&EPA
United States
Environmental Protection
Agency
                         Biosolids Technology Fact Sheet
                         Use of Landfilling for Biosolids Management
DESCRIPTION

Current options for managing wastewater biosolids
in the United States include both beneficial reuse
technologies (such as land application, landfilling
with biogas recovery,  and energy recovery through
incineration)  and non-reuse options,  including
landfilling.   While implementing some type of
beneficial reuse  is  the  preferred method  for
managing wastewater biosolids, this is not always
practical. For example, land acquisition constraints
or poor material quality may limit beneficial reuse
options. In these situations, landfilling of biosolids
may be a viable alternative.

Biosolids landfilling options include disposal in a
monofill  (a landfill that accepts only wastewater
treatment plant biosolids),  or  in a co-disposal
landfill (a landfill that combines biosolids with
municipal solid waste).   Although co-disposal
landfilling  is more common than monofilling,
biosolids typically represent only a small percentage
of the total  waste in a co-disposal landfill (WEF,
1998).

Landfill  disposal of biosolids should  not  be
confused with use of biosolids to amend final cover
material at landfills. This practice is a form of land
application  in which biosolids are added to soil to
enhance conditions for growing cover vegetation.
The EPA fact sheet Land Application of Biosolids
addresses the  use of biosolids in  rehabilitating
disturbed lands.

Biosolids Monofilling

Biosolids monofilling consists of preparing the site,
transferring the biosolids to the  site, and covering
the  biosolids with a  layer of cover material.
Depending on the concentration of pollutants in the
biosolids, site preparation may include installing a
liner to  prevent  contaminants  from  migrating
downward  into the site soil.   The three most
                       common  methods  of  monofilling  wastewater
                       biosolids are the trench, area, and ramp methods.

                       Trench monofilling (Figure 1) involves excavating
                       a trench, placing the biosolids in the trench, and
                       then backfilling the trench to return the soil to its
                       original contours. Monofill trenches can be narrow
                       or wide, depending on the solids concentrations of
                       the  biosolids  to  be  filled.   Narrow trenches
                       (typically less than 3 m [approximately 10 ft] wide)
                       are generally used for disposal of biosolids with a
                       low solids content. Wide trenches (typically greater
                       than 3 m [approximately 10 ft] wide) are used for
                       disposal of biosolids with a solids  content of 20
                       percent or more. If the biosolids contain less than
                       20  percent  solids,  they will  not  support the
                       machinery used to place the cover material over the
                       trench.

                       Application rates  for trenches less than 3 m  in
                       width  are approximately  2,270-10,580 m3/ha
                       (1,200- 5,600 yd3/acre).  Typical application rates
                       for wider trenches range from 6,000-27,000 m3/ha
                       (3,200-14,500 yd3/acre) (U.S. EPA,  1978).

                       The trench  method provides  efficient  use  of
                       available land space.  However, this method is
                        FIGURE 1 EXCAVATED CROSS-SECTION
                                 OF BIOSOLIDS TRENCH

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generally  not  used at sites that  require a liner
because of the potential to damage the liner during
trench excavation.

In the area method, biosolids are placed in a natural
or excavated depression, or they are mixed with soil
and  placed on  top  of the existing  soil layer.
Biosolids  to be  landfilled in this manner  are
generally  stabilized prior to landfilling because
these sites do not always apply daily cover.  The
area method is particularly well  suited to areas
where bedrock or  ground water are shallow, and
excavation (as is required for the trench method) is
difficult. However, this method requires substantial
amounts of soil for fill and results in changes to the
local topography.

The   ramp  method   involves   spreading  and
compacting the biosolids along a  slope.  The soil
higher on the slope is pushed  over the top of the
biosolids as a cover material.

Applicable Regulations

Landfilling of biosolids in monofills is regulated by
the  Environmental  Protection   Agency  under
Subpart C of 40 CFR, Part  503, Standards for the
Use  and Disposal of Sewage Sludge as surface
disposal.   The Part  503  Regulations establish
maximum concentrations of arsenic, chromium, and
nickel in biosolids to be landfilled in a monofill
without a liner.  The limits vary with  distance to
property lines as  presented in Table 1.  If the
concentration of any of these pollutants  exceeds the
criteria, the facility must be  lined.  The regulations
also allow establishment of site-specific pollutant
limits at the discretion of the permitting authority.

