a Assistant Manager of Technical Services, Water Pollution Control Federation, Washington, D. C., U.S.A.
b Professor, Department of Biological Sciences, University of Delaware, Newark, Delaware, U.S.A.
Abstract:
The Murderkill River is a partially tidal body of water with summer-time 50-percentile freshwater flows ranging from 17.9 to 27.6ft3s?1 (0.5 to 0.77m3s?1) at a point coincident with the effluent discharge from the Kent County Regional Wastewater Treatment Plant (start-up late 1972). Chloride concentrations were determined over six summers to characterize river conditions prior to start-up of the 10-million gal day?1 (37.850 m3 day?1) (design) plant. Use of a one-dimensional steadystate model for a conservative substance shows that chloride values would be reduced by up to 20% at low water slack (LWS) periods for wastewater flows of 10 million gal day?1 (37,850 m3 day?1). The LWS chloride concentrations in the area of oyster production would be reduced to 3–6 ppt (5.9–10.8 ppt salinity) for wastewater loadings greater than 10 million gal day?1 (37,850 m3 day?1) . It is suggested that chloride additions in the treatment plant effluent be implemented to maintain minimum summertime low-water-slack levels of 5.6 ppt chloride (10 ppt salinity), consistent with a proper environment for oyster development.