Accessing Assimilative Capacity through a Dual Discharge Approach

Abstract

The historical development of environmental stressors in the watershed of Onondaga Lake (N.Y.) and the adjoining Seneca River is outlined as a prelude to the presentation of a novel approach for accessing assimilative capacity in this water quality-limited system. Proposed efforts to reclaim lost uses in the lake through heroic treatment at a major metropolitan wastewater treatment plant with continued discharge to the lake have been called into question. One option, diversion of the treatment plant effluent to the Seneca River, is complicated by phenomena impacting receiving water oxygen resources. A dual discharge strategy, which takes advantage of seasonal variations in assimilative capacity and the differing response times of the lake–river systems, is proposed as an alternative. In this approach, the effluent is routed to the river except when oxygen standards may be compromised, in which case all or part of the effluent is routed to the lake. Mathematical models demonstrate the feasibility of this option to meet water quality goals for both the lake (phosphorus) and the river (oxygen).