&EPA
United States
Environmental Protection
Agency
Office of Water
Program Operations (WH-547)
Washington.DC 20460
May 1980
430/9-80-002
Water
Assessment Of Current
Information On Overland
Flow Treatment Of
Municipal Wastewater
MCD-66
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Assessment Of Current Information On Overland
Flow Treatment Of Municipal Wastewater
By
Daniel J. Hinrichs
Justine A. Faisst
David A. Pivetti
Culp/Wesner/Culp
and Edward D. Schroeder
University of California, Davis
May 1980
Project Officer
Richard E. Thomas
Office of Water Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
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EPA Comment
This report provides a technical discussion of recent information
on design and performance of the overland-flow treatment process.
Overland-flow treatment of municipal wastewaters is a rapidly developing
technology which is attractive as a simple and low cost solution for
smaller communities. It is the land treatment approach which is suited
to locations with impermeable soils that could not be used for other
land treatment approaches.
This report is an interim publication providing needed information
on a subject for which new information is being produced rapidly. The
EPA design manual on land treatment technologies is being revised and
the information in this report will be updated with issuance of the
revised manual.
Harold P. Cahill, Jr.
Director
Municipal Construction Division (WH-547)
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ACKNOWLEDGEMENTS
Preparation of this report was enhanced through comments and references pro-
vided by Richard Thomas. Cost information was developed by Robert Williams.
Figures were prepared by Candy Erwin and Robert Livingston. Typing and editing
were completed by Karen Busse and Sharon Robbins with assistance from Sue Howard,
Sherry Olives, and May Bray.
Information on site visitations was provided by Dr. Curtis Harlan and Bert
Bledsoe, Ada, OK; Dr. Charles Muchmore, Carbondale, IL; James Martel, Hanover,
N.H.; Robert Smith, Davis, CA; Dr. A. Ray Abernathy, Clemson University, S.C.;
and Charles Neeley, Paris, TX.
iii
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PREFACE
Land treatment of municipal wastewater is becoming a popular method of
treatment and reclamation. One of the newest land treatment methods is overland
flow. Developments in overland flow treatment understanding and design have been
recent. At this time most literature is lacking in specifics of overland flow
treatment. This report has been developed to fill this need for understanding of
overland flow treatment.
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TABLE OF CONTENTS
Subject Pages
ACKNOWLEDGEMENTS lli
DISCLAIMER lv
PREFACE v
ABBREVIATIONS x
CONVERSION FACTORS xi
SECTION I - INTRODUCTION 1
SECTION II - REVIEW OF EXISTING PROJECTS 4
SECTION III - PROCESS MECHANISMS 55
SECTION IV - DESIGN CONSIDERATIONS 57
SECTION V - DESIGN EXAMPLES 67
SECTION VI - STATE REGULATIONS 79
SECTION VII - CONCLUSIONS AND RECOMMENDATIONS 80
REFERENCES 81
APPENDIX A - COSTS
APPENDIX B - STATE OF MARYLAND AND DESIGN GUIDE FOR LAND TREATMENT
APPENDIX C - STATE OF MISSISSIPPI DESIGN GUIDANCE FOR LAND TREATMENT
vi
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LIST OF FIGURES
Number Page
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Overland flow schematic
Schematic of Davis pilot overland flow site
City of Davis, schematic of new overland flow system
Schematics of distribution systems used at Pauls Valley
Utica, Mississippi overland flow site
Cedar Lane Trailer Park oxidation pond
Overland flow slope at Cedar Lane Trailer Park
BOD^ removal vs. hydraulic loading rate
BOD5 removal vs. organic loading rate
BODg removal vs. detention time at Carbondale
Suspended solids removal vs. detention time at Carbondale
Nitrogen removal vs. detention time at Carbondale
Phosphorus removal vs. detention time at Carbondale
Diagram of Hanover overland flow system
Average weekly runoff BOD concentration vs. soil temperature
(primary section) at Hanover
Average weekly runoff NH^ concentration vs. soil temperature
for primary and secondary sections
BOD removal vs. detention time for CRREL overland flow site
receiving primary effluent
Suspended solids removal vs. detention time for CRREL overland
flow site receiving primary effluent
Relationship between hourly hydraulic loading and detention
time at Hanover and Utica
Hydraulic loading
Hydraulic loading
2
6
9
15
22
25
27
32
33
35
36
37
38
40
43
44
46
47
48
59
60
Vll
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LIST OF TABLES
Number __ Page
1 Summary of discharge requirements city of Davis 5
2 Oxidation pond effluent application rates to Davis
pilot overland flow system 11/7/75 to 2/7/76 5
3 Oxidation pond effluent application rates to Davis
pilot overland flow system 2/27/76 to 3/28/76 5
4 Monthly average effluent suspended solids values at Davis , mg/L 7
5 Monthly Average BOD^ values at Davis, mg/L 7
5 City of Davis system (under construction) 8
7 Hunt-Wesson site characteristics 12
8 Ada site characteristics 13
9 Mean wastewater characteristics, mg/L 14
10 Wastewater characteristics at Pauls Valley, mg/L 16
11 Average results and significant design factors from the raw system
for the winter application at Pauls Valley 17
12 Average results and significant design factors from the raw system
for the summer application at Pauls Valley 18
13 Average results and significant design factors from the secondary
system for the winter application at Pauls Valley 19
14 Analytical results and significant design factors from the
secondary system, for the summer application at Pauls Valley 20
15 Utica overland flow site characteristics 21
16 Oxidation pond effluent characteristics at Utica 23
17 Treatment results at Utica - 1976-1977 ' 23
18 Percent nitrogen removals at Utica - 1976-1977 24
19 Percent phosphorus removal at Utica - 1976-1977 24
20 State of Illinois water quality standards 26
21 Oxidation pond effluent characteristics at Cedar Lane 26
22 Carbondale site characteristics 28
23 1976-77 loading rates of Cedar Lane Trailer Park
overland flow system 29
24 Detention time as a function of position and application rate 30
25 BOD5 removal in Carbondale overland flow system 30
26 Suspended solids removal in Carbondale overland flow system 30
27 Phosphorus removal in Carbondale overland flow system 31
28 Nitrogen removal in Carbondale overland flow system 3-]
29 Hanover site characteristics 39
30 Average wastewater quality applied to CRREL overland flow slopes
May 30, 1977 to April 1, 1978 41
31 Average performance from CRREL overland flow slopes 42
32 Easley site characteristics 49
33 Easley, SC overland flow system performance 49
34 Campbell's Soup, Paris, Texas site characteristics 50
35 Performance summary at Campbell's Soup, Paris, Texas 5^
36 Existing overland flow system descriptions and data- summer /winter 54
37 Site characteristics - design examples 67
38 Design criteria - example 1 gg
39 Design example 1 - water balance 1 eg
40 Design example 1 - BOD5 removal 1 7Q
viii
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LIST OF TABLES (Continued)
Number Page
41 Design example 1 - water balance 2 71
42 Design example 1 - BOD^ removal 2 71
43 Design criteria for example 2 72
44 Example 2 - facilities sizing 73
45 Water balance - example 2 74
46 BOD5 reduction - example 2 75
47 Design criteria - example 3 75
48 Example 3 - facilities sizing 76
49 Design example 1 - water balance 77
50 Example 3 - nitrogen removal 78
51 Capital cost estimate - design examples 78
IX
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ABBREVIATIONS
ave average
ft-c foot-candle
lx lux
mg/L milligram/liter
m /d cubic meter/day
m meter
kg kilogram
ha hectare
d day
hr hour
rain minute
wk week
mo month
yr year
cm centimeter
km kilometer
psig pounds/per square inch (gage)
°C "Celsius
°F °Fahrenheit
mgd million gallons per day
BODg biochemical oxygen demand
SS (V) suspended solids (volatile)
SS (T) suspended solids (total)
NH4~N ammonia nitrogen as nitrogen
NOg-N nitrate nitrogen as nitrogen
NO2~N nitrite nitrogen as nitrogen
PO4~P phosphate as phosphorus
gal gallon
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CONVERSION FACTORS
From: To:
Application English Units SI Units Multiply By
application rate gallon/minute liter/minute (L/min) 3.785
area acre hectare (ha) 0.4047
distance mile kilometer 1.609
flow million gallon/day cubic meter/day (m /d) 3,785
illumination foot-candle lux (Ix) 10.76
length foot meter (m) 0.3048
hydraulic loading inch centimeter (cm) 2.54
organic loading pound/acre kilogram/hectare (kg/ha) 1.121
pressure pounds/square inch kilopascal (kPa) 6.895
temperature °F °C (°F-32)/1.8
volume per area gal/acre liter/hectare (L/ha) 9.354
XI
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ASSESSMENT OF CURRENT INFORMATION ON OVERLAND FLOW
TREATMENT OF MUNICIPAL WASTEWATER
SECTION I
INTRODUCTION
Since the mid-1970's land treatment has become a popular, although contro-
versial method of wastewater treatment and disposal. The controversy has pri-
marily resulted from the conceptual differences between land treatment and con-
ventional mechanical treatment processes. The major differences are the decep-
tively simple characteristics of land treatment systems, the as yet unclear
regulatory constraints, and the lack of understanding of land treatment system
design. The least understood type of land treatment is overland flow.
At the present time very little information is available to design engineers
on overland flow treatment other than that presented in the 1977 document Process
Design Manual for Land Treatment of Municipal Wastewater1. At that time consid-
erable experience and data were available on treating cannery wastes by overland
flow, but little was available on municipal wastewater treatment. Since 1977 a
number of full scale municipal facilities have been designed, two have begun
operation and results from many research projects have become available.
Current overland flow treatment systems are of two types; those that are
used to polish secondary effluent (e.g. from an oxidation pond) and those that
are used for secondary (and possibly primary) treatment. In either case substan-
tial nutrient and heavy metal removal can be accomplished in addition to the
removal of organics and suspended solids.
Typical overland flow systems are shown schematically in Figure 1 . An over-
land flow system provides wastewater treatment by applying influent at the top of
a sloped terrace (2-8% slope) and allowing a film flow down the slope to a col-
lection ditch. This terrace is constructed on impermeabile or nearly impermeable
soils planted with grass. Little infiltration occurs. The treatment process is a
combination physical- chemical-biological process. The planted grass provides
protection from erosion as well as being an integral part of the treatment pro-
cess. The process has been described as being very similar to a trickling filter
treatment process.
The purpose of this report is to provide a review of the recent applications
of overland flow and a design guide based on recent operating experience. Visits
were made to seven systems: Davis, CA (research, industrial and completed full
scale design); Carbondale, IL (research data to full scale); Hanover, NH
(research); Easley, SC (full-scale operation); Ada, OK (research) Utica, MS
(research); and Paris, TX (full-scale cannery). Detailed descriptions of these
projects, as well as observations made during the site visits, are presented in
the following section. This information, together with information from the
literature, is used to develop and present recommendations on preapplication
treatment, design procedures and cost estimation.
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OPTION A - DISTRIBUTION BY SPRINKLERS
OPTION B - DISTRIBUTION BY GATED PIPE
Figure I Overland flow schema tic.
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This report has been prepared to be used independently for overland flow
system design. Much of the information presented in Reference 1 will be used and
supplemented or updated as necessary.
The following parameter definitions2 are used for this report.
Hydraulic loading rate (HLR) is the volume of wastewater applied per day or
per week, cm/day or cm/wk.
Application rate (AR) is the volume of wastewater applied to the slope
divided by the application time period, ml/min or 1/min.
Application time period (ATP) is the length of time water is applied to the
slope in a 24-hr time period, hr/d.
Application frequency (AF) refers to the sequence of application days and
nonapplication days (e.g. 6 days on - 1 day off).
Organic loading rate (OLR) is the mass of organic material applied per day
divided by slope of area, kg/ha-d.
Nitrogen loading rate (NLR) is the mass of nitrogen applied per day divided
by the slope area, kg N/ha-d.
Smith and Schroeder2 recommended standardization of hydraulic loading rate
by noting the slope length of the rate (e.g. cm/d/30m). Similarly, application
rate is standardized by expressing on a unit width basis (e.g. 1/min-m).
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SECTION II
REVIEW OF EXISTING PROJECTS
Site visitations were conducted between October and December, 1979. Prior to
each visit, information on the overland flow system to be visited was collected
and studied. Information available on each site varied considerably. A number of
the sites were research facilities. Because of their small size and constrained
objectives of the research investigation, usuable construction and generating
cost information was lacking. A summary of the data obtained from these visits is
presented at the end of this section (Table 36).
DAVIS, CA
Davis, CA is the location of three overland flow projects worthy of review:
the Hunt-Wesson foods facility which provides treatment of tomato processing
wastes, the research work being conducted at the University of California, Davis
Campus (UCD), and the design of the City of Davis" municipal treatment system,
which included pilot plant studies.
Davis, CA is a university community of approximately 38,000 persons located
20 km west of Sacramento in California's Central Valley. Hunt-Wesson, a seasonal
tomato processor, operates a separate treatment and disposal system using the
overland flow process. The City of Davis sewage consists entirely of residential
and commercial wastewaters. Current average dry weather flow is about 13,250
m3/d.
The climate of the Davis area is Mediterranean, with wet, mild winters and
hot, dry summers. Temperatures below 0°C occur 17 days per year on the average
and the frost-free growing season is 258 days. Precipitation averages 42 cm/yr
with 70 percent coming in the months of December through March. Summer tempera-
tures are usually in excess of 32° C and frequently exceed 38° C.
City of Davis
The present Davis wastewater treatment system consists of comminution, grit
removal, primary sedimentation, and secondary treatment in three oxidation ponds
operated in parallel followed by chlorination.
Discharge requirements of the City were set by the California Regional Water
Quality Control Board and are shown in Table 1. An overland flow system was
chosen to upgrade the ponds to meet these new standards.
Pilot studies were made during the period October, 1975 through March, 1976
using three, 15 x 30-m plots located at the wastewater treatment plant.
The overland flow test plots were constructed on a two percent slope on
clayey soil- Each plot was flooded with digester supernatant and seeded with
annual rye grass on October 1, 1975. Five spray nozzles were installed on 0.6-m
risers at 3-m intervals along the upper edge of each plot.
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Constituent
BOD5
Suspended solids
pH must be greater
Units
mg/L
kg/day*
mg/L
kg/ day*
than 6.5
30 day average
30
568
30
568
and less than 8.5
7 day average
45
852
45
852
Max
90
90
*kg/day value is the mass concentration times the flow rate. The design flow rate
of the Davis Wastewater Treatment Plant is 18,925 m3/d.
Pond effluent was pumped from the chlorination basin effluent line at a
nominal pressure of 550 kPa. Separate pressure regulators and solenoid valves
were used to control flow to each plot. A schematic of the system is shown in
Figure 2.
Germination and growth of the annual rye grass was rapid and controlled
effluent loading was begun on November 7, 1975. The grass was not cut during the
5-month study and eventually reached a height of about 30 cm. Pond effluent was
applied to the plots at the rates shown in Tables 2 and 3.
TABLE 2. OXIDATION POND EFFLUENT APPLICATION RATES TO DAVIS
PILOT OVERLAND FLOW SYSTEM 11/7/75 to 2/7/76
Plot
Application time, hr
Morning
Afternoon
Average flow rate
m3/ha-hr
Daily application rate
m3/ha-d
cm/d
TABLE 3.
Plot
Application time, hr
Morning
Afternoon
1
3
3
32
195
2
OXIDATION POND
PILOT OVERLAND
1
3
3
2
2
2
.5 31.3
125
1.2
EFFLUENT APPLICATION
FLOW SYSTEM 2/27/76
2
4
4
3
1
1
34.8
69.6
0.7
RATES TO DAVIS
to 3/28/76
3
12
Average flow rate
m3/ha-hr
Daily application rate
m3/ha-d
cm/d
51.7
310
3.0
51.4
412
4.1
43.3
520
5.3
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Figure 2. Schematic of Davis Pilot Overland Flow Site.
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Effluent quality from the overland flow systems was satisfactory, and the
ability to meet the standard of 30 mg/L suspended solids and BODs was demon-
strated. As the grass cover crop matures and thickens the overland flow system
performance should improve. Since the pilot study covered a relatively short time
period, the results shown in Tables 4 and 5 should be considered a conservative
estimate of process performance.
TABLE 4. MONTHLY AVERAGE EFFLUENT SUSPENDED SOLIDS VALUES AT DAVIS, mg/L
Effluent loading rate cm/d
Month*
November
December
January
March
Influent
82
64
59
59
0.7
29
19
11
1.2
30
18
14
2.0
33
25
18
3.0 4.1 5.3
22 30 31
*Change of loading rate occurred in mid-February.
TABLE 5. MONTHLY AVERAGE BOD5 VALUES AT DAVIS, mg/L,
Effluent loading rate, cm/d
Month*
November
December
January
March
Influent
73
47
41
42
0.7
20
11
11
1.2
13
15
11
2.0 3.0 4.1
21
20
15
18 27
5.3
24
*Change of loading rate occurred in mid-February.
Conclusions stated in the pilot study report included:
Hydraulic loading rates up to 210 m /ha-d are suitable for process
design.
Rye grass would be a suitable cover for a prototype system.
Chlorinated effluent will not damage the grass.
Data obtained are conservative estimates of eventual process perfor-
mance because the microbial population and surface thatch had minimum
opportunity to develop. The time required to develop optimum microbial
population and surface thatch is not known, but the study team felt
there could be improvement.
The effect of precipitation could not be predicted because the studies
were carried out during an extreme drought.
Construction of the Davis overland flow system is scheduled to begin in
Spring, 1980. Design has been completed by Brown and Caldwell Consulting Engi-
neers, land acquisition is in progress, and the contracts were advertised for
bids on December 6, 1979. The low bid was $1,976,900. The general design plan is
to pump chlorinated effluent from the existing oxidation ponds to an 81-ha area
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having a 69 net ha overland flow application area. Chlorination was provided
ahead of the overland flow system so that dechlorination requirements prior to
discharge could be minimized. (Some dechlorination will occur as the wastewater
travels down the slope). Treated effluent will continue to be discharged to
Willow Slough Bypass.
Storage of the wastewater will not be necessary because the treatment pro-
cess will be operational throughout the year. Equalization storage is provided
in the oxidation ponds to allow continuous application of wastewater during the
summer months. At the present time, evaporation losses from the ponds exceed
inflow for two or more months per year, thus water levels in the oxidation ponds
will drop considerably in the late summer.
The overland flow system has been designed using the following criteria
shown in Table 6. The system will be divided into 15 zones, each consisting of 2
overland flow terraces and extending from the centerline of one collection ditch
to the next collection ditch. Zones will be 92-m wide and approximately 500-m
long. A flow diagram of the entire treatment system is shown in Figure 3. Efflu-
ent from each terrace is collected and either pumped into Willow Slough Bypass or
recycled. Recycling will allow grass maintenance during extreme drought periods.
TABLE 6. CITY OF DAVIS SYSTEM (under construction)
Type of wastewater
Capacity
Land area
Preapplication treatment
Disinfection
Storage
Soil type
Application
Control method
Cover crop
Slope
Application
Application period
Annual rainfall
Temperature,
Ave Max, summer
Ave Min, winter
Evapotranspiration
Class A pan evaporation
Discharge requirements
Suspended solids
BOD5
Domestic Sewage
19,000 m3/da
69 ha
Comminution, grit removal, primary sedi-
mentation, oxidation ponds
Chlorination prior to application
None
Clay and silty clay
Gated pipe
Butterfly line control valve
Mixture of grasses; fescue and rye
2%
15 cm/wk
4-12 hr/da
42 cm/yr
35°C
4°C
130 cm/yr
173 cm/yr
30 mg/L (ave)
30 mg/L (ave)
The distribution system will consist of 0.25-m gated, aluminum irrigation
pipe. Five-cm slide gates will be set on 0.6-m centers. The irrigation pipes
will rest on a 2-m wide rock and gravel bed at the head of each terrace. Pipes
8
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.GATED PIPE
COLLECTION DITCH
CROSS SECTION
(1 of 10 areas)
SUPPLY PIPELINE
COLLECTION DITCH
Ill
1
GATED PIPE x i
111
li
(
ROADWAY
ill
II!
iff
+u
Iff
50.5m
COLL
E1
ECTOR
DITCH
1*
A
*'
i
>
GATED PIPE
PLAN VIEW
(1 of 10 areas)
Figure 3. City of Davis, schematic of new overland fl.ow system.
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will come off a 0.6-m header and flow in each distribution pipe will be con-
trolled by a butterfly line control valve.
Chlorinated oxidation pond effluent will be pumped to the header with two-
12.5 m3/min pumps rated at a dynamic head of 5.6 m. The two effluent/recycle
pumps are each rated at 10 m3/min with a 8.2-m dynamic head.
Cost of the Davis overland flow suspended solids removal system is not known
at this time. As noted above, contract documents for construction were released
to potential bidders on December 6, 1979 and the low bid was $1,976,900. Costs
associated with preapplication treatment need to be determined. Available
information on overland flow allows the conclusion that system size is not
linearly related to organic loading. Thus, design criteria for the Davis system
cannot be extrapolated to systems having no pretreatment.
Brown and Caldwell Consulting Engineers estimated the construction costs
(based on an ENR Index of 3200) as shown below:
Item Estimated Cost
Gravity line to sump $ 55,000
Distribution and runoff collection sump 45,000
Terrace construction 250,000
Distribution system 290,000
Distribution pumping 290,000
Runoff collection 30,000
Electrical 45,000
Service roads 70,000
Fencing 120,000
Subtotal $1,195,000
Engineering and contingencies 420,000
Land (81 ha @ $4,400/ha) 360,000
TOTAL CAPITAL ESTIMATED COST $1,975,000
Actual bid price (w/o land or engr.) $1,976,900
Operation and Maintenance Costs (1 yr)
Labor $ 48,000
Materials , 10,000
Power 30,000
TOTAL O&M (1 yr) $ 88,000
Labor is estimated at 2.3 man-years/year of staff time to operate the
overland flow system. In addition, the Consultant assumed that heavy maintenance
would be contracted to outside specialists, and that harvesting of the grass
would be done by City employees or local farmers at nominal cost. These costs are
presented in Section III.
Research Facility
Four of the overland flow system terraces have been modified to allow their
use as an experimental facility. Each of the terraces is divided into 10 sub-
terraces each 50-m wide. Two of the terraces are used to treat 950 m3/d of
10
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comminuted raw wastewater and the other two slopes to treat 950 m3/d of primary
effluent. Both wastewaters are conveyed via surface aluminum pipe to gated alum-
inum pipe distribution laterals. Flow onto each 50-m experimental unit is metered
and controlled by a manual valve. Flow from the units is collected, metered by
weirs, and discharged to the main collection channel.
The field studies are part of a pilot and demonstration project supported by
the California State Water Resources Control Board and conducted by the Depart-
ment of Civil Engineering of the University of California, Davis. The Principal
Investigators for the project are E.D. Schroeder and George Tchobanoglous and the
work is under the direct supervision of Robert G. Smith. Pilot studies began in
fall, 1978 with the objectives of identifying the design and operating parameters
that govern overland flow process performance and developing functional design
relationships .
