Research On Application Optimization And Treatment Efficiency Of Anoxic+Waterwheel Driving Rotating Biological Contactor Process

With the continuous development of rural areas in China,the pollutant load caused by the discharge of rural domestic sewage is increasing year by year,and the current situation of the rural water environment is not optimistic.At present,the rural domestic sewage treatment facilities that have been built have problems such as high failure operation rate and unstable effluent quality.Therefore,it is particularly important to develop a high-efficiency,low-consumption,high-adaptability,easy-to-maintain and sustainable rural domestic sewage treatment process.The biological treatment process from the bio-ecological combined process of"anoxic+waterwheel driving rotating biological contactor+constructed wetland"has been researched.The main contents and conclusions of the work are as follows:（1）A laboratory-scale test on the three materials of felt,carbon felt and non-woven fabric shows that the non-woven fabric carrier has good biocompatibility,and the microbial biomass on the surface can reach 24.58±1.82 g VSS·m^-2 on the 14th day.The average removal rate of COD and NH₄⁺-N on the laboratory-scale turntable with non-woven filler carrier is 84.3±2.2%and 82.5±3.0%,respectively.Two stairs waterwheel driving rotating biological contactors are used as the aerobic treatment unit which started with the rapid sludge discharging method,the average removal rate of COD and NH₄⁺-N after stabilization are 86.8±0.9%and 92.2±1.5%,respectively.The reactor has strong organic removal and nitrification capabilities.（2）The evaluation results of the two oxygenation methods in the waterwheel driving rotating biological contactor show that rotating oxygenation is the main oxygenation method;the change of the rotation speed of the disc has a more significant effect on the total oxygen mass transfer coefficient of the reactor（=0.05,p<0.01,F=321.15）.Therefore,it is recommended to optimize the rotation oxygenation effect under the premise of fixing the best water-drop oxygenation effect.When the drop height changes from 0.3m to 0.9m,the total oxygen mass transfer coefficient(_（6）of the reactor increases from 0.0104±0.0006min^-1 to0.0237±0.0024min^-1.The relationship between the standard oxygen mass transfer coefficient(_（6）and the drop height（?）with temperature（）is₍（6）（?,）=0.02297?^{0.6696（20-）}.When the rotating speed of the turntable increases from 2rpm to 8rpm,the total oxygen mass transfer coefficient(_（6）of the reactor increases from 0.0056±0.0002min^-1 to 0.0133±0.0003min^-1.The relationship which established by the modified Kim&Molof model between the standard oxygen mass transfer coefficient(_（6）and the rotation speed（）with temperature（）is₍（6）（,）=0.00336?^{0.666（20-）}.（3）The optimal operating conditions determined by the experiment are anoxic hydraulic retention time of 6h,nitrification liquid reflux ratio of 200%,aerobic hydraulic retention time of 2.5h,and rotation speed of 4.5rpm.The average removal rates of COD,NH₄⁺-N,TN and TP in the overall process are 84.79±1.74%,83.70±1.30%,40.94±2.22%and 37.5±5.1%,respectively.The concentration of COD and NH₄⁺-N in the effluent from the combination process of anoxic+waterwheel driving rotating biological contactor can meet the first-level A standard in the"Water Pollutant Discharge Standard for Rural Domestic Sewage Treatment Facilities"（DB32/3462-2020）in Jiangsu Province.However,TN and TP needs to be further removed from the ecological unit.Nitrogen-containing pollutants in the effluent of the biological treatment process mainly exist in the form of nitrate nitrogen,and most of the phosphorus is retained,which creates better conditions for the ecological unit to realize the function of nitrogen and phosphorus resources.