United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-178 Oct. 1981
Project Summary
Evaluation of On-Site
Wastewater Treatment and
Disposal Options
James A. Heidman and Robert P. G. Bowker
A literature review of published and
unpublished data was conducted to
identify conceivable on-site systems,
including wastewater manipulation,
treatment, and disposal options.
Wastewater manipulation options
included flow reduction, wasteload
reduction, and waste segregation.
Treatment options included disinfec-
tion and biological and physical/
chemical methods. Disposal options
included air, soil, and surface water
methods and practical combinations.
Both tested and untested systems
were identified, and combinations of
the various components were devel-
oped. An equipment inventory was
then performed to determine the
availability of hardware for the sys-
tems, and system components were
identified. Data on engineering, eco-
nomic, and environmental acceptabil-
ity characteristics were collected.
These systems were evaluated on
the basis of performance, operation
and maintenance, environmental
acceptability, and total annual cost for
15 specific site conditions. Site condi-
tions were defined by soil percolation
rate, soil depth, slope, available land
area, direct discharge effluent require-
ments, and net evaporatibn.
Where site conditions are appropriate
(conventional septic tank—soil ab-
sorption systems) were found to be
the least-cost and top-ranked method
of on-site wastewater treatment and
disposal. Under other conditions,
systems incorporating other methods
of disposal, such as soil disposal with
modified distribution, mounds, evapo-
transpiration, irrigation, evaporation,
or direct discharge, are appropriate. A
septic tank normally provides adequate
pretreatment for most of these dis-
posal methods. Where irrigation or
surface discharge disposal is used,
additional treatment, such as that
provided by an intermittent sand filter
and iodine disinfection, may be re-
quired. Use of low pressure membrane
filtration where high quality effluent is
required also appears promising,
based on very limited operating
experience.
This Project Summary was devel-
oped by EPA '$ Municipal Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction '
The major objectives of a review of the
available literature for on-site waste-
water treatment and disposal were:
1. To identify potential in-the-house
and individual home on-site
wastewater treatment, handling,
reuse, and disposal options. The
on-site unit components included
water conservation devices,
waterless systems, recycle sys-
tems, separation systems, and
other wastewater manipulation
schemes; biological and physical/
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chemical treatment options; and
disposal options.
2. To conduct a technological and
economic comparative analysis of
all manipulation, treatment, and
disposal options so that alterna-
tives could be ranked and a small
number of selected, most feasible
alternatives could be identified.
The data base for the project included
both published and unpublished litera-
ture and personal interviews. After
pertinent data were extracted from the
published literature, individual re-
searchers, sanitarians, and consultants
were contacted to supply lacking or
incomplete unpublished data. Equip-
ment manufacturers were also con-
tacted to obtain nonproprietary data and
to discuss relevant specific topics. Data
collection and subsequent system
evaluations focused on the following
topical areas: (1) performance, (2)
operation and maintenance require-
ments, (3) environmental acceptability,
and (4) cost.
Wastewater Character and
Manipulation
Data on wastewater quantity and
quality characteristics, reported by
several investigators, consisted of
wastewater flow from various house-
hold sources, combined household
wastewater characteristics, wastewater
constituent contributions from various
sources, and a summary of blackwater,
greywater, and garbage disposal char-
acteristics, the data indicated that on-
site systems must be able to accom-
modate considerable fluctuations in
potlutant and hydraulic loadings.
A summary of generic types of flow
reduction devices was compiled for both
greywater and blackwater sources.
Flow reductions of 10% and 40% should
be consistently achievable using flow
reduction devices for batch flow sources
(i.e., toilet, laundry, and dishwasher).
Limited information was presented on
cost and operation characteristics of gas
and oil-fired and electric incinerating,
and recirculating and composting
toilets. Matrices were developed of 18
potential waste segregation options and
potential impacts. In general, segrega-
tion options were indicated to have
limited applicability.
Wastewater Treatment
Biological systems for which on-site
hardware and performance information
was available included suspended
growth extended aeration units, fixed
growth rotating disks, and fixed growth
packed reactors. The use of nondis-
charging lagoons for disposal, such as
infiltration/evaporation lagoons, was
assessed. Physical/chemical treatment
systems reviewed included pressure
filtration, gravity filtration, ultrafiltra-
tion, and chemical addition and sorption
processes. Disinfection options reviewed
were for use of chlorine, iodine, ozone,
and ultraviolet irradiation.
