and other well defined areas. Costs
resulting from amortization of capital
equipment were not included.
During the site visits, data were also
collected on factors that hinder the
operation and maintenance of a land
treatment facility. Included were factors
such as design deficiencies, mechanical
reliability problems, plant layout, wea-
ther, operator limitations, and other fac-
tors contributing to less than optimum
operation and maintenance.
The adequacy of groundwater moni-
toring practices was also assessed dur-
ing the site visits. Neighbors whose pro-
perty was adjacent to, or in the vicinity
of the land treatment system were
interviewed to determine the impact of
the land treatment system on private
individuals.
Phase 2
The second phase of the study was
the developed definitive recommenda-
tions for procedures to improve the
operation and maintenance of land treat-
ment systems. The recommendations
were developed from two different
viewpoints: (1) the type of land treat-
ment system, and (2) the degree of pre-
application treatment. Thus all three
major types of land treatment systems
were visited—slow-rate (irrigation), rapid
infiltration (infiltration-percolation), and
overland flow system—and facilities us-
ing primary-, secondary-, and tertiary-
treated wastewater were visited. In
addition, facilities with different types
of treatment (e.g., trickling filter versus
activated sludge secondary treatment)
were visited. The potential effects of
climatic conditions were also included,
where possible, and one site in a nor-
thern climate was visited to assess the
effect of winter conditions.
Site Selection
The first step in selecting facilities to
be visited consisted of reviewing the
output from the EPA-1 computer pro-
gram, which gives the results of the
1978 Needs Survey. These indicated
that approximately 720 facilities were
either using land treatment or consider-
ing the addition of a land treatment
system. The data from the Needs Survey
were then summarized in terms of:
1. Whether or not the facilities were
existing or planned, and
2. What the future of the facilities
would be (i.e., whether they were
to be abandoned, upgraded, or
enlarged.)
Plants were then characterized by
flow, degree of preapplication treat-
ment, and climatic location. A decision
was made to omit visits to plants that
were to be abandoned, if possible, since
the operation and maintenance of these
facilities would probably not reflect
normal practices. In addition, it was
decided that no plant smaller than
0.0022 m3/s (50,000 gpd) or larger
than 0.876 m3/s (20 mgd) would be
visited, since most treatment facilities
in the United States fall within this
range.
To reflect the geographic distribution
of plants, plants were visited in propor-
tion to the total percentage of operating
plants in a particular area. Multiple facil-
ities were therefore visited in California,
Texas, and Michigan, as these three
states account for a large percentage of
the Nation's land treatment facilities.
Twenty-eight sites were chosen in all.
Site selections were based on a variety
of factors, including degree and type of
preapplication treatment, climatic con-
ditions, and type of land treatment
system.
The facility name, location, type of
system, flow rate, type of preapplica-
tion treatment, and other background
information are presented in Table 1 for
each of the 28 sites visited.
Data Collection
During the site visits, data were col-
lected in one of three ways: Filling out a
field trip questionnaire/checklist; record-
ing the site investigator's comments on
a tape recorder; and taking photographs
of each site. A trip report was prepared
for each site visit.
The data collected during the site
visits included:
1. Background information (budget,
loadings, etc.)
2. Staffing
3. Maintenance
4. Physical facilities (preapplication
and land treatment)
5. Facility layout
6. Operational strategies
7. Crop management
8. Operational problems
Some of the data collected during the
site visits are presented in Table 2.
System loading rates for each of the
sites are presented in Table 3.
Site Survey
Land Treatment Operation and
Maintenance Costs
During the site visits, data were
collected on the cost of preapplication
treatment and land treatment systems.
Difficulties were encountered during the
collection of these data because munici-
palities often keep total operating bud-
gets that cover both wastewater treat-
ment and wastewater collection. Thus
for these facilities, the cost of collection
first had to be separated from the entire
budget. In addition, plants typically do
not keep separate budgets for land
treatment as opposed to preapplication
treatment. These figures therefore had
to be worked out during the site survey.
Following conclusion of the onsite sur-
vey, figures were checked and compared
with energy and manpower usage.
