Surface disposal is placing biosolids on an area of land for final disposal. Examples of surface disposal practices include:
• Sludge-only landfills (monofills)
• Sludge piles or mounds
• Sludge lagoon used for final disposal
• Surface application sites where biosolids are applied at rates in excess of the agronomic rate
Surface disposal of biosolids differs from land application in that it principally uses the land for final disposal instead of using the biosolids to enhance the productivity of the land.
The Part 503 rule allows for storage of biosolids up to two years without any restrictions or control. However, biosolids remaining on the land for longer than two years is considered final disposal.
If a sludge disposal site is equipped with a liner and a leachate collection system, there are no pollutant limits because the liner retards the movement of pollutants in sludge into the groundwater. Sludge placed in an active unit without a liner and a leachate collection system must meet pollutant limits for arsenic, chromium, and nickel. The limits are listed in Table 1.4.
Disposal of sewage sludge in a municipal solids waste landfill (MSWLF) is not regulated by Part 503 other than requiring compliance with 40 CFR Part 258. To meet Part 258 requirements, the preparer must ensure that the sludge is nonhazardous and does not contain free liquid as defined by the paint filter test. If sludge is used as an alternative cover material, it may have to be treated for vector attraction reduction prior to its use.
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