In all cases, information on system
performance, operation and mainte-
nance requirements, environmental
acceptability, and costs was summa-
rized. Component comparisons were
made for systems with available on-site
hardware.
Disposal Options
Soil disposal in the form of a con-
ventional soil absorption field is the
most common and accepted on-site
disposal method. Site-specific limita-
tions, however, often make other
methods of disposal necessary or
desirable. Disposal options and their
applicability to on-site systems are
summarized in Table 1. The options with
available on-site hardware and per-
formance data are discussed in the full
report.
Comparative Analysis
Technical ranking criteria were devel-
oped for a comparative analysis of on-
site treatment and disposal systems for
a variety of site conditions. The ranking
criteria considered system performance,
operation and maintenance require-
ments, scheduled maintenance fre-
quency, reported equipment failure,
hardware complexity, and environmen-
tal acceptability. The systems were
evaluated in three separate categories:
(1) systems with available hardware and
on-site performance data, (2) systems
with available hardware but incomplete
(if any) on-site performance data and (3)
systems without existing hardware for
on-site application that require develop-
ment.
For systems with available hardware
and performance data, the following
general conclusions were drawn:
1. A combined septic tank and con-
ventional soil absorption field was
the top-ranked and least costly
system where site characteristics
permit its use.
2. Where shallow soils (0.3 to 1.2 m)
would not provide adequate treat-
ment for the combined septic tank.
conventional soil absorption field,
and mound systems were the top-
ranked and least costly systems, if
adequate land area is available.
3. Use of combined flow reduction,
holding tank, and off-site disposal
was the top-ranked and least
costly system only where (a)
topography prevents "area inten-
sive" construction and direct
discharge is not feasible, or (b)
where depth to bedrock or grou nd-
water is less than 0.3 m (1 ft) and
direct discharge and evapotran-
spiration (ET) disposal is not
feasible. Even with flow reduction,
costs were very high.
4. ET disposal (with septic tank pre-
treatment)wastop-rankedandthe
least costly system where disposal
to the soil and direct discharge
were not feasible and where
evaporation minus precipitation
was greater than 5 cm/mo (2
in./month).
5. Disposal by direct discharge was
the top-ranked method where (a)
soil and ET disposal were not
feasible or (b) where limited land
area was available for disposal
and sufficient flow reduction was
not feasible. The top-ranked and
least costly treatment for direct |
discharge was a combined septic
tank, covered intermittent or
recirculating gravity sand filter,
and disinfection system if nutrient
discharges were not limited. If
nitrogen discharge was limited
«10mg/L)anda limit of 10mg/L
BOD and SS was required, a
combined septic tank, covered
intermittent or recirculating gravity
sand filter, fixed growth anaerobic
reactor, and disinfection system
was the top-ranked treatment. If
phosphorus was also limited (<2
mg/L), use of the same system
with a sand/"red mud" filter
substituted for the sand filter
and/or elimination of phosphate
detergents was the top-ranked
treatment system. Nitrogen may
also be significantly reduced
through the use of a nonwater
carriage or recirculating toilet
system, but variable household
wastewater characteristics make
consistent achievement of effluent
nitrogen concentrations of <10
mg/L uncertain.
6. Combined septic tank soil absorp-
tion with pressure distribution
systems were the top-ranked and
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Table 1. Disposal Options
Performance
Selected Constituents
Generic Type
Air
- evapotranspiration
(lined)
- lined evaporation
lagoon
- mechanical
evaporation
- thermal
evaporation
Soil
• soil absorption
.. "conventional"
.. modified
distribution
.. soil
modification
- irrigation
.. drip
. . spray
.. overland flow
Surface Water
- direct discharge
Combinations
• evapotranspiration/
absorption
- un/ined lagoons
• lagoon
w/overflow
Affected
BOD. SS. N. P.
microbiological
BOD. SS. N. P.
microbiological
BOD. SS. N. P.
