Impacts of WWTP Performance Enhancements and Major Facility Upgrades on the Water Quality of Hypereutrophic Onondaga Lake, NY

The water quality of Onondaga Lake, a 12-km2, dimictic, water body located in central New York, has been compromised by a 100-year history of municipal and industrial pollution. The Syracuse Metropolitan Wastewater Treatment Plant (Metro), an 85 MGD tertiary treatment facility serving the City of Syracuse and surrounding area, discharges to the lake and accounts for 20% of its annual average inflow, over 80% of the annual ammonia loadings, and between 40% and 50% of the annual total phosphorus loadings. Contravention of state water quality standards for dissolved oxygen (DO), ammonia, nitrite, and bacteria led to the development of a Municipal Compliance Plan and Amended Consent Judgment (ACJ) that required Metro treatment plant upgrades and abatement of combined sewer overflow discharges to the lake. The upgrades to Metro have included: 1) a complete upgrade to the plant's aeration system to facilitate nitrification (1998); 2) construction of an advanced tertiary, biologically active filter, for ammonia removal (2003); and 3) construction of an advanced high rate flocculation and filtration system for the removal of phosphorus (2004). These treatment facility improvements have had an impact on the lake's water quality as measured by the ACJ required ambient monitoring program (AMP) for the lake. This paper summarizes the initial changes in receiving water quality that may be attributable to the Metro treatment plant improvements.