Study On Water Pollution Control Technologies For Small Town Rivers In Water-deficient Area Of North China

Urban river management is a comprehensive system engineering,involving many subjects such as transportation,biochemistry,environmental sciences,hydraulics,river landscape design and so on.Aspects of including but not limited to humanity,ecology,economy,sustainability and social effect have to be taken into account to achieve both goals of social developmentand improvement of residential environoment.Comprehensive improvements of water environment of small towns in China has become an urgent issue,which is of great significance to the constructionof newrural and harmonious society.River pollution in the water-deficient area of North China has become more and more severe,which seriously affects the sustainable development of economy and society in the watershed.Thus it is imperative to improve the water enviroment.The Zhonghong river in Cha gugang town of Tianjin city in a typical water-deficient area of North China is selected as the reserch object in this work.Main pollution sources which have worsen the river into aninferior five classaccording to the national standard include domestic and industrial wastewater,domestic garbage and livestock and poultry breeding wastewater.Several water treatment technologies were adopted to improve the water quality and it revealed that enhenced topical reoxygenation pretreatment could effectively reduce the levels of chemical oxygen demand(COD),nitrogen and phosphorus in the overlying water and proper aeration strength would not disturb the sediment;chemical coagulation pretreatment was an effective method to remove the tuibidity,chroma,phosphorus and chlorophyll(a);and reed filter bed purification technology could achieve removal rates of turbidity and algae up to above 90%.Optimal process prameters are as follows:(1)aeration time of the enhenced topical reoxygenation is 30 minites and aeration strength is 14 L /(Lwater·min);(2)for the coagulation pretreatment,the dosage of polymeric ferric sulfate(PFS)is 40 mg/L,the mixing strength is 300 round per minite(rpm),the reaction strength is 10 rpm and the pH value maintains at 8.0;(3)bio-ceramics can be selected as filler in the sidestream treatment project,and a baffle vertical flow type is recommended in the reed filter bed system with a hydraulic retension time of 1 day.