Optimization Of Operating Parameters And Applied Research Of CASS Process In Municipal Sewage Plant

With the rapid development of China’s economy and urbanization，water pollutionproblems people face growing，construction of urban sewage treatment plants isparticularly important. The topics to practical engineering Harbin PF sewage treatmentplant for the study, conducted trials and studies of the CASS process municipalwastewater treatment. Adjust the operating parameters based on actual test results,research and exploration problems appears after the water plant running, for example:sludge bulking.Through the urban sewage field tests, studied various operating parameters ofCASS process, such as operation period, drainage ratio, return sludge ratio, temperatureand so on.The results showed that, the best operating cycle of CASS process is6hincluding feed0.5h, feed and aeration1.0h，aeration2.0h, settling1.0h and decant1.5h,The water quality was detected with drainage ratio of1/2.5,1/3and1/4, the resultsdemonstrate that the drainage ratio was lower the higher removal was, but consideredthe running costs,1/3is the best drainage ratio; Temperature has a significant effect onthe treatment performance of CASS process， when the temperature changes from highto low, all indicators of effluent quality increased significantly besides COD removal;The result of study on CASS process with and without return sludge showed that theeffluent quality was lower without return sludge than that with return sludge, Takinginto account economic factors,30%is the best return sludge ratio; It is found that C/Nhas little effect on the COD and SS effluent concentration, but things were differentwith total nitrogen and ammonia. when C/N rose from5.6to8.6, Little change inammonia removal, but rose to12.0, Ammonia nitrogen removal rate has shown asignificant decline.After CASS process put into practical operation, found the indicators are exceededrunning under the design parameters. Therefore, adjust the operating parameters of theCASS process on the test conclusions. process running for some time after changed theparameters， the system is operating normally and water quality fully meet the designstandards. There are many problems after CASS process officially put into operation The firstproblem is sludge bulking phenomenon, thought to be caused by mud tube blockage，which was controlled effectively by removing excess sludge, increasing return ratio,adding the decant ration, controlling DO concentration in oxidation zone and so on; Thesecond problem is the phenomenon of floating sludge, thought to be caused byprolonged precipitation, which was controlled effectively by adding the decant rationand reducing settling time; The third problem is the effluent ammonia and totalnitrogen,it is caused by the sudden increase in the concentration of COD, growth andreproduction of nitrifying bacteria is inhibited, finally the problem solved by increasingreturn ratio and controlling DO concentration, effectively improve the effluent ammoniaand total nitrogen concentration.