The pilot facilities initially financed by Campbell Soup Company are located
indoors and consist of three beds, each 1 .5-m wide, 6-m long, and 0.2-m deep.
Light at a surface intensity of 27,000 Ix is provided from light banks made up of
very high output fluorescent and 100 watt incandescent bulbs that operate 14
hr/d. Evapotranspiration is monitored using an adjacent, 1 .2-m diameter hydrau-
lic pillow lysimeter subjected to the same light intensity. Clay soil was
obtained from the Davis overland flow system site and a bermuda grass sod was
used as the cover.
Parameters varied in the study have included bed slope , application time
period per day, application rate per unit of slope width, application frequency,
hydraulic loading rate, organic loading rate and nitrogen loading rate. Fecal
coliform removal was examined in a separate study using the same facilities.
Initial studies were conducted using a soluble synthetic wastewater composed
of Bactopeptone , sucrose, ammonium chloride, potassium phosphate and tap water.
The BODtj and TOG concentrations were approximately 145 and 95 g/m3, respec-
tively. Following completion of these studies, experiments were conducted using
primary effluent obtained daily from the Davis treatment plant.
Bed slope was varied from 2 to 6 percent without a measurable effect on rate
of organic removal down the bed. Similar results were obtained by varying hydrau-
lic loading rate up to 15 cm/wk. Loadings of 30 cm/wk resulted in significantly
decreased organic removal rates.
Experiments using City of Davis primary effluent were begun in October,
1979. Wastewater BOD^ and TOC concentrations have been in the ranges of 60 to
80 mg/L and 40 to 50 mg/L, respectively. Results to date (December, 1979) have
been very similar to those obtained for the soluble substrate. In general,
organic removal can be described by a function of the form:
C
o
where C,, = Organic mass concentration a distance z down the slope, SS
z
,, ,'
z volume
C_ = Organic mass concentration of the application point, -
0 volume
Q = Volumetric flow rate, volume/ time
11
-------
K = Rate coefficient with units dependent on a
^c = Emperically determined coefficient
Removal of fecal coliforms and nitrogen have also been studied using the
pilot facilities. This work will be complete in June, 1980. Progress to date has
been reported in Reference 2. Conclusions thus far are as follows:
Differences in slopes within the 2 to 6 percent range do not have a
significant impact on organic removal rate.
For a given hydraulic loading rate, a lower application rate will
result in a higher organic removal rate.
At the same application rate, the hydraulic loading rate has little
effect on the organic removal rate in the range of 10 to 15 cm/wk/30 m.
When the hydraulic loading rate is increased to 30 cm/wk/30 m, the
organic removal rate decreases. Whether this phenomenon is caused by
the high hydraulic loading rate or the correspondingly high organic
loading rate is not known.
Industrial Treatment
Current data are limited for the Hunt-Wesson project. The site was visited
and the observations made were favorable. The effluent stream showed no signifi-
cant objectionable color or turbidity. There were no odors apparent. The grasses
grown appeared hardy and lush. Hunt-Wesson operates the facility only during the
canning season. Application rates are 9-12 cm/wk. Evapotranspiration accounts for
more than one half of the applied flow. Site characteristics are presented in
Table 7.
TABLE 7. HUNT-WESSON SITE CHARACTERISTICS
Type of wastewater - tomato cannery wastes
Capacity - 15,000 m3/d
Land area - 69 ha
Pretreatment - screening
Disinfection prior to treatment - none
Storage - none (usual operation July through September)
Soil type - silty clay and clay
Application method - solid set sprinkler
Control methods - automatic air-controlled valves and time clocks
Crop - Mixed grasses including, fescue, trefoil, reed canary, and annual rye
grass
Slope - 2.5 percent
Application rate - 9 cm/wk
Application period - 6-10 hrs/d for 6 days/wk
Yearly Rainfall - 42 cm/yr
Temperature
Ave Max - 32°C
Ave Min - 4°C
12
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ADA, OKLAHOMA
Ada, OK is the location of the Robert S. Kerr Environmental Research Labora-
tory (RSKERL). This facility has been the center of land treatment research and
study for the US EPA. Overland flow systems have been studied at the Lab's field
site as well as at off-site facilities. The on-site system characteristics are
shown on Table 3.
TABLE 8. ADA SITE CHARACTERISTICS
Type of wastewater - domestic sewage
Capacity - 790 m3/d
Land area - 3.2 ha
Pretreatment - screened or primary sedimentation and oxidation pond
Disinfection prior to application - no
Storage - none
Soil type - clay
Application method - rotating spray boom, fixed riser with fan nozzle
Control methods - electrically actuated gate valves and time clocks
Crop - Kentucky 31 fescue, annual rye grass and bermuda grass
Slope - 2 percent
Application rate - 15-23 cm/wk
Application period - 8-12 hr/d
Yearly rainfall - 100 cm/yr
Temperature
Ave Max - >10°C
Ave Min - > 0°C
The climate at Ada is normally mild, with temperature minimums averaging
above freezing except during January when the average minimum is -1°C. Daily
maximum temperatures consistently exceed 10°C. Average annual precipitation is
about 100 cm.
Research emphasis at Ada has been placed on minimizing the degree of pre-
treatment. Studies of overland flow treatment have been conducted using raw
wastewater, primary effluent, and pond effluent. The principal goal has been to
demonstrate satisfactory performance of a system with minimal complexity and min-
imal operating cost. This objective is especially important to small communities
that are required to upgrade pond systems. Treatment levels better than secondary
were obtained in early work3 utilizing overland flow for treatment of raw
domestic wastewater. Results, reported separately for winter and summer opera-
tions, are summarized in Table 9. Loading rates were varied with 9.3 cm/wk being
the highest rate reported.
13
-------
TABLE 9. MEAN WASTEWATER CHARACTERISTICS*, mg/L
Effluent
Parameter
Suspended solids
BOD
COD
Total nitrogen
Kjeldahl nitrogen
Ammonia
Nitrate & nitrite
Total phosphorus
Raw wastewater
160
150
314
23.6
22.8
17.0
0.8
10.0
Summer
8
7
58
2.2
1 .7
0.6
0.4
4.3
Winter
9
8
46
6.8
2.9
1.3
3.7
5.1
*9.8 cm/wk loading rate used for this test
A second study considered treatment of raw wastewater by overland flow with
improved phosphorus removal by alum addition4. Additions of 1.5 to 2.0 mg
alum/mg phosphorus resulted in effluent phosphorus concentrations less than 2
mg/L and corresponded to a 85 percent removal. Other constituent removals were
essentially the same as shown in Table 9.
A third RSKERL report provides the results of work done at Pauls Valley, OK.
This work consisted of overland flow treatment of both raw sewage and oxidation
pond effluent. The system consists of 32 terraces, each having an area of 0.1 ha.
Screened raw wastewater is applied to 24 cells with pond effluent applied to the
remaining 8 cells. The slopes used are 2% and 3%. Terrace dimensions are 23 m
wide by 46 m long. Three types of distribution systems are used. They are fixed
fan nozzles, rotating boom with fan nozzles, and bubbling orifices. These are
shown by schematic in Figure 4.
Temperature effects on operations were particularly noticeable and are
summarized in Table 10. Fecal coliform reductions were less than one order of
magnitude. Sub-freezing temperatures hampered 3005 anc^ ammonia removals.
Treatment of pond effluent by overland flow resulted in limited improvement of
removals of the constituents measured. Results are in Table 10. Detailed
comparisons of factors imparting process performance are shown on Tables 11, 12,
13, and 14.
14
-------
FAN SPRAY NOZZLE
a. FIXED FAN SPRAY
r
/ II \
.l-f»
b. ROTATING BOOM WITH FAN NOZZLE
c. PIPE WITH ORIFICES
Figure 4. Schematics of distribution systems used at Pauls Valley
15
-------
TABLE 10. WASTEWATER CHARACTERISTICS AT PAULS VALLEY, mg/L
Parameter
Raw wastewater
Summer
Winter
Overland flow
effluent*
Summer
Winter
Pond effluent
Summer
Winter
Overland flow
effluentt
Summer
Winter
Suspended solids 105
BOD 117
Nitrate as N <0.05
Ammonia as N 16.7
Organic nitrogen 8.5
Total phosphorus
Fecal coliform 5x10
(MPN/100 ml)
.3
6
90.7
130
0.04
16.5
7.28
8.46
3.9x10
3.6-10.6
8.3-21.0
0.16-1.04
3.1-6.9
2.9-5.0
7.9-9.2
4.8-18x10"
11.0-15.6
24-42.1
0.19-0.74
6.89-13.4
2.66-4.01
6.87-9.64
1.0-2.4xlOe
114
27.7
0.08
1.70
13.8
6.31
3.3xl04
26.1
16.2
0.06
13.5
3.93
12.1
6.0xl04
60.9-101
18.6-25.0
0.10-0.29
0.21-0.48
9.1-14.0
4.21-5.87
1.6-10xl04
6.33-19.9
9.30-17.2
0.15-0.94
8.41-11.0
2.24-4.04
10.1-10.9
1.8-6.4xl04
*From overland flow treatment of raw wastewater.
tFrom overland flow treatment of pond effluent.
-------
TABLE 11. AVERAGE RESULTS AND SIGNIFICANT DESIGN FACTORS FROM THE RAW SYSTEM FOR THE WINTER
APPLICATION AT PAULS VALLEY - NOVEMBER 28, 1977 - MARCH 10, 1978
Application method
Riser
c
Anal. par.
BOD
mg/L
Sus. Sol-
ids mg/L
Fecal Coli-
form per
100 ml
Total P
mg/L
NO3
N mg/L
NH3
N mg/L
Org. N
mg/L
%
Slope
3
2
3
2
3
2
3
2
3
2
3
2
3
2
Eff.
cone.
37.7
42.1
15.6
11.2
6
1.5x10°
6
1.3x10
7.55
7.64
0.24
0.19
6.89
9.56
3.47
4.01
%
Red.
71
68
83
88
62
67
11
10
58
42
52
45
Trough
Eff.
cone.
39.1
40.4
11.0
11.9
6
1.2xlQr
D
1.0x10
6.87
7.75
0.21
0.26
8.47
8.56
3.65
3.64
%
Red.
70
69
88
87
69
74
19
8
49
48
50
50
Boom
Eff.
cone.
24.0
39.8
12.1
12.0
6
2.3x10,.
0
2.4x10
9.55
9.64
0.74
0.44
11.4
13.4
2.66
3.12
%
Red.
82
69
87
87
41
38
-13
-14
31
19
63
57
Significant factors
Infl. cone. in performance
130 Slope
90.7 None
6
3.9x10 Appl. Mtd.
8.46 Appl. Mtd.
0.04 Appl. Mtd.
16.5 Appl. Mtd
7.28 None
-------
TABLE 12. AVERAGE RESULTS AND SIGNIFICANT DESIGN FACTORS FROM THE RAW SYSTEM FOR THE SUMMER
APPLICATION AT PAULS VALLEY - MARCH 20, 1978 - OCTOBER 27, 1978
CD
Application method
Riser
Anal. Par.
BOD
mg/L
Sus. Sol-
ids mg/L
Fecal Coli-
forin per
100 ml
Total P
mg/L
NO3
N mg/L
NH3
N mg/L
Org. N
mg/L
%
Slope
3
2
3
2
3
2
3
2
3
2
3
2
3
2
Eff .
cone.
14.2
18.2
9.4
6.4
6
1.4x10,
O
1.2x10
7.9
8.7
0.18
0.18
4.2
6.9
4.0
4.6
%
Red.
88
84
91
94
72
76
5
-5
75
59
53
46
Trough
Eff.
cone.
21.0
18.3
10.6
6.6
6
1.8x10
1.2x10
8.5
8.9
0.16
0.24
7.4
6.9
4.8
5.0
%
Red.
82
84
90
94
64
76
-2
-7
56
59
44
41
Boom
Eff.
cone.
8.6
8.3
3.6
3.6
6
1.2x10
4.9x10
9.2
9.2
1.04
0.67
3.1
3.4
2.9
3.1
% Significant factors
Red. Infl. cone. in performance
93 117
93
97 105
97
6
76 5.0x10
90
-11 8.3
-11
<0.05
81 16.7
80
66 8.5
64
Appl. Mtd.
Slope
Appl . Mtd .
Slope
Appl. Mtd.
Appl. Mtd.
Interact. *
Slope
Appl . Mtd .
Interact.
Slope
Appl . Mtd .
*Interaction between slope and application method.
-------
TABLE 13. AVERAGE RESULTS AND SIGNIFICANT DESIGN FACTORS FROM THE SECONDARY SYSTEM FOR THE
WINTER APPLICATION AT PAULS VALLEY - NOVEMBER 28, 1977 - MARCH 10, 1978
Application method
Riser
Anal. Par.
BOD
mg/L
Sus. Sol-
ids mg/L
Fecal Coli-
form per
100 ml
Total P
mg/L
NO
N mg/L
NH
N mg/L
Org. N
mg/L
%
Slope
3
2
3
2
3
2
3
2
3
2
3
2
3
2
Eff.
cone.
13.8
9.30
15.7
6.67
4.5x10^
2.5x10
10.4
10.7
0.57
0.94
8.41
11.0
2.81
2.42
%
Red.
15
43
40
74
25
58
14
12
38
19
28
38
Trough
Eff.
cone.
17.2
9.40
19.9
6.33
6.4x10^
1.8x10
10.9
10.1
0.15
0.60
10.8
9.28
4.04
2.24
% Significant factors
Red. Infl. cone. in performance
-6 16.2
42
24 26.1
76
4
-7 6.0x10
70
10 12.1
17
0.06
20 13.5
20
-3 3.93
43
Slope
Slope
Slope
None
Slope
Appl. Mtd.
Interact.
Slope
-------
TABLE 14. ANALYTICAL RESULTS AND SIGNIFICANT DESIGN FACTORS FROM THE SECONDARY SYSTEM,
FOR THE SUMMER APPLICATION AT PAULS VALLEY - MARCH 20, 1978 - OCTOBER 27. 1978
. .
Application method
Riser
Anal. Par.
BOD
mg/L
Sus. Sol-
ids mg/L
Fecal Coli-
fonn per
100 ml
Total P
to m9/L
o
N°3
N mg/L
NH3
N mg/L
Org. N
mg/L
%
Slope
3
2
3
2
3
2
3
2
3
2
3
2
3
2
Eff.
cone .
18.7
19.8
60.9
63.0
4
9.3x10^
1.6x10
4.21
5.87
0.10
0.29
0.21
0.48
10.5
9.1
%
Red.
32
29
47
45
-182
52
33
7
88
72
24
34
Trough
Eff.
cone.
25.0
18.6
101
66.3
5
1.0x10
1.9x10
4.62
5.60
0.13
0.17
0.27
0.44
14.0
9.4
%
Red.
10
33
11
42
-203
42
27
11
84
74
-1
32
Significant factors
Infl. cone. in performance
27.7
Interact.
114
Appl . Mtd .
4
3.3x10 None
6.31 Slope
0.08 None
1.70 Slope
13.8 Slope
Appl. Mtd.
Interact.
-------
UTICA, MISSISSIPPI
The overland flow facility at Utica is a small, continuously operating
research site treating 76 m3/d of lagoon effluent. Research at this site was
carried out by the Corps of Engineers in cooperation with the EPA. Design
characteristics are summarized in Table 15. The facility was designed to allow
investigation of a variety of treatment modes. There are twenty-four, 4.6 x 46-m
plots, plot slopes of 2, 4 and 8 percent are used (8 plots at each slope). Rate
of flow and duration of application are .automatically controlled to each of the
24 beds. This experimental system allows observation of duplicate modes of opera-
tion at different slopes. Photos of the site are shown in Figure 5. Results of
the studies have been reported in Reference 5.
TABLE 15. UTICA OVERLAND FLOW SITE CHARACTERISTICS
Type of wastewater - domestic
Capacity - 76 m3/d
Land area - 0..5 ha
Pretreatment - facultative oxidation pond
Disinfection prior to application - none
Storage - none
Soil type - silty, clayey loam
Application method - perforated trough
Control methods - electric timed solenoid valves
Crop - mixed grasses (reed canary, Kentucky 31 tall fescue, perennial rye grass,
common Bermuda)
Slopes -2,4 and 8 percent
Application rates - 6.5-18 cm/wk
Application period - 6, 8, 18, 24 hr/d at 5 and 7 d/wk
Yearly rainfall - 137 cm
Temperature
Ave Max - 24°C
Ave Min - 12°C
A variety of grasses is grown on each plot including reed canary, fescue,
perennial rye grass and common Bermuda. Grass is harvested three to four times a
year to prevent shading of short varieties. Crop yields have been similar to
grass production obtained on better agricultural soils (11,700 kg/ha-yr for reed
canary at 6.5 cm/wk and 10,000 kg/ha-yr for overseeded rye grass at both 6.5 and
18 cm/wk). The same annual yield has been obtained for either three or four cuts.
By regular harvesting and by mixing the grasses, the researchers can maintain a
dense mat of vegetation conducive to the bacterial growth required for wastewater
treatment.
A trough with a perforated bottom is used to evenly distribute wastewater
across the top of each berm. Flow from the trough can be varied from 3.5 to 21.2
m3/hr. Application times are controlled by electrically timed solenoid valves.
Periods of 6, 18, and 24 hr have been used on both a 5- and 7-day week basis. The
hydraulic loading rate has been varied between 1.27 and 5.08 cm/d.
21
-------
RYE
llN.ISHRS
ALUM
Figure 5. Utica, Mississippi Overland Flow Site.
22
-------
Application continues throughout the winter but at reduced flow rates. No
storage is provided. Wastewater is pretreated in a 2.4-ha facultative pond.
Effluent from the pond contains significant amounts of algae which make up the
bulk of the suspended solids being applied to the overland flow site. The
influent is low in soluble nitrogen, phosphorus and heavy metals so these
elements are added at the site for research purposes. Pond effluent
characteristics are shown in Table 16.
TABLE 16. OXIDATION POND EFFLUENT CHARACTERISTICS AT UTICA
Parameter
BODtj i mg/L
SS , mg/L
Total N, mg/L
Total P, mg/L
Fecal coliforms/100 ml
summer
winter
Cu, mg/L
Ni, mg/L
Cd, mg/L
PH
Range
6-37
8-75
-
5-15
5,000-12,000
600-8,000
-
-
-
7-11
Average
22
35
20*
10§
5,000
1,000
0.10#
0.10#
0.0 5#
^
* Additional Nitrogen added as NH4C1, NH4H2PO4
§ Additional phosphorus added as NH^jI^PC^
# Added
Mosquitos have not been a problem at the Utica facility. The researchers
have maintained flowing water and eliminated depressions where ponding and
breeding of mosquitoes can occur. The facility has been in operation since 1971
and during the first year of operation, research was effectively curtailed by an
invasion of army worms that consumed the entire grass crop. This problem occurred
throughout the Utica locality, but was eliminated and has not occurred again.
Research Results
Parameters investigated included: BOD and suspended solids removal, nutrient
and heavy metal removal, and fecal coliform removal. Removals of BOD and SS were
not affected by slope. Typical performance values are presented in Table 17.
TABLE 17. TREATMENT RESULTS AT UTICA - 1976-1977
Lagoon
effluent ave
Parameter mg/L
BOD, mg/L
SS, mg/L
Fecal Coliforms/100 ml
summer
winter
22
35
5,000
1,000
Hydraulic
loading
cm/wk
6.5
6.5
6.5
6.5
18.0
Slope Removals
percent percent
2, 4, 8 55
2, 4, 8 57
( net increase
recorded)
50
80
23
-------
The bulk of the Utica research involved nutrient removals. Nitrogen removal
was found to vary seasonally. During most of the year about 90 percent removal
was obtained on all slopes for wastewater applied at 6.5 cm/wk. During the
winter, nitrogen removals dropped significantly, with the greatest nitrogen
removal occurring on the 8 percent slope. At higher rates of application, (18
cm/wk) nitrogen removals were similar to those at lower rates of application.
Results are summarized in Table 18.
TABLE 18. PERCENT NITROGEN REMOVALS AT UTICA - 1976-1977
Hydraulic
loading
cm/wk
6.5
18
18
Application
period
hr
6
6
18
2
summer
90
-
80
Percent slope
winter
75
45
4
summer winter
91 78
-
8
summer winter
90 80
-
* Additional nitrogen added as NH4C1, NH4H2pO4
Phosphorus removal was greater for wastewater applied at 6.5 cm/wk than that
applied at 18 cm/wk. However, when the application duration was increased from 6
hr to 18 hr, removals were similar for both hydraulic loadings. Alum addition
resulted in significantly increased phosphorus removal. Effluent phosphorus con-
centrations as low as 1.0 mg/L resulted from dosages of 1:1, Al:P. Phosphorus
removals are shown in Table 19.
TABLE 19. PERCENT PHOSPHORUS REMOVAL AT UTICA - 1976-1977
Hydraulic
loading
cm/wk
6.5
18
Application
period
hrs
6
18
No alum
added
fall winter
50
40
40
25
1:1 A1:P
summer
85
85
Alum added
spring
50
50
Heavy metal removals up to 90 percent have been observed at Utica. The
accumulation of heavy metals in plants and soil has not yet been investigated.
Design Recommendations By Utica Researchers
Hydraulic loading rates should be chosen as a function of the discharger
requirements. Loadings in the range of 6.5 to 18 cm/wk with a 6-hr/d application
on a 5-day week basis have resulted in effluent 6005 and suspended solids con-
centrations of less than 20 mg/L each. Differences were not detectable for slopes
of 2 to 8 percent. Lower slopes can result in local depressions and ponding
while higher slopes require more grading and may be financially less feasible.
Mixed grasses and regular harvesting are essential for production and maintenance
of a dense vegetative mat. Occasional mulching of grasses may be helpful in some
areas.
24
-------
CARBONDALE, ILLINOIS
Carbondale, IL is the site of small, full-scale operation where overland
flow is used to treat pond effluent. This facility treats domestic wastewater
from the Cedar Lane Trailer Court. Cedar Lane Trailer Court is a small, 54 unit
mobile home park located 3 km south of Carbondale. The terrain is slightly roll-
ing and the park is wooded. The population of the Cedar Lane Trailer Court is
135, and has been relatively stable since construction in the 1950's.
Prior to the development of the present overland flow system, in 1976, the
park's sewage was treated in two, 38-m^ septic tanks followed by a 0.28 ha oxi-
dation pond located approximately 20 m from the nearest trailer. A partial view
of the oxidation pond and the trailer park is shown in Figure 6.
I ,
*.' *» '':
Figure 6. Cedar Lane Trailer Park oxidation pond.
25
-------
Effluent from the oxidation pond did not meet the discharge requirements of
the Illinois Environmental Protection Agency Pollution Control Board (Table 20).
TABLE 20. STATE OF ILLINOIS WATER QUALITY STANDARDS6
pH: Within range of 6.5 to 9.0 except for natural causes.