Facilities personnel were called back to
eliminate discrepancies.
Because the various authorities and
municipalities kept records for different
periods, the first task was to update the
costs to second quarter 1980 to make
them compatible with the updated
costs from the literature. This task was
accomplished by using the EPA Opera-
tions and Maintenance Costs Index.
The budget information collected con-
sisted of approximately 10 different
categories of operation and maintenance
costs (Table 4).
The least expensive preapplication
treatment costs $0.011/m3 at facility
-------
Table 1. Background Data for Land Treatment Sites Visited
Facility Name and Location
Site
No.
Flow Rate
Im3/sl
Type of Land
Treatment
System
Degree of Preapplication
Treatment
Percent of
Preapplication
Effluent to
Land Treatment
Drinking
Water
Source in
Vicinity
Years in
Operation
Village of Lake George
WWTP,NY
North Branch Fire District
No. 1 WPCF, VT
City of Hart WWTF, Ml
City of Fremont WWTP, Ml
Village of Ravenna STP, Ml
City of Wayland WWTP, Ml
Fontana Regional Plant
No. 3, CA
Pomona WRP, CA
001 0.0280
002
003
004
005
006
007
008
0.0049
0.0267
0.0133
0.0032
0.0110
0.1265
0.3505
0.7010
0.0811
0.3505
0.1490
0.0228
0.1008
0.0197
0.0009
0.0012
Whittier Narrows WRP, CA 009
Palmdale WRP, CA 010
Irvine Ranch Water District,
CA 011
City of Tulare WPCF, CA 012
City of Kerman WWTP, CA 013
City of Manteca WWQCF,
CA 014
El Dorado Hills WWTP, CA 015
U.S. Army COE, WES
Overland Flow Site, MS 016
Falkner, WWTF, MS 017
Easley Combined Utilities
System, SC 018 0.0044
Town of Wareham, WPCF,
MA 019 0.0140
Chatham WPCF, MA 020 0.0035
Town of Barnstable WPCF,
MA 021 0.0252
Kendal/Crosslands Lagoon
System, PA 022 0.0022
Landis Sewage Authority, NJ 023 0.1753
Campbell Soup (Texas), Inc.,
TX 024 0.2234
City of Coleman, WWTP, TX 025 0.0175
City of Santa Anna, WWTP,
TX 026 0.0033
City of Winters WWTP, TX 027 O.O131
City of Sweetwater WPCP,
TX 028 0.0438
Rl
SR
SR
SR
SR
SR
Rl, SR
SR
Rl
SR
SR
SR
SR
SR
SR
OF
OF
OF
Rl
Rl
Rl
SR
Rl
OF
SR
SR
SR
SR
Intermediate
100
Secondary with disinfection 100
Intermediate 100
Secondary with disinfection 100
Intermediate 100
Intermediate with disinfection 100
Primary 100
Tertiary with disinfection Winter 33
Summer 66
Tertiary with disinfection 100
Intermediate 100
Tertiary with disinfection 100
Intermediate 100
Secondary 100
Intermediate 100
Secondary with disinfection 40
Intermediate 33
Intermediate with disinfection 100
Prel./lntermed. w/disinfection 100
Secondary with disinfection 100
Secondary 100
Primary 100
Secondary with disinfection 100
Primary 100
Preliminary 100
Secondary with disinfection 70
Intermediate 100
Intermediate 100
Secondary 100
Public
Well
Well
Well
Well
Well
Public
Public
Public
Public
Public
Well
Well
Well
Public
Public
Public
Public
Public
Well & Public
Public
Public
Public
Public
Public
Public
Public
Public
41
5
6
5
11
9
27
50
18
23
11
35 +
4
17
5
4
3
8
9
45
7
30
16
50
14
56
22
Key
WWTP
WPCF
WWTF
STP
— Wastewater treatment plant
- Water pollution control facility
- Wastewater treatment facility
— Sewage treatment plant
WWQCF - Wastewater quality control facility
027 (Winters, Texas), at which the pre-
application treatment consisted of an
Imhoff tank followed by oxidation/
holding ponds. The most expensive
operation and maintenance cost for pre-
application treatment occurred at facil-
ity 020 (Chatham, Massachusetts) —
$0.725/m3. Preapplication treatment
at this facility consists of an activated
sludge system.
