Research Of A Integrated Contact-oxidation Reactor With Air-lift Recycling Technology For Rural Wastewater Treatment

With the development of society, economy and the increasing of population in rural areas, the water pollution problem was becoming more serious. Parts of the surface water and groundwater suffered different degrees of pollution in rural areas, which was a serious damage to human health and a threaten to ecological sustainable development.Based on the rural wastewater characteristics of disperse, large fluctuant in quantity and quality, hard to collect, in this study, the rural decentralized wastewater treatment technology called contact-oxidation process was used. It included collection, disposal and reuse of wastewater and the effective air-lift recycling technology in the reactor which could enhance the wastewater treatment effects and save energy. The reactor had a treating capacity of1m3/d in this study for treating town’s wastewater. By experiments and data analysis, it concluded that:(1) The amount for recycling in air-lift recycling technology was influenced by lifting pipe diameter, the submerging depth of lifting pipe, the lifting height of reflux and aeration intensity, among which aeration intensity was the most important in these factors. The optimal operating parameters was showed as follows:the lifting pipe diameter of15cm, the lifting pipe submerging depth of60cm, air lift height of5cm and aeration intensity of0.4～0.5L/min.(2) Under the operating condition of high DO (5～6.5mg/L) in backflow nitrifying liquid, the optimal nitrogen removal working condition was nitrated liquid reflux ratio of2:1, C/N of5:1, and the nitrated liquid reflux zone to the fist one.(3) By the synergistic effect of tow stages anoxic tank, tow stages contact oxidation tank and air lift recycle system, ammonia nitrogen, total nitrogen, suspended solids and COD in town’s wastewater could be effectively removed during the long-term of operation and the average removal rate could reach to87.3%,65.8%,91.7%and85.1%, respectively. Through the four stages series operation of the reactor, the contaminant removal efficiency and resistant ability to wastewater were all strengthened.(4) During the operation in winter, nitrification and denitrification were all inhibited, which led to the decrease of total nitrogen removal rate. When the wastewater temperature was below6.5℃, the ammonia nitrogen and TN removal rate was only about50%and40%, respectively, which meant that the denitrifying bacteria were in dormant condition and the denitrification effect was weak.