Innovative Solutions to Meet Permit Limits
The City of Kingston, NY received a renewed State Pollutant Discharge Elimination System (SPDES) permit which included effluent ammonia limits requiring upgrades to the existing Wastewater Treatment Plant (WWTP) to treat wastewater to a higher level of quality. While the City had completed preliminary analysis and engineering reports which indicated extensive and energy-intensive WWTP upgrades were required, the City determined that additional evaluation was necessary and asked our consultant team for a fresh perspective.
We collaborated with the City to provide a plan to the New York State Department of Environmental Conservation – Region 3 (NYSDEC) which outlined the proposed steps forward to achieve SPDES permit compliance. Project partners, including Tighe & Bond and Schnabel Engineering (watershed consultant), collaborated with NYSDEC to determine how mixing and dilution impacted the WWTP effluent in Rondout Creek.
Analysis found that the dilution factor had not been updated since the 1960s; redoing the water quality analysis in the Rondout allowed the project team to design a deepened outfall structure that worked with the current state of the river. Through detailed analysis and effective communication, the consultant team was able to negotiate increased permit limits with NYSDEC through improvements to the WWTP outfall and upgrades to the existing aeration system.
The upgrades included implementing a nitrification process that was specialized for the site needs of the Kingston WWTP. The Kingston WWTP utilizes a modified Ludzack-Ettinger process using a “swing zone” which can operate as either anoxic or aerobic, depending on season. The use of a swing zone reduces the plant’s energy costs, while also allowing the plant to operate during wet weather events while in step-feed mode, which is critical at a plant receiving combined sewage.
During wet weather events, the aeration tanks will go into step-feed or contact stabilization mode and store a portion of the solids in the swing zone to limit the loading to the secondary clarifiers. The step-feed mode temporarily converts the swing zone into a stabilization tank, allowing the clarifier to operate within capacity for high flow wet weather events.
Due to the location and potential environmental impacts, substantial coordination with permitting agencies was required for the outfall modifications. Tighe & Bond began early communication and collaboration with the US Army Corp of Engineers, NYSDEC, NYSDOS, and NYSOGS.
The success of the project relied on communication between the City, consultant team, state authorities, and Kingston residents. The City and consultant team were active in engaging residents and messaging the cost savings and water quality benefits to the project approach. In addition to its import impact on receiving water quality, the outfall project had significant public impact. It removed the exposed plant outfall in the bustling riverfront area, and its design facilitates construction of a future segment of the Empire State Trail which will pass over the outfall.
The innovative approach to design led to immediate and long-term cost savings throughout the project, saving an estimated $8 million in capital and operating costs over the next 25 years. Now fully constructed, the improvements have enabled the Kingston WWTP to meet its permit limits for summer and winter performance.
Services Snapshot
Tighe & Bond’s engineers provided design, permitting, and construction observation services for this project. The upgrades to the WWTP resulted in lowered levels of ammonia in effluent, ensuring good quality of water in the area surrounding the outfall in Rondout Creek.