WPCP - Water pollution control plant
WRP — Water reclamation plant
Rl — Rapid infiltration
SR — Slow-rate
OF — Overland flow
The least expensive land treatment
system was facility 012 (city of Tulare,
California), where the operation and
maintenance cost was $0.0005/m3.
This facility used a slow-rate system
where the fields were irrigated by both
ridge and furrow and border strip irriga-
tion. All water flowed by gravity, and all
irrigation was carried out by a farmer.
Costs incurred by the city were therefore
low. The most expensive land treat-
ment system was facility 018 (Easley,
South Carolina), where the operation
and maintenance cost was $0.207/m3.
This project was not necessarily the
most expensive, however, as this plant
is a combined operating plant and re-
search project. Aside from this facility,
the second most expensive land treat-
ment system in terms of operation and
-------
Table 2. Physical Facilities at Land Treatment Sites
Site
No.
001
002
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
019
020
021
022
023
024
025
026
027
028
Instru-
Type of mentation
System System
Rl
SR
SR
SR
SR
SR
RI,SR
SR
Rl
SR
SR
SR
SR
SR
SR
OF
OF
OF
Rl
Rl
Rl
SR
Rl
OF
SR
SR
SR
SR
No
Yes
No
No
No
No
No
Yes
No
No
Yes
No
No
No
No
Yes
No
Yes
No
No
No
Yes
No
Yes
No
No
No
No
Land
Wastewater Area
Storage 1 Used2
(days) (ha)
0
162
102
472
297
258
0
0
0
42
98
28
3
4
7
N/A
118
44
0
0
0
51
0
0
0
369
9
15
2.2
13.8
34.8
24.1
8.1
31.6
20.3
29.1
405 +
80.9
607-809
205
87.8
106
8.1
0.50
1.06
1.9
1.6
0.38
3.2
3.2
26.3
235
23.1
10.9
10.5
115
Average
Electrical
Usage
(kwh/mo)
1,365
4,700
16,228
3,505
0
14,000
1 1,250
16,933
0
0
Not known
0
194
10,000
Not known
Not known
360
2,326
0
0
0
3,630
3,460
Not known
0
727
3,000
2,700
Months Number of
System Groundwater
in Monitoring
Use3 Wells
1-12
1-12
4-11
4-11
4-11
5-9
Rl 1-12
SR4-10
1-12
1-12
2-10
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
1-12
24
6
6
32
0
5
0
0
16 +
2
0
0
0
9
0
0
0
5
0
0
0
7
3
0
0
0
0
0
Wastewater
Distribution Wastewater Application
System System
G,P
P
P
G,P
G
P
G,P
G,P
G
P
P
G
G,P
G,P
P
P
P
P
G
G
G
P
G,P
P
G
P
G,P
G,P
Infiltration beds
Fixed nozzles
Gated pipe, ridge and
furrow
Border strip
Border strip
Center pivot, big gun
spray
Infiltration beds, ridge
and furrow
Spray, ridge and furrow
Infiltration beds
Side-wheel roll spray
Spray, ridge and furrow.
drip
Border strip, ridge and
furrow
Ridge and furrow
Border strip
Spray
Trough distribution
Spray
Fixed nozzle, trough.
open pipe
Infiltration beds
Infiltration beds
Infiltration beds
Spray
Infiltration beds
Spray
Border strip
Side-wheel roll spray
Border strip
Border strip
'Includes potential storage, such as variable levels in oxidation ponds.
^Includes only land area in use, not land available for use.
3January = 1, December =12.
maintenance was facility 002 (Dove,
Vermont), where the operation and
maintenance cost was $0.136/m3. At
this facility, secondary effluent is chlori-
nated and sprayed on a woodland site.
