Technical Comparison And Integrated Application Evaluation For Black-odor Rivers In A City Of South China

In recent years,due to the mismatch between the urban economic development and water environment management facilities,the phenomenon of water blackening and stink of urban rivers is commonly existed.Controlling black-odor rivers and eliminating black odor within a limit time has become one of the most urgent tasks for government.The treatment of black-odor rivers is a systematic project involving multiple links and technologies.Choosing the wrong technology and following the trend blindly not only del ay the elimination of black-odor rivers,but also cause huge investment waste.In this study,taking the black-odor river in a city of south China as the research objective,the applicable technology founded on the sewage interception for the treatment of black-odor rivers was proposed by literature and data review,engineering case investigation,in-suit monitoring,and partial experimental research.The effectiveness of this technology was evaluated through technology integration applications.For the control of authigenic pollution,in view of the large thickness and serious pollution of river sediments in the city,in-situ technology(i.e.environmental dredging)was first carried out so as to remove the heavily polluted sediment in the upper layer,and in-situ chemical technology(e.g.chemical oxidizer)was then employed after dredging for the treatment of the lightly polluted sediments remaining at the bottom of the river.Endogenous treatments needed to be carried out after blocking external pollution.For the ecological restoration,considering the rapid flow rate and fragile ecosystem of the river in the city during the flood season,the ecological stone cage revetment,artificial wetland construction,and living water aeration were utilized to reconstruct the ecological environment of the river,restore the self-purification of the water body,and achieve the water quality maintenance.Ecological restoration technology was mainly applied to the treatment of mild black-odor rivers after their external and internal pollutions were basically controlled.In terms of other treatment measures,freshwater supply could significantly improve the current situation of poor water flow in the river.Decentralized bypass treatment helped improve the river water qualities that were not well controlled by external pollution.Addition of chlorine-containing oxidants as an emergency measure causing direct devastating damage and long-term potential hazards to the organism should be avoided.Based on above results,the author selected a typical black-odor river in the city for the study on the integrated application evaluation of the treatment technology.The integrated technologies taking the sewage interception as precondition included environmentally friendly dredging,ecological hydration and water aeration.After the comprehensive treatment,the ammonia nitrogen concentration in the water was stabilized at 1~2 mg/L,and the DO,transparency,and ORP could be maintained at a level higher than 35 cm,300 mV and 6 mg/L,respectively.In this case,the black-odor river could be eliminated and the water quality could achieve stable maintenance.