These regulations also require that biosolids placed
in a  landfill meet either  Class  A or  Class B
pathogen reduction requirements  or that they be
covered with soil or  other  material at the end of
each operating day.

In addition, many state regulations for monofills
have more  stringent  requirements, which  may
include  installing  a liner regardless of pollutant
concentrations.
     TABLE 1 MAXIMUM POLLUTANT
     CONCENTRATION FOR SURFACE
         DISPOSAL OF BIOSOLIDS
                    Pollutant Concentration
                      (Dry Weight Basis)
 Distance from
 Boundary of
 Active Biosolids
 Unit to Property
 Line, m

 0 to less than 25

 25 to less than 50

 50 to less than 75
Arsenic   Chromium    Nickel
 mg/kg      mg/kg     mg/kg
  30

  34

  39
 75 to less than 100      46
200

220

260

300
210

240

270

320
100 to less than
125
125 to less than
150
Equal to or greater
than 150
53
62
73
360
450
600
390
420
420
Source: Part 503 Regulations
Co-Disposal Landfilling

Co-disposal   landfilling   involves   combining
wastewater solids with municipal solid waste and
placing  the  mixture  in   a  permitted  landfill.
Generally, a layer of municipal solid waste is spread
near the working face of the landfill.  Wastewater
solids are then spread over the municipal waste and
the two are thoroughly mixed using typical landfill
machinery. The ratio of waste to wastewater solids
is dependent, in part, on the solids content of the
wastewater solids.  Ten percent biosolids to 90
percent solid waste (by volume) is common.  The
mixture is then compacted and covered with a daily
cover.

Applicable Regulations

The design and operation of co-disposal landfills is
regulated by EPA under Subpart I of 40 CFR, Part
258, Criteria for Municipal Solid Waste Landfills.
Standards set forth in the Part  258 Regulations
address  general requirements,  pollutant limits,
management  practices,  operational standards for

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pathogens and vector attraction, and monitoring,
record keeping, and reporting requirements.

Accepting  wastewater  solids  at  a co-disposal
landfill generally does not add significant regulatory
hurdles  or  permit  constraints to  the  landfill
operator. In addition, co-disposal typically does not
result in additional operational requirements for the
landfill  other than the mixing  the biosolids and
waste prior to placement in the permanent cell.

APPLICABILITY
TCLP method (Method 1311) is defined in EPA
SW-846.

Finally, economics also factor into any decision to
manage biosolids  through landfilling.  Landfill
tipping  fees can be less than the full cost of land
application or other reuse options. Because tipping
fees change in response to  market conditions,  a
periodic reassessment  of  solids  management
decisions is recommended.

ADVANTAGES AND DISADVANTAGES
Landfilling is generally considered for wastewater
biosolids management when land application or
other beneficial reuse is  not  possible.   Typical
scenarios that lead to selection of landfill disposal
rather than beneficial reuse include:

       Land acquisition constraints;

•      High concentration of metals or other toxins
       in the biosolids; or

•      Odorous material that may create a public
       nuisance if managed through other options.

Solids concentrations of the biosolids are also a
factor in determining whether landfilling is a viable
disposal option. For biosolids monofills, the solids
concentration  should be  15 percent or greater.
Although  soil may be  mixed with  biosolids to
increase the solids concentration to this level, this
may not be cost effective.  Biosolids are usually
stabilized prior to monofilling.

As a general rule, municipal solid waste landfills
will not accept materials with solids content less
than about 18 percent. The operator will  generally
perform a paint filter test on the biosolids prior to
allowing them to be deposited due to the regulatory
prohibition of materials containing  free liquids.
The paint filter test is described in detail in  EPA
publication SW-846, Test Methods for Evaluating
Solid Waste, Physical/Chemical Methods, Method
9095.  In addition to the paint filter test for free
liquids, a  Toxicity  Characterization  Leaching
Procedure (TCLP) must also be performed to verify
that the biosolids  are non-hazardous.  Passing this
test is generally not a problem for biosolids.   The
Advantages
       Landfilling is suitable for biosolids with
       high concentrations of metals  or other
       toxics.