BODcj: Average BOD^ shall not exceed 4 mg/L on intermittent streams*
Phosphorus: Shall not exceed 0.05 g/m as P in any reservoir or lake or in
any stream at the point where it enters any reservoir or lake-
Dissolved oxygen: Shall not be less than 6.0 g/m during at least 16 hr of
any 24-hr period, nor less than 5.0 g/m at any time.
Ammonia nitrogen: Shall not exceed 1.5 mg/L as N.
Nitrite plus nitrate: Shall not exceed 10.0 mg/L as N for public and food
processing water supply.
* The receiving stream is an intermittent stream.
Preliminary Treatment
Characteristics of the septic tank effluent have not been monitored. The
oxidation pond effluent characteristics were monitored during 1976 and
19777'8 and are presented in Table 21.
TABLE 21. OXIDATION POND EFFLUENT CHARACTERISTICS AT CEDAR LANE9
Parameter Range of values
BOD5, mg/L 30 - 110
Suspended solids, mg/L 20 - 60
Phosphorus, mg/L 3-4
Ammonia nitrogen, mg/L 20 - 40
Nitrate and nitrite nitrogen, mg/L 0
Fecal coliforms, MPN/100 ml Approx. 35,000
During the 1976-77 research program, maximum ammonia nitrogen concentrations
were desired in the pond effluent. Duckweed was allowed to predominate on the
pond surface to minimize algal growth and prevent nitrification. This was done to
maximize organic and nitrogen loadings on the overland flow facility. Since July,
1977, the pond has been operated without effluent monitoring.
26
-------
Oxidation pond effluent flows into a 3.8 m3 cylindrical tank from which it
is pumped through 90 m of 5-cm plastic pipe to the top of a grassy slope approxi-
mately 7-m in elevation above the pond. The overland flow slope is shown in
Figure 7. The pump is submersible and is operated by a float activated switch.
Figure 7. Overland flow slope at Cedar Lane Trailer Park.
Overland Flow Site
The overland flow slope runs for approximately 30 m at 7 percent, at which
point the slope increases to approximately 12 percent for an additional 30 m and
then flattens out. A small channel that eventually discharges into Drury Creek is
about 40 m from the base of the 12 percent slope. Flow in the channel is inter-
mittent and consists of runoff from the small surrounding watershed.
27
-------
Soil in the area is a fine granular glaciated material with low permeabil-
ity. Runoff from the slopes accounted for over 80 percent of the applied
wastewater.
The site available for overland flow was approximately 90 m wide. A 10-m
section near one edge was chosen for the system. This section is shown as the
darker portion near the left edge of the slope in Figure 7. Tall fescue was the
predominant grass on the slope and has remained so since wastewater application
began. Site characteristics are summarized in Table 22.
TABLE 22. CARBONDALE SITE CHARACTERISTICS
Type of wastewater - domestic sewage
Capacity - 38 m3/d
Land area - 0.06 ha
Pretreatment - septic tanks and oxidation pond
Disinfection prior to application - none
Storage - none
Soil type - fine glacial till, low permeability
Application method - perforated pipe
Control methods - manual throttling valve on pump, intermittent flow
Crop - natural grasses
Slope - 7-12 percent
Application rate - 44 cm/wk
Application period - 0-24 hr/d
System Design
The site consists of two 5-m x 60-m sections. Aluminum garden edging was
inserted along the boundaries of the overland flow system to contain the flow.
The upper 30-m (the 7 percent slope section) was divided into two, 5 x 30-m por-
tions. Grass on one side was maintained at a height of less than 30 cm during
the research while the other was allowed to grow unchecked. Following completion
of the research project in June, 1977, the entire system was not cut until
November, 1979, shortly before the site visit.
Two distribution systems were used during the 1976-77 research project; the
initial system at the top of the slope and a redistribution system at the end of
the first 30-m. The latter system was essentially the same as the intial system.
It fell into disuse following the completion of the research, probably due to
lack of maintenance of the header boards used to channel flow to the distribution
box.
The distribution system at the top of the slope consists of a distribution
box and two, 5-m long, perforated 10 cm distribution pipes. Perforations are on
30 cm centers and are approximately 1 cm in diameter. Flow into each pipe is con-
trolled by a V-notch weir in the distribution box. Equal flows are maintained to
each distribution pipe.
28
-------
During the 1976-77 studies, a range of application rates and periods were
used. One finding was that continuous application (24 hr/d) had no negative
effects for operating periods of several weeks. Since the end of the study,
application has been controlled by the oxidation pond levels through use of the
float activated switch. Thus, wastewater may be applied to the overland flow sys-
tems for several days on a 24-hr basis, followed by a period with no wastewater
application. Length of periods depends on flow into the pond and seasonal evapo-
ration rates.
During the 1976-77 studies, samples were taken from the influent, at 15-,
30-, and 60-m points and in the receiving channel upstream and downstream of the
overland system. Flow was monitored with weirs in the distribution box and in the
channel at points both upstream and downstream of the discharge. Since July,
1977, sampling has been the minimum required by the Pollution Control Board.
Suspended solids and BOD5 samples were taken on a weekly basis in 1976-77-
Nutrient samples were taken on a daily basis during most of this period.
As noted above, dosing is presently based on a float operated pump switch.
During the 1976-77 studies a number of hydraulic loading rates were used; these
are shown in Table 23. Operation during spring and early summer 1976 was limited
by oxidation pond drawdown at the end of periods one and two. The third operation
period was limited by a leak in the oxidation pond dike. Before the oxidation
pond could be refilled unusually harsh winter conditions resulted in heavy ice
formation and prevented flow from the pond. Suitable operating conditions did not
occur again until March, 1977. Since that time, operation has been continuous,
including the winter months.
Tracer studies were run during experimental operating periods. Results are
given in Table 24 in terms of detention time.
Performance of Overland Flow System
Performance of the system during the experimental periods is indicative of
overall performance. Removal and loading data are presented in Tables 25 through
28.
TABLE 23. 1976-1977 LOADING RATES OF CEDAR LANE TRAILER PARK
OVERLAND FLOW SYSTEM
Period
1
2
3
4
5
6
7
Dates
3/22/76-
4/21/76
6/3/76-
7/8/76
9/23/76-
10/13/76
3/16/77-
3/21/77
3/22/77-
4/12/77-
4/17/77
4/21/77-
5/12/77
No. of
days
31
36
21
6
21
6
4
Application
time
hr/d
12
12
9.25
24
24
8
4
hrs/wk
Application
rate
m3/hr
4.1
4.1
\
4.1
5.7
2.8
2.8
2.8
Hydraulic
loading rate
cm/day
8.18
8.18
6.31
22.80
11.36
3.73
1.87
cm/wk
29
-------
TABLE 24. DETENTION TIME AS A FUNCTION OF POSITION AND APPLICATION RATE
Distance, m
Application rate, mj/hr
2-8 4.1
15
30
45
60
Resulting Detention time, mini
31 19
50 48
66
88 81
Period
1
2
3
4
5
6
7
TABLE 25.
Hydraulic
loading
rate,
m3/ha-d
818
818
631
2,280
1,136
373
27
BOD 5 REMOVAL
Influent
BOD 5,
mg/L
27.4
18.0
69.6
43.6
20.2
9.2
15.0
IN CARBONDALE
BOD loading
rate,
kg/ha- d
22.1
14.7
43.9
99.4
23.0
3.4
0.4
OVERLAND
30-m
19.7
5.9
12.4
17.0
16.7
7.0
11.5
FLOW SYSTEM
BOD , mg/L
60-m*
12.1
2.7
5.0
13.3
5.0
4.5
-_ _
90-m**
10.8
2.8
13.7
4.9
3.7
End of slope
** Nearly level area past end of slope
TABLE 26. SUSPENDED SOLIDS REMOVAL IN CARBONDALE OVERLAND FLOW SYSTEM
Period
1
2
3
4
5
7
Influent,
mg/L
22
24
35
34
24
26
Loading rate,
kg/ha-d
18.0
19.6
22.1
77.5
27.3
0.7
SS,
30-m
12
20
10
mg/L
60-m*
__
12
40
30
13
*End of slope
30
-------
TABLE 27. PHOSPHORUS REMOVAL IN CARBONDALE OVERLAND FLOW SYSTEM
Period
1
2
3
4
5
6
7
Influent,
mg/L
3.25
1.78
3.44
5.05
3.34
2.50
3.00
Phosphorus
loading rate,
kg/ha-d
2.66
1.46
2.17
11.51
3.79
0.93
0.09
P,
30-m
1.17
0.61
1.81
2.77
2.56
1.88
2.50
mg/L
60-m
0.48
0.21
0.32
2.31
1.70
1.30
1.80
TABLE 28. NITROGEN REMOVAL IN CARBONDALE OVERLAND FLOW SYSTEM
Period
1
2
3
4
5*
6
7
Influent,
mg/L
4.5
8.0
31.6
29.1
16.8
13.6
9.8
Nitrogen
loading
rate,
kg/ha-d
3.7
6.5
19.9
66.4
19.1
5.1
0.3
NH3-N,
30-m
2.9
2.6
9.9
21.6
5.3
4.2
5.0
mg/L
60-m
1.0
0.7
0.4
20.3
0.6
0.2
0.8
N03-N,
30-m
2.3
0.4
3.5
1.1
4.6
3.8
~
mg/L
60-m
0.5
0
0.6
0.7
6.0
3.9
6.0
*Two distinct periods are reported, the better of which is reported here.
Actual loading of the system averaged approximately 38 m3/d and 630
m /ha-d. This corresponds to 44 cm/wk or 6.3 cm/d, a very high loading rate in
comparison to other sites. Operating period three in Tables 25 through 28 is a
reasonable estimate of expected system performance.
Comparisons of BOD5 removal with hydraulic and organic loading rates are
shown on Figures 8 and 9. BOD5 removal and hydraulic loading correlate well
except for two points. Point #1 represents the first period of operation. The
relatively poor performance could represent an inital period of system adaptation
or buildup of humus to provide good treatment. Point #6 can not be explained.
Because the effluent suspended solids concentration (Table 26) is greater than
the influent suspended solids concentration in one instance, a source of solids
must exist on the slope. The most likely source is humus (that collected prior to
initiation of overland flow treatment) and/or erosion. Erosion does not seem
likely because visible effects are not evident after 3 years of operation. Also,
higher effluent suspended solids would have resulted with the higher loading
rates if erosion was occurring.
Phosphorous removal performance was very good during 1976 and much less
satisfactory during 1977. There could be a possibility of saturation of the sys-
tem adsorption capacity for phosphorus. The soil mantle adsorbs phosphorus. Each
31
-------
100-
90.
60-
70
~a
> 60
o>
D
§
40
30
20
10
500 1000 -1500
HYDRAULIC LOADING RATE, m3/ha-d
2000
Figure 8. BOD removal vs. hydraulic loading rate at Carbondale'
32
-------
100 ,
90-
80-
70-
60 '
50-
40
30
20-
10'
10 20 30 40 50 60 70 80
ORGANIC LOADING RATE, Kg/ha-d
90 100
Figure 9. BOD5 removal vs. organic loading rate at Carbondale .
33
-------
soil has a limit which it can adsorb, or its adsorption capacity. Asaturian
performed a limited number of adsorption capacity experiments and estimated the
capacity, x, to be given approximately by Equation (2)
x = 0.14 c* (2)
where x = Phosphorous sorption capacity gP/g soil
c* = Equilibrium solution concentration of P, g/m3
For a system with short detention times due to steep slopes, .soil contact
would be limited and true equilibrium would be unlikely.
Nitrogen removals were excellent throughout the studies. There are three
primary modes of nitrogen removal by land treatment. Some nitrogen is removed by
plant uptake. Some ammonia nitrogen is nitrified and thus converted to nitrate.
1 The nitrate is then leached through the root zone or denitrified to nitrogen gas
and goes into the air. The mechanism for nitrification (which requires oxygen)
and denitrificaiton (which requires anoxic, or absence of oxygen, conditions)
occurring simultaneously is not completely understood. Nitrification occurs in
the thin sheet of water as it flows over the slope. The nitrate most likely
accumulates in the humus. This accumulation is limited but the limit is not
known. The humus may or may not be aerobic during operation. It will probably be
anaerobic near the end of a wetting cycle. After drying for some time the layer
would then become aerobic. While in the anaerobic state denitrification will
result in conversion of nitrate to nitrogen gas. Since relatively little water
leaches through the soil, losses to leachate are insignificant. The requirement
of tall fescue is estimated to be 0.02 kg N/kg grass grown. At a flow rate of 38
m /d and an influent nitrogen concentration of 30 mg/L (which must be con-
sidered high), over 1 kg N will be placed on the system each day. Thus, the pri-
mary mode of nitrogen removal must be nitrification-denitrification. Excellent
removals were recorded during experimental operating periods 1 through 4. The
last three periods show much less removal. In operating periods 5 and 6 the
decrease is probably due to a lack of anaerobic conditions necessary for denitri-
fication. Some doubt must be directed toward the value of effluent NO^-N for
period 5 because it is larger than the 30-m value.
Removals of BOD5, suspended solids, nitrogen, and phosphorus with deten-
tion time are shown in Figures 10, 11, 12, and 13.
Cost of System
Costs were not available for this system since the construction was minimal
(provided by Southern Illinois University).
HANOVER, NEW HAMPSHIRE
Hanover, NH is the home of the U.S. Army Cold Regions Research and Engi-
neering Laboratory (CRREL). Since May, 1977, CRREL staff have been investigating
;overland flow as a method of treating domestic wastewater. In the initial studies
process performance was compared using tap water, primary effluent, and secondary
effluent for application9'10- More recently the design relationships for
treatment of primary effluent using overland flow techniques have been studied.
The Hanover site characteristics are shown in Table 29.
34
-------
UJ
LH
OI
Q
O
CQ
50
40
0 10 . 20 30 40 50 60 70 80 90 100 110 120 130 140 150
30-
20
10-
Figure 10. BOD^ removal vs. detention time at Carbondale.
-------
30 -,
INCREASE DUE TO STEEP SLOPE
FROM 100 M TO 200 M POINT
AVERAGE OF ALL LOADINGS
10 20 30 40 50 60 70 80 90 100 110 120 130
DETENTION TIME Min
Fiqure 11. Suspended solids vs. detention time.
-------
35,
170 cm/wk
100
110
120
130
140
150
DETENTION TIME nin
Figure 12. Total nitrogen removal vs. detention time.
-------
U)
CO
10
20
30
40
50
100
110
120
60 70 80 90
DETENTION TIME, nin
Figure 13. Phosphorus removal vs. detention time at Carbondale.
130
140
150
-------
TABLE 29. HANOVER SITE CHARACTERISTICS
Type of wastewater - domestic sewage
Capacity - 2.1 m3/d
Land area - .03 ha
Pretreatment - primary sedimentation or secondary treatment
Disinfection before application - none
Storage - 20 m3
Soil type - Hartland silt loam (23 percent clay)
Application method - 3.8 cm PVC perforated pipe
Control methods - Manual
Crop - orchard grass, tall fescue, reed canary, perennial rye grass
Slope - 5 percent
Application rate - variable (5.8 - 47 cm/wk)
Application period - 7 hr/d
Yearly rainfall - 95 cm
snowfall - 185 cm
Temperature
Ave annual - 7°C
Days below 0°C - 160
The CRREL overland flow test facility consists of a three-cell site each
30.5-m long and having total area of 0.03 ha. The slope of the system is 5 per-
cent. A schematic is shown on Figure 14. A rubber liner has been used to prevent
percolation below 15 cm. Wastewater was supplied via a nearby domestic sewer and
treated adjacent to the test cells. For the control cell, local tap water was
used.
The principal purpose of studying overland flow at this location was to
assess the effects of cold weather on the process and to develop design proce-
dures based on parameters other than the hydraulic application rate.
The principal research activities on the CRREL overland flow project were
terminated in the fall of 1979. A certain amount of information from the study
has been reported9, however, the major portion of the data analysis will not be
completed until late 1980. The information on the initial studies conducted at
CRREL on overland flow is summarized herein; that available from the more recent
research is also presented.
Treatment Performance
First year performance information on the CRREL overland flow systems was
obtained during the period from May, 1977 to April, 1978. As noted above, three
sources of water were used on the plots. Tap water was taken from a local source
and wastewater was drawn from a local sewer and given either primary or primary
and secondary treatment by extended aeration on site. The quality of these three
sources of water is given on Table 30. Note the relatively small difference
between primary and secondary effluent.
39
-------
^'CUTAWAY VIEW:
SUBSURFACE FLOW
CATCH BASIN
../<.. ,»
METAL CATCH BASIN
PRIMARY WASTEWATER ^)
SECONDARY WASTEWATER (
,,/
2
PIPE
Figure 14. Diagram of Hanover overland flow system (9).
40
-------
TABLE 30. AVERAGE WASTEWATER QUALITY APPLIED TO CRREL OVERLAND FLOW SLOPES
MAY 30, 1977 to APRIL 1, 1978
Application concentrations
Parameter
Total nitrogen, N
Ammonia nitrogen as N mg/L
Nitrate nitrogen as N, mg/L
Total phosphorus, mg/L
BOD^ , mg/L
Total suspended solids, mg/L
Volatile suspended
solids, mg/L
Cond, mhos/cm
pH , pH units
Fecal coliform, MPN/100 ml
Potassium mg/L
Tap
0.3
0.1
0.0
0.6
0.4
1.4
0.7
91
7.1
0
,1.4
Primary
36.6
33.1
0.5
6.3
85.3
74.6
60.7
524
7.4
7.9x104
12.4
Secondary
33.5
27.3
5.1
5.9
53.2
30.2
21.7
519
7.5
1.8x104
11 .9
Source: Reference 10
Results of the study have been divided into warm and cold weather periods
with average performance values from these periods given in Table 31. As is
apparent from the data, a marked decrease in performance occurred during the cold
weather. To determine the temperature below which treatment performance was
unacceptable (BOD and SS greater than 30 mg/L each), the effluent BOD was
correlated to the soil temperature. Optimum operating soil temperature was found
to be about 14°C. The minimum soil temperature at which an effluent BOD of 30
mg/L with primary effluent could be achieved was 4°C. The 5 cm/wk loading rate is
one of the lowest loading rates of the case histories reviewed.
A mathematical formula used to describe the runoff BOD vs soil temperature
relationship is included with the graph of the data given on Figure 15. A similar
relationship was established for estimating ammonia nitrogen in the runoff. The
data presented in Figure 16 are for both primary and secondary effluent. At 4°C,
the minimum temperature for acceptable effluent BOD, the ammonium concentration
would be about 22 mg/L. The optimum performance would be about 17°C, 3° higher
than for optimum BOD removal.
Nitrogen removals in the systems fed primary effluent were greater than in
the system to which secondary effluent was applied. Neither wastewater was highly
nitrified (despite the secondary treatment system being extended aeration). Con-
sidering the extent of removal during the summer months denitrifiers must have
been active in both systems. Nitrification rates were greatly reduced during cold
weather. The higher concentration of nitrate in the secondary effluent agrees
with conclusions of other 'researchers. That is, the denitrification process is
suppressed by the relatively high oxygen content in applied secondary effluent.
A surprising phenomenon of the cold weather operations was that even under a
snowpack, the effluent irrigated plots remained green, while the tap water plot
and surrounding vegetation were brown. The reasons for this have not been fully
investigated; however, there was speculation that it could be related to the
temperature of the effluent with the snow cover acting as insulation, or to the
nutrient load provided by the wastewater. In either case adequate light transmis-
sion through the snow would be necessary.
41
-------
TABLE 31. AVERAGE PERFORMANCE FROM CRREL OVERLAND FLOW SLOPES*
Runoff concentrations
Warm weather
May 30, 1977
to October 16, 1977
Cold weather
December 12, 1977
to March 19, 1978
Parameter
Tap Primary
Secondary
Total nitrogen, mg/L 0.7 5.4(94%)** 8.0(87%)
Ammonia nitrogen,
as N, mg/L 0.1 3.2 2.6
Nitrate nitrogen
Primary
Secondary
37.2(25%) 26.2(32%)
24.3
21 .5
as N , mg/L
Total phosphorus,
mg/L
BOD5 , mg/L
Total suspended
solids, -mg/L
Volatile suspended
solids, -mg/L
Cond mhos/cms
pH, pH pH units
Fecal Coliform,
MPN #/100 ml
0.1
0.2
1 .4
2.8
1 .4
211
7.9
72
1.6
1 .9(89%)
11.2(91%)
6.7(97%)
5.2
395
7.7
6.3 x 102
5.2
2.2(80%)
4.6
3.8(96%)
3.2
324
7.6
13
2.0
5.9
65.3(58%)
13.6(84%)
11 .4
606
7.2
8.1 x 104
3.8
4.4(
13.9 (
4.1 (
3.5
616
7.3
6.3 x
30%)
80%
88%)
103
Application rate of 5 cm/wk
**Numbers in parentheses refer to mass percent removal
Removal of bacteria is given in terms of fecal coliforms. The increase in
fecal coliforms after treatment on the tap water plot indicates that this
parameter is not a satisfactory measure of the sanitary quality of the runoff (as
also concluded by the Utica researchers). Origin of the coliform bacteria is not
necessarily human and a number of species are soil bacteria. Thus, the result is
not surprising.
The conclusions drawn from the results of the first year of
presented in Reference 9 are:
operation as
Wastewater application should cease whenever the soil temperature on
the overland flow slope decreases to 4°C. The system should not be
restarted until soil temperature increases to 4°C. Soil temperatures
were taken at 2 cm below surface
The effect of temperature on ammonium removal from overland flow sys-
tems is similar to that of conventional biological systems.
Ammonium is more effectively removed in overland flow systems than
nitrate. Nitrate is not immobilized and is carried into the runoff.
Warm weather performance of the overland flow system was excellent.
BOD^ and suspended solids removals were greater than 90 percent.
Fecal coliform concentrations in the runoff were found to be a poor
measure of the sanitary quality of overland flow runoff (interference
likely from soil bacteria).
42
-------
90
80
70
60
- 50
CD
E
in
8 40
a
30
20
10
=0.226 [SOIL TEMP] 2 -6.53 [SOIL TEMPJ+SS.O
R = 0.783
N = 19
10 12 14 16
SOIL TEMPERATURE C
18
20
22
24
Figure 15. Average weekly runoff BOD concentration
vs. soil temperature (primary section)
at Hanover (9).
43
-------
E
I
.45
40
35
30
25
20
15
10
JNH4+] =0.114 [SOIL TEMP^ 2 -3.94 [sOIL TEMpJ +35.1
R = 0.936
N = 86
A SECONDARY SECTION
O PRIMARY SECTION
Figure 16. Average weekly runoff NH4 concentration vs.
soil temperature for primary and secondary
sections at Hanover (9).
