NYC Department of Environmental Protection Plans for Treated Sludge Reuse

Dec. 16, 2011

Cost-effective program will replace former contract

New York City's Environmental Protection Commissioner Carter Strickland announced the selection of WeCare Organics in response to a request for proposals to transport, process and market biosolids for beneficial reuse.

The city's Department of Environmental Protection's (DEP) 14 wastewater treatment plants handle an average of 1.3 billion gal of wastewater every day, which generate approximately 1,200 tons per day of solid byproducts that are also known as biosolids or treated sludge. This proposed contract will replace a contract with the New York Organic Fertilizer Company (NYOFCo) that was terminated in 2010 due to its increasing costs in processing treated sludge for use as fertilizer at a facility in Hunts Point, N.Y.

Under the new proposed contract, WeCare Organics will bring up to 400 tons per day of biosolids to its processing site in rural eastern Pennsylvania where it will be stabilized with lime and made into a product suitable for beneficial reuse. WeCare will use the organic material for mine reclamation projects or sell it as compost to garden centers, nurseries and landscape supply companies. Once approved, the new five-year contract will start in spring 2012 at a cost of approximately $56 million.

Sewage sludge is the bulk of the residual material removed during the wastewater treatment process. Wastewater treatment plants use physical, chemical and biological processes to remove on average more than 90% of the organic material in sewage.

Raw sludge is first digested in oxygen-free tanks where it is heated and mixed for several days. This digestion process stabilizes the sludge by converting much of the organic material into water, carbon dioxide and methane gas. The digested sludge is what is then transported by pipeline or sludge vessel to dewatering facilities where centrifuges remove much of the water. This final treated sludge, also known as biosolids, is treated to remove nearly all of the pathogens that can be found in raw sludge.

Source: New York City Department of Environmental Protection

Image courtesy Institute of Chemical Research of Catalonia (ICIQ).
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