Combined Process Of Bioflocculation And Three-stage Constructed Wetland For Treatment Of High Concentration Domestic Sewage In Small Town

This topic is"an particular item of science and technology for small town constuction in Chong qing—research and demonstration of the key technique for small town constuction in Chongqing"for Chongqing science and technology committee. Aiming at developing a kind of wastewater treatment technique that high efficiency, low invest, low operation cost and operation simply, object to the problem of low efficiency and jammed easily in traditional constructed wetland, the treatment technique of"bioflocculation and three-stage constructed wetland"is put out. Many factors are studied to explain the results of the research into treatment of high concentration domestic sewage in small town by combined process in this paper such as removal variation of contamination along process flow, effects of season changes, constructed wetland clogging and plant harvest to combined process treatment efficiency, utilizing coagulation and recirculation to enhance combined process treatment efficiency, the operating management and maintenance of constructed wetland system and so on.The main conclusions can be made in this experiment:â‘ Combined process of bioflocculation and three-stage constructed wetland has good removal efficiency for high concentration domestic sewage in small town. The removal rates of SS and COD are 93.1% and 92%, effluent concentration of SS and COD are 15mg/L and 48mg/L,and reaches the classâ… -A criteriaspecified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002). The removal rates of NH₄⁺-N and PO₄^3--P are 63.8% and 72.3%, and reaches a higher treatment efficiency. The experimental results show that, pretreatment system has main function to removal of organic matter, while constructed wetland system has main function to removal of NH₄⁺-N and PO₄^3--P.â‘¡The experimental results shows that, season changes has very small effect to SS removal efficiency, has some effect to COD and PO₄^3--P removal efficiency, and has big effect to NH₄⁺-N removal efficiency. As a whole, the removal efficiency of each contamination is the best in summer which is the worst in winter.â‘¢Addition of coagulant can increase removal efficiency of pretreatment system, reduce PO₄^3--P influent load of follow-up constructed wetland system. When the dosage of PAC is 40mg/L, removal rate of COD and PO₄^3--P is respectively improved 14% and 37.2%, then adding more dosage of PAC, removal rate of COD and PO₄^3--P is improved unobviously.â‘£Circumfluence makes purifying effect of constructed wetlands improved obviously. Removal rate of various pollutants increases most quickly, such as removal rate of COD,NH₄⁺-N,TN and PO₄^3--P is respectively improved 16%,18.5%,13.3% and 3.6% when the cycling rate is 1. Effluent recycling makes removal efficiency of COD and NH₄⁺-N increased obviously, and makes removal efficiency of PO₄^3--P increased unobviously.⑤When combined process operates more one year, clogging has happened in the head of constructed wetland. Removal efficiency of wetland is reduced after clogging, removal rate of various pollutants is reduced to around 75% that before clogging.â‘¥Periodic plant harvest can slove the problem of wetland logging partly, promote the plant growth, and remove new organism from the constructed wetland, remove pollutant from sewage. Removal rate of COD and NH₄⁺-N is decreased after plant harvest, whereas plant harvest has a little influence on the PO₄^3--P removal rate.⑦Many factors are studied to discuss main item that need to be considered in the operating management and maintenance of constructed wetland system such as plant management, the pest control, deposition cleanness, dike maintenance, the smell control, the mosquito and fly control and so on, which draw lessons from meaning for building up perfect management system of constructed wetland in future.In conclusion, the combined process has a strong anti-shock loading capability and good performance of adaptability to higher concentration town wastewater, which widden the applying area, explore a new approch for wastewater treatment that high efficiency, low invest and low operation cost in small town, and have important realistic meaning.