Temporal Variation of BOD_5 in Combined Sewer Systems during Storm Events

摘要

A sewer system is an essential part of the urban wastewater system. Within this work, the relationship between COD and BOD_5 in combined sewer flows was established first based on the data from relevant literature. The BOD_5/COD relationship is BOD_5 = 0.3566 COD-1.9977 (R~2 = 0.71). The BOD_5 concentrations are shown to comprise a linear rising limb from the ambient pollution concentration in the dry weather flow to a peak concentration, followed by a recession limb during storm events at both Clayton-Le-Moors and Great-Harwood catchments. The peak BOD_5 concentrations are influenced by rainfall parameters, such as antecedent dry weather period, storm duration time and total rainfall in different order of importance at the two catchments, but site specific variables play an important role as well. The times to peak BOD_5 concentration are 36 and 39 minutes at Clayton-Le-Moors and Great-Harwood respectively, which are determined mainly by site specifications. Exponential function, BOD_5(t) = Ae~(-kt), was established to describe decay of BOD_5 after peak concentration. Sensitivity analysis and verification of the model showed that the model can applied to predict temporal variation of BOD_5concentrations during storm events with a first flush of pollutants.