       Landfills may require smaller land area than
       land application.

       Landfilling improves packing of solid waste
       and increases biogas production.

       Landfills may  be  the most  economical
       biosolids management solution, especially
       for malodorous biosolids.
Disadvantages
       Landfilling biosolids eliminates their reuse
       potential and is contrary to the EPA national
       beneficial reuse policy.

       Landfilling requires extensive planning,
       including selection  of a proposed landfill
       site, and operation, closure, and post closure
       care of the site.

       Operation,  maintenance, and post closure
       care of landfills are labor intensive.

       Landfill  sites   have   a   potential   for
       groundwater contamination from leachate.

       Decomposition of biosolids in a landfill
       produces methane  gas which must  be
       collected and reused  or disposed of  by
       flaring or venting. Energy can be recovered

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       through methane capture systems to offset
       the cost of the necessary collection system.

       Landfills  have   a  potential  for  odor
       generation.

Environmental Impacts

There are several  potential environmental impacts
associated with landfilling of wastewater biosolids.
Leachate from the landfill may transport  nitrate,
metals, organics, and/or pathogens to groundwater
if the landfill site has not been properly selected or
if the liner has been damaged. In addition, rainfall
runoff  from   an  active  landfill   may   carry
contaminates to nearby surface waters.  Specific
impacts will vary  among landfill locations

Other potential impacts from these landfills include
impacts on traffic volume, land use, air quality,
public health,  aesthetics, wildlife, and habitats of
endangered  species.  Adverse impacts should be
mitigated during  the site selection process or by
specific measures in the design (U.S. EPA, 1979).

DESIGN CRITERIA

Design  of  monofills  and co-disposal landfills
includes selecting an appropriate site, evaluating
wastewater solids quality, and approving a method
of operation. Preliminary planning is followed by
detailed design, site development, site  operation
and maintenance,  and closure.

Site Evaluation

Landfill   sites  must meet  the  siting  criteria
established by either the Part 503 (for monofills) or
the Part 258 regulations (for co-disposal landfills).
Both  regulations  contain  similar  requirements,
including:

•      A landfill shall not be  developed  if it is
       likely to adversely affect a threatened or
       endangered species.

•      The landfill cannot be located in a wetland
       unless a special permit is obtained.
•      A landfill cannot restrict the flow of a 100-
       year flood event.

       The landfill  must  not be  located  in  a
       geologically unstable area.

       The landfill must be located 60 m (200 ft)
       or  more  from  a  fault  area  that  has
       experienced displacement in Holocene time.

•      If the landfill is located in a seismic impact
       zone, it must be designed to resist seismic
       forces.

•      The landfill must be located at least 300 m
       (1,000 ft) from an airport runway.

Some  states  have   additional  siting  criteria,
including  setbacks from property lines, public or
private drinking water wells, surface drinking water
supplies, and buildings or residences.

Preliminary Planning

The preliminary planning phase for landfill design
should include a determination of the biosolids
characteristics and an estimate  of the average
biosolids quantity. Once the biosolids quantity is
determined, the area required for the landfill site, as
well as its probable lifespan, can be  calculated.
Generally,  a site should provide 10 to 20 years of
operational capacity.

Other  factors  to consider  during  preliminary
planning include haul distance and route from point
of generation to the facility;  topography; surface
water and soils; geology; groundwater; vegetation;
meteorology;  environmentally  sensitive   areas;
archaeological  and historical  significance;  site
access; final site use; and cost. Each of these issues
could affect the final location of the landfill.

Site Development

Once the  landfill  site is determined,  initial  site
development  can begin.    During  the  initial
development of the landfill site, utilities such as
water, sewer, and electricity must be provided for
daily operations. In addition, support facilities such
as  an  equipment garage,  office building,  and

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leachate  pumping  stations  may  need  to be
constructed.

