| The activated sludge method is currently the most widely used treatment process in urban sewage treatment plants that have been built in my country.After years of application and development,the activated sludge method can not only remove organic matter,but also have the function of removing nitrogen and phosphorus and other nutrients.However,in the actual operation of urban sewage treatment plants,problems such as sludge expansion and sludge floating often occur.Not only will the effluent water quality deteriorate,it will also affect the stability of the entire activated sludge system.This study is based on the problem of poor settlement of four sewage treatment plants in Xi’an.First,the operation of the sewage plant is analyzed.Then,common microscopy,staining analysis,and fluorescence in situ hybridization(FISH)were used to identify the filamentous bacteria in the expanded sludge and floating sludge.At the same time,the poor sedimentation and pollution of sewage treatment plants were analyzed.Reasons for mud bulking and upswing.Finally,by measuring the maximum specific phosphorus uptake and release rate of the mixed liquid and floating sludge from the fourth sewage treatment plant,the effect of filamentous bacteria on the phosphorus removal of the system was analyzed.The main conclusions are as follows:(1)The sludge floating phenomenon generally exists in the four sewage treatment plants in Xi’an.Due to the high sludge concentration,the SV is greater than 90%,and it is difficult to settle,but the effluent of each sewage treatment plant can reach the national level A standard.By analyzing the operating parameters and sludge morphology of the four sewage treatment plants,it was found that the third sewage treatment plant had sludge bulking during the winter period.(2)There are a certain number of filamentous bacteria in the activated sludge of the four sewage treatment plants,and a large amount of filamentous bacteria in the floating sludge.The identification of the filamentous bacteria in the floating and expanded sludge proves the expansion The filamentous fungus in the floating sludge is Microthrix parvicella.(3)The measurement of zeta potential shows that the negative charge of microfilariae is less than that of ordinary activated sludge flocs,which means that its hydrophobicity is stronger than that of ordinary activated sludge flocs.Therefore,this is also an important reason why the content of microfungi in floating mud is more than that in the mixed solution.(4)A large number of black particles can be seen in the mycelium of Micromycetes under Nessler staining.By dyeing and comparing the phosphorus content of the sludge and the mixed liquid,the black particles in the mycelium of Micromycetes are phosphorus particles.(5)The maximum specific phosphorus uptake rates of the mixed solution with low content of microfungi and the floating sludge with high content of microfungi are 8.07 and 6.40 mg PO3-4-P/(g VSS·h).respectively,and the maximum specific phosphorus release rates are 11.56,10.14 mg PO3-4-P/(g VSS·h).The P/HAc values were 0.353 and0.307 g P/g HAc,respectively.Microfilariae has the ability to compete with phosphorusaccumulating bacteria for VFA,and the presence of microfilamenta is not conducive to systematic phosphorus removal. |