02 4 6 8 10 12 14 16 18 20 22 24
SOIL TEMPERATURE C
44
-------
Design Methods
Ongoing research at CKREL has involved developing methods for designing
overland flow systems. The results of this work are being presently analyzed;
therefore, the available information is limited. This discussion is based on the
preliminary findings; the major portion of the research will not be reported
until late 1980.
In the past, the methods for designing overland flow systems have been based
on hydraulic loading rates, which were not directly related to BOD or nitrogen
removals . Current efforts at CRREL are directed at developing a rational
method for designing such systems. The basic design parameter being studied at
CRREL is detention time. On the premise that if a given BOD removal can be
related to the length of time waste remains on the treatment site, systems can be
designed for treatment with any reasonable slope. Other factors such as climate,
vegetation, and soil type must also be considered in design.
The preliminary results of data analysis are given on Figures 17, 18, and
19. The percent BOD and suspended solids removal have been plotted against the
average detention time as shown on Figures 17 and 18. The design relationship is
based on the plot of application rate vs. detention time shown on Figure 19. Data
for this graph were obtained from WES as well as CRREL. The equation provides a
proposed basis for rational design methods being developed for overland flow.
45
-------
100.
0
AVERAGE DETENTION TIME nin
Figure 17. BOD removal vs. detention time for CRREL ovo.'land flow site receiving primary effluent.
Source: Unpublished data by Martel, C.J. et al to be presented in July 1980.
-------
100
80'
>
o
LU
EC
CO
Q
Q
LU
Q
LU
CL
co
CO
_l
<
h-
O
60'
40-
LU
O
o:
LU
D.
20- ,
10
Figure 18.
20
30 40 50 60
AVERAGE DETENTION TIME min
70
80
90
Suspended solids removal vs. detention time for CRREL overland
flow site receiving primary effluent.
Source: Unpublished data by Martel, C.J. et al to be presented in July 1980.
-------
E
III
o
111
1-
UJ
D
1 f \J\J\J
9
8
7
6
5
4
3
t
2
100
9
8
7
6
5
4
3
2
in
X
\
\
w
x
>
y
\
\,
\
\j
s
s
* HANOVER
( LENGTH =
A UTICA TES
(LENGTH=
V
K
\
TEST SITE
30 m. SLOPE =0.05)
TSITE
46 m. SLOPE = 0008)
\
0.1
3 456789
1.0
3 456789
10
HYDRAULIC LOADING RATE cm/hr
Figure 19. Relationship between hourly hydraulic loading and detention
time at Hanover and Utica.
48
-------
EASLEY, SOUTH CAROLINA
Easley, S.C. has a full-scale municipal overland flow system. This system
provides for overland flow treatment of oxidation pond effluent and/or raw domes-
tic wastewater. Site characteristics are described in Table 32. System perform-
ance data for the period January 4 to May 30, 197^, the first 4 1/2 months of
operation, are summarized in Table 33. Raw sewage was applied at 11.8 cm/wk.
Lagoon effluent hydraulic loadings ranged from 10.3 cm/wk to 19.3 cm/wk. BOD5
and suspended solids removals are less than expected based on work conducted at
other sites visited. Problems with establishing a good groundcover occurred due
to drought which adversely affected performance during the period reported (The
grass cover must be established by rainfall or irrigation prior to beginning
overland flow operation). Algae removal has not met expectations of the opera-
tors, but improved grass cover in 1980 should result in improved performance.
TABLE 32. EASLEY SITE CHARACTERISTICS
Type of wastewater - domestic sewage
Capacities - 91 m3/d
Land area - 2 ha
Pretreatment - screened and comminuted or oxidation ponds
Disinfection before application - none
Storage - 45 m-*
Soil type - red clay with small amounts of sand
Application method - low pressure fan nozzles
Control methods - hand operated gate valves and automatic solenoid valves and
time clocks i
Crop - predominately Kentucky 31 tall fescue
Slope - 6 percent
Application rate - 12-15 cm/wk
Application period - 6-8 hrs/d
Yearly rainfall - 117 cm
Temperature
Ave Max - 24°C
Ave Min - 12°C
TABLE 33.
Parameter, mg/L
BOD 5
TOC (filtered)
Suspended solids
Total phosphorus
Orthophosphorus
NH4
EASLEY, SC OVERLAND FLOW SYSTEM PERFORMANCE15
Raw sewage
Raw sewage
158
28
161
4.7
5.0
15.3
application
Overland flow
effluent
36
23.8
(2 samples)
54
3.7
(1 sample)
3.9
5.0
Lagoon effluent application
Lagoon Overland flow
effluent effluent
24 14
22 27
57 42
3.2 2.1
1964 and has been expanded
2.3 1.7
1.1 0.4
49
-------
PARIS, TEXAS
Campbell's Soup owns and operates the largest overland flow facility in this
country. This facility has been in operation since 1964 and has been expanded
several times. Presently up to 35,000 m-^/d of cannery wastewater is applied
year-round to 310 (360 gross) wetted hectares. Site characteristics are described
in Table 34.
TABLE 34. CAMPBELL'S SOUP, PARIS, TEXAS SITE CHARACTERISTICS
Type of wastewater - industrial
Average flowrate, m-^/d - 17,000
Land area - 365 ha (gross), 285 ha (wetted)
Pretreatment - grease separation, coarse screening
Disinfection prior to application - none
Storage - none
Soil type - grey clay loam overlying red clay subsoil
Application method - sprinklers
Control methods - time clocks and pneumatically operated valves
Crop - predominantely reed canary
Slope - 2-8 percent
Ave application rate - 4.2 cm/wk (.84 cm/d, 5d/wk)
Application period - 6 hrs on 18 hrs off
Yearly rainfall - 114 cm
Pretreatment consists of grease separation and coarse screening by large
rotary screens. After screening the water is pumped to the adjacent site and
distributed through a network of pipes and sprinklers. Distribution is controlled
by four time clocks, one for each raw wastewater pump. The time clocks signal the
opening and closing of pneumatically operated valves at the head of each pipe
lateral. Time clocks are set to operate laterals and sprinklers on a 6 hr on 18
hr off cycle. By this method flow is evenly distributed across the entire site.
Both the influent and effluent characteristics are monitored. Typically
influent BOD ranges from 500 to 900 mg/L while effluent BOD ranges from 3 to 10
mg/L. Treatment performance for 1979 is summarized in Table 35.
50
-------
TABLE 35. PERFORMANCE SUMMARY AT CAMPBELL'S SOUP, PARIS, TX
Influent
Month
Jan
Feb
March
April
May
June
July
August
Sept
Oct
Nov
Dec
Ave
f lowrate
m3/dx103
14.5
20.1
18.3
18.3
19.5
17.4
14.2
16.2
15.9
18.0
17.6
16.5
Ave
BOD5
mg/L
935
1,270
835
1,010
330
525
930
574
790
227
323
-
Ave
TSS
mg/L
284
609
413
1,126
214
236
602
370
506
354
516
-
Effluent
Ave
flowrate
m3/dx103
14.4
18.6
15.0
14.0
14.4
12.3
12.5
13.8
15.4
17.0
17.4
14.2
Ave
BOD
mg/L
10.6
13.1
5.8
7.5
4.7
5.8
4.3
3.3
5.0
4.0
5.0
6.5
Ave
TSS
mg/L
20.7
23.0
56.2
35.3
54.9
39.9
58.5
27.7
27.6
17.4
25.4
21.7
Per cent
removal
(mass
BOD
98.9
99.0
99.4
99.4
98.9
99.2
99.6
99.5
99.4
98.3
98.5
-
basis )
TSS
92.8
96.5
88.8
97.4
81.0
88.0
91.4
93.6
94.7
95.4
95.1
-
Annual Ave 17.2
704
475
14.9
6.3
34.0
99.2
93.4
As shown, excellent results are obtained in both BOD and TSS removal. Two
important factors that contribute to the high performance are the relatively low
hydraulic loading, 4.2 cm/wk, and the highly degradable cannery waste. Results
similar to those above would not be expected from overland flow treatment of
domestic sewage even at lower loadings. Also shown above is that treatment per-
formance is not effected by winter operation. Average minimum temperatures in
winter range from -3°C to 10°C. Some reduction in system performance would be
expected because of reduced bacterial activity, however performance during this
period is essentially the same as for other times of the year. Research has shown
that while individual bacterial metabolism is reduced the population of bacteria
increases during the winter maintaining the same gross bacterial activity^.
Because of this action wastewater application can be made year around and no
storage is required.
The site was originally planted with a mixture of grasses including Reed
Canary, red top, and tall fescue. It was expected that native grasses would even-
tually dominate, however the Reed Canary has become the predominate crop. Grass
is harvested 1-2 times per year by contract with local farmers. Revenue from har-
vesting offsets operating costs by 5-8 percent. In the past grass was cut and
then removed from the field while it was still green. It was then chopped and
pelletized for cattle feed. Treatment was interrupted to allow the field to dry
out enough to support equipment and to cut the hay. Future plans are for the
grass to be cut, windrowed and allowed to dry on-site. Once dry the grass will
also be baled and stacked on-site. The new procedure will take much longer than
before and require portions of the field to be out of service longer.
51
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Sprinklers are located about 25-m below the top of each sloped terrace to
prevent the circular spray pattern from overlapping the terrace above. Slopes
range from 100 m long at the older portions of the site to 50-m long at the newer
portions. It was found after early investigations that the 50-m long slopes gave
equivalent treatment. Slopes tend to follow natural contours and range from 1 to
12 percent.
Operation and maintenance problems have been minimal at Paris. Army worm
infestation is a recurring problem but is controlled by spraying insecticide from
the air. Mosquitoes have not been a problem. Originally many of the laterals were
constructed from aluminum irrigation pipe; because of corrosion this pipe is
gradually being replaced by buried PVC pipe. Buried butterfly valves were used
in the older areas. Seating problems with these values led to the selection of
totally enclosed diaphragm valves for newer areas. Butterfly valves that had to
be exposed for repair and all the newer valves were placed in valve boxes for
ready access.
Research Results
During 1968 a detailed research program was conducted at Paris . The
project included a coordinated study of climatological, agricultural, biological,
hydrological, and chemical factors. At the time the site consisted of 197 ha of
which 35 were isolated and studied. The conclusions of this report are summarized
below.
It was expected that a microclimate is created on the field due to
evaporative cooling that makes conditions similar to northern climates.
This was found not to be the case.
Hay harvested from the site was found superior in quality and preferred
by cattle over local grasses. Analyses showed high levels of
nutrients.
Bacteria found on the site are similar to typical soil microrganisms
but are specific for the organic matter found in the wastewater.
An increase in bacterial population during winter offsets a decrease in
metabolic activity.
Insecticides have no effect on microbial populations but are effective
in controlling army worms and snails.
20 percent of the applied water is lost through percolation and 10 to
30 percent is lost by evapotranspiration. About 60 percent of applied
wastewater runs off.
The system is capable of consistently removing 99 percent of the
applied BOD and up to 90 percent of the applied nitrogen and
phosphorus.
52
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Little or no change in the organic content of the soil occurs.
Vegetation, living and dead, provides the surface area for growth of
bacteria.
Design Information
Campbell's Soups has compiled the following design information based on
their work in Paris16.
Length of slope 60-75 m
Slope 3-6 percent
Application period 8 hr on-16 hr off
Size of sprinkler nozzles 6.5 (50 L/min)-8 (80 L/min) mm
Distance between sprinklers 25 m
Hydraulic loading rate 4-9 cm/wk
Operating cost/nv* effluent $0.041
Construction costs (1979) $1600-$2500/ha (not including cost
of la nd)
Operating pressure at sprinkler heads 340-480 K^a
BOD applied 500-900 mg/L
BOD in effluent 10 mg/L
Costs
Construction costs per ha for the first 197 ha site built during 1960-1963
are given below .
Clearing and grading $ 894.00
Planting 267.00
Piping and sprinklers 860.00
Misc. 465.00
Total per ha $2,483.00
The above described overland flow systems descriptions and performance data
are presented in Table 36.
53
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TABLE 36. EXISTING OVERLAND FLOW SYSTEM DESCRIPTIONS AND DATA - SUMMER/WINTER
Ln
b,
Type of
Location facility
Davis, CA Research
Pilot Studies
Hunt Wesson* Full Scale
Davis, CA
Ada, OKt Research
Utica, MS* Research
Carbondale, Full Scale
IL
Hanover, NH Research
Easly, SC Full Scale
Paris, TX Full Scale
Type of
wastewater
Domestic
Sewage
Food
Processing
Domestic
Sewage
Domestic
Sewage
Domestic
Sewage
Domestic
Sewage
Domestic
Sewage
Food
Processing
*Nitrogen added to promote grass or for
tFor spray application.
iNH only.
4
Preapplication Runoff %
treatment of applied
Oxidation Pond 87
Screening 21
Screening 47
Primary 50
Oxidation Pond 50
Oxidation Pond
Oxidation Pond 83
Primary 25
Secondary 80
Screening 70
Oxidation Pond 70
Screening, 87
Grease Removal
research purposes.
Ave. Hydraulic
Slope Wetted flow loading
Slope length area rate rate
% m ha m /d cm/wk
2 30 .05 15 20
2.5 30 97 12,000 9
2 36 2.4 510 10-20
2 36 0.8 260 15-20
2 36 0.8 260 25-40
2-8 46 0.50 46 6.5
130 18
7-12 60 0.06 38 44
5 30 .03 2.1 5
55 .53 91 12
6
47 1.4 290 15
2-8 60-75 285 17.2 4.2
Organic
loading
rate
kgBOD/ha-d
16
166
61/68
14/9
7.4/4.3
2.2
6.2
26
6.0
3.7
32
15
42
Nitrogen
loading
rate
KgN/ha-d
**
8.1
13/12
5/6
4.6/4.1
2.0
5.6
13
2.6
2.3
3.7§
0.7i
.44
Ave. percent removal
BOD S3 N P
70 69 ** **
97 99 84
98 98 90 50
98 98 90 50
98 98 90 50
55 57 90 50
** ** 75 30
76 ** 64 64
91/58 97/84 94/25 89/30
95/80 96/88 87/32 80/30
84 76 77 45
59 48 74 52
99 93 90 58
"Not reported
-------
SECTION III
PROCESS MECHANISMS
The overland flow process is a combination physical, biological, chemical
process. Solids settling on the upper slope and filtration by the grasses
throughout constitute the physical process which reduces the suspended solids.
This process is affected by distribution method and type of grass cover. The
distribution method will determine the solids concentration near the influent
application point. Gravity application will result in solids concentrating near
the openings. Spray systems provide dispersed solids.
The biological process is similar to a conventional trickling filter. A
bacterial or biological growth occurs on the soil surface. This growth is similar
to the zoogleal mass growing on trickling filter media. As such performance is
affected by temperature changes and flow variations.
The chemical process is the interaction of the soil and applied wastewater.
Phosphorus is adsorbed on soil until the adsorption capacity is reached. Soil
type determines this value.
Beyond this, the processes are not well understood. Until ongoing research
is completed, the actual kinetics of this system are unknown. Researchers
referenced in Section II hypothesised formulae but have not proven them at loca-
tions other than their own.
Organics removal is being investigated at the University of California,
Davis, CA. Preliminary results have been published showing factors which impact
organic removal (as well as those which do not). However, process kinetics have
not yet been developed.
Organic removal as affected by cold weather conditions has been studied at
Hanover, N.H. (CRREL). A relationship was developed between soil temperature and
organic removal capability. This relationship needs to be tested elsewhere.
Suspended solids removals have been consistently excellent at all sites and
during all weather conditions. Most solids seem to be removed readily on the
upper portions of the slope.
Nitrogen removals are reduced during cold weather - Minimization of pretreat-
ment seems to enhance complete nitrogen removal (leave carbon source in to aid
denitrification). This relationship has not been developed.
55
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Impact on nitrogen removal due to temperature has been studied at Hanover
with results presented in Section II of this report. These results should be
verified elsewhere.
As discussed previously, phosphorus removals are generally limited to soil
adsorptive capacity. Alum has been used successfully to aid in phosphorus
removals. Removal of phosphorus by alum addition is well understood and easily
predicted. If the process mechanisms for phosphorus removal were better under-
stood, less alum addition might be possible.
Impacts of rainfall on performance has been reviewed at Paris, TX and Utica,
MS. Results have shown increased suspended solids mass discharge due to washing
off of vegetative debris from the site. Results also showed dissolved solids are
diluted. At Paris, rainfall events of 6.25 cm or greater, reduced total dissolved
solids concentration.
56
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SECTION IV
DESIGN CONSIDERATIONS
Principal considerations in the design of overland flow treatment systems
include preapplication treatment, storage needs, loading rates, distribution sys-
tem type and the selection and maintenance of vegetation. System geometry is not
important as long as slopes are in the two to eight percent range and lengths are
of the order of 30 to 60-m. Loading rates chosen in combination with the distri-
bution system design will constrain the choice of slope length to a large degree.
PREAPPLICATION TREATMENT
In discussing preapplication treatment, a separation must be made between
preapplication treatment needed and the fact that many overland flow processes
will be "add ons" to existing secondary treatment systems. For example, an over-
land flow system may be added to an existing pond system. Even though the over-
land flow process can effectively treat raw wastewater, the pond system may be
used for economic reasons (slightly smaller overland flow area may result). Thus,
the loading rate chosen will depend on the level existing or planned of preappli-
cation treatment, however neither primary nor secondary treatment is necessary
for the design of a successful overland flow treatment system.
Required preapplication treatment consists of those operations that will
prevent damage and unsanitary or unsightly conditions, and improve in process
performance, of greatest concern are the removal of grit, sand, debris, rags and
other large objects that could result in damage to pumps, plugging of the distri-
bution system or deposits on the upper slope areas. Screening or comminution and
degritting would prevent these problems and should be included in all cases.
Where primary or secondary effluents (including oxidation ponds) are available
additional pretreatment measures are not usually necessary. Existing disinfection
systems may be maintained with chlorination carefully controlled to prevent grass
damage. Normally, disinfection would be provided after overland flow for surface
application.
The degree of preapplication treatment required prior to treatment depends
on the type of distribution system. Bar screening or comminution and degritting
will be satisfactory in most cases where distribution is by gated pipe, side
delivery flume, perforated pipes having perforations greater than 1 cm and spray
nozzles having diameters greater than 0.6 cm.
In some cases specialized preapplication treatment may be necessary.
Examples would include municipal wastewaters containing grease from meat pro-
cessing, fiber from pulp wastes, or systems subject to high storm water flows.
Industrial discharges should be required to remove materials deleterious to the
treatment process at the source, but this will not be feasible in all cases.
Climate conditions can affect treatment performance. Jenkins et alq recom-
mended that process operation be suspended when soil temperatures are less than
4°C, and when precipitation rates exceeded 1 .3 cm/A. The former recommendation is
related to decreases in biochemical reaction rates (for both organic
57
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removal and nitrification) at low temperatures while the latter results from the
possibility of both decreased process performance and erosion due to higher
flows. Experience with treating cannery wastes treatment using the overland flow
process has included operation at soil surface temperatures near freezing.
Organic removals were not seriously affected16. Because most wastewaters are
substantially above freezing in temperature overland flow processes can be
expected to perform satisfactorily at ambient air temperatures well below
freezing.
In general, information on climatic effects is very limited. Because both
organic removal and nitrification are carried out by microorganisms on the soil
surface, reaction rates should be sharply affected by temperature. Lack of sensi-
tivity to temperature, as measured by nearly constant effluent BOD values, would
result from overdesign. If populations and/or detention times are high enough
temperature effects on reaction rates are masked. Very few field studies have
incorporated measurements along the slope and the corresponding temperature
information. Thus, limitations imposed by weather are not well understood.
The relationship between degree of pretreatment and hydraulic loading rate
is critical in a cost analysis. If a higher degree of pretreatment can result in
an increased hydraulic loading rate, then reduced land costs should be reviewed
to see if the pretreatment cost is justified. In his literature review and analy-
sis, Overcash concluded that overland flow treatment of secondary effluent did
not produce significantly better effluent quality than overland flow treatment of
raw sewage or primary effluent1 . This conclusion was made on systems with
varying hydraulic loading rates for treatment of both primary and secondary
effluents. There was no substantial difference in results with different pre-
treatment levels and hydraulic loading rates. The most likely reason for this
result is that the high oxygen transfer rates in overland flow systems are
coupled to relatively low surface loading rates. Secondary effluents place little
demand on the biological potential of the systems and a relatively small demand
on the physical (solids removal) potential.
The EPA Manual recommends 6.4 to 15 cm/wk loadings for treating primary
effluent and 15 to 40 cm/wk for treating secondary effluent . Deemer recom-
1Q
mends the following loading rates:
Pretreatment Level Loading Rate, cm/wk
Raw 6.3 to 15
Primary 10.0 to 20
Secondary 20.0 to 40
Hydraulic loading rates chosen for a particular application will vary within
the ranges as a result of varying BOD and suspended solids concentrations, sea-
sonal temperature variation and possible precipitation effects. Predictive rela-
tionships between performance and loading rate are being developed through work
at CRREL, RSKERL and the University of California, Davis. Preliminary results
obtained at Davis were that performance, as measured by soluble organic removal,
decreased when the hydraulic loading rate was increased from 15 to 20 cm/wk.
These results support the EPA manual recommendations of hydraulic loading rate,
between 10 and 20 cm/wk. Variations in reductions of Nitrogen and BODc- with
different hydraulic loading rates are shown in Figures 20 and 21.
58
-------
100,
80.
60
O
Q
in
DC
I 40
tr
20-
/"'
6<\
HANOVER
UTICA
0 HUNT WESSON
A
UTICA
EASLEY
ADAO
CARBONDALE
10
A SECONDARY
O RAW OR PRIMARY
20 30
LOADING cm/week
40
50
Figure 20. Hydraulic loading.
59
-------
100-.
80-
Q
O
O
Z>
Q
ULJ
o:
o
Q:
LU
Q.
60 -I
40-
20.
| O HUNT WESSON
-HANOVER
CARBONDALE
EASLEY
ADA
10
& SECONDARY
O RAW OR PRIMARY
20 30
LOADING cm/week
40
50
"igure 2].. Hydraulic loading.
60
-------
The variation of hydraulic loading rate with different levels of pretreat-
ment effectively constrains the organic loading rate. Consideration of variations
in wastewater strength results in relatively small variations in mass BOD loading
rates (kg/d) over the entire range of hydraulic loading rates. Review of avail-
able information on overland flow process performance under various loading con-
ditions supports the conclusion that organic loading rates are not a strong
function of pretreatment.
Oxidation pond effluent characteristics impact overland flow treatment per-
formance mainly through algal cell concentrations and possibly prevailing algal
species. The conclusion reached in the Pauls Valley system study was that
overland flow treatment of pond effluent resulted in effluent suspended solids
concentrations greater than 30 mg/L. Excellent suspended solid removals with
overland flow treatment of pond effluent were obtained at Davis, CA., where ter-
race runoff suspended solids concentrations were consistently less than 30 mg/L.
