Abstract: With dibutyl phthalate(DBP) as a typical pollutant, a novel method of calculating the allowable permitted assimilative capacity is put forward. The effects of flow velocity, sediment concentration, and particle size on the degradation of contaminants in water were analysed through indoor flume experiment, numerical simulation experiment and tracer experiment in river. And the analysis results were coupled with water quality model to establish this new method. The allowable permitted assimilative capacity of DBP in Qingshan industrial water functional zone was calculated respectively by this simulation-based method and the given methods from Standard Practice for Calculating Pollutant Carrying Capacity of Water and Supplementary Technical Rules for Surface Water Resources Protection of the National Integrated Water Resources Plan. Calculation results prove that this method solves the problem of the values of degradation parameters, and offers a technological support for confirming the allowable permitted assimilative capacity of river more accurately.

Key words: allowable permitted assimilative capacity of river, DBP, degradation coefficient, numerical simulation, tracer test