| The problem of rural water pollution is becoming increasingly serious in China, small-sized decentralized rural sewage treatment technology has become the research focus at home and abroad Inorder to solve current rural sewage treatment plant’s low nitrogen removal efficiency and ineffective oxygen enrichment status, a falling water driving rotating biological contactor had been designed to apply to the "anaerobic-anoxic-falling water driving rotating biological contactor-constructed wetland" bio-ecological combined process.Through experimental results, we got the following conclusions:(1)The anaerobic reactor started successfully after 42 days at normal temperature. During the stable running period, when the hydraulic retention time (HRT) was 24h,48h and 72h, the removal rate of chemical oxygen demand (COD) is 42.1%,37.8%,51.1% and 58.3%, respectively. When HRT was 72h and the volumetric load of COD from 0.15kgCOD/(m3·d) to 0.25kg kgCOD/(m3·d), the removal rate of COD decreased from 50% to 43%. This suggests that the anaerobic reactor of rural domestic sewage has stronger ability to resist impact load.(2) Studying the denitrification effect of reflux ratio on anoxic device. When the reflux ratio was 50%,100%,200% and 300%, the total nitrogen removal rate is 30.0%,54.6%,66.9% and 54.6%, respectively.(3) Under the condition of same drop height, same unit-width discharge, same water temperature, The oxygen transfer efficiency of falling water driving rotating biological contactor is higher than traditional oxygen filling way. During the stable running period, When the flow rate is 20L/h, the dissolved oxygen in the first, second, third grade biological rotating contactor is higher than 2mg/L and 3mg/L. Studying the hydraulic retention time on the removal rate of COD and ammonia nitrogen. When the hydraulic retention time were 1.25h,1.67h,2.5h and 5h, the removal rate of COD were 45.5%,51.1%,62.3% and 42.2%. The removal rate of ammonia nitrogen were 77%,88.7%,91.5% and 67%.(4) The vegetated constructed wetland had high efficiency for wastewater treatment and ran steadily. When the hydraulic load is 0.25m3/(m2·d) and the average COD concentration is 44.8mg/L, the removal rate of COD was 57.8%. When the average concentration of total phosphorus is 3.29mg/L, the removal rate of COD was 87.1%. When the average concentration of total Total nitrogen is 3.29mg/L, the removal rate of COD was 87.1%. In addition, the total nitrogen removal rate is about 50%.(5) The combined process achieved good removal efficiency of COD, total nitrogen, ammonia nitrogen and total phosphorus. When the average COD, total nitrogen, ammonia nitrogen and total phosphorus were 276.1mg/L,27.8mg/L,27.6mg/L and 3.26mg/L, the average removal rate in turn were 93.1%,76.4%,95.4% and 87.2% with the average concentration of the effluent were 18.7mg/L,6.5mg/L,1.2mg/L and 0.41mg/L. All indicators reached the class A emission standard in the "urban sewage treatment plant pollutant discharge standard" (GB 18918-2002).The results showed that:the "anaerobic-anoxic-falling water driving rotating biological contactor-constructed wetland" bio-ecological combined process to deal with decentralized domestic sewage could achieve good removal effect. It has the advantages of low energy consumption, high efficiency and convenient, easy to manage and using of water nutrient output of aquatic vegetables which is suitable for rural domestic sewage treatment in Taihu area. |
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