Spatial impact of organic matters from point sources on stream water quality

To get a better understanding of the spatial impact of organic discharges on stream water quality, a “scenario-testing” approach was proposed to examine how a change in plant treatment efficiency would affect dissolved oxygen (DO) concentration along a stream. An “upper-lower” boundary technique was applied to conduct sensitivity analysis to observe the responses of DO concentration to different DO-related parameters. The results show a non-linear discrepancy of biochemical oxygen demand (BOD) and DO concentration among different treatment scenarios, which indicates the higher the efficiency of the plant treatment, the shorter the time the stream needs to recover. The sensitivity analysis reveals that the larger the amount of the waste discharge, the more sensitive the BOD to the biological removal parameter. In addition, the DO is more sensitive to the biological removal parameter than to the reaeration parameter.