Diagnosis Of Sludge Bulking And Floating In A2/O Process For Urban Waste Water Treatment

A2/O process is one of the most popular process used in waste water treatment plants?WWTPs?.This process not only removes organic matter from wastewater,but also achieves better nitrogen and phosphorus removal effect.Its own has many advantages,but in actual operation,there are often sludge bulking and floating problems.This is not only detrimental to separate mud with water in the secondary sedimentation tank,deterioration of the effluent quality,but also cause sludge loss,and even lead to the collapse of the entire activated sludge system.In this study,the operation of the WWTP was analyzed based on the sludge bulking and floating problems in Xi'an Fifth Wastewater Treatment Plant.Then,the filamentous bacteria in the mixed liquor and float sludge were identified by ordinary microscopy,dyeing analysis and fluorescence in situ hybridization?FISH?,and the reasons for the formation of sludge bulking and floating problems were analyzed.Finally,the effects of filamentous bacteria on denitrification and dephosphorization were analyzed by measuring the maximum specific phosphorus uptake,release rate and denitrification rate of mixed liquor and float sludge.The main conclusions are as follows:?1?The results showed that the influent of BOD5: N: P was 100: 17.6: 2.8,nitrogen and phosphorus nutrient content is not balanced,nitrogen content was high,which may become the cause of sludge bulking and floating problems.Sludge bulking occurs mainly in the winter when the temperature is low,therefore,Temperature change is an important cause of sludge bulking.?2?Through the analysis of the sludge bulking and floting of A2/O system inXi'an Fifth Wastewater Treatment Plant,and the identification of filamentous bacteria appeared in this time,we can see that the microorganisms that cause sludge bulking and floting was Microthrix Parvicella.?3?The presence of Microthrix Parvicella has a negative effect on the phosphorus removal of A2/O system.It was found that anaerobic phosphate release and uptake rates of mixed liquor and float sludge were 14,4.5mgPO₄^3--P/gVSS·h and9.8,3.7mgPO₄^3--P/gVSS·h,and the P/HAc ratios were 0.27 and 0.29gPO₄^3--P/gHAc.The results showed that the content of Microthrix Parvicella in the floating sludge was higher than that of the mixed liquor.It was also suggested that the floating sludge was caused by the large amount of Microthrix Parvicella,and the Microthrix Parvicella had the ability to compete VFA with PAO.?4?The maximum denitrification rates were 5.9,3.6 and 1.7 mgNO₃^--N/?gVSS·h?and 6.9,3.7,1.1mgNO₃^--N/?gVSS·h?,respectively.The amount of Microthrix Parvicella in the floating sludge is higher than that of the mixed liquor,and the rapid and slow maximum denitrification rate of the floating sludge is larger than that of the mixed liquor,which indicates that M.P can breathe with nitrate and enhance the denitrification.