v>EPA
                     United States
                     Environmental Protection
                     Agency
                     Office of Water
                     Washington, D.C.
EPA 932-F-99-068
September 1999
Decentralized  Systems
Technology Fact Sheet
Septage  Treatment/Disposal
DESCRIPTION

In 1990 the U.S. Department of Commerce, Census
Bureau, estimated that the number of housing units
with septic tanks or cesspools in the U.S. was 24.6
million and approximately 5.5  billion gallons of
septage were being generated each year. "Septage"
is the liquid and solid material pumped from a septic
tank, cesspool, or other primary treatment source.
Scum accumulates on the surface while the sludge
settles at the bottom,  comprising 20 to 50% of the
total septic tank volume when pumped.  A septic
tank will usually retain 60 to 70% of the solids, oil,
and grease that passes through the system.

Septage is classified according to the environment in
which it is generated. This fact sheet will focus
solely on domestic septage. Treatment and disposal
of domestic septage is governed by the U.S. Code
of Federal  Regulations  (40  CFR) Part  503.
Municipalities can also establish local regulations for
septage handling, treatment, and disposal in addition
to the federal and state regulations.

There are several approaches to septage treatment
and disposal which include private  or public
ownership.  Larger municipalities are capable of
managing the whole process from handling and
treatment to disposal, while other municipalities opt
to use privately owned facilities that alleviate some
of the responsibilities of operating a facility.  Land
disposal of septage after adequate treatment is also
a popular option.
                    Septage characteristics

                    Factors that affect the physical characteristics of
                    septage are: climate, user habits, septic tank size,
                    design,  and  pumping  frequency,  water supply
                    characteristics, piping material, and the use of
                    water-conservation  fixtures,  garbage disposals,
                    household chemicals, and water softeners. Table 1
                    lists the  characteristics  and  limits of  domestic
                    septage.

                        TABLE 1 CHARACTERISTICS OF
                           SEPTAGE CONVENTIONAL
                                 PARAMETERS
Concentration
Parameter Minimum
Total solids
Total volatile solids
Total suspended
solids
Volatile suspended
Biochemical oxygen
demand
Chemical oxygen
demand
Total Kjeldahl
nitrogen
Ammonia nitrogen
Total phosphorus
Alkalinity
Grease
PH
Total coliform
Fecal coliform
1,132
353
310
95
440
1,500
66
3
20
522
208
1.5
107/100 ml_
106/100 ml_
Maximum
130,475
71,402
93,378
51,500
78,600
703,000
1,060
116
760
4,190
23,368
12.6
109/100 ml_
108/100 ml_
                                          Note: The measurements above are in mg/L unless otherwise
                                          indicted.
                                          Source: U.S. EPA, 1994.

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     TABLE 2  SOURCES OF SEPTAGE
 Description
 Rate
  Removal
  Pump-out
 Characteristics
 Septic tank
 Cesspool
 Privies/portabl
 e toilets
 Aerobic tanks
 Holding tanks
 (septic tank
 with no drain-
 field, typically
 a local
 requirement

 Dry pits
 (associated
 with septic
 fields)

 Miscellaneous
 May Exhibit
 Characteristic
 s of Septage

 Private
 wastewater
 treatment
 plants

 Boat pump-
 out station

 Grit traps
 Grease traps
2-6 years, but
can vary with
location local
ordinances
2-10 years
1 week to
months
Months to 1
year
Days to weeks
2-6 years
Variable
Variable
Variable
Weeks to
months
Concentrated BOD,
solids, nutrients,
variable toxics
(such as metals),
inorganics (sand),
odor, pathogens,
oil, and grease

Concentrated BOD,
solids, nutrients,
variable toxics,
inorganics,
sometimes high
grit, odor,
pathogens, oil, and
grease

