Study On Enhanced Constructed Wetland For Treatment Of Domestic Sewage In Northern Area

ABSTRACT:Constructed wetland system is suitable for medium and small town sewage treatment with its advantages of low energy, easy to administer and good effect of nitrogen and phosphorus removal. But because of low temperature in winter, the operation of the constructed wetland system were affected. How to ensure the efficiency of constructed wetland in northern winter is a research hotspot in recent years.Enhanced constructed wetland system which with multi-media was used to treat domestic sewage. Impact of seasonal variation, hydraulic loading, aeration on treatment efficiency of system were investigate. By reinforcing measures for system in winter, The mechanism of the organic matter and denitrifying phosphorus removal were explored. The reaction orders under different conditions were solved, and the effect of measures for constructed wetland strengthened was verified by kinetics. Results show that:(1) Seasonal variation, hydraulic loading and aeration have great impact on treatment effect of improved artificial wetland. Best hydraulic loading range is0.2m3/(m2·d) to0.5m3/(m2· d); The optimum position was located in middle and the intermittent aeration is better than continuous aeration.(2) Increase the reinforcement measures in winter:to increase the protective layer for water facilities and buried underground; to covered with reed for the bed surface; to increased aeration facility. After increasing strengthening measures and under the optimum hydraulic load, making the removal rate of COD、NH3-N、TN、TP can reach80%、85%、80%、98%respectively.(3)There is a certain regularity of the transformation of nitrogen and phosphorus along the way in the system:TN rapidly decreased from52.78mg/L to20.54mg/L and then slow down to10.59mg/L; the regular of NH3-N is similar with TN, it also quickly reduced from49.47mg/L to3.42mg/L, although there is a rising trend in the middle, it can be down to7.26mg/L; NO3--N is reduce in the system; change of NO2--N is relatively stabled; the regular of TP is similar with TN.(4)Because of the coupling reaction of biological effect with adsorption of media, catalytic role of the media and primary batteries role of the media, the system can get good removal efficiency.(5)According to the data of TN in different conditions, solved of the reaction order. The value of summer, winter, winter with strengthening are0.4777,0.2031,0.4820respectively.(6)The economic cost analysis for a10m3/d handing capacity was investigated. Calculated the operating cost for one unit is0.325RMB/m3,and capital cost of1168.85RMB/m3.In conclusion, By increasing the reinforcement measures, the enhanced constructed wetland can obtain good effect of organic matter and nitrogen and phosphorus removal in winter. And with the features of simple management, energy conservation, low cost, this technology will be the most important technology in small sewage waster.