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Biosolids Management Overview
The City of Philadelphia Water Department developed during the mid-1970s alternatives to the ocean disposal of biosolids. This development was part of a comprehensive agreement with the USEPA for the upgrade of the City's three regional wastewater plants and the establishment of land-based recycling programs.
The Water Department ended ocean disposal in 1980, and in 1984 selected composting as its principal mode of biosolids processing. In 1988, the Water Department opened its Sludge Processing and Distribution Center, since renamed the Biosolids Recycling Center (BRC). This is a regional facility for the dewatering and processing of the biosolids collected from the three wastewater plants, which have a combined service population of 2.3 million people.
Philadelphia has operated a diversified program for biosolids disposition, with a strong emphasis on employing the soil enrichment properties of its products. The products meet federal and state standards for stability and for allowable contaminant levels. Approximately 65 percent of Philadelphia's biosolids have been put to recycling programs since 1988. The programs for disposition of biosolids include:
The program for biosolids processing and disposition has undergone several changes since it was first started in 1980. One important change is the greatly reduced quantity of cake arising from improvements made in 1993 and then again in 2002, to centrifuge denaturing equipment. Cake production from the centrifuges decreased from 330,000 tons in 1992 to 234,000 in 1997, and currently average 195,000 tons. The average solids content in the biosolids cake increased from 17% to 26% (in 1997) and now averages 30% total solids. Secondly, the BRC is currently producing two, as opposed to four, products: cake and screened compost. In response to competitive landfill prices, approximately 30 % of biosolids are directly landfilled. Also, reclamation and agricultural utilization programs have been shifted away from mine mix and into biosolids cake for direct utilization. Unscreened compost is no longer being put to recycling purposes, but instead all compost is being screened to supply product for the commercial markets in suburban locations and to satisfy the demand for compost at in-city giveaway centers.
The Biosolids Recycling Center is located in the southwestern section of Philadelphia, adjoining the Southwest Water Pollution Control Plant and the Philadelphia International Airport. The BRC has approximately 130 municipal employees, including operators, trades people, laborers and engineers. At the approximate cost of $250 per dry ton for dewatering, processing and utilization, Philadelphia's biosolids management program is among the lower cost programs operated by major cities in the United States.
In recognition of Philadelphia's successful and cost-effective biosolids program, the US Environmental Protection Agency awarded the Philadelphia Water Department the 1995 Biosolids Beneficial Use Award and the 1999 Excellence Award for Biosolids Utilization.
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