Variable  BOD,
soilds, inorganics,
odor, pathogens,
and some
chemicals

Variable  BOD,
inorganics, odor,
pathogens, and
concentrated solids

Variable  BOD,
solids, inorganics,
odor, and
pathogens, similar
to raw wastewater
solids

Variable  BOD,
solids, inorganics,
and odor
Septic tank
Portable toilets
Oil, grease, solids,
inorganics, odor,
and variable BOD

Oil, grease, BOD,
viscous solids, and
odor
Source: Septage Handling Task Force (1997), copyright
Water Environment Federation, used with permission.
APPLICABILITY

Septage is  highly variable  and  organic,  with
significant levels of grease,  grit, hair,  and debris.
The liquids and solids pumped from a septic tank or
cesspool have an offensive odor and appearance, a
tendency to foam upon agitation, and a resistance to
settling and dewatering. Septage is also a host for
many   disease-causing   viruses,  bacteria,   and
parasites.  As a result,  septage  requires  special
handling and treatment.  However, the polymers and
chemical    conditioners  available  today  have
considerably reduced these requirements.

The handling and disposal of septage are based on
the characteristics  and  volume of  septic waste.
Knowldege of this information is also useful  for
design  purposes and  determining typical design
values  for treatment  and  disposal.    Table  2
summarizes the sources of septage.

ADVANTAGES AND DISADVANTAGES

Advantages

The advantage of using treatment plants is that they
provide regional solutions to septage management.

Disadvantages

•      May need a holding  facility during periods
       of frozen or saturated soil.

       Need a relatively large, remote land area for
       the setup of the septic system.

•      Capital and operation and maintenance costs
       tend to be high.

        Skilled operators may be required.

        Some limitations to  certain management
       options of untreated septage include lack of
       available  sites  and   potential   odor  and
       pathogen problems. These problems can be
       reduced by pretreating and stabilizing the
       septage before it is applied  to the land.

•       Septage treated at a  wastewater treatment
       facility has the potential to  upset processes
       if  th  septage  addition  is  not  properly

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       controlled, and increased requirements for
       handling and disposing of residuals.

DESIGN CRITERIA

Surface application

Septage can be applied to the land as a fertilizer and
soil conditioner.  Application rates depend on the
slope, soil type, depth of application, drainage class,
and hydraulic loading. Septage must not be applied
before or during rainfall or on frozen ground.  Thus,
an interim storage facility is needed.  Some states
require septage to be disinfected before application.

       Spray Irrigation-pretreated (e.g., screened)
       septage is pumped at 80 to 100 psi through
       nozzles and sprayed directly onto the land.
       Spray  irrigation can be used on steep  or
       rough  land and minimizes disturbances to
       the  soil  by trucks.   It is  important  to
       consider the wind patterns  and the site
       location when using spray irrigation because
       of the  offensive  odors  associated  with
       septage.

•      Ridge and Furrow Irrigation-this is used for
       relatively level land, with slopes no greater
       than 0.5 to 1.5%.  In this disposal method,
       pretreated  septage is  applied  directly  to
       furrows or to  row crops that will not  be
       directly consumed by humans.

       Hauler Truck Spreading-septage is applied
       to the soil directly from a hauler truck that
       uses a  splash plate to improve distribution.
       The  same truck that pumps out the septic
       tank can be  used for transporting and
       disposing the septage.

•      Farm Tractor and Wagon Spreading-liquid
       septage or septage solids are transferred to
       farm equipment for spreading. This allows
       for application of liquid or solid septage.
       However,  if the  septage  was not  lime
       stabilized,  then  the  septage  must  be
       incorporated into the soil within 6 hours.
Subsurface Incorporation

Subsurface incorporation places untreated septage
just  below the soil  surface, reducing odors  and
health risks while fertilizing and conditioning the
soil. Septage can only be applied to slopes less than
8%, and the soil depth to seasonal high water table
must be at least 20 inches (or as mandated by local
regulations).  A holding facility  is required during
periods of wet or frozen ground. To prevent soil
compaction  and allow   sufficient   infiltration,
equipment must not be driven over the site until 1 to
2 weeks after application.

