Research On Ex-situ Biological Contact Oxidation Process For Heavily Polluted Urban River

Urban river is often heavily polluted as rapid development of economy and improvement of people's living standards.So river restoration including water purification and landscape construction has been an urgent work.It is necessary to develop an appropriate and acceptable river restoration technology.Among all technology used,biotechnology is widely concerned because of environmental friendliness and sustainability.This study takes a typical polluted urban river Tongji river in Changzhou as the target river,and discusses the pollutant removal by the ex-situ biological contact oxidation process.Besides,pollutant removal by the ex-situ biological contact oxidation combined sediment and aquatic plants is compared.The result would provide a reference for polluted urban river restoration in China.Results of Tongji river's water quality analysis revealed that nitrogen and phosphorus was the main pollutant.One year's sampling and water quality monitoring told that the mean value of COD_Cr,NH₃-N,TN and TP were 23.24mg/L,3.25mg/L,5.92mg/L and 0.367mg/L.Ammonia nitrogen accumulation was serious.Tongji river was more seriously polluted in dry season than rainy season and in western river than middle and eastern river.Comparing influence of different HRT and aeration rate on system's pollutant removal potential,the results indicated the condition that HRT was 8h and aeration rate was 80m³/h was better.Under this condition,the system was capable of achieving efficient and stable NH₃-N removal.The average removal percentage of NH₃-N and COD_Cr was 86.3%and 10.2%.The removal of TN and TP was not very well.The experiment on combined biological contact oxidation and aquatic plants showed that aquatic plants was favorable for decreasing COD_Cr,TN and TP.The average removal of COD_Cr,NH₃-N,NO₃-N,TN and TP was 46.2%,9.7%,1.8%,6.3%and 22.8%.The microbial community structure of biological contact oxidation influent and effluent,sediment effluent,sediment-aquatic plants effluent and biofilm on the packing was analyzed.It found that different water quality resulted in different microbial community structure.The microbial diversity of biological contact oxidation influent was relatively low,and the biological contact oxidation system changed the river water's microbial community structure.