These differences appeared in spite of relatively similar hydraulic and solids
loading rates and use of similar slopes (2 to 3 percent). The climates are als.~>
similar (note that problems occurred during summer operation but not during
winter operation at Pauls Valley while the Davis pilot system was only opera-
tional in the winter) . Differences in algal species or grass cover character-
istics may have accounted for the differences in performance at the two installa-
tions. Algal species were not identified in either report. Grass cover at Davis
was annual rye grass while the cover at Pauls Valley was a mixture of Kentucky 31
fescue, annual rye, and bermuda grass.
STORAGE NEEDS
Storage needs are based on two considerations : temperature effects and pre-
cipitation effects . 8005 removal and nitrif ication/denitrif ication rates are
reduced during cold weather. Jenkins et al recommend overland flow systems not be
operated when the soil temperature is below 4°C9. They found the optimum NH4
removal to occur at a soil temperature of 17°C, and suggested the following
equations for:
BOD5 = 0.226 (Soil Temp)2 - 6.53 (Soil Temp) +53 (3)
NH4 = 0.114 (Soil Temp)2 - 3.94 (Soil Temp) + 35.1 (4)
= Remaining concentration in runoff
NH4 = Remaining concentration in runoff
Soil temperature is at 2 cm below surface.
These equations have not been applied elsewhere. Variations due to other
site chracteristics or climate are not known. The above formulae were developed
using a hydraulic loading rate of 5 cm/wk. There was no apparent difference in
the relationships when applying primary or secondary effluent.
Using design of effluent standard values for BOD^ and NH4 concentrations
in equations (3) and (4) allows calculation of critical soil temperatures.
Coupling the critical soil temperature with background data on soil temperatures
and expected effects of the wastewater on soil temperature , the number of storage
days can be determined.
61
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Decreased organic removals during cold weather were reported in other
studies3'4' , but those areas were not exposed to the extreme cold
found in New Hampshire. The EPA. Manual suggests use of winter rates (October 1
to April 30) one half those for the summer months (10 cm/wk and 20 cm/wk,
1 ft
respectively) . Days are deducted for expected freezing conditions. This
approach provides both a number of application days and modified application
rates. Application area and storage needs are then derived from the compilation.
The advantage of this approach is that a more accurate estimate of storage needs
can be made than a gross approximation based on climatic data. General applica-
tion of this approach, or any other requiring storage, should be reserved to
regions with extremely low winter temperatures. Excessive differences in winter
and summer area requirements can result in operating problems in arid regions
where summary flows may not be enough to satisfactorily maintain vegetation. A
second factor is that lowering winter application rates and storage will result
in lowering applied wastewater temperature and therefore soil temperature will be
lowered also.
Storage is also needed for days with heavy rainfall. The actual storage
needs depends on the statement, presentation, and interpretation of discharge
O Q
standards. Peters, et al , have studied the influence of storm runoff on
overland flow treatment for nutrient removal. When failure occured maximum allow-
able N and P concentrations were not exceeded but maximum allowable mass effluent
1Q
loads were. Deemer' reported similar experience for BOD5 removals. He
concluded that overland flow operation should not be halted during storm events
and that storm runoff from an operating overland flow system was of the same
quality as storm runoff from an adjacent nonoperating system. If the discharge
standards are based on concentration only, then storage for storm events is
unnecessary. If the discharge standard includes a maximum mass discharge rate,
storage should be provided. 8005 mass discharge limits may be exceeded as the
result of heavy precipitation even during nonoperating periods. Storage will
lessen the possibility of partially treated effluent entering the receiving
stream (partially treated due to high flow and corresponding low detention
time).
In areas having long dry summers and high evapotranspiration rates, such as
the southwestern United States, storage may also be necessary to provide enough
water for summer irrigation requirements. Conventional irrigation would maintain
the cover but not the bacterial population.
DISTRIBUTION SYSTEM
Wastewater can be distributed on the overland flow slope by sprinkling or by
gravity flow from a pipe or trough. The results of the Pauls Valley project12
showed little difference between distribution by sprinkler (2 types used) or by
pipe with orifices. These results were found with treatment of both raw sewage
and pond effluent. The spray system has the advantage of spreading solids and
high strength organic wastewater over a larger area. This advantage is not
apparent until the wastewater strength exceeds typical raw municipal wastewater
BOD5 and suspended solids levels (200-250 mg/L each). Cannery wastes with
BOD5 levels greater than 400-600 mg/L can kill the grass next to distribution
pipe. The exact level where this becomes a problem is unknown at this time.
62
-------
A comparison of spray and gated pipe distribution system is shown below:
System Advantages
Spray 1. Larger area for initial dis-
tribution of solids (avoids
high initial concentrations)
2. Greater distribution of high
strength wastes to prevent
grass damage
Disadvantages
1. Aerosol potential
2. Clogging nozzles unless
fine screened
(preapplication)
3. Pumping energy required to
provide pressure
1. Solids concentrations at
pipe discharge
Gated pipe 1. Low pressure, minimal energy
2. No aerosols
3. No moving parts to maintain
For treatment of domestic wastewater, at any preapplication level, gated
pipe (or similar type of low pressure system) is preferred. This is due to low
energy required, absence of aerosols, and ease of maintenance. Solids accumula-
tion at the pipe can occur but the magnitude of this problem is such that main-
tenance required would be infrequent (e.g. annual).
Low pressure pipe systems of several types are available. The most common is
gated pipe. Gated pipe is readily available from irrigation suppliers. Openings
of 2.5 cm diameter or square are equally spaced along the pipeline. Other sizes
are available. These openings have slides which can be adjusted to allow the
desired flow out of the pipe. In lieu of gates bubbling orifices can be used.
Some installations have utilized plastic pipe with openings cut in the pipe
sidewall.
There are many options available for sprinkler systems. Piping may be buried
or laid on the surface. Surface piping is usually aluminum tubing. Aluminum
should not be buried. Plastic pipe has been preferred for buried systems (lower
cost for plastic than other material). Surface systems are usually portable and
can be moved if the operation is to be changed. Solids set systems lack flexi-
bility in placement but are not in the way of field operations. Selection of the
preferred option depends on preferences of the designer or operator and cost.
While the solid set (buried) system is more costly for installation, the O&M cost
is less than the movable system.
Selection of the type of sprinklers to use depends on designer or operator
preference. Sprinklers can be chosen to provide fine or coarse spray, operate at
pressures from 138 to 414 kPa and greater, and provide almost any application
pattern. Techniques for sprinkler selection and sizing as well as lateral design
can be found in (13) and (14), as well as in most major sprinkler manufacturers
literature.
Distribution sytems must be designed to handle variation in wastewater flow
and cyclic loading of benches. Controls can be manual or automatic. Control
63
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devices consist of electrically or pneumatically operated valves located in dis-
tribution laterals. Operation can be by on-off switch or by time clock. In larger
systems with two or more constant speed pumps automatic controls must be designed
to increase or decrease the number of laterals on line as a pump comes on or off.
In this type of system separate time clocks controlling sets of laterals should
be provided for each pump. No matter what the size of the system, flexibility
should be built into the system to allow changes in spray programs. Pump capacity
and operating pressures should be sufficient to take advantage of the entire site~
area but flexible enough to allow higher rates on partial areas without excessive
pressures at individual sprinkler heads or gates.
Selection of the distribution systems also depends on the arrangement of the
benches or terraces. Ideal locations have slopes of 2-8 percent occuring natu-
rally. The benches then follow natural contours. There may be one continuous
bench or several in series with collection uphill from the next bench. Runoff is
collected and routed around lower benches. On level areas the benches may be
placed such that one distribution lateral serves two benches. Similarly, one
drainage ditch serves two benches. This type of layout is shown on Figure 3, the
schematic for Davis, CA. The layout selection is based on economics of earth
moving and pipeline layout.
SELECTION AND MAINTENANCE OF VEGETATION
Vegetation is a critical element in an overland flow system because it pro-
vides soil erosion protection, filtration, an environment for beneficial bacteria
growth, a mechanism for nutrient removal assimilation, and potential revenue to
help defray operating cost. Selection of vegetation must include consideration of
alternative plant species that will provide the benefits above as well as having
a high water tolerance and be adaptable to the local climate. In some instances
salt and/or metal tolerance may be necessary.
Grasses or forage crops are necessary to prevent erosion. Certain species
that tend to grow in sparce clumps are not desirable since channeling could
develop. Filtration of wastewater would be limited with grasses that bunch.
The most commonly used grass has been reed canary grass. Bermuda grass has
also been popular, but is usually limited to warm climates because growth stops
when soil temperature drops below 16°C. During dormant periods, plots can be
overseeded with other grasses such as rye. The Werribee Farm System in Australia
has had excellent success with Italian rye grass. Most often a variety of grasses
should be planted and the most suitable species will eventually predominate. In
some areas, this may be a native grass.
The forages that are adaptable to an overland flow system are not usually
readily marketable. However, when grown under overland flow conditions nutrient
contents are increased to a point where they are comparable to higher quality
varieties^. The nutritive value of the forage depends on harvesting at the
proper time.
Weeds and insects can be a problem. If slopes are less than 2 percent or
grading was inadequate, mosquito breeding may occur in standing water. Other
types of insects associated with the particular crop (e.g. cutworm) are agricul-
ture-related and must be controlled by pesticides. Weeds are not a problem unless
64
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they interfere with marketing the crop. A large percentage of weeds can degrade
crop quality or cause rejection of the harvest. From a treatment point of view,
the weeds are not likely to cause a problem.
It is important to remember that the grass is of primary concern as a treat-
ment media and secondarily as a crop. Grass growth should be developed to
increase treatment performance and not for maximum yields. For example, the bac-
teria required for treatment of wastewater needs a dense mat of vegetative matter
in the line of the wastewater flow. If grasses are allowed to grow too high they
may shade out lower species and create bare patches close to the soil thereby
effecting treatment performance and creating potential for erosion.
Overland flow slopes attract birds to an extent. High grass provides a habi-
tat from small mammals and the moist soil provides excellent conditions for
insect breeding. Hawks and similar birds are attracted because of the concentra-
tions of prey.
PERFORMANCE AND RELIABILITY
Overland flow performance results from systems reviewed were presented in
Table 36. Secondary treatment requirements for both BOD and suspended solids
effluent concentrations are consistently met or exceeded. Nitrogen removals are
excellent during warm weather. Phosphorus removals are marginal except when alum
is added.
The reliability of overland flow systems appear to compare favorably with
other secondary and AWT systems, but more data are required. This is especially
critical in cold climates and where systems may be subject to high intensity
storms.
DISCUSSION
Experience with overland flow systems has been limited. With the exception
of the Werribee, Australia and the cannery waste treatment systems, there are no
long-term, full-scale systems in operation. Considerable pilot scale work has
been accomplished at the Ada, OK; Hanover, NH; Carbondale, IL; and Utica, MS
sites. The most recent results of experiments at these sites have not been pub-
lished at this time. Pilot and full scale research work is underway at Davis, CA.
Preliminary data have been reported in full-scale systems at Pauls Valley, OK and
Easley, SC. Information from these varied sources is difficult to compare. Cli-
mates are different and results are reported in different forms. The actual mech-
anism of treatment by overland flow is not completely understood but is appar-
ently similar to an attached growth biological treatment system. Design equations
modeled after trickling filter analyses will be developed in the future (Davis,
CA).
As with other biological systems, cold temperatures reduce BODg and nitro-
gen removal efficiencies. Work at Hanover, NH has confirmed this and has resulted
in equations predicting removal efficiencies based on soil temperature. Cold
weather impacts have been reviewed at Ada, OK. The limitation here has been the
lack of severe winter temperatures.
65
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There are several areas where all results are similar. Overland flow systems
consistently produce effluent qualities better than secondary, in terms of BODg
and suspended solids. This applies to overland flow treatment of both raw sewage
and primary effluent. Nitrogen removal is excellent during summer months with
deterioration during cold weather (below freezing or ground temperatures below
4°C). Phosphorus removal is limited unless enhanced by adding alum.
Loading rates have been expressed in several ways. The most commonly
reported measure is the hydraulic loading rate. Organic loading rates have not
been reported as frequently but do impact results. The rate at which results are
impacted has not been determined. Application rates, frequencies, and durations
are rarely reported but impact performance also.
Based on the success of overland flow treatment with high-strength cannery
wastewater and raw municipal sewage, pre-application treatment should be mini-
mized, depending on land costs and the cost of pre-application treatment trade-
offs. In general, more land is required for higher strength wastewater. If pre-
application treatment (beyond screening and grit removal) is provided, then less
land is required. The more preapplication treatment provided, the less land
required. Based on the information gained through this report, there is inade-
quate knowledge concerning the specific point where land areas should be
increased due to high strength wastewater. Work quoted showed successful opera-
tion at various loadings but there have been no demonstrated systems loaded to
failure so the maximum is unknown.
66
-------
SECTION V
DESIGN EXAMPLES
Three examples were developed to highlight the importance of climate on
design. The design flow and sewage strength is the same for each case. Example
one is typical of an arid, western location in the United States. Example two is
typical of the northeastern United States where harsh winters can be expected. In
both of the first two examples raw domestic wastewater is treated for the removal
of BOD5 and suspended solids. Example three represents the southern part of the
United States where large amounts of rainfall occur. In this example oxidation
pond effluent is treated by overland flow to remove nitrogen. Site characteris-
tics for each example are given in Table 37-
TABLE 37. SITE CHARACTERISTICS - DESIGN EXAMPLES
Parameter
1
Location in U.S.
Type of wastewater
Preapplication treatment
Raw Sewage Characteristics
Flow
Ave - m^/d
Peak - m3/d
Ave BODg - mg/L
Ave SS - mg/L
Ave Total N - mg/L
Discharge Requirements
Mo Ave BODg - mg/L
SS - mg/L
Total N - mg/L
Climate
Rainfall, cm/yr
Evapotranspiration, cm/yr
No. Days Ave temp O4°C
Soils
West
Domestic Sewage
Screening
10,000
30,000
250
250
50
30
30
25
125
0
clay
Northeast
Domestic Sewage
Screening
10,000
30,000
250
250
50
30
30
100
79
100
clay
Southeast
Domestic Sewage
Oxidation pond
10,000
30,000
250
250
50
15
15
10
145
45
30
clay
Design Example 1 - Western United States
In this example the required discharge standard is 30 mg/L BOD^ and 30
mg/L suspended solids and 85 percent removal efficiency. Design criteria was
developed from information given in this report and is listed in Table 38.
67
-------
TABLE 38. DESIGN CRITERIA - EXAMPLE 1
Hydraulic loading, cm/wk - 15
Application period, hr/d - 6-8
Application frequency - days on/days off 5/2
Expected BOD5 removal (mass basis), percent - 92
Expected SS removal (mass basis), percent - 95
Slope, percent - 2
Slope, length, m - 40
Land Area
Land area is determined as follows:
(5)
A = Wetted land area, ha
Q = Design flow rate, rrr/d
H = Hydraulic loading, cm/yr
H = 15 cm/wk x 52 wk/yr = 780 cm/yr
A = (3.65) x (10,000) = 47 ha
780
Additional land area will be required if plans call for dewatering slopes
before grass mowing and if grass will be dryed and baled on the field. The extra
land required depends on the frequency of grass harvesting. For this example 30
days is allowed for two cuttings a year. Land area is increased by 30/365 or 8.2
percent.
Adjusted Wetted area = 1.08(47) = 51 ha
Allow 10 percent for ditches and roads
1 .10(51) = 56 ha
Depending on local ordinances and the type of distribution device, a buffer
zone encircling the site may also be required. Actual land area will be dependent
on the site geometry.
Buffer zone - 50-m; assume application area is square.
4 x 56 ha x 10,000 m2/ha x 50-m - 150,000 m? or 15 ha (6)
Total land required = 56+ 15= 71 ha
Water Balance
A water balance to determine runoff volumes is necessary for accurate sizing
of collection ditches, catch basins and pumps and to estimate effluent wastewater
strength.
P+H=ET+Wp+R (7)
P = precipitation, cm ET = evapotranspiration, cm
H = hydraulic loading, cm Wp = percolating water, cm.
R = runoff, cm
58
-------
Precipitation data can be obtained locally or from reference 23. Several
methods are available for calculating evapotranspiration and are given in refer-
ences 13, 14, and 24. Precipitation and evapotranspiration for grasses for exam-
ple 1 are given in Table 39 and are typical of the western United States. Perco-
lation is best determined by field testing (see ref 25). Calculated runoff is
also given in Table 39.
TABLE 39. DESIGN EXAMPLE 1 -
Month
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Totals
P
Precipi-
tation
cm
4.80
4.47
4.34
2.39
1.02
0.18
0.03
0.03
0.43
1.17
1.96
4.00
24.80
H
Hydraulic
Loading
cm
65*
65
65
65
65
65
65
65
65
65
65
65
780
ET
Evapotrans-
piration
cm
3.04
5.47
6.08
8.51
15.2
20.5
21.3
16.7
10.6
8.51
6.08
3.04
125
WATER BALANCE 1
WP
Perco-
lation
cm
5
5
5
5
5
5
5
5
5
5
5
5
60
cm
61 .8
59.0
58.3
53.9
45.8
39.7
38.7
43.3
49.8
52.7
55.9
61.0
620
R
Runoff
m^xlO^
290
277
274
253
215
187
182
204
234
248
263
287
2,910
% of H
95
91
90
83
71
62
60
67
77
82
87
94
80
* 65 cm/mo = 15 cm/wk
Runoff volumes shown in Table 39 as m3/mo were calculated as the product
of land area and runoff given in cm/mo.
Effluent Characteristics
The effluent 6005 concentration is dependent on the runoff volume and is
calculated as follows:
/ 3\
BOD applied, kg = Hydraulic Loading[m \x
mo \fiol
Influent BOD Cone.
1000 mg/L/Kg/M~
BOD remaining, kg_ = BOD applied, kg (1 - Percent Removal)
100
mo
mo
Effluent BOD5 cone, mg/L = BOD remaining, /kcAx 1000 mg/L/Kg/m"
\mo)
Mm /mo)
Runoff
(8)
(9)
(10)
69
-------
Effluent BODg concentrations for Design example 1 at 92 percent removal
are given in Table 40.
TABLE 40. DESIGN EXAMPLE 1 - BOD ^REMOVAL 1
BOD^_applied
Month kg x 10-* kg/ha
rema i ni ng
kg x 103
Effluent Cone.
mg/L
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
76
76
76
76
76
76
76
76
76
76
76
76
1 ,620*
1,620
1,620
1,620
1,620
1,620
1,620
1,620
1,620
1,620
1,620
1,620
6.1
6.1
6.1
6.1
6.1
6.1
6.1
6.1
6.1
6.1
6.1
6.1
21
22
22
24
28
33
34
31
26
25
23
21
* Equivalent to 53 kg/ha'd
In this example the discharge requirement of 30 mg/L is not met during the
dry months of June, July- and August. The mass 6005 removed has not decreased
from 90"%. However, the runoff volume is substantially less than the volume of
wastewater applied, so the remaining BODg strength is concentrated. Based on
existing information exact 8005 removal percentages can't be accurately pre-
dicted with slight changes in hydraulic loading rate. Based on information
acquired by Thomas et al4, dry periods between loadings result in poorer BODr
removal. The theory presented was that BODg removal suffered due to the drying
of microorganisms on the soil surface. This theory was proven by the researchers
but at this time an accurate design prediction is not possible. If the overland
flow system is likened to a trickling filter, an increased hydraulic loading
should result in a decreased BOD5 removal rate. The impact of combining these
two effects is unknown. For illustrative purposes with this example, assume an
increase in hydraulic loading from 15 cm/wk to 20 cm/wk at this location still
results in a BOD5 removal rate of 92%. The BOD5 removal rates are purely
assumptions developed for this example. Using the same procedures outlined above
this changed assumption results in the following Water Balance and BOD5 Removal
as shown in Table 41 and Table 42.
This second set of values for example one (Table 41) shows the impact of
increasing runoff in meeting a discharge concentration. The designer must
consider the concentrating effects of arid climates. He must also provide an
operating plan that insures minimum drying of slopes. For example, operate 6 days
on/1 day off instead of 5 on/2 off.
Design Example 2 - Northeastern United States
In this example cold weather with mean air temperatures of less than 0°C are
experienced for 140 days with corresponding soil temperatures of 4°c experienced
for 100 days. There is no correlation for air temperature related to soil temper-
atures. The soil temperature is a function of snow cover depth and duration. The
70
-------
TABLE 41. DESIGN EXAMPLE 1 - WATER BALANCE 2
P H
Precipi-
Month
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Total
tation
CITl
4.80
4.47
4.34
2.39
1.02
0.18
0.03
0.03
0.43
1.17
1.96
4.00
24.80
ET WP
Evapotrans- Perco-
Hydraulic piration
loading,
87
87
87
87
87
87
87
87
87
87
87
87
1044
cm cm
3.04
5.47
6.08
8.51
15.2
20.5
21.3
16.7
10.6
8.51
6.08
3.04
125
lation
cm
5
5
5
5
5
5
5
5
5
5
5
5
60
cm
83.8
81 .0
80.3
75.9
67.8
61 .7
60.7
65.3
71.8
74.7
77.9
83.0
883.9
R
Runoff
nr* x 103
394
381
377
357
319
290
285
307
337
351
366
390
4154
% of H
96
93
92
87
78
71
70
75
82
86
90
95
85
TABLE 42. DESIGN EXAMPLE 1 - BOD ^REMOVAL 2
Month
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
BOD5 applied
Kg x 103 Kg/ha
101
101
101
101
101
101
101
101
101
101
101
101
2160
2160
2160
2160
2160
2160
2160
2160
2160
2160
2160
2160
BOD5
Kg x 103
8.1
8.1
8.1
8.1
8.1
8.1
8.1
8.1
8.1
8.1
8.1
8.1
Effluent Cone.
mg/L
20
21
21
23
25
28
28
26
24
23
22
21
soil temperature is taken at 2 cm depth below the surface. Based on information
developed at the Hanover, CRREL, wastewater should not be applied when soil
temperature, 2 cm below the surface is less than than 4°C. Application when air
temperatures below 0°C is acceptable as long as the soil temperature criteria is
met.
Land Area
The amount of storage and overland flow area required is related and the
calculation procedure is as follows:
71
-------
Select design seasonal hydraulic loading based on desired preformance
Find number of aplication days per month
Find actual monthly hydraulic loading as the product of application
days and design loading
Sum monthly hydraulic loadings
Use the equation shown under Land Area to find wetted area required for
overland flow
Find volume of wastewater applied per day as product of actual
hydraulic loading and wetted area
Calculate storage requirement as cumulative volume of wastewater
available but not applied
Design criteria are presented in Table 43.
TABLE 43. DESIGN CRITERIA FOR EXAMPLE 2
Hydraulic loading, cm/wk
summer 15
winter 10
Expected BOD removal (mass basis) percent - 90
Expected SS removal (mass basis) percent - 90
Application period, hr/d - 6-8
Application frequency days on/days off - 5/2
Slope, percent - 2
Slope length, m - 40
Number of days air temperature <_0°C - 140
Number of days soil temperature <4°C - 100
Land area and storage volume are calculated in Table 44. The land area
required from Table 44 is 71 wetted hectares.