•      Plow  and   Furrow  Cover-typically,  a
       moldboard plow is used with furrow wheels
       and coulters.  The coulter blade slits the
       ground ahead of a plow.  Liquid septage is
       discharged from a tank into a narrow furrow
       about 15 to 20 cm deep and is then covered
       by a second plow.

•      Subsurface   Injection-liquid  septage  is
       injected in a narrow cavity created by  a
       tillage tool. The opening is about 10 to 15
       cm below the  surface.  Some equipment
       uses a forced closure of the injection swath.

Burial

Septage burial includes disposal in holding lagoons,
trenches, and sanitary landfills. There is a high odor
potential  during  septage application until a final
cover is placed on top.  It is essential to select an
appropriate site for  disposal  not only to control
odors, but to avoid groundwater pollution.

       Holding  Lagoons- these disposal lagoons
       are a maximum of 6 feet deep, with septage
       placed in small incremental lifts of 15 to 30
       cm and no infiltration. Multiple lagoons are
       loaded in sequential  order for  optimum
       drying. To decrease  odors, the lagoon inlet
       pipe can be placed below liquid level.

•      Trenches-multiple    trenches   are   filled
       sequentially with septage  in small lifts of 15
       to 20 cm for optimum drying.  Each trench
       is  then covered with soil (2  feet), and new
       trenches  are opened.  Another option is to

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       leave  a filled trench uncovered to enable
       some   solids  to  settle  and  liquids  to
       evaporate and leach out. The solids, along
       with some bottom and sidewall material, are
       removed and the trench can be reused.

•      Sanitary Landfills- the primary problems that
       need  to  be considered when septage is
       added  to  a  sanitary  landfill   are  the
       production of leachate, treatment, and odor.
       Therefore, septage must not be disposed of
       in landfills with areas that have over 90 cm
       of rainfall, landfills that do not have leachate
       prevention and control facilities, or those
       not having isolated underlying rock. Each
       area that is  filled with septage  should be
       covered with 15 cm of soil  each day and 2
       feet of final cover within 1 week after the
       placement of  the final  lift.  In  general,
       sanitary  landfills are  not  cost-effective
       disposal options for  septage.

Septage is resistant to dewatering  and as a result
conditioning chemicals are  used.  The amount of
chemical  used  is  based   on  the  load  and  its
characteristics.  A combination of lime and ferric
chloride  has  been successfully used, along with
certain polymers. Septage treatment plants also use
other processes to dewater conditioned septage
such as screw presses,  plate  and frame presses, belt
presses,  rotary  vacuum   filters,  gravity   and
vacuum-assisted drying beds, and sand drying beds.

Another  feasible  option  for  septage  treatment
facilities is composting in locations where bulking
agents are available  and  the  humus product is
needed as  a  soil conditioner.   If the necessary
bulking agents are not accessible, this method can
be expensive.  For  this reason, it is preferable to
dewater septage before composting.

OPERATION AND MAINTENANCE

The three basic alternatives for septage treatment
and  disposal  are land application,  treatment at
wastewater treatment  plants, and treatment at
independent septage treatment plants.
Treatment at independent septage treatment
plants

       Stabilization lagoon.

•      Chlorine oxidation.

       Aerobic digestion.

       Anaerobic digestion.

       Biological and chemical treatment.

       Conditioning and stabilization.

       Composting

Treatment at wastewater treatment plants

       Addition to upstream sewer manhole.

       Addition to plant headworks.

       Addition to sludge handling process.

       Addition to both liquid stream and sludge
       handling processes.

Land application

•      Surface application.

•      Subsurface incorporation.

•      Burial.

Selecting  the  appropriate  septage management
option depends on technical  issues and regulatory
requirements.  Some of the factors that influence the
process of selection include: land availability and
site conditions, buffer zone requirements, hauling
distance, fuel costs, labor costs, costs of disposal,
and other legal and regulatory requirements.

