RISK EQUIVALENT SEASONAL DISCHARGE PROGRAMS FOR MULTIDISCHARGER STREAMS

Water quality management programs that allow different waste discharge rates during different seasons of the year are an innovative approach for reducing the cost of waste treatment. This paper presents an approach for designing such seasonal waste discharge programs for river basins with several dischargers and illustrates it for the control of biochemical oxygen demand, BOD. By this approach, the risk of water quality violation is defined as the probability of incurring one or more water quality violations in any given year, and the seasonal waste effluent rates of the dischargers are designed to maintain a specified level of risk while minimizing the total waste treatment effort of the dischargers. Two seasonal waste discharge programs are proposed as surrogates for rriinimizing waste treatment effort, the minimum average uniform treatment program and the maximum total discharge program. Simulations of these programs suggest that either seasonal discharge program would significantly reduce waste treatment costs relative to a nonseasonal program. Furthermore, comparison of costs of seasonal waste discharge programs indicates that for the example river basin, a seasonal uniform treatment program may be implemented that is potentially more acceptable to the dischargers and is less costly than a seasonal maximum total discharge program. © ASCE. © ASCE.