Allow 8% for maintenance (see example 1)
71 ha x 1.08 = 77 ha
Allow 10% for collection ditches, and roads
77 ha x 1.10 = 85 ha
Allow 50 m for buffer, assume square site
4x\/85 ha x 10,000 x 50 = 18 ha
10,000
Total area required = 85 + 18 = 103 ha
Water Balance
The water balance for Example 2 is given in Table 45.
72
-------
TABLE 44. EXAMPLE 2 - FACILITIES SIZING
Wastewater
Month
January
February
March
April
May
June
July
August
September
October
November
December
f lowrate
m3 x 103
304*
304
304
304
304
304
304
304
304
304
304
304
3,650
Days w/
soil temp.
<4°C
20
20
20
15
5
0
0
0
0
0
5
15
100
Applied
days
10.4
10.4
10.4
15.4
25.4
30.4
30.4
30.4
30.4
30.4
25.4
15.4
265
Design
hydraulic
loading
cm
43§
43
43
43
43
65t
65
65
65
65
43
43
Actual
hydraulic
loading
cm
15
15
15
22
36
65
65
65
65
65
36
22
486
Wastewater
applied
m3 x 103
113
113
113
165
270
488
488
488
488
488
270
165
3,650
Storage
m3 x 103
173
364
555
746
885
919#
735
551
367
183
0
34
* Equivalent to 10,000 m3/d assuming 30.4 d/mo
§ Equivalent to 10 cm/wk
t Equivalent to 15 cm/wk
A = 3.65 (10,000) = 71 ha
486
# Storage required
-------
Month
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
P
Precipi-
tation
cm
9.80
11.3
6.05
6.12
5.34
4.62
3.98
2.17
8.60
9.37
8.78
10.6
86.7
TABLE 45.
H
Hydraulic
loading
cm
15
15
15
22
36
65
65
65
65
65
36
22
486
WATER BALANCE
ET
Evapotrans-
piration
cm
0.00
0.00
1 .98
4.67
5.32
14.3
16.2
16.0
8.70
3.56
1.52
0.00
72.3
- EXAMPLE
Wp
Perco-
lation
cm
5
5
5
5
5
5
5
5
5
5
5
5
60
2
on
19.8
21.3
14.1
18.5
31.0
50.3
47.8
46.2
59.9
65.8
38.3
27.6
441
R
Runoff
rrr'xIO-3
149
160
106
139
233
377
359
347
449
494
287
207
3,310
% of H
132
142
94
84
86
77
74
71
92
101
106
125
91
Effluent Characteristics
The storage provided in this example will be in the form of oxidation ponds.
BOD reduction will occur in these ponds so that the BOD concentration applied to
the overland flow field will be less during the times wastewater is removed from
the ponds and added to the incoming raw sewage. BOD concentration to the field
can be calculated as follows:
BODa = BODp (Qp) + BODi (Qi)
P-n + Q1
(11)
BODa = BODcj applied to field, mg/L
BOD = BOD5 of pond effluent, mg/L
BOD, = BODc of raw wastewater, mg/L
-5
Q = Flow from pond, mj/mo
Qi = Influent flowrate of raw wastewater, m^/mo
Because the ponds are used for storage they will have a variable volume and
a variable influent and effluent flowrate. This complicates the determination of
BOD removal in the oxidation ponds. One method is given in Reference 25. A
conservative approach would be to assume no reduction occurs or that some minimal
reduction occurs only during the summer months. Values for BOD reduction given in
Table 46 were calculated with the method of Reference 25. BOD reductions on the
overland flow field were based on 90 percent removal (mass basis) year-round.
Design Example 3 - Southern United States
The objective in this case is to meet the discharge standard of 10 mg/L
nitrogen. Oxidation ponds with a minimum of 30 days storage are provided as pre-
treatment before land application. Design criteria is given in Table 47.
74
-------
TABLE 46. BODc REDUCTION - EXAMPLE 2
Applied raw Pond
wastewater effluent
Flow BOD5 Flow BOD5
Overland
flow influent
Flow
Mo. m3x!03 mg/L m3x!03 mg/L m3x!03
Jan 113 250 0 250
Feb 113 250 « 0 250
Mar 113 250 0 250
Apr 165 250 0 250
May 270 250 0 230
Jun 304 250 184 180
July 304 250 184 84
Aug 304 250 184 37
Sept 304 250 184 14
Oct 304 250 184 5
Nov 270 250 0 250
Dec 165 250 0 250
113
113
113
165
270
488
488
488
488
488
270
165
BODs
mg/L kgxlO3
250 28
250 28
250 28
250 28
250 68
223 109
187 81
169 82
161 79
158 77
250 68
250 41
Overland
flow effluent
Flow BOD5
m-^xlO^ kg mg/L
149 2.8 19
160 2.8 18
106 2.8 26
139 2.8 20
233 6.8 29
377 10.9 29
359 8.1 23
347 8.2 24
449 7.9 18
494 7.7 16
287 6.8 24
207 4.1 20
TABLE 47. DESIGN CRITERIA - EXAMPLE 3
Oxidation pond, detention time, days
Overland flow, Hydraulic loading rate
summer, cm/wk -
winter, cm/wk -
Expected nitrogen removal
summer, percent -
winter, percent -
Application period, hr/day -
Application frequency - days/days off
Slope, percent -
Slope, length, m -
_
30
12
7
90
75
6-8
5/2
2
30
Land Area
Land requirements are calculated as in example 2 and are presented in Table
48. The volume of ponds required are found as the sum of required storage and the
minimum 30 day volume.
75
-------
TABLE 48. EXAMPLE 3 - FACILITIES SIZING
(Ti
Wastewater
Month
January
February
March
April
May
June
July
August
September
October
November
December
f lowrate
m3 x 103
304
304
304
304
304
304
304
304
304
304
304
304
3,650
Days w/
soil temp.
<4°C
8
6
3
0
0
0
0
0
0
1
3
9
30
Application
days
cm
22.4
24.4
27.4
30.4
30.4
30.4
30.4
30.4
30.4
29.4
27.4
21.4
Design Actual
hydraulic hydraulic
loading loading
cm cm
30.4(7 cm/wk)
30.4
30.4
30.4
52.1(12 cm/wk)
52.1
52.1
52.1
52.1
30.4
30.4
30.4
22.4
24.4
27.4
30.4
52.1
52.1
52.1
52.1
52.1
29.4
27.4
21.4
443
Wastewater
applied
m3 x 103
184
200
225
249
427
427
427
427
427
241
241
171
3,650
Storage
m3 x 103
675
779
858
913*
790
667
544
421
300§
363
426
555
* Required storage volume
§ 30 day storage
-------
Minimum Storage = 30 d x 10,000 m3/d = 300 x 1QJ mj
A = 3.65(10,000) = 82 ha
443
Allow 8% for maintenance
82(1.08) = 89 ha
Allow 10% for ditches and roads
89(1.10) = 98 ha
Allow 50 m for buffer zone, assume square site
4 x 50 98 x 10,000 = 20 ha
10,000
Total area required = 20 + 98 = 118 ha
Water Balance
The water balance for example 3 is given in Table 49,
TABLE 49. DESIGN EXAMPLE 3 -
Month
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
P
Precipi-
tation
cm
15.0
15.0
13.3
7.44
14.2
14.8
10.9
1.98
20.2
9.04
16.0
6.91
145
H
Hydraulic
loading
cm
22.4
24.4
27.4
30.4
52.1
52.1
52.1
52.1
52.1
29.4
27.4
21.4
443
ET
Evapotrans-
piration
cm
0.59
0.64
1.08
2.65
4.99
7.70
7.91
8.63
5.06
3.51
1.69
0.57
45.0
WATER BALANCE
Wp
Perco-
lation
cm
7
8
8
9
7
7
8
6
7
8
8
8
91
cm
29.8
30.8
31.6
26.2
54.3
52.2
47.1
39.5
60.2
26.9
33.7
19.7
452
R
Runoff
nr'xIO'3
244
253
259
215
445
428
386
324
494
221
276
162
3,710
% of H
133
127
115
86
104
100
90
76
116
92
115
93
102
Effluent Characteristics
In example 2 only a portion of the total flow passed through the storage
oxidation ponds. In this example all influent wastewater receives at least 30
days of treatment in oxidation ponds. Nitrogen will be removed to some degree in
the ponds depending on the temperature and detention time. As in example 2, the
method for determining nitrogen removal through the pond is beyond the scope of
this report. In this example the method given in Reference 25 was used. The
nitrogen reduction for example 3 is given in Table 50.
77
-------
TABLE 50. EXAMPLE 3 - NITROGEN REMOVAL
Raw
wastewater
Mo.
Jan
Feb
Mar
Apr
May
Jun
July
Aug
Sept
Oct
Nov
Dec
Flow
m3x!03
304
304
304
304
304
304
304
304
304
304
304
304
Nitro-
gen
mg/L
50
50
50
50
50
50
150
50
50
50
50
50
Pond
effluent
Flow
m3x!03
184
200
225
249
427
427
427
427
427
241
241
175
Nitro-
gen
mq/L
33
37
38
35
26
22
17
17
15
22
23
31
Overland
flow influent
Flow
m3xl03
184
200
225
249
427
427
427
427
427
241
241
175
Nitrogen
mg/L
33
37
38
35
26
22
17
17
15
22
23
31
kgxlOJ
6.07
7.40
8.6
8.72
11.1
9.39
7.26
7.26
6.41
5.30
5.54
5.43
Overland
flow effluent
Flow
m3xl03
244
253
259
215
445
428
386
324
494
221
276
162
Nitrogen*
kgxlOJ
1 .56
1 .89
2.15
0.87
1.11
0.94
0.73
0.73
0.64
1 .31
1 .39
1 .39
mg/L
6.4
7.5
8.3
4.2
2.6
2.3
1 .9
2.3
1.3
5.9
5.0
8.6
Cost Estimate
Costs for all examples were made using the cost curves included in Appendix
A. Capital cost estimates are shown in Table 51 . Costs for chlorination
facilities were included for examples 1 and 2 because raw wastewater is applied
directly to the land and there is a chance of pathogens entering the receiving
water through the runoff. In example 3 all wastewater receives a minimum of 30
days storage in oxidation ponds where pathogens would be effectively removed
prior to land application.
TABLE 51. CAPITAL COST ESTIMATE - DESIGN EXAMPLES
Raw wastewater pumps
Forcemains
Oxidation ponds
Land @ $2,500/ha
Field preparation
-site clearing
-terrace construction
Distribution piping
Chlorine contact basins
Chlorine feed and storage facilities
Collection ditches
Lined channels
Totals
1
$ 700,000
20,000
175,000
25,000
300,000
25,000
50,000
30,000
45,000
91 ,000
$1 ,461 ,000
2
$ 700,000
20,000
1 ,727,000
259,000
30,000
550,000
37,000
50,000
30,000
60 ,000
109,000
$3,567,000
3
$ 700,000
20,000
1 ,727,000
291 ,000
35,000
600,000
42,000
70,000
121,000
$3,606,000
As shown in Table 51, the
costs for overland flow systems.
need for storage greatly increases the capital
-------
SECTION VI
STATE REGULATIONS
About half of the states have guidelines or regulations dealing with land
treatment of wastewater26. These cover the topic to varying degrees, with
some being quite general and others being more specific. Some of the states have
flexible regulations while others have strict guidelines to be followed. Many of
the states without formal regulations have policies of reviewing land application
projects on a case by case basis.
A major source of controversy regarding overland flow is classification as a
land application method or as a treatment method. Many states do not consider the
treatment capabilities of vegetation and soil so land application is viewed as a
means of disposal, requiring conventional primary or secondary treament prior to
application. This philosophy does not really apply to overland flow since runoff
is collected from the site and subsequently disposed of. In this case, the upper
layers of soil and the vegetative cover provide treatment of the wastewater and
extensive pretreatment is not generally necessary.
Of the states with guidelines regulating land application, most are directed
toward irrigation and infiltration-percolation. This can be attributed to the
fact that overland flow has only recently received attention as a viable method
of treating domestic wastewater. As overland flow becomes a more popular treat-
ment practice, federal and state governments should develop guidelines to regu-
late design and operation.
Recently, the State of Maryland adopted a set of design guidelines for land
treatment27. These guidelines are intended to help planners and designers
with the implementation of new land treatment facilities. The general philosophy
associated with the guidelines is that they should be as flexible as possible as
long as the public health is protected. Those sections of the guideline pertain-
ing to land treatment in general and specifically to overland flow have been
included in Appendix A. Among the topics covered in the guidelines are site
selection, preapplication treatment, storage, surface drainage and buffer zones,
equipment requirements, monitoring and crop management. Draft guideline for land
treatment systems for the State of Mississippi are included as Appendix B. They
have not yet been adopted.
79
-------
SECTION VII
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
Overland flow systems effectively treat raw municipal wastewater with
resulting effluent quality better than secondary standards.
Overland flow systems resemble conventional attached growth biological
systems and apparently exhibit first order kinetics.
Predictive relationships among the process design, operating para-
meters, and treatment performance have not been developed at this time.
In general, the following treatment efficiencies have been observed:
% reduction
BOD 90+
SS 90+
Nitrogen 70-90
Phosphorus 40-80
Fecal Coliform 90-99.6
These reductions apply with all types of applied wastewaters if hydrau-
lic loadings are adjusted for different preapplication treatment
levels.
Phosphorus removal may be enhanced with alum addition (1-2 mg alum/mg
phosphorus)
There is enough information available to provide conservative design of
overland flow systems. More information is necessary to develop cost
effective designs.
RECOMMENDATIONS
Conduct more pilot and full scale study to determine critical design
and operating parameters. Existing systems could be studied for infor-
mation not reported in the literature.
Combine this information with results of Corps of Engineers work to be
published in the Spring of 1930.
Conduct studies to determine the effects of precipitation on process
performance.
Further work on nitrogen removal mechanisms and process control is
necessary.
80
-------
REFERENCES
1. U.S. Environmental Protection Agency, U. S. Army Corps of Engineers, U.S.
Department of Agriculture, Process Design Manual for Land Treatment of
Municipal Wastewater, EPA 625/1-77-08 (COE EM 1110-1-501), October, 1977.
2. Smith, R.G. and Schroeder, E.D., "Investigation of Overland Flow Design and
Operating Parameter", presented at the Workshop on Overland Flow for
Treatment of Municipal Wastewater, Greenville, S.C., November 27-28, 1979.
3. Thomas, R.E., Jackson, K., and Penrod, L., Feasibility of Overland Flow for
Treatment of Raw Domestic Wastewater, U.S. Environmental Protection Agency,
EPA-660/2-74-087, July 1974.
4. Thomas, R.E., Bledsoe, B., and Jackson, K., Overland Flow Treatment of Raw
Wastewater with Enhanced Phosphorus Removal, U.S. Environmental Protection
Agency, EPA-600/2-76-131, June 1976.
5. Peters, R.E. and Lee, C.R., "Field Investigations of Advanced Treatment of
Municipal Wastewater by Overland Flow", in State of Knowledge in Land
Treatment of Wastewater, International Symposium, U.S. Army Corps of
Engineers, Hanover, NH, August 1978.
6. Illinois Pollution Control Board (1972) Rules and Regulations.
7. Asaturians, A. (1977), "Overland Flow as Advanced Treatment for
Wastewater", thesis submitted in partial fulfillment of the requirements
for the Degree Master of Science in Engineering, Southern Illinois
University.
8. Stephen, S.K. (1977), "Nitrogen Removal from Wastewater by Overland Flow",
thesis submitted in partial fulfillment of the requirements for the Degree
Master of Science in Engineering, Southern Illinois University.
9. Jenkins, T.J., Martel, C.J., Gaskin, D.A., Fisk, D.J., and McKim, H.L.,
"Performance of Overland Flow Land Treatment in Cold Climates", in State of
Knowledge in Land Treatment of Wastewater, International Symposium,
U.S. Army Corps of Engineers, Hanover, NH, August, 1978.
10. Martel, C.J., Jenkins, T. F., and Palazzo, A. J., "Wastewater Treatment in
Cold Regions by Overland Flow", Preliminary draft.
11. Martel, C.J., Adrian, D.D., Jenkins, T.J., and Peters, R.E., "Rational
Design of Overland Flow Systems", Abstract.
12. Hall, D.H. et al, Municipal Wastewater Treatment by the Overland Flow
Method of Land Application, U.S. Environmental Protection Agency,
EPA-600/2-79-178, August 1979.
13. Sprinkler Irrigation, Sprinkler Irrigation Association, Silver Spring, Md.,
1975.
81
-------
14. Israelsen, O.W. and Hansen, V.E., Irrigation Principles and Practices,
Wiley, New York, 1962.
15. Abernathy, A. Ray, communication.
16. Gilde, L.C. et al, "A Spray Irrigation System for Treatment of Cannery
Wastes," JWPCF Vol. 43, pp 2011-2025, October 1971.
17. Overcash, M.R., "Implications of Overland Flow for Municipal Waste Manage-
ment," JWPCF, Vol. 50, pp 2337-2347, Oct. 1978.
18. Crites, R. et al, Process Design Manual for Land Treatment of Municipal
Wastewater, U.S. Environmental Protection Agency, et al, EPA 625/1-77-008,
October 1977.
19. Deemer, D.D., "Overland Flow Treatment of Wastewater", presented at the
U.S. EPA/Clemson University Workshop Overland Flow for Treatment of Munic-
ipal Wastewater, Greenville, SC, Nov 27-28, 1979 (proceedings available
through Clemson University).
20. Peters, R.E., et al "Influence of Storm on Nutrient Runoff from Overland
Flow Land Treatment Systems," draft report to be published.
21. Seabrook, B.L., Land Application of Wastewater in Australia, The Werribee
Farm System, U.S. Environmental Protection Agency, May 1975.
22. Tucker, D. et al, Overland Flow of Oxidation Pond Effluents at Davis, CA,
prepared for U.S. Environmental Protection Agency, January 1977.
23. Atmospheric Administration, "Climatic Summary of the United States".
24. "Consumptive Use of Water and Irrigation Water Requirements", Technical
Committee on Irrigation Water Requirements, Irrigation and Drainage
Division, ASCE, September 1973.
25. Haith, Douglas A., Koenig, A., and Loucks, D., "Preliminary Design of
Wastewater Land Application Systems", Journal WPCF, December 1977, 2371.
26. Morris, C.E. and Jewell, W.J., "Regulations and Guidelines for Land
Application of Wastes - A 50-State Overview," Land as a Waste Management
Alternative, Raymond C. Loehr, Ed. Ann Arbor Science, 1977
27. "Design Guidelines for Land Treatment of Domestic Wastewater," Environmental
Health Administration, Department of Health and Mental Hygiene, State of
Maryland, 1978 Edition.
82
-------
APPENDIX A
COSTS
Costs for overland flow systems including pre-application treatment are
presented in cost curve form as shown in Figures C1 - C13 show construction
costs. Operation and maintenance requirements are shown in Figures OM1-OM17. Each
system will have differing components. With the cost curves presented, any system
cost can be determined by adding the individual component costs. Construction
materials and supply costs are current to July 1979.
To use these cost curves the preliminary design must first be determined.
Costs are then determined for each unit within the system. These costs are then
adjusted to the local conditions by using the appropriate cost index. The cost
curves and materials and supplies curves are based on an ENR index of 3052 or EPA
index of 346. The energy and labor curves are shown as energy units and labor
hours so do not require adjustment.
CONSTRUCTION COST CURVES
Item
Collection ditches
Lined channels
Forcemains
Storage reservoirs 100 - 100,000 m3
Storage reservoirs 100,000 - 1 x 108m3
Field preparation - terrace construction
Field preparation - site clearing
Construction cost for distribution piping
Raw wastewater pumps
Recycle pumping
Aerated grit removal and flow measurement
Chlorine contact basins
Chlorine feed and storage facilities
OPERATION AND MAINTENANCE COST CURVES
Wastewater pumping, labor
Wastewater pumping, energy
Wastewater pumping, maintenance supply costs
Grit removal and flow measurement, labor
Grit removal and flow measurement, energy
Grit removal and flow measurement, maintenance and supply costs
Chlorination, labor
Chlorination, energy
Chlorination, maintenance materials and supplies
Storage reservoirs, 100 - 100,000 m3
maintenance materials and supplies
Storage reservoirs, 100 - 100,000m3
labor (3 m depth)
Storage reservoirs, 100,000 - 1 x 108m3
(5 m depth)
A-1
Figure Number
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
OM-1
OM-2
OM-3
OM-4
OM-5
OM-6
OM-7
OM-8
OM-9
OM-10
OM-11
OM-1 2
-------
OPERATION AND MAINTENANCE COST CURVES (Cont'd)
Item Figure Number
Storage reservoirs, 100,000 - 1 x 108m3
maintenance materials and supplies OM-13
Forcemains, labor OM-14
Forcemains, maintenance materials and supplies OM-15
Lined channels, labor OM-16
Lined channels, maintenance materials and supplies OM-17
A-2
-------
10,000
9
8
7
6
5
O
TJ
t/3
O
O
O
H
o
a:
i-
co
z
O
O
1,000
9
8
7
6
5
4
3
100
i
7
6
5
4
10
10
3 4 5 6789
100
3 4 56789
1,000
3456 789
10,000
FIELD AREA, ha
ASSUMPTIONS: GRASS LINED OPEN DITCH
Figure Cl. Construction costs for collection ditches.
C-l
-------
1,000
E
to
o
TJ
8
o
o
I-
o
D
cc
i-
w
O
O
100
10
3456 789
0.1 1.0 10
CHANNEL PERIMETER, m
ASSUMPTIONS: CONCRETE LINE CANALS, TERRAIN AS SHOWN
100
Figure C2. Construction costs for lined channels.
C-2
-------
1.000
10
100
3456 789
1,000
PIPE SIZE, cm
ASSUMPTIONS: CLASS 150 REINFORCED CONCRETE PIPE OR EQUIVALENT. NO MAJOR
UTILITY, ROADWAY OR RIVER CROSSINGS.
Figure C3. Construction cost for forcemains.
C-3
-------
100
_B
"o
o
o
o
co
8
O
OC
I-
co
O
O
0.1
2 3 456789
1 10
STORAGE VOLUME, 1,000 m3
ASSUMPTIONS: EXTERIOR SLOPE 2:1, INTERIOR SLOPE 3:1. MATERIALS ACQUIRED LOCALLY
3m WATER DEPTH
Figure C4. Construction costs for storage reservoirs. (100-100,, 000 m )
C-4
-------
10,000
9
8
7
6
5
£2
.25
"o
a
o
8
C/3
8
o
z
o
o
a:
CO
z
O
O
1,000
9
8
7
6
5
3
2
100
i
7
6
5
4
10
100
3 4 5 6789
1,000
3 4 5 6 7 89
10,000
3456 789
100,000
STORAGE VOLUME, 1,000 m3
ASSUMPTIONS: EXTERIOR SLOPE 2:1, INTERIOR SLOPE 3:1. MATERIALS ACQUIRED LOCALLY
5m WATER DEPTH
Figure C5. Storage reservoirs. (100,000-100,000,000 m )
C-5
-------
10,000
8
7
6
5
4
3
jg 1,000
^ i
o 8
o 7
§ 6
O
O
o
CC
o
o
100
7
6
5
4
3
2
10
10
2 3 456789
100
2 3 456789
1,000
2 3456 789
10,000
FIELD AREA, ha
ASSUMPTION: MATERIAL CUT & FILL ESSENTIALLY BALANCED WITHIN SITE
BOUNDARIES
Figure C6. Field preparation - terrace construction.
