23 october 2018


improves health of the Long Island Sound

The New Rochelle Wastewater Treatment Plant, located in Westchester County, New York, discharges to the Long Island Sound. It serves a population base of 65,000 people and is permitted to treat average flows of up to 20.6 MGD. Operating with primary clarification and pure oxygen-based activated sludge treatment since a 1979 upgrade, the plant used to remove only BOD and TSS from the wastewater.
It has long been known that nitrogen discharges into the Long Island Sound are a key factor in its water quality. New SPDES limits issued in 2005 and a negotiated Order-of Consent would require an upgrade to the New Rochelle WWTP to meet a total nitrogen (TN) discharge limit of 4.0 mg/l or less on average at design flow. In addition, tighter restrictions on CBOD and TSS would be included in the new permit.
Land availability in New York is scarce, so the solution needed to fit on the existing site. Dozens of technologies were evaluated by Savin Engineers, PC, including pilot-scale testing, to determine the preferred solution. At the conclusion of the evaluation phase, a competitive life-cycle based procurement was bid and the Veolia BIOSTYR® Biologically Active Filter (BAF) technology was selected as the preferred alternative.

The solution
BIOSTYR® is a high-rate biological system that offers full treatment capabilities for BOD, TN and TSS removal in a single process, in 10% of the footprint of other technologies. The system utilizes multiple treatment cells operating in parallel to biologically treat and simultaneously filter the wastewater, producing an effluent free of contaminants and solids.
Biological growth occurs on a fixed bed of innovative BIOSTYRENE™ media, which is contained within each cell and not exposed to the atmosphere. Flow enters at the bottom of each cell and clean effluent collects at the top of each cell. This makes for a very clean installation that fits well into facilities with nearby communities such as urban, densely populated areas.

Process description
To meet the new SPDES permit requirements of this facility, Veolia designed a BIOSTYR® system containing two distinct stages of operation. The first stage is fully aerobic and targets complete nitrification to convert incoming ammonia into nitrate. The second stage is anoxic in the lower portion of the BIOSTYRENE™ biological filter bed to target denitrification of the incoming nitrates.
The system was designed to meet future flow needs of up to 31 MGD average and 61.5 MGD peak with guaranteed effluent nitrogen performance. In addition to the BIOSTYR® system, Veolia provided an upgrade to the existing pure-oxygen activated sludge system to improve CBOD removal and produce a more stable influent to the BIOSTYR® process.
The New Rochelle WWTP has been operational since late 2014 and has been a tremendous success, reducing the plant TN discharge from 2,000 lb/day in 2014 to 200 lb/day in 2015. Summer and winter performance tests were completed in 2015 to fully demonstrate the system’s capabilities, and exceptional nitrogen removal has continued throughout 2016. Thus, the BIOSTYR® system is allowing Westchester County to improve the health of the Long Island Sound.