Soil Cation Exchange
Capacity (meq/100g)

Metal 45 5to15 315
Lead 500 1,000 2,000
Zine 250 500 1,000
Copper 125 250 500
Nickel 125 250 500
Cadmium 5 10 20

Table 2 Maximum Amount of Metal
(Ib/acre, cumulative) Suggested for
Application to Agricultural Soils

Addressing Project Concerns

Land application of sludge is often opposed by local
groups because of concerns over potential odor
generation and risks to human health and the
environment. These concerns can be addressed by
taking the following precautions:

Use sludges that are well stabilized and that have
relatively low concentrations of critical
contaminants.

© Apply sludges at rates which meet crop nitrogen
or phosphorus requirements.

® Maintain soil pH near neutral.

Provide adequate monitoring of sludge quality
and soils.

For high application rate disposal practices, or
when sludges contain relatively high concentrations
of critical contaminants and/or sludge stabilization is
limited, one or more of the following additional
precautions can be helpful:

© Select remote application sites or limit access to
the sites.

@ Apply sludge to areas used for the production of
animal feed or non-food chain crops.

© If needed, provide adequate monitoring of
vegetation, surface and ground water.

Current Use

Land application of sludge is currently practiced
throughout the country with municipal sludges and
many different types of industrial wastes. For
biodegradable wastes applied at proper loading

it
Background
It Soil pH is
Soil Background Above 6.5 or
Cation Soil Maintained
Exchange pH is at 6.5

Capacity Below6.5 by Liming
(meq/100g) (Ib Cd/acre) (Ib Cd/acre)

25 5 5
510 15 5 10
M15 5 20

Table 3 Maximum Amount of Cadmium
(cumulative) Suggested for
Application to Agricultural Soils

rates to suitable sites, the process represents a
very efficient and cost-effective sludge treatment
and disposal alternative. It is currently estimated
that over 40% of the municipal sludge produced in
this country is eventually applied to the land in one
form or another.

Costs

As with most sludge management processes, the
construction and operating costs are tod
site-specific to generalize. Operating costs range
from as low as $40/dry ton to over $210/dry ton
depending on specific conditions and what is
included in the cost estimates. The following factors
are typically found to have a major influence on the
cost-effectiveness of sludge treatment by land
application:

The purchase or lease price of the land, if
necessary.

@ The transport distance from the point of sludge
generation (sewage treatment plant) to the land
application site.

© Climatic constraints (excessively wet or cold
weather) which will substantially limit the number
of favorable application days and create a need
for storage facilities or other methods of sludge
utilization and disposal at certain times of the
year.

On projects where the above conditions are
moderate to favorable, land application of sludge
will usually be competitive with other sludge
utilization and disposal alternatives.

Summary

Land application of sludge is a process which is not
equipment oriented or energy intensive. Because of
this, both capital and operating costs often compare
favorably against other alternatives for sludge
utilization and disposal.

In order for land application of sludge to be used
effectively, suitable application sites must be
available. The soils and geology of a potential site
must be assessed, including an on-site evaluation,
prior to judging its suitability. Other factors
influencing site suitability will be the availability and
cost, if any, of the land, the distance from the
sewage treatment plant to the site, and the
operating restrictions imposed by local climatic
conditions.

Land application of sludge is a widely used process
which in many cases offers a practical and
cost-effective disposal alternative. To be successful,
however, thorough planning is required. A good
public education and participation program can
usually go a long way towards helping to assure
the success of a land application project.

Photos courtesy of Ag-Chem Equipment Co.

For additional information contact:

EPA-OWPO(WH-547) EPA-MERL (489)
401 M Street, SW 26 West St. Ciair Steet
Washington, DC 20460 Cincinnati, OH 45268,
(202)982-7370/7369 (619684-7614

EPA 1 EPA Region 6

John F. Kennedy Federal Building 1201 Eim Street

Boston, MA 02203 Dallas, TX 75270

EPA Region 2 EPA Region 7

26 Federal Plaza 324 East 11th Street
New York, NY 10278 Kansas City, MO 64106
EPA Region 3 EPA Region 8

6th & Walnut Streets 1860 Lincoin Street
Philadelphia, PA 19106 Denver, CO 80203

EPA Region 4 EPA Region 9

345 Couriand Street, NE 215 Fremont Street
‘Atta, GA 30308 San Francisco, CA 94105
EPA Region 5 EPA Region 10

220 South Dearbomn Street 1200 6th Avenue
Chicago, IL 60604 Seattle, WA 98101

United States September
Environmental Protection 1983
‘Agency

SEPA A Practical
Technology

Land 832R83108
Application
of Sludge

A Viable
Alternative



Land Application of Sludge - A Viable Alternative

Needed: Cost-Effective Alternatives

As we provide increased wastewater treatment, we
generally remove increased quantities of solids from
the wastewater. Handling, treating, and ultimately
disposing of these solids (sludge) in an
environmentally acceptable, yet cost-effective,
manner is often even more complex than the
wastewater treatment process itself.