C-6
-------
10.000
9
8
7
6
5
4
3
|81-000
O
8
o
OE
100
I
7
6
5
4
10
10
vV
oS>
^y
1,000
100 2
CD
o
o
o
0
o
p
o
D
CC
10 §
o
2 345 6789
100
2 3 4 5 6 789
1,000
2 3456 789
10,000
CLEARED AREA, ha
ASSUMPTION: CLEARED MATERIAL PUSHED TO EDGE OF SITE OR DISPOSED OF
WITHIN SITE
Figure C7. Field preparation - site clearing.
C-7
-------
1,000
E
in
co
O
O
z
o
H-
O
D
CC
O
o
100
10
2 3 456789
2 3456789
100
1 10
PIPE SIZE, cm
ASSUMPTIONS: BURIED PIPE IS PLASTIC, SURFACE PIPE IS ALUMINUM
2 3456 789
1,000
Figure C8. Construction cost for distribution piping.
C-E
-------
100,000
9
10,000
,- 0
JS T
13 5
o °
§ A
*
1- a
8
0 2
1,000
100
-a
"
X
>
^
X
x^
>
x
X
x
^
/
x
s
/
/
/
j
/
^
2
f
2 3 456789
1,000 10,000
2 3 4 5 6 789
100,000
2 3456 789
1,000,000
FIRM PUMPING CAPACITY, m3/d
ASSUMPTION: LOW LIFT PUMPS ( 3-9m TDH) OPEN IMPELLOR TYPE
Figure C9. Construction costs for raw wastewater pumps.
C-9
-------
100,000
8
7
10 000
CD 7
0 6
~° 5
o
o A
*
I- 3
co
O
O o
1,000
7
5
2
100
/
s
X
X
X*
^
X
^
^x
_x^
^^
^
X
x
x
^
x
^
^
1.000
2 3 456789
10,000
2 3456789
100,000
2 3456 789
1,000,000
FIRM PUMPING CAPACITY, m3/d
ASSUMPTIONS: LOW LIFT, CENTRIFUGAL PUMPS
Figure CIO. Construction costs for in-plant and recycle pumping.
C-10
-------
100,000
6
7
10,000
We
CO «
4
o
g ,
fe 2
o 2
O
1,000
100
-*-"
^
x^
x
x
X
X
ri
X
X
X
*
s
x
J
x
/
/
/
^
/
/
X
2 3 456789
2 3456789
1,000
2 3456 789
10,000
10 100
VOLUME,m3
ASSUMPTIONS: GRIT REMOVAL FOR SEWER WITHOUT STORM WATER INFLUENCE
Figure Cll. Construction cost for aerated grit removal and flow measurement.
C-ll
-------
»
8
7
4
10 000
» ,
s I
-o 5
o
4
3*-
co
8 2
1 000
§
100
0
Z
1
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J 4
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X
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X
> 7
^
' £
4
J9
1
X
z
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x
J
/
,/
I 4
^
5
j
6
^
7
£
19
1
2
0
/
~.
4
5
e
> 7
8
9
100
VOLUME, 1,000 m3
ASSUMPTIONS: BASIN VOLUME PROVIDES 30 MIN DETENTION TIME AT PEAK DAILY FLOW
Figure C12. Construction cost for chlorine contact basins.
C-12
-------
10,000
9
8
7
6
5
4
3
2
1,000
9
8
^ 6
(B 6
0 S
o
o 4
°" 3
8 2
0
100
i
7
6
10
*>
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^
^
^-
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^^
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^x
X*
^
^
^
s
^r
4 ^
/
/
/
/
/
2 34 56789 2 34 56789 2 34 56789
10 100 1,000 10,000
FEED CAPACITY, kg/d
ASSUMPTION: FEED CAPACITY BASED ON A DOSAGE OF 10 MG/L
Figure CIS. Construction costs for chlorine feed and storage facilities.
C-13
-------
100,000
9
8
7
6
S
CO
of
O
CD
10,000
9
8
7
6
5
4
3
1,000
i
7
6
5
4
100
1,000
3 456789
10,000
3 4 5 6 7 89
100,000
456 789
1,000,000
FIRM PUMPING CAPACITY, m3/d
Figure OM1. Labor requirements for wastewater pumping.
OM-1
-------
100,000
8
7
6
5
4
3
2
x 10,000
f 9
* 8
8 I
o 6
^ 5
(3 4
CC
LU
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o
tr
i-
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LU 9
O
7
6
5
4
3
2
100
/
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y
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s
s /
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^
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^ ^
2
r
2 34 56789 2 34 56789 2 34 56789
1,000 10,000 100,000 1,000,000
AVERAGE FLOW,
Figure OM2. Energy requirements for wastewater pumping.
OM-2
-------
100,000
9
7
i_
£ 10,000
(0 Q
O
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,n R
m 5
_i 5
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Q
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100
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^
^
^
^
^
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^
X
^
^
^'
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f
f
f
/
^
/
/
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^
/
/
1,000
3 4 5 6789
10,000
2 3 4 5 6 789
100,000
AVERAGE FLOW, m3/d
2 3456 789
1,000,000
Figure OM3. Maintenance material and supply costs for wastewater pumping.
OM-3
-------
100,000
9
8
7
6
5
4
3
10,000
9
8
7
6
I
CO
CC
O
CD
1,000
7
6
5
4
100
1,000
3 456789
10,000
3 4 5 6 7 89
100,000
3456 789
1,000,000
AVERAGE FLOW, m3/d
Figure OM4. Labor requirements for grit removal and flow measurement.
OM-4
-------
1,000 .
9
CD
DC
HI
2
LU
_J
<
g
tr
i-
o
LU
_1
111
2 3 456789
1,000 10,000
2 3456789
100,000
AVERAGE FLOW, m3/d
2 3456 789
1,000,000
Figure OM5. Energy requirements for grit removal and flow measurement.
OM-5'
-------
MATERIALS AND SUPPLIES, dollars/yr
p i
a o
o 9
o oJ * ucn-Joxo ro w * « cn-^ODio ° ro w * w o»->itpto
1 000
-"
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s
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^
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A
2 34 56789 2 34 56789 2 34 56789
1,000 10,000 100,000 1,000,000
AVERAGE FLOW, m3/d
Figure OM6. Maintenance material and supply costs for grit removal and
flow measurement.
OM-6
-------
c
ra
DC
O
CD
9
8
7
6
5
4
3
2
10,000
9
8
7
6
5
4
3
2
1,000
1
7
6
5
4
3
2
100
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t
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t
10
2 3456789
100
2 3 4 5 6 7 89
1,000
CHLORINE FEED, 1,000 kg/yr
2 3456 789
10,000
Figure OM7. Labor requirements for chlorination.
OM-7
-------
1,000
o
o
o
o
or
LLJ
z
LU
o
EC
o
LLJ
LU
»
8
7
6
5
4
3
2
100
9
8
7
6
5
4
3
2
10
7
6
5
4
3
2
1
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f
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f
/
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/
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/
f
/
s
/
f
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2 34 56789 2 34 56789 2 34 56789
10 100 1,000 10,000
CHLORINE FEED, 1,000 kg/yr
Figure OM8. Energy requirements for chlorination.
OM-8
-------
I
T3
CO
UJ
Q.
D.
D
CO
Q
oc
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1 ,000,000
9
8
7
6
5
4
3
2
1 00,00(
9
8
7
6
5
4
3
2
10,000
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7
6
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3
2
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,
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*
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234 56789 2 34 56789 2 34 56789
10 100 1,000 10.00C
CHLORINE FEED, 1,000 kg/yr
Figure OM9. Maintenance material and supply costs for chlorination.
OM-9
-------
10,000
9
8
7
6
5
o
T3
O
<
z
<
1,000
9
8
7
6
S
4
3
100
i
7
6
5
4
10
0.1
3 456789
3 4 5 6 789
1.0
10
456 789
100
STORAGE VOLUME, 1,000 m3
Figure OM10.
Maintenance materials and supply costs for storage reservoirs.
(100-100,000 m3)
OM-10
-------
9
8
7
6
5
4
3
2
100
9
8
t I
k «
E
3
§
< 2
10
i
6
5
4
3
2
1
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^
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4*
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^
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r
2 34 56789 2 34 56789 2 34 56789
0.1 1.0 10 100
STORAGE VOLUME. 1,000 m3
Figure OM11. Labor requirements for storage reservoirs. (100-100,000 m )
OM-11
-------
CO
of
O
m
8
7
6
5
4
3
2
1,000
9
8
7
6
5
4
3
2
100
1
7
6
5
4
3
2
10
^
X
x
X
^
X
X
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APPENDIX B
STATE OF MARYLAND
DESIGN GUIDE FOR
LAND TREATMENT
(Sections Dealing with Overland Flow)
-------
FOREWARD
In recognition of the needs for public health protection and water resource con-
servation, Maryland State Environmental Health Administration is adopting Techni-
cal Bulletin, M-DHMH-EHA-S-003, as design guidelines for land application of
domestic wastewater.
The prime purpose of this publication is to assist planners in scheduling commun-
ity development and to assist engineers in preparing plans and specifications. So
long as public health is protected and discharge effluent limitations are met,
application of the guidelines should be flexible to suit the practical needs of
local conditions. With substantive and adequate evidence and subsequent approval
by the Environmental Health Administration's technical staff, design details may
deviate from the guidelines established.
This technical bulletin has been reviewed by a Technical Panel consisting of 14
members which represent the State Environmental Health Administration, the Water
Resources Administration, County officials, the Washington Suburban Sanitary
Commission and consulting firms.
These guidelines are subject to future modifications and revisions based upon
further operational experience of land application systems. All users are encour-
aged to submit suggested revisions and pertinent information to the Division of
Design Review, Environmental Health Administration, 201 West Preston Street,
Baltimore, Maryland 21201.
Original Signed
Donald H. Noren, Director
Environmental Health Administration
October 24, 1978
Effective Data
B-1
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CHAPTER I - INTRODUCTION
Land treatment or land application is the treatment of wastewater by using plant
cover, soil surface, soil profile, and geologic materials to remove certain
wastewater pollutants.
Land treatment of municipal wastewater encompasses a wide variety of processes or
methods. The three principal processes are: (1) Slow Rate (Spray Irrigation), (2)
Rapid infiltration, and (3) Overland Flow. Other processes, which are less widely
used, include: (1) Wetlands, (2) Subsurface, and (3) Bermed Infiltration Ponds.
1.3. Overland Flow
In overland flow wastewater is applied over the upper reaches of sloped
terraces and allowed to flow across the vegetated surface to runoff collec-
tion ditches, usually for subsequent surface discharge. The pollutants are
removed by physical, chemical, and biological means as it flows in a thin
film down a relatively impermeable slope.
CHAPTER II - SITE SELECTION
2.1. Administrative Procedures
When a site is proposed for land treatment, the administrative procedures
to be followed are:
1) A joint inspection shall be made by representatives of the Environmen-
tal Health Administration, the Water Resources Administration and local
government in conjunction with the applicant and/or the applicant's
authorized engineers to determine if the proposed site will be techni-
cally feasible for land treatment. Considerations are generally given
to soil characteristics, topography, groundwater table and available
buffer area provided at the proposed land application site.
2) Based on findings of the preliminary site evaluation, the applicant
will be advised whether or not to retain a consultant to conduct a
hydrogeological study and prepare a report.
3) The applicant shall submit an application to the Water Resources Admin-
istration for a groundwater or surface discharge permit.
4) The detailed hydrogeological report will be further evaluated by the
Environmental Health Administration and the Water Resources Administra-
tion to determine the use of a suitable land treatment process and to
recommend a practical rate of application.
5) Upon issuance of a discharge permit by the Water Resources Administra-
tion, the engineer retained by the applicant may proceed with the
design of the selected system in accordance with guidelines established
by the Environmental Health Administration.
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6) Subsequent to a complete review of the design documents, the Environ-
mental Health Administration will issue a construction permit for
installation of the land treatment system.
2 .2. Soil Characteristics
C. Overland Flow
Dense, well packed soils with limited or poor permeability such as heavy
clays, clay soils, and soils underlain by impermeable lenses (fragipans)
are required. A mantle of 6" to 8" of good top soil is recommended.
2.3. Topography
The land application site shall be properly planted, sodded, and/or
adequately covered with vegetation except in rapid infiltration systems.
The needs for vegetative cover are:
1) prevention of soil erosion,
2) elimination of direct surface runoff of wastewater applied (except for
the overland flow process), and
3) enhancement of application rate and treatment.
The design shall also consider possible erosion and storm water runoff in
the areas adjacent to the land application site.
C. Overland Flow
A sloping terrain is necessary to allow applied wastewater to flow slowly
over the soil surface to the runoff collection system. Formed slopes of 2%
to 8% will be required, with 2% to 6% preferred. The length of the slope
generally ranges from 100 ft to 300 ft.
2.4. Groundwater
Investigation of groundwater at a prospective land application site must be
conducted to evaluate the effect of groundwater levels on renovation capa-
bilities as well as the effect of the applied wastewater rate on ground-
water movement and quality.
C. Overland Flow
Groundwater depth is not critical in an overland flow system as the system
is designed principally for runoff of applied effluent rather than percola-
tion, but should not rise to root zone and interfere with plant growth or
slope construction.
B-3
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CHAPTER III - PREAPPLICATION TREATMENT,
LOADING RATE AND CYCLE TIME
3.1. Preapplication Treatment
3.1.1. General
Prior to land treatment, the wastewater generated from domestic estab-
lishments shall be treated to a degree sufficient to accomplish the
following goals:
1) To permit the effluent to be amenable to treatment by soils and to
meet the discharge effluent limitations.
2) To prevent solids cloggings in the distribution system, and
maintain a reliable system.
3) To provide effective disinfection, if disinfection is required.
In general, preliminary or primary treatment is required for overland
flow, and secondary treatment is required for both rapid infiltration
and slow rate. Guidelines and criteria for design of wastewater pre-
treatment facilities should conform to design guidelines set forth by
the Maryland State Environmental Health Administration.
3.1.2. Disinfection
The purpose of disinfection is to destroy all pathogenic micro-
organisms and thereby prevent transmission of disease through the
agency of air or water. Disinfection can be applied at any point in the
treatment system.
Disinfection of pretreated wastewater must be accomplished if it is to
be applied to land by the technique of spraying. Where flooding and/or
ridge and furrow methods are used, disinfection may not be required.
However, the site should be fenced to discourage trespassing.
When the proposed land application site is in an isolated area and
effective measures for the prevention of human contact are taken, the
Environmental Health Administration may determine that disinfection
will not be necessary. However it should be emphasized that each site
will be evaluated on a case-by-case basis.
3.2. Loading Rate
The hydraulic loading rate should not exceed the infiltration capacity of
the soil except for an overland flow system and should be evaluated in
accordance with the water balance principle delineated below.
Precipitation Hydraulic _ Evapotranspiration Percolation
rate loading rate rate rate of soil + Runoff
For an annual water balance, the following rates shall apply.
B-4
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Where, (1) precipitation rate should be the annual rate of the wettest year in
the past 10 years,
(2) evapotranspiration rate should be the annual average rate in the past
10 years, and
(3) runoff should be zero for slow rate and rapid infiltration.
In addition, a monthly water balance shall be prepared using appropriate
monthly rates for each component system.
Where requirements for discharge to groundwater are very stringent for
nitrogen, loading rate shall be adjusted to protect the groundwater against
pollution from excessive nitrate.
C. Overland Flow
Hydraulic loading rates, when preliminary or primary effluent is applied,
may range from 2.5 to 8 inches per week. Lower values of 3 to 4 inches per
week should be observed for (1) slopes greater than 6%, (2) for terraces
less than 150 feet, or (3) because of reduced biological activity during
cold weather.
For secondary effluent, a maximum loading rate of 16 inches per week is
recommended. Lower values of 7 to 10 inches per week should be observed
when (1) to (3) described above apply. Application technique should be
selected to minimize spray drift and preferrably should be surface
application.
3.3. Cycle Time
The cycle time is defined as the period between two consecutive applica-
tions of pretreated wastewater on a specific site.
C. Overland Flow
Loading rates and cycles for an overland flow system are designed to main-
tain active microorganism growth in grass litter and on the soil surface.
Optimum application times generally are 6 to 8 hours daily during 5 to 7
days a week. Application cycles may be extended during warm weather.
CHAPTER IV - STORAGE
4.1. General
Storage capacity for treated wastewater shall be provided since land dis-
posal facilities are not designed to handle the surge flow or to operate
during inclement weather periods.
4.2. Storage Capacity
Storage capacity depends upon wastewater flow, land treatment technique,
storage period, direct rainfall, etc. It shall be adequate to hold treated
B-5
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wastewater for at least 60 days and to store any direct precipitation
during the inclement weather periods of a wet season.
4.3. Lining
The bottom of storage ponds shall be lined with impervious material to pre-
vent leakage and to preserve effective storage capacity especially during
the wet season when the groundwater table is high. Underdrainage shall be
provided where groundwater levels or pressures affect the lining or founda-
tion of storage ponds.
4.4. Screening Device
Screening devices shall be installed at the outlets of storage ponds to
remove solids and floating debris to protect downstream facilities against
plugging. Procedures must be established to inspect and to clean screening
devices on a routine basis.
4.5. Fence and Warning Signs
Storage ponds should be in fenced areas to keep the public from tres-
passing, fishing, or swimming. Fences should be at least 6 feet high and
fence gates should be equipped with chains and locks. Warning signs should
be posted at proper locations to keep the public from trespassing the
premises and from engaging in fishing or swimming activities.
4.6. Storage Pond Bypass
A bypass around the storage ponds shall be constructed to permit pretreated
effluent to flow directly from the pretreatment process to the site where
facilities are available for land application. Bypass lines between the
pretreatment process and storage ponds shall be properly valved to
facilitate flexible operations of the land application system.
4.7. Aeration Facilities
Aeration equipment may be required in storage ponds for one or both of the
following purposes:
1) To minimize effects of ponds' turnover during freezing and thawing
cycles.
2) To provide supplemental oxygen for protection against odors when stor-
ing primarily treated wastewater.
CHAPTER V - SURFACE DRAINAGE SYSTEM,
BUFFER ZONE AND LAND REQUIREMENT
5.1. Surface Drainage System
Surface drainage systems should be designed to collect surface run-off
resulting from precipitation on land application sites. Surface drainage
B-6
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systems should be sized for a 10-year storm recurrence interval, but should
also be capable of withstanding hydraulic erosion.
Run-off entering surface drainage system should be channelled through an
online sediment collection basin and connected to a storm drain system.
Deposits of grit, debris, etc., collected in the basin should be removed
periodically so as to maintain required sediment capacity.
5.2. Buffer Zone
Where wastewater is applied to the land via spraying, a 20D-foot minimum
buffer area is recommended from the wetted perimeter of the spray field to
property lines, streams, public roads, etc. Where spray fields are located
in areas adjacent to housing developments, a 500-foot buffer zone is
desirable. However, variance to these restrictions may be considered where
it can be demonstrated that an adequate windbreak or other techniques are
provided to prevent spray from going beyond the boundaries of land treat-
ment site.
Where spraying is not a method of distribution, a 50-foot minimum buffer
area is recommended from the boundaries of wetted basins to property lines,
streams, public roads, etc.
5.3. Land Requirement
The total land requirement associated with a given land apolication project
shall include the following areas.
C. Overland Flow
Data available from overland flow treatment of municipal wastewater con-
sists of experimental and pilot study results. Evaluation of these data
suggest the following for design of such systems.
To achieve a nitrified effluent: calculate similarly to slow rate systems
except that the hydraulic application rate shall be taken as that for warm
weather rates plus 25% land allowance for grass management.
1) Irrigation field (sized according to the weekly average application
rate).
Wetted Field Area (acrea) = Q x 257_ x 365
A 365-T
Q = average daily flow in mgd
A = hydraulic loading rate in inches per week
T = lagoon storage period in days
2) Storage ponds (discussed in Section 4.2).
3) Buffer zone (discussed in Section 5.2).
B-7
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4) Installation of sewage treatment facilities, and accessories.
5) Future expansion if desired.
6) An additional 25% of land above the wetted field area be reserved in
case the application rate needs to be adjusted after the system is in
operation. This extra 25% of land may be used for future expansion, if
the system is achieving the desired effluent quality limitation at the
design rate.
To achieve a denitrified effluent: calculate similarly to slow rate systems
except that the hydraulic application rate shall be taken as that for
winter weather rates.
CHAPTER VI - PUMPING STATION
6.1. General
Pumping stations for delivering wastewater to land application sites should
be designed according to the "Design Guidelines for Sewerage Facilities",
Technical Bulletin: M-DHMH-EHA-S-001, Published by the Environmental Health
Administration, Maryland State Department of Health and Mental Hygiene.
However, special consideration should be given to these items specified in
the following sections of this chapter.
6.2. Number of Pumps and Pump Capacity
One standby pump must be provided and available for service at all times.
The capacity of the pumps excluding the standby unit shall not exceed the
maximum permissible hydraulic loading rate on the designated area for one-
day operation, and shall not be less than the theoretical pumping rate
calculated on the basis of the following equation.
P = Q x 365 x 2A_
(365-T H
P = Pumping rate in "gpm11
Q = Average daily flow in "gpm"
T = Non-operating period in "day"
Non-operating period for a spray irrigation system should include
those days when the system is shut down due to freezing tempera-
ture, high wind velocity, high intensity of rainfall, and crop
harvesting if any.
H = Operation period in "hours per day"
For crop consumption and management, pumping-rate design will be determined
accordingly.
B-8
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6.3. Intakes from reservoirs or lagoons
Each pomp shall have an individual intake with a screening device described
in Section 4.4. Intakes should be designed to avoid turbulence and should
be capable of drawing treated sewage at various elevations as desired by
field operator.
6.4. Valves
Suitable shut-off valves shall be placed on suction lines and discharge
lines of each pump system. A check valve shall be placed in discharge
lines between shut-off valves and pumps. Selection of check valves should
consider water-hammer effect.
6.5. Flow Measurement
A flow meter with recorder and totalizer shall be installed to measure
flows pumped to the land application field.
6.6. Pump Removal
Provisions shall be made to facilitate removing pumps and motors for
maintenance purposes.