Because of complications involved in
differentiating between preapplication
treatment and land treatment operation
and maintenance costs, the most valid
column in Table 4 is the one that pre-
sents total system operation and main-
tenance costs. Based on these data,
facility 012 (Winters, Texas) currently
affords the least costly wastewater
treatment facilities, as the combined
costs are only $0.014/m3. The most
expensive treatment operation is facility
020 (Chatham, Massachusetts), where
the total system operation and mainten-
ance costs were $0.744/m3. These
costs are 50 times those for the Winters,
Texas, plant.
Land Treatment System
Staffing Levels
During the site visits, the staffing
requirements for operation and main-
tenance of the preapplication treatment
and land treatment portions of each
facility were also collected. These data
are presented in Table 4 for both the
preapplication and the land treatment
systems. Most of the treatment plants
were manned one shift per day, although
some of the larger facilities were manned
for either two or three shifts. Typically,
plants were manned 7 days per week.
In terms of man-days/1,000 m3 nec-
essary for preapplication treatment,
facility 011 (Whittier Narrows, California)
required the least amount of operation
and maintenance time, requiring only
0.04 man-day/1,000 m3. Conversely,
facility 020 (Chatham, Massachusetts)
had the highest operation and mainten-
ance needs, as it required 4.68 man-
days/1,000 m3.
The land treatment system associated
with facility 027 (Winters, Texas) was
the least labor intensive, as the operator
reported that he spent no time in con-
junction with the land treatment system.
The most labor-intensive systems were
facility 016 (U.S. Army Corps of Engi-
-------
Table 3. Land
Type
Site of
No. System
001
OO2
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
019
020
021
022
023
024
025
026
027
028
Rl
SR
SR
SR
SR
SR
SR
Rl
SR
Rl
SR
SR
SR
SR
SR
SR
OF
OF
OF
Rl
Rl
Rl
SR
Rl
OF
SR
SR
SR
SR
Treatment System Loading Rate
Hydraulic
mm/wk m/yr
1,130 40.5
22 1.1
69 2.4
76 2.6
1.2
42 1.1
55 1.6
330 17.3
Cannot be calculated
49. 72
33 1.4
Cannot be calculated
43 2.3
17 0.9
58 3.0
Cannot be calculated
63-254 3.3-13.2
183
Raw 1 19 -
Pond 103- 193 -
2,110 27.1
Winter 380 28.8
Summer 720
12.0
40 2.1
400 21.0
40 2.1
32 1.7
18 1.0
76 4.0
46 1.2
s
5-Day
BOD
23,862
41
1,208
316
—
287
1,623
17,162
—
637
2,253
89
1,471
88-349
—
11,810
1,446-2,740
4,103
5,616
—
320
—
12,790
67
266
1,775
215
Suspended
Solids
8,897
45
2,101
817
—
—
7,247
12,771
—
1,699
4,070
53
1,382
139-555
—
10,982
3,098-5,871
5,471
4,405
—
428
—
5,535
17
578
2,365
132
Ammonia
Nitrogen
ikg/ha/yr)
—
5
—
_
—
472
4,395
—
93
454
—
445
55-222
_
344
43-8?
_
—
—
219
—
3804
—
_
—
—
Nutrients
Nitrate
Nitrogen
—
64
—
—
—
6
43
—
—
—
—
17
—
—
80
28-53
—
—
—
—
—
—
—
—
—
—
Total
Phosphorus
—
161
43'
87
—
—
4/0
4,335
1571
—
—
—
39-158
_
772
64-727
—
—
—
743'
—
760
—
—
—
—
'Phosphorus measured as PO4.
2Based oft total water infiltration, not only reclaimed water.
3Design application rate.
4Total nitrogen.
neers Overland Flow Site, Utica, Missis-
sippi), which required 9.18 man-days/
1,000 m3 and facility 018 (Easley,
South Carolina), which required 2.07
man-days/1,000 m3. These are re-
search facilities, however, and not typi-
cal of an operating facility. The next
highest labor requirement for a nonre-
search system was that for facility 017
(Falkner, Mississippi), which required
1.72 man-days/1,000 m3.
