&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
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