Analysis of water quality variation of rainfall in Xi´an

Through the analysis of different underlying surfaces during rainfall in Xi´an stormwater runoff water quality. This paper studies the sources of pollutants in stormwater and water quality variations. The results showed that: The major pollutants in the rainfall are SS, COD, NH₃-N, TP. SS, COD and TP are mainly from rainfall runoff process by the underlying surface erosion, NH3-N is mainly from the leach of atmosphere caused by rainfall. Concentration of each pollutant in runoff exceeds V water requirements of GB3838-2002 in “Surface Water Environmental Quality Standard”. The concentration of pollutants shows overall downward trend in rainfall process, tending to be stable eventually. SS, and COD, TP, NH₃-N has a strong correlation. All kinds of pollutants are mostly attached to the particles. To remove the SS is the key to control of the stormwater runoff pollution and stormwater treatment. The values of BOD/COD for rainwater were less than 0.3. Biochemical process performance is poor and it´s fitted to uses physicochemical treatment.