Treatment at Independent  Septage Treatment
Plants

Independent  septage  treatment  plants use  such
processes as chlorine oxidation, aerobic digestion,
anaerobic digestion, and biological and chemical

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treatment.  Many septage treatment plants also use
lime to provide both conditioning and stabilization
before the septage is dewatered.  The liquid residual
can be discharged to a privately owned treatment
facility  or undergo further treatment and then be
discharged.  Septage solids are then sent to either a
landfill,  composted,  applied  to the  land, or
incinerated.

When suitable land is unavailable and wastewater
treatment facilities are too distant or do  not have
adequate capacity, independent septage treatment
plants can be of use.  Such treatment plants have
been designed exclusively for treating septage and
have many unit processes to handle both the liquid
and solid portions of septage.

Stabilization is a  treatment method that decreases
odors, the levels of disease-causing organisms, and
the   potential   for  putrefaction  of  septage.
Pretreatment/stabilization is achieved by  physical,
chemical, or biological processes. Some methods of
stabilizing septage are discussed below.

Alkali (Lime) Stabilization

Lime or other alkaline material is added to liquid
septage to raise the pH to 12.0 for a minimum of 30
minutes.  Although there is  a  lot of variation in
septage  characteristics  and  lime requirements,
mixing is not very difficult, and approximately 20 to
25 pounds of lime are used for every  1,000 gallons
of septage. The three main stabilization approaches
before land application are to add lime slurry:  1) to
the pumper truck before the septage is pumped, 2)
to the pumper truck while the septage  is being
pumped, or 3) to  a tank that is storing septage that
was  discharged from a pumper truck.  The septage
and  lime  may  sometimes  be mixed  by  a coarse
bubble diffuser system located in the tank or truck.
In some states,  it  is prohibited to use hauler trucks
for the  stabilization process.  A  separate storage
tank is necessary for lime and septage mixing.  This
is beneficial because a separate holding tank allows
for more uniform  mixing and easier  sampling,
monitoring, and control.
Aerobic Digestion

Septage is aerated for 15 to 20 days in an open tank
to achieve biological reduction in organic solids and
odor potential. The time requirements increase with
lower  temperatures.   Normally,  this  is  not  a
cost-effective option.

Anaerobic Digestion

Septage is retained for 15 to 30 days in an enclosed
vessel  to achieve biological reduction of organic
solids. Anaerobic digestion is generally not  used
except  for   co-treatment with  sewage  sludge.
However, one advantage is that anaerobic digestion
generates methane gas,  which can be used for
digester heating or other purposes.

Composting

Liquid septage or septage solids are mixed with a
bulking agent (e.g., wood  chips,  sawdust) and
aerated mechanically or  by turning.   Biological
activity generates temperatures that are sufficiently
high to destroy pathogens.  The composting process
converts septage into a stable, humus material that
can be used  as a soil amendment. This process
tends to create odors that can be a problem if not
handled properly.

After the septage is stabilized, it is then sent for
further treatment or disposal, which is  described in
the sections that follow.

Land application

Land application  of septage is currently the most
commonly used disposal  method in the U.S.  It is
relatively simple and cost-effective, uses low energy,
and recycles  organic material and nutrients to the
land.

With  proper  management, domestic septage is  a
resource containing nutrients that can condition the
soil and decrease the reliance on chemical fertilizers
for agriculture.  Septage  management maximizes
these benefits of septage while protecting public
health and the environment.

