Sodium Hypochlorite Control The Sludge Bulking In The Municipal Wastewater Treatment Plant

The problem of sludge bulking in municipal wastewater treatment plant has caused difficulties in sludge precipitation,increased SS in effluent,large loss of sludge,and poor quality of effluent water,seriously affecting the normal operation of municipal wastewater treatment plant.Therefore,how to control the phenomenon of sludge bulking and maintain the excellent settling performance of activated sludge is an important problem faced by the operation and management of municipal wastewater treatment plant with nutrient removal.A~2O process is currently the most important process of municipal wastewater treatment plant in China,and it has the advantages of simple operation and easy control.In this paper,the sludge bulking phenomenon in the A~2O process of xi’an fifth wastewater treatment plant was studied.The Microthrix parvicella(MP)bulking sludge was used as the research object.Sodium hypochlorite was used as a bactericide to investigate the killing effect,The improvement of the sedimentation properties of activated sludge and the damage and recovery of the functional microorganism(PAOs)were investigated with different dosages,images,SVI,the maximum rate of phosphorus release,the maximum specific phosphorus uptake rate and the maximum specific phosphorus release ratewere used to characterize the treatment effect.The main conclusions are as follows:(1)Using dyeing and Fluorescence in situ hybridization(FISH),it was found that the activated sludge bulking in the A~2O process of the wastewater treatment plant was caused by MP.The control of sludge bulking should aim at inhibiting or killing the MP in the sludge;(2)Sodium hypochlorite has a good killing effect on MP.The added sodium hypochlorite can break the mycelia of the MP exposed outside the activated sludge flocculation,the mycelium becomes shorter,no longer twining between each other,the SV of the sludge is reduced,and sedimentation of activated sludge is improved;with the running time,so that sedimentation of activated sludge is improved with the proliferation of non-filamentous bacteria and the discharge of residual sludge;(3)The higher dosage of sodium hypochlorite was employed,the greater damage on the functional microorganisms.Take PAOs as an example,the greater the effect on the rate of pHospHorus uptake and release,and the effect on the rate of phosphorus uptake by the PAOs is greater than Effect of phosphorus release rate;(4)The optimal sodium hypochlorite dosage was 5.3 g/kg MLSS(based on available chlorine),and SVI was reduced from 202 mL/g when no sodium hypochlorite was added to 134 m L/g.The maximum rate of phosphorus release and the maximum rate of phosphorus uptake Respectively lower by 11%and 40%.Sodium hypochlorite can effectively control the sludge bulking caused by MP.