Experimental Study On Rural Domestic Wastewater Treatment Using Combined Hybrid Anaerobic Reactor-Horizontal Subsurface Flow Constructed Wetland

With the development of rural economy, rural water and effluent discharge grow increasingly, and environmental problem becomes more serious. Since the power of rural economy is relatively weak and the lack of professional treatment staff, the existing centralized sewage treatment is not suitable for the treatment for rural domestic sewage. Therefore, seeking treatment technology of rural sewage which is economic, effective, simple is becoming more urgent.According to water quality characteristics for rural sewage and water features, this paper puts forward that the experiment use the composite system that hybrid anaerobic reactor combined with horizontal subsurface flow constructed wetland to treatment rural domestic wastewater. And make up the lakes that use simple anaerobic treatment process or wetland.The start-up which directly affected the running of system was critical. Hybrid anaerobic reactor was vaccinated with used aerobic sludge of oxidation dith. Intial HRT was 48h, and hydraulic loading was 0.25kgCOD/(m3·d) in the conditions that temperature were 15～25℃.Removal efficiency of COD was steadily about 60% after about 40 days. Then HRT became 36h, removal efficiency of COD reduced. After 3 days, removal efficiency of COD increased. Removal efficiency of COD was steadily above 80% and anaerobic reactors started successfully after about 80 days.The wetland started at the same time as anaerobic reactors after planting was rushed in. After 3 months, with plants survived and growed steady, effluent of system was clear. Total removal rate of COD was above 85%, and SS was 50mg/L below. We thinked the whole composite system started successfully.HRT of the operation process were 24～4h. The experiment studied the removal effects of COD, removal effects of the nitrogen and phosphorus and factors of the composite system. The experiment results showed that: The average removal rates of COD,TN,NH₄⁺-N,TP were 79.7%,39.5%,27.0%,79.5% respectively for composite system.For hybrid anaerobic reactor, the average removal rates were 68.7%,9.62%,7.68%,16.5%, and the average removal rates were 11.0%,29.9%,19.4%,63.2% for wetland. The anaerobic reactor played a major role with the removal of COD, and the wetland played a major role with the removal of nitrogen and phosphorus.HRT, temperature, concentration of influent and organic loading rate were main influence factors for composite system.Temperature and HRT influecced the treatment effect of system most, organic load next, and concentration of pollutants of inflow least. Of them, removal rates of pollutant increased with the temperature rising. When the temperature was 27～30℃, the average removal rate of COD,TN,NH₄⁺-N,TP were 85.6%, 42.7%, 37.5%, 90.6% respectively. When the temperature was 15～18℃, the average removal rates were 63.7%,28.8%,25.2%,44.8%.With the shorting of HRT, the removal rate for COD and TP is reduced gradually. When HRT is at 24h, the removal rate reached the most and the average removal rates were 86.8%, 93.9% respectively. When HRT was more than 8h, the removal rate for TN and NH₄⁺-N were increasing with the shorting of HRT and reached the most at 8h, and the average removal rates were 48.3%, 33.9% respectively. When HRT was less than 8h, the removal rates for TN and NH₄⁺-N were reducing with the shorting of HRT.The higher concentration of influent, the better removal rate of pollutants for system; otherwise, the higher organic load, the worse removal rate of COD.The best HRT of system was between 8h and 12h by the combination of factors.The removal of nitrogen was mainly affected by the influence of the temperature and plant growth. The removal of phosphor was mainly affected by precipitation and adsorption of matrix, and absorption of plant had less effect.The whole system for removal efficiencies of COD and TP were good, but denitrification was not satisfactory.