The most accurate data can be pre-
sented by using the operation and main-
tenance labor requirements for the total
system (preapplication and land treat-
ment). The reason is that treatment
plants do not typically keep track of
time spent on preapplication versus
land application portions of the facility.
The least labor-intensive system was
the Winters, Texas, facility, which re-
quired only 0.13 man-day/1,000 m3.
Aside from the U.S. Army Corps of
Engineers site, the most labor-intensive
treatment system was the Chatham,
Massachusetts, facility, which required
4.92 man-days/1,000 m3..
Design Deficiencies Hindering
Operations
This portion of the study identified
existing design deficiencies in land treat-
ment systems visited during the site
survey. Design deficiencies for preappli-
cation treatment were also included if
they could affect the subsequent land
treatment facility.
To classify design deficiencies, six
categories were designated:
1. Layout, arrangement, and place-
ment of components
2. Civil and structural considerations
3. Hydraulic design considerations
4. Mechanical design considerations
5. Electrical and instrumentation de-
sign considerations
6. Agronomic considerations
Preapplication Treatment
Design Deficiencies—
Basically, only one design deficiency
showed up at multiple plants—namely,
that oxidation ponds were unprotected
from the effects of erosion caused by
wind-induced waves. At several plants.
-------
Table 4. Treatment System O&M Costs and Staffing
Type of Lan
Site Flow Rate Treatment
No. Im3/s) System
001
002
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
019
020
021
022
023
024
025
026
027
028
0.0280
0.0049
0.0267
0.0133
0.0032
0.01 10
0. 1265
0.3505
0.7010
0.081 1
0.3505
0. 1490
0.0228
0.1008
0.0197
0.0009
0.0012
0.0044
0.0140
0.0035
0.0252
0.0022
0. 1 753
0.22343
0.0175
0.0033
0.0131
0.0438
Rl
SR
SR
SR
SR
SR
Rl, SR
SR
Rl
SR
SR
SR
SR
SR
SR
OF
OF
OF
Rl
Rl
Rl
SR
Rl
OF
SR
SR
SR
SR
d
O&M Costs
($/m3)
Degree of Preapplication
Preapplication Treatment Treatment
Intermediate
Secondary with disinfection
Intermediate
Secondary with disinfection
Intermediate
Intermediate with disinfection
Primary
Tertiary with disinfection
Tertiary with disinfection
Intermediate
Tertiary with disinfection
Intermediate
Secondary
Intermediate
Secondary with disinfection
Intermediate
Intermediate with disinfection
Prel./lntermed. w/disinfection
Secondary with disinfection
Secondary
Primary
Secondary with disinfection
Primary
Preliminary
Secondary with disinfection
Intermediate
Intermediate
Secondary
0.083
0.298
0.082
0.075
0.129
0.068
0.027
0.061'
0.030'
0.045
0.181
0.170
0.173
0.101
N/A
N/A
0.059
—
0.266
0.725
0.114
0.199
0.042
—
0.077
0.025
0.011
0.052
Land
Treatment
0.059
0.136
O.016
0.056
0.022
0.027
0.022
0.002
—
0.002
N/A
0.0005
0.003
0.009
N/A
N/A
0.062
0.207
0.003
0.019
0.032
0.073
0.018
0.0384
0.003
0.029
0.003
0.003
Staffing
(man-days/ 1,000m3)
Total Preapplication Land
System Treatment Treatment
0.142
0.434
0.098
0.131
0.151
0.095
0.049
0.063
0.030
0.047
—
0.170
0.176
0.110
—
—
0.121
0.2072
0.269
0.744
0.146
0.272
0.060
0.038
0.080
0.055
0.014
0.055
0.77
1.48
0.40
0.78
0.67
0.30
0.19
0.25
0.04
0.19
0.30
0.32
0.71
0.44
0.79
1.72
2.36
4.68
0.71
1.88
0.21
N/A
0.41
0.65
0.13
0.71
0.69
1.32
0.15
0.25
0.07
0.12
0.19
0.006
N/A
0.01
0.14
0.007
0.02
0.05
0.05
9.18
1.72
2.07
0.09
0.24
0.18
0.94
0.15
0.30
0.09
0.50
0
0.03
Total
System
1.46
2.80
0.55
1.03
0.74
0.42
0.38
0.26
—
0.20
0.44
0.33
0.73
0.49
0.84
9.18
3.44
2.07
2.45
4.92
0.89
2.82
0.36
0.30
0.50
1.15
0.13
0.74
'Does not include sludge treatment and disposal costs.