The landfill design must also include site-specific
criteria to meet environmental requirements. These
requirements include mitigating the environmental
impacts of runoff, infiltration of water through the
landfill and  into the  underlying soil,  and  gas
generation. Depending on regulatory requirements,
the landfill may also require  a lining. Design
considerations  for  these  impacts are  discussed
below.

Mitigation of Runoff

EPA requires that surface water runoff from an
active  landfill  be  collected and disposed  of in
accordance  with NPDES requirements (WEF,
1998).   The runoff collection  system  must be
designed to contain a 25-year, 24-hour storm.

Infiltration

As water percolates through  a landfill, it  may
become contaminated as it dissolves various soluble
components of the biosolids. The resulting leachate
must  be contained  and treated  to  eliminate the
potential for groundwater pollution and/or public
health problems. Methods for controlling leachate
include implementing proper drainage, installing a
liner, allowing the leachate to attenuate naturally, or
collecting and treating the leachate. A leachate
collection system may consist of a drainage layer
(usually sand or geonet), leachate collection piping,
a sump or series of sumps, and manholes.

Gas Generation

The anaerobic decomposition of biosolids  in  a
landfill contributes to the  generation of "natural"
gas consisting  primarily of methane (45 to 55
percent) and carbon dioxide. Methane is explosive
in the atmosphere  at concentrations of 5 to 15
percent.  Either passive or active gas  collection
systems  can  be  effective  in  preventing  the
accumulation and possible migration of landfill gas.
A passive collection system consists of perforated
collection pipes and header pipes placed just below
the landfill  cap to collect and vent gas to the
atmosphere.  Active systems consist of a series of
gas wells drilled into the waste or a series  of
horizontal trenches and a blower to collect the gas.
Active gas collection  systems are used to control
odors at a site and may also be used to recover
energy from the methane.  If cost effective,  the
methane recovered  from the landfill gas may  be
used in boilers or space heaters, or in turbines to
generate electricity.  It may also be  upgraded to
pipeline-quality gas.

Landfill Liner

Another critical design consideration  is facility
lining. Three types of materials are typically used
for landfill liner  systems.   They  include low
permeability soil (clay),  geosynthetic clay  liners
(GCL), and geomembrane liners.  The Part 503
regulations  require   a  maximum  hydraulic
conductivity of IxlO"7 cm/s (2xlO"7 ft/min) for a
monofill liner (when a liner is required). The Part
258 regulations require all co-disposal landfills to
have a composite liner. The top component of the
liner must consist of  a minimum 30-mil  flexible
membrane liner, while the bottom component must
consist of at least a 60 cm (2  ft) thick layer of
compacted soil with a hydraulic conductivity of
Ix 10"7 cm/s (2x 10"7 ft/min). The flexible membrane
component must be installed in direct and uniform
contact with the compacted soil.

Both natural and synthetic liners have advantages
and disadvantages.    While synthetic  liners  are
virtually impermeable to liquids, they do not have
the self-healing characteristics  of natural liners.
Natural liners have slightly higher permeability than
synthetic liners, but are less susceptible to possible
subbase changes.

OPERATION AND MAINTENANCE

Each municipal solid  waste landfill is required to
have an operation and maintenance (O&M) plan
that  describes  its  procedures.   Monofills  are
encouraged to maintain a similar plan. Operational
considerations addressed in these plans include:

•      Hours of operation.

•      Material weighing procedures.

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•      Traffic flow and unloading procedures.

•      Cover  material excavation (or purchase),
       stockpiling, and placement.

       Maintenance procedures and schedules.

       Inclement weather operations.

•      Environmental  monitoring  and  control
       practices.

Management and reporting required under the Part
503 and Part 258 regulations include maintaining
activity, performance, and cost records, as well as
required regulatory reports.  Activity records may
include  equipment  and   personnel  accounts,
biosolids receipts, cover material quantities, etc.

Regular O&M activities at  a landfill containing
biosolids may involve the following:  providing
periodic cover for the biosolids; capping  sections
(or "cells") of the landfill   once  they  are full;
monitoring the site to ensure  that leachate from the
landfill does not contaminate groundwater;  and
closing the  landfill site when it has reached its
capacity.  These O&M activities are discussed in
more detail below.