6.7. Alarm System
An alarm system should be provided for pumping stations and telemetered to
the area where 24-hour attendance is available. If 24-hour attendance is
not available, an audio-visual device shall be installed at the station for
external observation.
CHAPTER VII - DISTRIBUTION SYSTEM
7.1. General
The two distribution techniques generally used for land treatment are sur-
face application and sprinkler application.
Surface distribution employs flow from piping systems or open ditches to
flood the application area.
Sprinkler distribution, which simulates rainfall, may be of the permanent
set or movable type.
7.2. Piping Systems
Piping shall be arranged to provide flexibility for expansion, modifica-
tion, inter-connection, and partial isolation.
B-9
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7.2.1. Pressure Control
Lateral lengths and pipe sizes shall be selected properly so that
pressures along laterals will not vary more than 20%. Devices for regu-
lating the pressure through distribution systems are required to
maintain uniform discharge rates and uniform pressures if pressure is
beyond this range. Employment of high pressure class pipes or installa-
tion of devices to delay valve closing times in distribution systems is
recommended to prevent pipe failure due to high pressure surges.
7.2.2. Drain System
Drain valves shall be located at low points and at the end of each
lateral to allow water to drain and prevent in-line freezing. Drainage
shall be returned to the storage facility or discharged properly in
gravel pits within the land application field.
7.2.3. System Protection
Where a buried system is utilized, proper buttresses at bends of the
system shall be installed. To protect against freezing the frost line
of the area should be considered before design. In general, laterals
should be buried deeper than 2.0 feet and mains should have a minimum
cover of 3.0 feet.
For above-ground systems, mains and laterals shall be anchored
properly.
7.3. Solid Set Sprinklers
7.3.1. Risers
Sprinklers shall be elevated on risers high enough to ensure uniform
distribution with the lowest possible trajectory. Risers shall be
adequately supported to prevent damage from vibration and should have
sufficient height to clear crops. Usually 3 to 4 feet of riser is used
for a grass field.
7.3.2. Spacing
For uniform application, sprinklers need to be spaced properly so their
distribution areas overlap. In general, the distance between sprinkler
heads on laterals should not exceed 0.5 of the distribution area
diameter; the distance between laterals should not exceed 0.65 of the
distribution area diameter. Lateral spacings should be reduced where
high wind velocities occur frequently.
7.3.3. Discharge Pressure
Discharge pressures at the sprinkler nozzles should be selected prop-
erly so that a uniform distribution of effluent over the distribution
B-10
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area can be expected. Typical nozzle discharge pressures generally
range from 50 to 60 psi. The use of non-obstructive pressure regulators
is recommended.
7.3.4. Distribution Area Diameter
The distribution area diameter shall be selected to allow even distri-
bution. Large distribution area diameters usually involve high trajec-
tories resulting in greater distortion of the distribution pattern,
especially during excessively high winds.
The diameter shall not exceed 140 feet on any type of application.
Generally, smaller diameters are desirable in wooded and steeper slope
areas.
7.5. Surface Application Systems
Surface flooding systems should be designed to apply pre-treated wastewater
at a rate which will constantly flood the field in use at a relatively uni-
form depth. Care must be taken to minimize erosion at the point of applica-
tion. This method of distribution is used mainly for rapid infiltration
systems. Surface distribution methods include ridge and furrow
irrigation, surface flooding irrigation, bubbling orifices and gated
surface pipe.
7.5.3. Bubbling Orifices
Bubbling orifices are small diameter outlets from laterals used to
introduce flow to overland flow systems. These outlets may be orifices
in the laterals or small diameter pipe stubs attached to the laterals.
7.5.4. Gated Surface Pipe
Gated surface pipe denotes a pipe with multiple outlets. The pipe can
be attached to hydrants fixed to valved risers. Slide-gated or screw-
adjustable orifices must be provided at each outlet to control the
flow.
CHAPTER VIII - MONITORING
8.1. General
As with any wastewater treatment facility, a comprehensive monitoring pro-
gram will be required to ensure that proper renovation of wastewater is
occuring and that environmental degradation is not taking place.
8.2. Renovated Water
The monitoring of renovated water may be required for either groundwater,
or recovered water, or both. Recovered water is the runoff from overland
flow, or water from recovery wells, or underdrains if used.
B-11
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Water quality parameters that should be analyzed in groundwater and
renovated water include those that are required by the discharge permit and
those that are necessary for system control.
8.4. Soils
In almost all cases, the application of wastewater to land will result in
some changes in the characteristics of the soil. Consequently, a soil
monitoring program will be helpful for most systems.
8.4.1. Levels of Various Chemical Elements
The long-term build-up of various elements to unacceptable levels in
the application site should be evaluated. One area of major concern in
many cases is the Sodium Adsorption Ratio (SAR). High values may
adversely affect the permeability of soil. The formula for evaluation
of Sodium Adsorption Ratio is shown as follows:
SAR = Na+
Ca+++Mg++ 1/2
2
where Na+ = Sodium ion concentration in milliequivalents per liter of water
Ca++ = Calcium ion concentration in milliequivalents per liter of
water
Mg++ = Magnesium ion concentration in milliequivalents per liter of
water
The Sodium Adsorption Ratio should be maintained below 9 to prevent the
dispersion of clay to avoid the sealing of the soil. Sodium Adsorption
Ratio can be reduced by adding Calcium ions or Magnesium ions, such as gyp-
sum, into the water.
CHAPTER IX - CROP MANAGEMENT
9.1. General
Because the renovation of wastewater is dependent in part upon crops and
vegetation (except in rapid infiltration systems), consultants must
develop a crop management program at the design stage. Assistance in design
and planning can be provided by the U.S. Department of Agriculture, Soil
Conservation Service, and local farm advisers. Detailed procedure should be
programmed in conjunction with the design of land application systems.
9.2. Crop Selection
Factors which influence crop selection are nutrient removal efficiency,
suitability to the climate, soil, and wastewater applications, and toler-
ance to wastewater constituents. The four general classes of crops that may
be considered are: (i) Annuals, (ii) Perennials, (iii) Landscape vegetation
and, (iv) Forest vegetation.
B-12
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9.3. Cultivation and Harvesting
For the simple operation of systems, ease of cultivation and harvesting of
selected crops is important.
It is critical to maintain soil vegetation systems in healthy, productive
and renovative states. This involves regular harvesting and cutting of
grass crops and vegetation, adequate drying periods after application, and
care in operating farm machinery which may cause excessive soil
compaction.
B-13
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REFERENCES
1 . CH2M Hill, Design Seminar for Land Treatment of Municipal Wastewater Efflu-
ents - Design Factors Part II, Prepared for United States Environmental
Protection Agency Technology Transfer Program. (September 1975).
2. Foster, H. B., Jr., Ward, Paul C., and Prucha, Arnold A., "The Removal of
Nutrients by Spraying Effluent on a Saturated Hillside - Lake Tahoe, Cali-
fornia" . Staff Report, Bureau of Sanitary Engineering, California State
Department of Public Health (May 1975).
3. Great Lakes - Upper Mississippi River Board of State Sanitary Engineers,
Recommended Standards for Sewage Works (Ten States Standards). (1973).
4. Lappo, Richard L., "Living Filter, Perks up Regional Sysem". Water and
Wastes Engineer, P. 13, (June 1976).
5. Metcalf & Eddy, Inc., Design Seminar for Land Treatment of Municipal Waste-
water Effluents - Design Factors Part I, Prepared for United States
Environmental Protection Agency Technology Transfer Program. (August 1975).
6. Metcalf & Eddy, Inc., Wastewater Engineering - Collection, Treatment and
Disposal, McGraw-Hill Book Company (1972).
7. Pennsylvania Department of Environmental Resources, Spray Irrigation Manual,
Publication No. 31, Bureau of Water Quality Management, Harrisburg,
Pennsylvania (1972).
8. U.S. Department of Agriculture, Conservation Irrigation in Humid Areas,
Agriculture Handbook 107 - Soil Conservation Service (January 1957).
9. U.S. Environmental Protection Agency, Evaluation of Land Application
Systems, Technical Bulletin - EPA- 430/9-75-001 (March 1975).
10. U.S. Environmental Protection Agency, Land Application of Wastewater in
Australia, Technical Bulletin - EPA - 430/9-75-017 (May 1975).
11. U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, U.S.
Department of Agriculture, Process Design Manual for Land Treatment of
Municipal Wastewater, Technical Bulletin - EPA - 6215/1-77-008 (October
1977).
12. Metcalf & Eddy-Sheaffer S Roland, Preliminary Assessment Feasibility of Land
Treatment of Wastewater in Prince George's County, Maryland, prepared for
the Washington Suburban Sanitary Commission. (Draft copy, June 1977).
13. Oklahoma State Department of Health, Design "Guidelines for Land Application
of Municipal Wastewater."
14. The Irrigation Association, Wastewater Resource Manual, June 1977.
B-14
-------
15. R. Thomas K. Jackson, L. Penrod, "Feasibility of Overland Flow Treatment of
Raw Domestic Wastewater". Robert S. Kerr, Environmental Research Lab - EPA -
660/2-74-087 (July 1974).
16. R. Thomas, B. Bledsoe, K. Jackson, "Overland Flow Treatment of Raw Waste-
water with Enhanced Phosphorus Removal". Robert S. Kerr, Environmental
Research Lab - EPA - 600/2-76-131 (June 1976).
B-15
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APPENDIX C
STATE OF MISSISSIPPI
DESIGN GUIDE FOR LAND TREATMENT SYSTEMS
MISSISSIPPI AIR AND WATER POLUTION CONTROL COMMISSION
-------
FINAL DRAFT
DESIGN GUIDANCE FOR LAND TREATMENT SYSTEMS
MISSISSIPPI AIR AND WATER POLLUTION CONTROL COMMISSION
May, 1979
I. Overland Flow Land Treatment Systems
A. Preapplication Treatment - Preapplication treatment will be
provided to remove grit, large settable solids and to reduce
the potential for odor problems at the site. Generally,
treatment may be most effectively and economically
provided in a new or existing lagoon. If a lagoon system
is proposed, it should be designed with a 50 Ib/day/acre
organic loading based on BOD with a minimum three (3)
foot operating depth. A short detention time aerated
lagoon should be given due consideration when a lagoon
does not already exist. Also, aerators may be added
to an existing lagoon, which provides adequate storage,
to eliminate odor problems. The design engineer should
remember that the purpose of the system is to provide
storage and preapplication treatment.
B. Storage - A total effective storage of 30 to 60 days
above that required for treatment is recommended.
Storage volume may be provided in the pretreatment
lagoon by regulating the depth above the three (3)
foot operating depth. Short terra storage of 10 to
15 days located "off-line" will be considered when
it is demonstrated to be applicable to the project
purpose and site conditions.
C. Preapplication Chlorination - If the method of applica-
tion is designed and operated to minimize the production
of aerosals, preapplication chlorination will not normally
be required. This will be determined on a case-by-case
basis depending on the application system proposed.
D. Hydraulic Loading Rate - The application rate on the
site is to be a minimum of 2.5 inch/week for the
yearly average over the entire application area. The
hydraulic loading should be increased on a portion of
the application area during the summer months to allow
other areas to be dried and harvested. Greater loading
rates shall be considered where local research and/or
operating systems have demonstrated the capability
and reliability in handling such loadings.
E. Distribution System - The utilization of a low head
design is recommended whenever site conditions allow.
This type of system lowers the 0 & M costs, may lower
the capital cost and should minimize the production
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of aerosals. Gravity systems, gated pipe, bubble tube
orifices or fixed fan nozzles are recommended for
consideration.
F. Application Field Characteristics
1. Slope - Application slopes of 2% to 8% are recommended
with consideration given to the existing topography
to minimize the land forming requirements. The ter-
races should generally be 100 - 150 feet in length.
2. Soil Permeability - This may be measured by the
falling head laboratory method or by other proven
laboratory and/or field determination methods for
overland flow systems. The permeability should
be "slow" (Permeability of less than 0.2 inch/hour).
The permeability may be greater than this value if
an impermeable barrier appears in the soil profile
between the soil surface and the ground water table.
3. Depth to Ground Water - This is not a critical con-
sideration because this process is a surface treatment
phenomenon. In-depth percolation must be inhibited
by an impermeable layer in the soil profile above
the ground water table.
G. Vegetative Cover - A vegetative cover is required for
this system to provide nutrient uptake and protection
from erosion. This vegetative cover should be capable
of growing in a wet environment and have a higher
nutrient uptake rate. Argentine byhalia, Reed Canary,
and Coastal Bermuda should be considered with overseeding
of rye grass in the winter.
H. Drainage/Collection System - A drainage system should be
designed and constructed so as to eliminate rainfall runoff
from flowing onto or off of the site. A collection system
should be designed and constructed to collect all waste-
water and rainfall runoff from the terraces and transport
the flow to a single location for ultimate discharge to a
surface stream. Multiple discharge points may be more
appropriate and justifiable in some situations. These
collection/drainage channels may be grassed ditches,
tile or any material that will control erosion and
facilitate maintenance. Any discharge must be to state
waters.
I. Post Chlorination - The requirement for post chlorination
(after treatment and prior to discharge to the receiving
stream) will be assessed on a case-by-case basis. If
required, chlorination would be provided for wastewater
design flow only. Runoff above the design flow would
bypass chlorination. All systems must meet the stream
standards of 2000-4000 MPN/100 ml fecal coliforms as
specified in the State of Mississippi Water Quality
Criteria, adopted by the MAWPCC on April 12, 1977.
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J. Buffer Zones - Buffer zones shall be provided around
land treatment sites. The size of this border is
dependent upon application method, proximity to
dwellings, roads, land use, etc. Although the width
of the buffer zone is negotiable, a value of 50 to
100 feet would seem to be adequate for most cases
in which precautions have been taken to minimize
spray drift and aerosals. Where possible, the
application field should be built around the
preapplication treatment and storage facility
to provide the buffer for these units.
K. Public Access and Protection - This has been covered
in buffer zones and chlorination practices. Public access
to the site should be controlled through the use of fences
and gates to restrict public access and to prevent livestock
from entering the site. A 3 to 5 strand barb wire fence
is recommended.
L. Monitoring
1. Groundwater - Contact MAWPCC for these requirements.
2. Discharge to Surface Stream - MAWPCC will issue an
NPDES permit which will outline the frequency of
sampling and parameters to be monitored in the
influent and effluent.
II. Slow Rate Irrigation Land Treatment Systems
A. Preapplication Treatment - Generally provide a lagoon
with a design organic loading of 50 Ibs/acre/day BOD
using a three (3) foot operating depth. Secondary
treatment before land application is not required.
The preapplication treatment level will be directly
related to the intended irrigation use of the waste-
water. As the opportunity for public access increases,
pretreatment requirements should be more stringent. A
short detention time aerated lagoon should be given due
consideration when a lagoon does not already exist. Also,
aerators may be added to an existing lagoon, which provides
adequate storage, to limit odor problems. The design
engineer should remember that the purpose of the system is
to provide storage and preapplication treatment.
B. Storage - Normally provide a minimum of 30 - 60 days
of excess storage time above that provided in the
pretreatment lagoon. Storage volume may be provided
in the existing or proposed lagoon by varying the
operating depth. Specific storage requirements
are related to water balance. One system, such as a
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lagoon, could be used for both pretreatment and
storage. Short terra storage of 10 to 15 days
located "off-line" will be considered when it is
demonstrated to be applicable to the project purpose
and site conditions.
C. Preapplication Chlorination - The requirement for
chemical disinfection will be considered on a
case-by-case basis. Extended storage prior to
application may be effective in reducing fecal
coliform levels to that which would be consistent
with project objectives and requirements.
D. Hydraulic Loading Rate - A minimum application rate
of 1.00 inch/week as a yearly average will be used.
Loading rates of less than this value must be well
supported and justified. A water and nutrient balance
will be used to determine the specific application
rate. Seasonal variations in hydraulic application
should be considered to facilitate harvesting of crop
by rotation of application areas. The recommended
hydraulic loading rate and seasonal application
schedule shall be supported by soils information
specific for the project site and, as needed, on-site
loading rate capacity determinations.
E. Application System - These may be fixed fan nozzles,
traveling bridge sprinklers, impact sprinklers, or
other high head systems, to facilitate even distribu-
tion of the wastewater over the application area. Where
topography permits, ridge and furrow irrigation or
flooding may be desirable.
F. Application Field Characteristics
1. Slope - Limit application area slopes to a maximum
of 20% for cultivated land and 40% for noncultivated
land. Consideration should be given to the potential
for runoff and erosion.
2. Soil Permeability - A range of .2 to 0.6 inch/hour
will be considered as an acceptable percolation
rate.
3. Depth of Groundwater - Normally not less than 2
to 3 feet. If the groundwater depth is less than
this value, an underdrain system should be con-
sidered to maintain the groundwater at a depth
of 2 to 3 feet or more and to control groundwater
mounding.
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G. Vegetative Cover - Any crop not used for direct human
consumption, or that is not fed directly to dairy cows,
should be acceptable. Such crops would include corn,
cotton, soybeans, green crop, etc. Truck crops or
unprocessed vegetables (tomatoes, strawberries, etc.)
shall not be irrigated in this manner. Irrigation of
processed vegetables and/or fruits may be acceptable
in some situations.
H. Drainage/Collection System - This system may not have
a surface discharge during normal operation. All
surface drainage and underdrain flow should be directed
to controlled .discharge points. Any discharge must be
to State waters. Rain water falling outside the appli-
cation site should be excluded from the site.
I. Post Chlorination - This should not normally be required
because the system is generally designed not to have a
surface discharge. A system designed to have a surface
discharge must meet the stream standards of 2000-4000
MPN/100 ML fecal coliforms.
J. Buffer Zones - Buffer zones should be provided with a
minimum width of 100 - 200 feet. Vegatative screens
should be considered for use around the application
site to minimize aerosal drift and wind effects.
The buffer width would be directly related to the
public access to the site and the type application
system used. This will likely be determined on a
case-by-case basis.
K. Public Access and Protection - Fencing may be needed
around the entire application site to control livestock
and to discourage trespassing. A 3 to 5 strand barb wire
fence is recommended. Vegetative screens should be used
to limit spray drift. Use of posting in conjunction with
vegetative screens will be considered on a case-by-case
basis for projects with appropriate objectives. Projects
that are designed to have public access (golf courses,
medians, parks, etc.) should not require these steps
as long as access to the site is controlled during
spray periods.
L. Monitoring
1. Groundwater - Contact MAWPCC for these requirements.
2. Discharge to Surface Stream - MAWPCC will issue an
NPDES permit which will outline the frequency of
sampling and the parameters to be monitored in
both the influent and effluent on discharging
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systems. Should the system be designed for
zero discharge to surface water, a no-discharge
State permit will be issued by the MAWPCC.
III. Rapid Infiltration Land Treatment Systems
A. Preapplication Treatment - Generally provide a lagoon
with a design organic loading of 50 Ibs/acre/day BOD
using a three (3) foot operating depth. Secondary
treatment before land application is not required.
The preapplication treatment level will be directly
related to the intended irrigation use of the waste-
water. As the opportunity for public access increases,
pretreatment requirements should be more stringent. A
short detention time aerated lagoon should be given due
consideration when a lagoon does not exist. Also, aerators
may be added to an existing lagoon which provides adequate
storage to limit odor problems. The design engineer
should remember that the purpose of the system is to
provide storage and preapplication treatment.
B. Storage - If properly designed, none should be required.
However, recommend the availability of about 10 days for
possible mechanical failure should be adequate.
C. Preapplication Chlorination - If the method of applica-
tion is designed and operated to minimize the production
of aerosals, preapplication chlorination should not be
required. This will be determined on a case-by-case
basis depending on the application system proposed.
D. Hydraulic Loading Rate - 4.0 inches/week minimum
application rate on a yearly average. The design
should be made on the basis of a water balance and
on-site soils investigations to support the capability
of the selected site to accept the recommended loading
for the deisgn period.
E. Distribution System - Typically this is a flooding-resting
sequence utilizing ponds or trenches. However, high rate
irrigation may be used in which case the systems would be
much like that in the spray irrigation system.
F. Infiltration Basin Characteristics
1. Slope - Generally less than 2%.
2. Soil Permeability - Greater than 0.6 inches/hour.
3. Depth to Groundwater Table - Recommend minimum of
10 feet unless underdrains are provided.
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G. Vegetative Cover - Optional and not usually required
or recommended in flooding mode of operation but may
be desirable in some situations to enhance ancUor
maintain infiltration/perculation capacity.
H. Drainage/Collection System - Rainfall runoff must be
intercepted and routed around system. Failure to do
so may transport silt and fines which would clog the
infiltration system. Underdrains and a surface discharge
should be provided at the site except when the hydro-
geologic study shows a direct pathway to a surface
water. The direct recharge of a potable water supply
aquifer or a possible water supply aquifer is a
special case and will require special investigations
and clearances through and by the MAWPCC.
I. Post Chlorination - The renovated wastewater discharge
should be acceptable from the standpoint of fecal
coliform concentration and therefore would not require
disinfection. Consideration should be given to specific
limits that the system is being designed to meet and the
proximity of the discharge site to human habitation.
J. Buffer Zones - A buffer zone shall be provided around
the treatment site. The size of this border is dependent
upon application method, proximity to dwellings, roads,
land use, etc. Although the width of the buffer zone is
negotiable, a value of 50 to 100 feet would seem to be
adequate for most cases in which precautions have been
taken to minimize aerosal drift from the application
basin.
K. Public Access and Protection Systems - This has been
covered in buffer zones and chlorination practices.
Access to the site should be controlled through
the use of fences and gates to restrict public access
and to prevent livestock from entering the site. A 3
to 5 strand barb wire fence is recommended.
L. Monitoring
1. Groundwater - Contact MAWPCC for these requirements.
2. Discharge to Surface Stream - MAWPCC will issue an
NPDES permit which will outline the frequency of
sampling and the parameters to be monitored in both
the influent and effluent on discharging systems.
Should the system be designed for zero discharge
to surface water, a no discharge State permit will
be issued by the MAWPCC.
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SELECTED REFERENCES
1. Process Design Manual for Land Treatment of Municipal Waste-
water, EPA 625/1-77-008.
2. Applications of Sludges and Wastewaters on Agricultural Land:
A Planning and Educational Guide, MCD-35, March 1978.
3. Nutrient Removal from Cannery Wastes by Spray Irrigation of
Grassland; Law, Thomas and Myers, 16080, November 1969.
4. Highlights of Research on Overland Flow for Advanced Treatment
of Wastewater: Charles R. Lee et al; Misc. Paper Y-76-6, November
1976.
5. Overland Flow Treatment of Raw Wastewater with Enhanced Phosphorus
Removal; Thomas, Bledsoe and Jackson; EPA - 600/2-76-131, June 1976.
6. Wastewater Engineering - Treatment/Disposal/Reuse, Metcalf and
Eddy, Inc.; 2nd ed., 1979.
' ' ' *
7. Wastewater Treatment Plant Design, WPCF, Manual of Practice -
MOP 8, 1977.
&GPO 1980677-094/1122
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