Gloversville-Johnstown Joint Wastewater Treatment Facility Co-digestion Leads to a Sustainable Future

The Gloversville-Johnstown Joint Wastewater Treatment Facility (WWTF) serves the Cities of Gloversville and Johnstown in upstate New York. Like many areas of upstate New York, traditional industries opted to move operations overseas in an effort to reduce costs associated with labor, environmental regulations and taxes; leaving the communities with excess wastewater treatment capacity and unpaid debt service.In 2006, Fulton County Economic Development Corporation (EDC) was successful in attracting FAGE USA, Inc. (FAGE) to invest in sitting a new yogurt plant in the Johnstown Industrial Park located adjacent to the wastewater treatment facility. The facility had experience treating high strength wastes as several small cheese plants hauled whey for treatment in the facility's anaerobic digesters. Wanting to capitalize on obtaining a new industrial user to help stabilize rates and increase job opportunities in the communities, the Gloversville-Johnstown Joint Wastewater Treatment Facility retained Malcolm Pirnie, the Water Division of ARCADIS, to plan, permit and design improvements to accept the additional high strength wastes.Pirnie/ARCADIS prepared a feasibility study to develop solutions to treat the additional flows and loads through the existing two stage mesophilic anaerobic digesters and the existing conventional activated sludge process. A dedicated high strength wastewater sewer and whey forcemain were constructed from the adjacent industrial park to the wastewater treatment facility. Whey is pumped to the facility from industry to an on-site equalization tank and subsequently fed directly to the primary digester. High strength wastewater is treated in a new dissolved air floatation thickener (DAFT) where 60 percent of the biological oxygen demand (BOD) load is removed prior to treatment in the activated sludge process. The DAFT overflow, consisting primarily of fats, oils and grease (FOG), is then fed to the primary digester. The existing gravity thickeners were converted to sludge holding tanks to comingle primary and secondary sludge to be thickened by gravity belt thickeners (GBTs). In order to increase the solids residence time (SRT) of the primary digester an innovative recuperative thickening loop was added to the primary digester to return partially digested sludge to the GBTs in order to decouple the SRT from the hydraulic residence time providing more than 15 days of SRT.The increased loads to the digester and improved co-digestion led to significantly increased gas production and volatile solids destruction. As part of the upgrade the two existing 150 KW engine generators were replaced with two 350 KW engine generators. Waste heat is recovered from the engine generators to heat the digesters and the digester building. The facility is producing about 90 percent of its power requirements on site with the two new engine generators and has the ability to produce all of its electrical power requirements.