Unsafe sewage sludge or beneficial biosolids?: Liability, planning, and management issues regarding the land application of sewage treatment residuals

Boston College Environmental Affairs Law Review, Summer 1999 by Goldfarb, William, Krogmann, Uta

1. Pollutants

The 503 Rule sets numerical limits for ten trace elements in sewage sludge applied to land.119 In the risk assessment, allowable numerical limits in sewage sludge were calculated based on the application rate of ten dry metric tons per year for one hundred years.120 Additionally, EPA determined the ninety-ninth percentile sewage sludge concentration from the Agency's National Sewage Sludge Survey.121 EPA chose the lower of those two values as the concentration limit for each pollutant and the higher value became the ceiling concentration limit (see Table 3 of the Appendix). If the trace element concentration is below the pollutant concentration limit, no additional pollutant control requirements must be fulfilled. If the trace element concentration in the sewage sludge is above the pollutant concentration, but below the ceiling concentration, the cumulative loading to the soil is limited by the cumulative loading limit. The cumulative loading limit is the same cumulative loading as if sewage sludge complying with the pollutant concentration limit were applied for one hundred years at ten metric dry tons per year. This cumulative loading limit applies to both agricultural and nonagricultural land.122

Since EPA assumed that cumulative loading rate tracking would not be feasible for home gardens, the Agency established an annual pollutant loading rate for sewage sludge exceeding the pollutant concentration but complying with the ceiling concentration. The annual pollutant loading rate is based on a twenty-year application period instead of a 100-year application period.123

The final rule does not regulate organic contaminants such as dioxins, furans, and PCBs. However, a regulation establishing numerical limits for dioxins, furans, and coplanar PCBs in land-applied sewage sludge is expected to be promulgated by December 15, 2001.124

2. Pathogens and Vectors

The rule differentiates between Class A and Class B sewage sludges with regard to pathogen reduction. In Class A sewage sludge, pathogens have to be reduced to levels below those detectable by specific analytical methods.125 With regard to pathogens, no site or crop restrictions exist for Class A sewage sludge. For Class B sewage sludge, site and crop restrictions similar to, but more detailed than those contained in the 1989 proposal, are applicable (e.g., based on grazing animals, growing crops, and human contact). The final proposal does not include a Class C category as proposed in 1989. Class A pathogen reduction requirements are an EQ standard.126

In addition, the rule contains vector attraction reduction requirements. While vector attraction reduction options 1 through 8 reduce the vector attractiveness of the sewage sludge through stabilization, options 9 and 10 prevent vectors from coming in contact with the sewage sludge by soil incorporation or injection.127 Options 1 through 8 are part of the EQ standard.

3. Management Practices

If the sewage sludge is of EQ quality, it is exempt from further regulatory controls and may be used freely as a fertilizer or soil amendment.128 Otherwise, a number of general requirements and management practices apply to land application.129 The application rate to land should be less than the agronomic rate for nitrogen, and sewage sludge should not be applied to the land if it is likely to adversely affect a threatened or endangered species.130 Firms that make sludge commercially available are required to label or provide instructions for homeowners or landscapers who purchase non-EQ sewage sludge-derived products, and also to provide a statement that application is prohibited except in accordance with the instructions on the label.131