Page 261 - Materials Chemistry, Second Edition

CAT3525_C08.qxd 1/29/2005 10:03 AM Page 232
232 Waste Management Practices: Municipal, Hazardous, and Industrial
C:N ratio is maintained within the desired range, little excess N will leach from the pile since this
is rapidly utilized by microorganisms for growth (U.S. EPA, 1994).
The installation of a concrete pad for a compost base is valuable for collection and control of
any leachate produced. A simple method to handle leachate is to collect all liquids from the pad and
reintroduce them into the pile. Such leachate recycling should not be conducted once the compost
pile has completed the high-temperature phase, as any harmful microorganisms that were inacti-
vated by the high heat can be reintroduced with the leachate (CC, 1991). Leachate can also be trans-
ported to a municipal wastewater treatment plant. If the contaminant levels in the leachate are too
high, an on-site wastewater pretreatment system could be installed (U.S. EPA, 1994).
Measures to control leachate include:

● Diverting from the compost curing and storage areas to a leachate holding area
● Installing liner systems made of low-permeability soils such as clay or synthetic materials
● Using drain pipes to collect the leachate for treatment
● Curing and storing compost indoors to eliminate infiltration of leachate into the ground
(Wirth, 1989)

8.8.6 RUNOFF
Runoff is caused by heavy precipitation, by components within the feedstock, and by practices at the
facility that use water. For example, the water used to wash trucks can contribute to runoff. Polluted
water can be spilled in the tipping area of composting facilities when packer trucks from restaurants,
grocery stores, and food processors are emptied. Operations that compost MSW and yard waste can
produce runoff containing measurable quantities of inorganic nutrients and other pollutants.
For both yard waste and MSW composting facilities, water that has come into contact with
incoming raw materials, partially processed materials, or compost should not be allowed to run off
the site. Figure 8.10 shows several options for diverting water from composting piles and for con-
taining runoff. Provisions for isolating, collecting, treating, or disposing of water that has come in
contact with the composting feedstock can include (U.S. EPA, 1994):

● Maintaining sealed paving materials in all areas
● Grading facility areas (1 to 2% grade) where contaminated water will be collected
● Installing containment barriers to prevent contaminated water from contacting adjacent
land and waterways

Runoff diversion
Dike Dike channel

Compacted sand
or gravel pad Composting pad cross section
(6 in. minimum)

Runoff diversion Pad runoff collection
channel Pad length and window/pile length channel
2−4% slope
Dike
Possible holding pond
Dike
or infiltration area
View through the composting pad length

FIGURE 8.10 Methods to divert runoff water from a compost pile for eventual collection. (With kind permis-
sion of Rynk, R., Ed., On-Farm Composting Handbook, NRAES-54, 1992.)