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Land application includes spreading septage from
septage hauler trucks,  specially designed  land
application vehicles, or tank wagons onto sites using
spray irrigation, ridge and furrow irrigation, and
overland flow.
such as dewatering. Adding septage to the sludge
handling process may also cause clogging of the
pipes and increase wear on the pumps if the septage
is  not screened and  degritted in the receiving
station.
Treatment at Wastewater Treatment Plants

A convenient and attractive option for septage
treatment is  performing  the  treatment  at  a
wastewater treatment facility. The constituents of
septage are similar to domestic sewage, even though
septage is stronger and more concentrated.  The
advantages  of treating  septage at wastewater
treatment plants are that many plants are capable of
handling some septage and that it centralizes waste
treatment operations. The four main approaches to
treating septage at a wastewater treatment plant are:

To Upstream Sewer Manhole

When septage is added to a sewer upstream of the
wastewater treatment plant, substantial dilution of
septage occurs prior to it reaching the wastewater
treatment plant. This method is only feasible with
large sewers and treatment plants.  It is economical
due to the very  simple receiving station design.
However, there is the potential for grit and debris to
accumulate in the sewer and for odor problems near
the manhole.

To Plant Headworks

Septage  can be  added  to  sewage  immediately
upstream of  the  screening  and grit  removal
processes.  This method, like the one mentioned
above, is economical because  of the very simple
receiving station  design.   It  also allows  the
wastewater treatment plant staff to have control of
the septage discharge.

To Sludge Handling Process

Septage  can  also  be  handled  as  sludge  and
processed with wastewater treatment plant sludge
after pretreatment in the receiving station.   This
method  reduces  the  loading  to liquid  stream
processes,  and it eliminates the  potential  for
affecting effluent quality. However, there could be
an adverse effect on the sludge treatment processes,
To  Both Liquid Stream  and Sludge Handling
Processes

Septage can also be pretreated to separate liquid
and  solid  fractions, which are then processed
accordingly.   This provides more concentrated
sludge for processing and  reduces  the organic
loading to liquid stream processes and the hydraulic
loading to sludge processes.  Increased operations
are  required  for septage  pretreatment  at  the
receiving station.

COST

Cost considerations cannot be generalized because
of the wide range of options available for septage
management.  The cost of a septage management
system is dependent on the treatment and disposal
method used and the regulatory requirements of a
particular area.

Administrators of a septage management program
should be aware of disposal options and the cost
involved.  The median cost of disposal (or tipping
fee) typically ranges from 3 to 6 cents per gallon.

REFERENCES

1.     Brown, D. V. and R. K. White. December
       1977.  "Septage Disposal  Alternatives in
       Rural Areas." Ohio Agricultural  Research
       and Development Center. Research Bulletin
       1096. Cooperative Extension Service. The
       Ohio State University Extension Bulletin
       624.

2.     Septage  Handling  Task  Force.   1997.
       Septage  Handling.  Water  Environment
       Federation (WEF)  Manual of Practice No.
       24. WEF. Alexandria, Virginia.

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3.     Ungvarsky, J. andK. Mancl. 1982. "Septage
      Use and Disposal." Special Circular 317.
      The Pennsylvania State University. College
      of Agriculture, Extension Service.

4.     U.S.  EPA, 1984.  Handbook:  Septage
      Treatment and Disposal.  EPA Municipal
      Environmental  Research  Laboratory.
      Cincinnati, Ohio. EPA-625/6-84-009.

5.     U.S.  EPA,  1994.  Guide  to  Septage
      Treatment  and Disposal. EPA Office of
      Research and  Development.  Washington,
      D.C. EPA/625/R-94/002.

ADDITIONAL INFORMATION

Lisa Dvello
Director at Large
Town of Flower Mound
2121 Cross Timbers Road
Lewisville, TX 75028

Daniel Balboa
Director at Large
Balboa Septic Design
3470 Jack C. Hays Trail
Buda, TX78610

The mention of trade names or commercial products
does not constitute endorsement or recommendation
for use  by  the U.S. Environmental  Protection
Agency.
                                                         For more information contact:

                                                         Municipal Technology Branch
                                                         U.S. EPA
                                                         Mail Code 4204
                                                         401 M St., S.W.
                                                         Washington, D.C., 20460

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