Project Experience

Project Scope

Contract NR-38 is the main contract for the North River WWTP Cogeneration and Electrification Project to generate electrical power and heat for on-site use through the utilization of digester gas and natural gas. Work includes removal of 5 main sewage pump engines and 5 process air blowers and engines and replacement of the pump engines with motor drives; installation of a 6th motor-driven main sewage pump; and installation of 5 new gas engine generator units, and removal of 2 existing emergency generators. 

• The majority of the plant is comprised of an above-grade, cast-in-place concrete structure supported by caissons driven into the river. Treatment tanks are rectangular cast-in place concrete facilities for the liquid train and circular cast-in-place concrete facilities for the digesters. The footprint of the plant is covered with a concrete deck at Level +58, which supports Riverbank State Park. 
• The existing engines that drive the main sewage pumps will be replaced with electric motors, and the existing engines that drive the process air blowers will be replaced by high-speed turbo blowers driven with electric motors. Improvements to the electrical infrastructure and other related equipment will tie in enhanced electrical service with the engine generators and allow the plant to operate based on digester gas, natural gas, electricity, or a combination of any of these energy sources. Thermal recovery systems will be upgraded to utilize the heat produced by the engine generators, distributing it throughout the North River WWTP to support treatment processes and domestic use. Digester improvements are included with this project to increase digester gas production, repair non-functioning systems, and provide gas conditioning prior to use in the cogenerating engines. Oxidation catalysts are included with the engines for exhaust treatment to meet air permitting requirements. In order to expedite the work described above, several smaller advance projects are being designed and constructed separately including: 
• Digester mixing and temperature improvements, and sludge thickener pumping improvements (NR-39). 
• Repair of the digester gas holder and associated gas piping (NR-42). 
• Demolition of the fuel tanks and Laboratory to make room for new equipment (NR-43). 
• Separation of the electrical service for the Riverbank State Park (NR-44). 
• Installation of new process air blowers (NR-46) 
• Structures and equipment improvements include the following: 
• Installation of five 3 Megawatt continuous duty, spark ignited, reciprocating gas engine generators (cogeneration units) and to operate in parallel with the Electric Utility (Con Edison).