2Does not include oxidation pond preapplication treatment costs.
^Five-day average production flow. Yearly average flow = 0.1796, and costs are based on yearly average flow.
4Does not include electrical consumption.
maintenance personnel were in the pro-
cess of installing protection around the
embankments at the water levels.
Slow-Rate Land Treatment
Design Deficiencies—
The major problem noted in terms of
hydraulic design was that in some facili-
ties, pumping was required both to the
headworks of the treatment facility and
to the slow-rate land treatment system,
when the second pumping may not
have been necessary. A second
hydraulic design deficiency was that
many plants had insufficient
wastewater storage capacity to allow
for optimum facility operation.
The mechanical design deficiencies
included improper nozzle selection and
pumps unable to pass solids to the land
treatment system.
An agronomic design deficiency noted
was the effect of soil type and texture
on the selection of irrigation equipment.
This problem was particularly acute in
Wayland, Michigan, where the center-
pivot irrigation unit had made deep ruts
in the field. This situation necessitated
excavating and filling the ruts with
washed gravel to allow for subsequent
operation of the unit.
Rapid Infiltration Design
Deficiencies—
The major hydraulic design deficiency
noted was that in several systems it
was necessary to pump wastewater
both to the pretreatment facility and
subsequently to some or all of the rapid
infiltration beds. This dual pumping is
frequently an avoidable waste of energy.
Overland Flow Design
Deficiencies—
In terms of civil and structural consid
erations, the major design deficiency con-
cerned the tailwater collection ditches
These ditches, typically unlined, are dif
ficult to maintain and are subject tc
erosion. Another civil and structure
consideration is the effect of impropei
land grading during construction, which
manifests itself in ponding on the over
land flow fields. A range of mechanics
design deficiencies were noted durinj
the plant visits. At the Army Corps ol
Engineers site, problems occurred with
the plugging of valves, meters, anc
piping. At the Easley, South Carolina
overland flow site, mechanical problem:
occurred, including:
1. Raw wastewater nozzles that be-
came plugged.
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2. Valve pits that filled with water
(which rusts the solenoid valves),
3. Grass that was sucked up by chlo-
rine eductor systems, with resul-
tant clogging, and
4. In-ground PVC pipe that broke
underground when the above-
ground galvanized pipe to which it
was connected was hit.
One important agronomic deficiency
was the appli'cation of wastewater be-
fore the plots were fully seeded. This
problem occurred at the Easley site and
caused substantial erosion and subse-
quent poor wastewater distribution.
Establishing grass on the active site
was also difficult.
Recommended Operation and
Maintenance
The recommended operation and
maintenance practices for the three
types of land treatment systems based
on information collected during the site
visits and subsequent data analysis are
as follows.
Slow-Rate Systems
A person with a farming background
should either operate the land treatment
system or assist in its operation to allow
for farming decisions based on experience.
The operation of a slow-rate land
treatment system is basically fixed by
the design of the system. The operation
thus tends to be fairly straightforward,
and only the three following operational
parameters can be varied:
1. Amount of wastewater to be ap-
plied per application.
2. Frequency of application.
3. The field that should be irrigated.
The product of these decisions must
equal the total amount of wastewater
that must be applied annually (or in a
growing season ). This method is the
one by which most facilities are cur-
rently operated. During winter opera-
tions, however, some facilities occa-
sionally flood fields to maximize the
wastewater disposal option.
Maintenance requirements for a slow-
rate land treatment system are straight-
forward and should not cause any par-
ticular problems for maintenance staff
or operations. A routine maintenance
schedule is suggested.
