Evaluation Of On-site Wastewater Treatment and Disposal Options


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unpublished data was conducted to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

potentially
consistent
consistent

potentially
consistent

consistent

O&M Requirements
Frequency of
Scheduled
Maintenance Hardware
(K/yrJ

2-4

Complexity

simple

moderate

moderate -
complex

simple

moderate

Equipment
Failure
(requiring
unscheduled Environmental Acceptability
service)

infrequent

unknown

infrequent

unknown

infrequent

(potential hazards and nuisances)

—

odor and aesthetics

aesthetics

air emissions

groundwater quality impacts

odors, health effects, asethetics

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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