microbiological
BOD, SS, N, P.
microbiological
SS. BOD. P. N.
microbiological
SS, BOD, P. N,
microbiological
SS. BOD. P. N.
microbiological
SS. BOD, P. N.
microbiological
SS. BOD, P. N.
microbiological
SS. BOD. P. N.
microbiological
none
SS. BOD. P. N.
microbiological
SS, BOD, P. N,
microbiological
SS. BOD. P. N.
microbiological
Adequacy
consistent
potentially
consistent
potentially
consistent
potentially
consistent
consistent
consistent
consistent
potentially
consistent
consistent
potentially
consistent
consistent
consistent
consistent
consistent
O&M Requirements
Frequency of
Scheduled
Maintenance Hardware
(K/yrJ
4
X
0
<1
<7
2-4
2-4
2-4
<1
<1
2-4
2-4
Complexity
simple
simple
moderate
moderate -
complex
simple
simple
simple
simple
simple
simple
simple
simple
simple
moderate
Equipment
Failure
(requiring
unscheduled Environmental Acceptability
service)
infrequent
infrequent
unknown
unknown
infrequent
infrequent
infrequent
unknown
unknown
unknown
infrequent
infrequent
infrequent
infrequent
(potential hazards and nuisances)
—
odor and aesthetics
aesthetics
air emissions
groundwater quality impacts
groundwater quality impacts
groundwater quality impacts
odors, health effects, asethetics
odors, health effects, aesthetics
odors, health effects, aesthetics
BOD and SS < 30 mg/l, stream
water quality, and effluent
toxicity
groundwater quality impacts
odor, aesthetics and groundwater
quality impacts
BOD and SS < 30 mg/l stream water
quality, effluent toxicity. odor
and groundwater quality impacts
Range of
Total Annual
Cost
tsr
300-700+
200-3SO
600
1000
50-150
100-250
200-450
100-200
150-250
100-200
10-50
200-350
150-300
200-350,
"Amortized capital cost plus annual operation and maintenance costs. Does not include cost of pretreatment.
least cost systems where soils are
excessively permeable.
Additional conclusions reached during
evaluation of the top-ranked systems
were:
1. Wastewater reuse is a potential
method of flow reduction. The cost
of treatment for reuse of either
combined or segregated waste
streams, however, was not typically
offset by reduced disposal costs
resulting from reduced volume for
any of the site conditions con-
sidered. Thus, systems incorporat-
ing wastewater reuse were not
normally economically viable,
although they occasionally may be
applicable in specific situations
(e.g., very limited water availabil-
ity).
2. Systems incorporating wastewater
segregation options were generally
not cost-competitive for any of the
site conditions considered, unless
segregation was a part of flow
reduction and flow reduction in
excess of approximately 35% of
the normal household total was
required. Use of a nonwater
carriage or recirculating toilet
system to control wastewater
nitrogen concentrations or segre-
gation of bath and laundry waste-
water from kitchen and toilet
wastewater to facilitate denitrifi-
cation, however, may be appro-
priate if nitrogen discharge limita-
tions are applicable.
Systems with available hardware
and performance data were avail-
able at a reasonable cost for the
site conditions considered, except
(a) where steep slopes prevent
area-intensive construction and
direct discharge was not feasible;
(b) where soils have very limited
purification capacity and direct
discharge and evapotranspiration
disposal were not feasible; or (c)
where available land for disposal
was very limited, soil percolation
was slow, and direct discharge
was not feasible.
The full report, submitted in fulfill-
ment of Contract No. 68-03-2627 by
SCS Engineers under sponsorship of
the U.S. Environmental Protection
Agency, was authored by David H.
Bauer, E.T. Conrad, and Donald G.
Sherman.
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The EPA authors James A. Heidman and Robert P. G. Bowker (also the EPA
Project Officer, see below) are with the Municipal Environmental Research
Laboratory, Cincinnati. OH 45268.
The complete report, entitled "Evaluation ofOn-Site Wastewater Treatment and
Disposal Options," (Order No. PB 82-101 635; Cost: $18.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
• U S. GOVERNMENT PRINTING OFFICE, 1981 — 559-017/7381
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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