Rapid Infiltration Systems
The operation of a rapid infiltration
land treatment system is fairly simple as
it consists basically of bed rotation. The
latter is typically based on visual esti-
mates as to which bed is ready to re-
ceive the flow, and it usually follows
some sort of schedule. Many of the
operational strategies discussed in the
Process Design Manual for Land Treat-
ment of Municipal Wastewater for in-
creasing denitrification losses may sim-
ply not be possible on an operating
scale. The major reason is that the
denitrification losses are extremely diffi-
cult to measure in the laboratory and
more than likely impossible to measure
in the field, particularly for smaller
installations. In addition, the operator
may not have the luxury of dosing an
infiltration bed at the required schedule
to maximize the denitrification, since
other considerations may make such a
schedule impossible.
The major consideration for operation
of a rapid infiltration system is that the
operators stay ahead of the beds in
terms of maintenance and continually
ensure that sufficient capacity exists to
dispose of all influent wastewater. The
latter is extremely important, as the
systems are usually designed without
any facilities for wastewater storage.
Once a facility is in trouble, it may be
difficult to correct the problem, as
wastewater must be applied to beds
that may be flooded and therefore can-
not be raworked. The situation tends to
go from bad to worse. Aside from bed
maintenance, additional routine main-
tenance is required.
Overland Flow Systems
Unlike the other-two land treatment
systems, the overland flow system has
the greatest potential for process con-
trol, as the loading rate and the hours of
application can be varied. In addition,
various plots can be taken off-line to in-
crease further the operational modifica-
tions the operator has at his disposal.
Operation of the overland flow system
also requires knowledge of processes
that wastewater treatment personnel
may not have at their disposal. Addi-
tional training is therefore required. In
addition, various combinations of hy-
draulic loading rates and application
schedules should be considered follow-
ing start-up to optimize performance.
In addition to routine maintenance,
plot maintenance is also required. This
procedure consists of ensuring that a
healthy cover drop is maintained and
that any erosion problems are quickly
corrected. These maintenance require-
ments may necessitate additional oper-
ator training.
Recommendations
The following recommendations were
developed as a result of this study:
1. Operation and maintenance costs
for slow-rate systems can be sub-
stantially reduced by operating the
system in conjunction with a
farmer.
2. Joint operation of the slow-rate
system with a farm is recom-
mended, where possible, to reduce
staffing requirements and improve
operations.
3. Additional training is suggested for
land treatment system operators,
particularly for operators of over-
land flow systems.
4. Local farmers should be contacted
for input during the design of a
slow-rate land treatment system.
Conclusions
The following conclusions have been
drawn from this study:
1. Operation and maintenance costs
for slow-rate systems are typically
lower than reported in the literature.
2. Operation and maintenance costs
for rapid infiltration and overland
flow systems are in general agree-
ment with the literature data.
3. Staffing requirements for slow-rate
systems are typically less than re-
ported in the literature.
4. Staffing requirements for rapid in-
filtration and overland flow sys-
tems are in general agreement with
literature data.
5. Slow-rate and rapid infiltration sys-
tems typically are adequately
operated.
6. Insufficient data are available to
assess overland flow system oper-
ations.
7. Equipment at all three types of land
treatment systems is similar to
wastewater treatment plant equip-
ment and appears to be adequately
maintained.
8. Though design deficiencies do
exist, they interfered substantially
with normal operations at only one
facility.
The full report was submitted in fulfill-
ment of Contract No. 68-03-2775 by
Roy F. Weston under sponsorship of the
U.S. Environmental Protection Agency.
.S. GOVERNMENT PRINTING OFFICE: 1983/659 -095/577
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The EPA author of this Project Summary, Denis J. Lussier, is with the Center for
Environmental Research Information, Cincinnati, OH 45268.
Jon H. Bender is the EPA Project Officer (see below).
The complete report, entitled "Operation and Maintenance Considerations for
Land Treatment Systems," prepared by Roy F. Weston, Inc., West Chester, PA
19380 (Order No. PB 83-138 560; Cost: $28.00, 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:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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