Study On Enhanced Coagulation-biological Contact Oxidation For Treatment Of Rural Sewage

The new age of rural construction which has further comprehensive changed the face of countryside; the development rapid of economy with expanding continually urbanization rate. With the progress of rural construction, the concentrates of population and water consumption in daily life were added could lead to increasing domestic sewage release. In these case the problem of water shortage and contaminate would getting worse.The most country facing the same problem of drainage, which was poor and weak in basic constructed. Great majority polluted water was discharged in a simply way, which would contaminate subterranean river or infiltrate soil. Thus the issue of river water quality dropping, pollution and low soil quality indicator which could arouse flies breeding and pathophoresis will do bad influence on the country development and the healthy of peasant. If all no changing, the environmental effect by accumulation of contaminant would not be eliminated in short time. These were contradicting with the original intention of building good home for husbandman and new country. In this way, which most government, expert and the society focus on one tremendous problem: the village sanitary sewage.The unique characteristic of rural drainage which displays in several parts: first, the residence was dispersing in the country. Thus the drainage facility could not be programmed as the same way of city because diseconomy. Second, the discharge value and water quality of domestic sewage were distinguished by the living standard and habit. Thirdly the obvious intermittence of discharging, the yield and quality of water waved largely. Because of these characters, we compared many techniques such as methane tank, constructed wetlands, aquatic systems, and ecotechnology which would be suitable for country sewage. Then study the powerful mixture coagulant based on diatomite which could be using as an integration technology in the country domestic sewage system. In order to achieve inexpensive collecting and resource recovering in country domestic sewage, and which could be solve the problem of people healthy and environmental pollution arising from water.The experiment was divided into two parts. First using the diatomite as the major raw material and other three constant coagulants blended, this could confirm the best rate, content, time and pH parameter, dislodge effect in experiment. The second part diatomite and coagulation mixture were experimented with biological contact oxidation group. The first part was fostering microculture by contact oxidation and biofilm colonization, then detected water quality for biofacies. After the biological contact oxidation column and biofilm colonization were accomplished, then connecting the coagulation mixing system, changing inflow for depositing effluent.Study shows the suitable diatomite and coagulation mixture rate was the best way to deal with domestic sewage, orthogonal test was used to ensure technological parameter for aluminium polychlorid (PAC): Diatomite (mass ratio) =1:11, the best technological parameters should be as follows:dosage 25mg/L, stirring quickly at 300r/min for 2min, slowly at 70r/min for 10min and pH 7-7.5. The conclusion by the orthogonal experiment showed that the influencing factors on the effect of coagulant have following order: pH> dosage >stirring time, which means pH plays an important role on the effect of coagulant. Between the first and second order reactions, optimum technological parameter was used to do as first order reaction, and studying was confirmed the date: HRT was 4h at the second order reaction biological contact oxidation stage; DO concentration was controlled at 2~3mg/l. During the best technological parameter, the strainaway rate of COD, Ammonia Nitrogen and turbidity was separately 85.83%, 20.97% and 94.66%.The study shows, domestic sewage could be handled by strengthened coagulation with contact oxidation which would achieve effective dislodging CODcr, NH4+-N and turbidity. In addition this method of operation technique was consistently with country life, the advantage including little floor space, simplicity of operation, powerful impact load, the water stabilization, which was demonstrated the feasibility in country domestic sewage.