Many of today’s traditionally accepted methods of
sludge treatment and disposal are equipment
oriented and/or energy intensive. Although these
processes are reliable alternatives, they can also
result in high capital and operating costs. Needed
are new approaches which encourage the
development of innovative concepts and alternative
processes which can favorably compete with
conventional options. Sludge utilization and disposal
by land application is one such process. Although
not a new idea, it offers a practical alternative.

The potential benefits from recycling the organic
matter and nutrient resources in municipal sewage
sludge through various land application practices
have been well demonstrated and have led to an
increased use of these practices in many parts of
the country. Not only can land application help
municipalities by serving as a cost-effective sludge
disposal technique, it can also serve the farmer or
other land owner by improving soil characteristics,
reducing fertilizer costs, and increasing productivity.

The possible presence of pathogens, heavy metals
and toxic organics at varying concentrations in
different sludges has led EPA and many state
regulatory agencies to develop guidelines and
regulations. Adherence to the recommendations
and requirements that are issued by these agencies
should assure both safe and effective sludge
utilization. By following carefully planned
procedures for dispending the sludge at
predetermined application rates and using good
management techniques, land application projects
can be implemented successfully while avoiding
potential problems.

Process Description

Land application of sludge is the controlled
application of sludge to a soil. The process is used
primarily for the ultimate disposal or recycle of

sludge. However, the process also provides
additional sludge treatment, as well as disposal in a
single operation. Sludge application can be used
effectively in agriculture, forestry, and land
reclamation. Common to all sludge application
systems is the need to provide stabilization and
disinfection of the sludge prior to land application.
In some cases, the sludge may be stabilized as
part of the wastewater treatment system (e.g.
aerated lagoons, extended aeration), and the solids
need little or no further treatment prior to being
applied to the land. In other cases where the
sludge is much less stable (e.g., conventional
activated sludge), a separate digestion or other
stabilization process (e.g., composting, heat
treatment, lime stabilization, long term lagooning) is
normally required.

Sludge can be applied to the land in many forms
and by many methods. It can be applied directly in
liquid form, as a dewatered cake, or as composted
or dried material. The method of application will
vary according to the nature of the sludge, the type
of terrain, the vegetation on the site, and the
ultimate sludge use. Figures 1 and 2 show two
techniques for the application of liquid sludge, while
Figure 3 shows a method of applying dewatered
sludge.

Site Suitability

If proper steps are taken in designing the system,
very few sites are totally unacceptable for land
application of municipal sludge. However, there are

Figure 2 Subsurface Injection of Liquid Sludge

a number of site-specific factors which should be
assessed adequately prior to determining whether a
particular site can be used effectively for land
application. Table 1 lists major site conditions which
should be considered. Since many suitable sites
will not be ideal, the planner must carefully consider
such factors when choosing actual application sites
and designing projects.

Loading Rate Determination

Once a suitable application site has been selected
and the process objectives defined, proper sludge
loading rates are determined. This process often
involves characterizing the waste for a number of
constituents. The following constituents are
generally of most concern for municipal sludges:
pathogens, phosphorus, nitrogen, cadmium, copper,
nickel, lead, and zinc. When sludge is applied at
rates to meet the nitrogen requirements of the

© Soil type

© Site susceptibility to flooding

© Slope

© Depth to seasonal ground water table

© Permeability of the most restrictive soil layer
© Cropping patterns and vegetative cover

© Nutrient and organic matter content

Table 1 Major Sité Conditions for
Land Application of Sludge

Figure 3 Surface Application of Dewatered Sludge

crops being grown, nitrogen losses in excess of
those expected from commercial fertilizer use
should not be expected.

Regarding heavy metals, the useful life of land
application sites can usually be based on the
cumulative amounts of the five metals listed above.
The recommended limits shown in Tables 2 and 3
should not interfere with crop growth or use of the
crops at any future time, while serving to protect
human and animal health. Of the metals shown in
Table 2, EPA currently regulates only cadmium
applications to agricultural soils. However, agency
guidance has been issued pertaining to
recommended cumulative limits for the other metals
shown in the table. The cadmium limit is based on
the protection of food chain crops, and is
considered by many to be very conservative if used
for non-food chain crops. Specific federal, state and
local requirements have been issued which restrict
the application rates of some sludge constituents
such as cadmium and PCBs.

After the allowable loading rate of each constituent
has been calculated, the actual sludge loading rate
is based on the most limiting constituent of those
being considered. Frequently, the most limiting rate
is dictated by the nitrogen (or alternatively the
phosphorus) loading to meet crop needs. Higher
loading rates than those calculated above can be
used if: (1) non-food chain vegetation is used; (2)
the site is well monitored; (3) required state and
local regulatory approvals are granted.