Periodic Cover

Cover  materials are used at landfills to  manage
vectors,  control  odors,  increase   compaction,
decrease settling, and minimize wind erosion. If
the landfill site does not have sufficient available
soil, cover material  must be  obtained off-site and
transported  to the facility.  At  the end  of each
working day 15 cm (6 in) of cover is spread over
the compacted waste. An intermediate cover 30 cm
(1 ft) thick is applied when the cover material will
be exposed for more than one month but less than
six months.  If the cover material is to be exposed
for more than six  months, final cover with a
minimum thickness of 60 cm (2 ft) is required.

Cell Closure

Landfills  are  typically  developed  in phases to
minimize the area exposed to  rainfall and the rate of
leachate production. Based on the site topography
and the calculated amount of waste to be landfilled,
an area with an expected life of two to five years is
developed for each phase.  As an active cell nears
its capacity, a new cell is constructed.

Site Monitoring

Both the Part 503 and Part 258 regulations stipulate
that  landfills  shall  not contaminate an aquifer.
Most states  require groundwater  monitoring at
landfill sites. EPA has also established monitoring
requirements  for methane gas because  of the
explosive hazard. Monitoring is required during the
active  life  of the  landfill and for three years
following closure of the landfill.

Site Closure/Capping

When a landfill cell has reached capacity, a final
cap is placed to prevent infiltration of rainwater and
reduce leachate generation. The layers  of the cap,
from bottom to top,  include the following:

       Subgrade  Layer - Used to  contour the
       landfill and provide a base for construction
       of subsequent layers.

       Gas  Control Layer -  Transports gas to a
       venting system.

•      Hydraulic Barrier  - Limits infiltration of
       water to the landfilled  waste.

       Drainage Layer - Collects  and  transports
       water that percolates into the final cover.

•      Biotic Layer - Protects the hydraulic barrier
       from intrusions by animals or plants.

•      Filter Layer - Prevents the migration of
       fines from the vegetative support (surface)
       layer to the drainage layer.

       Surface Layer - May be either a soil capable
       of supporting vegetation  or  an armored
       protection layer.

The thickness and performance standards for each
layer  may  vary  depending  on  the  approving
authority.   Post closure monitoring of the cap

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should include monitoring of settlement, cover soil
integrity, grading, vegetation conditions, sediment
and erosion controls, gas controls, and security
fencing.

The Part 503 and Part 258 Regulations require the
owner/operator of a landfill to submit a closure plan
at least 180 days prior to closure of the facility. The
closure plan should describe both closure and post
closure  activities including  maintenance  of the
leachate collection system, monitoring of methane
gas production, and limiting public access to the
site, all required for three years following closure.

The final intended use of a closed landfill should be
identified during the design phase to  ensure that
appropriate decisions are made  regarding  cover
material,  grading, monitoring,  and  stormwater
management.   Typical uses for closed landfills
include athletic fields, game courts, golf courses,
playgrounds, picnic areas, and open spaces where
there is not a need for extensive tree planting.

COSTS

It is difficult to estimate the cost of landfilling
biosolids without individual program details. For
example, land acquisition costs vary from region to
region, and liners may  or may not be required.
Other factors that impact the cost of landfilling of
biosolids  include:

•      Capacity  of landfills serving the area.

•      Haul distance.

•      Method of leachate treatment and disposal.

•      Method of gas collection, disposal or reuse.

•      Post closure use.

•      Purchase and maintenance of equipment.

•      Regulatory compliance, such as preparation
       of reports, site monitoring, and biosolids
       analysis.

•      Local labor rates.
•      Importation  of cover material  if on-site
       quantity is insufficient.

In  1994,  the   municipalities  of  Las  Vegas,
Henderson,  and  the  Clark  County  Sanitation
District in Nevada were disposing all biosolids in a
privately owned and operated facility 25 miles from
the municipalities.   The total solids production of
545  wet  Mg/day  (600  wet  tons/day)  was
mechanically dewatered to a range of 10  to 33
percent solids.   The cost  for disposing of these
solids was approximately $107 wet Mg ($117 wet
ton), including transportation by a contract hauler
and landfill tipping fee.

