Retrospective Analyses of Inputs of Municipal Wastewater Effluent and Coupled Impacts on an Urban Lake

摘要

A retrospective review and analysis are presented of the evolution of treatment, point of discharge considerations, and constituent loading from the Metropolitan Syracuse Wastewater Treatment Plant (Metro), and the coupled water quality effects on the receiving urban lake (Onondaga Lake, New York) from the early 1970s to 2010. The analysis is based on long-term monitoring of the discharge, Onondaga Lake, and a nearby river system considered as a potential alternate to receive the effluent. The Metro discharge is extraordinarily large relative to the lake's hydrologic budget, representing approximately 25% of the total inflow, greater than for any other lake in the United States. The large loads of nitrogen and phosphorus received from the facility resulted in severe water quality effects in the lake during the early portion of record, including (1) violations of standards to protect against toxic effects of ammonia and nitrite, (2) violations of the water clarity standard for swimming safety, (3) exceedances of a limit for the summer average concentration of total phosphorus in the upper waters, and (4) lakewide violations of the oxygen standard during fall turnover. The effects of Metro were compounded by effects of discharges from soda ash/chlor-alkali and pharmaceutical manufacturing facilities. The sedimentary record of the lake indicates that even greater levels of cultural eutrophication prevailed before the monitoring commenced. Dramatic improvements in the water quality of the lake were achieved in recent years by implementing advanced treatment technologies. Exceedances of receiving water limits in the lake were eliminated, with the exception of the total phosphorus limit. A zebra mussel invasion compromised the oxygen resources and assimilative capacity of the nearby river for more than 15 years. This eliminated an option, previously supported by managers, of full diversion of the Metro effluent to the river.