Study On Land Treatment Of Civil Sewage Water In Northwest Region Of China

Land treatment of sewage water has a rapid development both at home and abroad as ithas lower investment and better effluent efficiency. VCW is better than HSCW in removalefficiency of pollutants, especially in dealing with high concentration of pollutants whileVCW is more suitable in Northwest area of China. This thesis adopted VCW as study subject,based on campus sewage water, mainly study the removal efficiency of pollutants during ayear, under different interval working conditions and with different plants. Consideringavoiding jam in VCW during a long operation, BAF was adopted to aerate the influentsewage water, the study of BAF of the removal efficiency of pollutants under differentGas-Water ratio. Conclusions can be drawn as follows,(1) During a year of operation, the temperature outside changes obviously, it’s typicalNorthwest weather. The temperature inside VCW varies in tandem with the changes outsideand has good heat preservation during winter, the temperature inside is6°C higher while thetemperature outside drops sharply.(2) The changes of DO varies seasonally, and outflow concentration is higher thaninflow. The outflow concentration of DO reaches its highest4.2mg/L on August and lowest1.9mg/L on January. The removal efficiency of COD, SS, N, P varies seasonally, and theremoval efficiency in spring and summer is better than in autumn and winter. During a year ofoperation, the removal efficiency of COD is between40%and80%; the removal efficiency ofSS is between30%and90%; the removal efficiency of TP is between10%and90%; theremoval efficiency of TN is between5.5%and73.1%; the removal efficiency of NH4+-N isbetween6.3%and73.6%.(3) We adapted the operation from continuously to interval and set up4different inflowoperations (2,4,6,8) through automatic system during a day. The removal efficiency of COD,SS, TN, TP, NH4+-N drop sharply with grow of inflow times during a day. Consideringremoval efficiency of pollutants and processing load, we choose inflow every6hours a day asthe best operation condition.(4) We adapted the original reed pond into3same sized and same matrix ponds. No.1isreed pond; No.2is PAL pond; No.3is non-plant pond. The outflow concentration of DO ofreed and PAL are far above high than the non-plant one which indicates that these two plantshave a sound aeration ability. The removal efficiency of COD of reed and PAL are72.3%and74.6%respectively which are far above high than50.2%of non-plant pond. The removalefficiency of TN of reed and PAL are71.65%and68.94%respectively which are far abovehigh than40.92%of non-plant pond. The removal efficiency of NH4+-N of reed and PAL are70.36%and70.22%respectively which are far above high than42.33%of non-plant pond. The removal efficiency of TP of reed and PAL are75.59%and74.53%respectively which arenearly the same with non-plant pond73.42%. Reed and PAL can be chosen as constructedwetland plants as it has a better removal efficiency of pollutants.(5) The test of BAF investigates the variation of the removal efficiency ofDO,COD,SS,NH4+-N,TN and TP under different gas water ratio(1:1,2:1,3:1,5:1,7:1,10:1)which indicates the device favors enriching oxygen. The results indicate that when the ratioincreases from1:1to5:1, the removal efficiency of COD,NH4+-N,TN and TP grow in tandemwith it. The removal efficiency of SS reaches its highest efficiency which is89.4%under theratio3:1, after3:1, the removal efficiency has a tendency of slightly drop with the growingratio. When the ratio increases from5:1to10:1, the removal efficiency of COD、TN、TP havea tendency of drop with the growing ratio and reach their maximum77.5%，82.7%and40.1%respectively under the ratio5:1. The removal efficiency of NH4+-N reaches its maximumunder the ratio7:1and after that, the removal efficiency has a slightly drop. Considering thepower consumption and analysis of the results, above mentioned indexes can reach their idealremoval efficiency under the ratio between3:1and5:1.