New York City's Wastewater Treatment System
Beneficial Use of Biosolids
Since 1938, sewage sludge had been treated as a waste byproduct and removed from New York City treatment plants by barge and disposed of at sea. In 1988, Congress passed the Ocean Dumping Ban Act, forbidding ocean disposal of sewage sludge by June 30, 1992. DEP devised a three-pronged approach — an immediate, an interim, and a longterm program — to administer the 1,200 wet tons of sludge produced each day. The immediate program resulted in a final design of eight dewatering facilities with construction to begin in March 1991. By December 1991 the first facility went on line. The other seven were finished and became operational by June 1992 at a cost of $670 million. Today, the remaining six plants not served by onsite dewatering facilities transport their sludge for dewatering either through force mains or sludge vessels.
For the interim program, three contractors were hired through five-year contracts at a cost of $100 million per year to provide land-based biosolids management. The contractors were responsible for the processing, production and shipment of biosolids as high-quality soil amendments and the application thereof. DEP currently has contracts with four companies to haul biosolids at a total cost of $37M annually. Two of the original eight dewatering facilities were retired after operational improvements were made at the remaining facilities. After dewatering, the sludge, now known as biosolids, can be beneficially used as a valuable resource because of its high nutrient and organic contents. Biosolids and biosolids products are used as fertilizers or soil conditioners which are spread on parkland, farmland, lawns, golf courses and cemeteries. Biosolids can also be used in mine reclamation, to cover inactive landfills or as a daily cover for active ones.