As part of a regional biosolids management plan
developed in 1994, the municipalities evaluated the
option  of building their own biosolids monofill.
Potential sites, ranging from less than 16 km (10
mi) to  up to 80  km (50 mi) away, were selected
based  primarily  on  their  distance  from  the
municipalities.   Other site  evaluation  criteria
included  topography,  hydrology,   land   use,
availability   of  utilities,   and   other
social/environmental  concerns.   The monofill
capacity was estimated at 31 million m3 (40 million
yd3), based on  accommodating the total annual
solids production for a period of 30  years.  The
amount of land required for the monofill and space
for  solids   processing was  estimated  to  be
approximately 200 ha (500 acres).  The estimated
costfor this alternative ranged from $25.71/wetMg
($28.32/wet ton) for the closest site to $28.32/wet
Mg ($31.20/wet ton) for the most remote site.

REFERENCES

Other  Related Fact Sheets

Odor Management in Biosolids Management
EPA 832-F-00-067
September 2000

Centrifugal Dewatering/Thickening
EPA 832-F-053
September 2000

Belt Filter Press
EPA 832-F-057
September 2000

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Filter Press, Recessed Plate
EPA 832-F-00-058
September 2000

Alkaline Stabilization of Biosolids
EPA 832-F-00-052
September 2000

Other EPA  Fact  Sheets  can be found  at  the
following web address:
http://www.epa.gov/owm/mtb/mtbfact.htm

1.     Bain, R. and R. Babu,  1996. "A Regional
      Approach  to  Biosolids  Management
      Planning in  the Las  Vegas  Valley"  in
      Proceedings of 10th Annual Residuals and
      Biosolids Management Conference. Water
      Environment  Federation.   Arlington,
      Virginia.

2.     Bastian, R., 1997.   Biosolids Management
      in the United States. Water Environment
      Federation (WEF),  Arlington, Virginia.

3.     Lue-Hing,  C., D.  R.   Senz,  and  R.
      Kuchenrither,  1992. Municipal  Sewage
      Sludge  Management.    Technomic
      Publishing, Lancaster, Pennsylvania.

4.     O'Dette, R., 1996. "Determining the Most
      Cost  Effective  Option for Biosolids and
      Residuals Management." InProceedings of
      10th  Annual  Residuals  and Biosolids
      Management  Conference.      Water
      Environment  Federation,   Arlington,
      Virginia.

5.     U.S. Code of Federal Regulations, Title 40,
      Part 25 8.

6.     U.S. Code of Federal Regulations, Title 40,
      Part 503.

7.     U.S. EPA, 1978. Process Design Manual
      for Municipal  Sludge Landfills.   EPA
      625/1-78-010, EPACERI, Cincinnati, Ohio.

8.     U.S. EPA, 1979. Process Design Manual
      for Sludge Treatment and Disposal. EPA
      625/1-79-011, EPACERI, Cincinnati, Ohio.
9.     U.S.  EPA,  1985.   Estimating Sludge
      Management Costs. Washington, D.C.

10.    Water Environment  Federation  (WEF),
      1998. Manual of 'Practice No. 8, Design of
      Municipal Wastewater Treatment Plants -
      4th Ed. WEF, Arlington, Virginia.

ADDITIONAL INFORMATION

Monterey Waste Management District
William M. Merry, P.E., DEE
P.O. Box 1670
Marina,  CA 93933

Virginia Department of Environmental Quality
Hassan Vakili
629 East Main Street
Richmond, VA 23219

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

               Office of Water
             EPA832-F-03-012
                 June 2003
             For more information contact:

             Municipal Technology Branch
             U.S. EPA
             1200 Pennsylvania Ave, NW
             Mail Code 4204M
             Washington, D.C.  20460
                    * 2002 *
                    THE YEAR OF
                    CLEAN WATER
          !MTB
         Excellence in compliance through optimal technical solutions
         MUNICIPAL  TECHNOLOGY B R A ff^H

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