Experimental Study On CASS Process For Residential Community Sewage Treatment

With the increasing degree of city modernization and industrialization, and the widespread use ofchemical fertilizers and pesticides, nitrogen and phosphorus nutrients causedeutrophication of water bodiesin question is outstanding day by day. The problem of water pollution has become increasingly acute, therelevant government departments has made emisson standards of sewage organic matter and nitrogen andphosphorus, to achieve the standards, many sewage treatment facilities need to consider the problem ofsimultaneousnitrogen and phosphorus removal,meanwhile choosing the suitable nitrogen and phosphorusremoval technology has become increasingly important in the treatment of domestic sewage.CASS (cyclicactivated sludge system) is a variant of SBR process for nitrogen and phosphorus removal, because of itscharacteristics of simple process, small occupied area, low investment, strong impact resistance, not easy tosludge bulking, in recent years it has been used more and more in China.The pilot test was first tested by single factor test on wastewater treatment, operation parameters ofCASS pool such as running cycle, aeration rate, ratio of drainage. The test shows that the cycle in6h,CASS pool with effluent discharge standard, and the energy-saving and consumption reduction, is desirable,therefore,6h was confirmed the optimal operating cycle; aerationrate has certain influence on variousindicators of removal effects of CASS process. It affects the nitrifying bacteria and denitrifying bacteria inwastewater removal rate, and the effluent quality is reduced, so the test with various factors affecting thefinal selection of aeration rate was0.25m3/h; the drainage ratio affects CASS removal effect, especially onthe concentration of ammonia nitrogen removal effect. Experiments show that, with the decrease of theratio of drainage, the removal of CASS process is better, but the drainage ratio is too low, thereactorvolume utilization ratio is smaller, considering the processing power and economy, to determine theoptimal drainage ratio is1/3.The operation cycle, aeration rate and drainage ratio as CASS process of sewage treatment factor,orthogonal test of three factors and three levels of experimental design used. Through the orthogonal test ofthe removal rate of COD and methods of range analysis and variance analysis, range analysis method toobtain the order of factors effect on removal of COD in domestic wastewater CASS process for B>A>C(aeration rate>> drainage operation cycle ratio), the apparent optimum combination is A2B2C2, parametersfor the operation period of4h,aeration at a rate of0.25m3/h, the drainage ratio is1/3; obtain the factor Band the other two factors significantly compared to the removal rate of COD by analysis of variance, factorA andfactor C on the removal rate of COD had no significant effect.