Implications of industrial loads for ammonia pollution in an urban lake

The recent history of loading of total ammonia (T-NH3) and organic nitrogen (N) from a pharmaceutical manufacturing facility to a municipal treatment plant (Metro) in Syracuse, New York, and the discharge of these constituent s from Metro to N-polluted Onondaga Lake is documented. Further, the benefi t of the implementation of pretreatment at the pharmaceutical plant, and th e effect of an upset event at this treatment facility on loading to Metro a nd the lake and in-lake concentrations are also documented. Models are used as analytical tools to couple loading and in-lake concentrations, to delin eate the role that this pharmaceutical facility has played in the lake's am monia pollution problem, and to evaluate the potential implications of futu re pretreatment upset events for the success of a rehabilitation program th at is underway for the lake. The responsiveness of the lake to reductions i n external loading is established by the lower T-NH3 concentration observed in the upper waters of the lake in the spring of 1999. Model analysis demo nstrates this reduction was primarily (similar to 75%) because of the decre ase in loading from the pharmaceutical facility achieved by pretreatment. A n abrupt increase in loading in May 1999 associated with an upset event at the pretreatment facility caused a corresponding increase in the T-NH, conc entration of the lake of approximately 0.5 mg N/L. Model projections demons trate that the load from the pharmaceutical plant before construction of th e pretreatment facility exacerbated the lake's ammonia problems by increasi ng the occurrence and margin of violations of the toxicity standard. Contin ued upset events at the pretreatment plant could compromise the lake rehabi litation program.