Study On Rapid Degradation And Acid Production Of Surplus Activated Sludge

At present,activated sludge process is the most widely used sewage treatment technology in municipal domestic sewage treatment plants.At the same time,a large amount of excess sludge will be produced.If this problem is not properly handled,it will cause large area,environmental pollution and resource waste.Excess sludge contains a large amount of organic matter,which has great potential for recycling.The fermentation of sludge is a good utilization method,and VFAs can be used as the carbon source in the denitrification process of sewage treatment.However,sludge fermentation has some problems,such as long fermentation time,slow fermentation rate and low utilization rate of sludge.In order to solve the problem of long fermentation time in sludge treatment process and accelerate the production of VFAs by anaerobic fermentation of sludge,a combined technology of ultrasonic pretreatment and surfactant addition was designed in this paper.In this paper,the secondary clarifier sludge of Datang Sewage Treatment Plant was taken as the research object,and the effects of ultrasound on sludge decomposition ability,surfactant type,dosage,initial pH and fermentation temperature on sludge fermentation were investigated.The results showed that the optimum conditions of ultrasonic treatment were determined by orthogonal experiment,the ultrasonic frequency was 70W/m~2 and the ultrasonic time was 30min.The effects of surfactant type,dosage,initial pH value,fermentation time,temperature and anaerobic bacteria on VFAs production were studied by single factor experiment.The results showed that under the same conditions,when APG,JFC,SAS,CMC,SDBS and TDP were used as surfactants,the acid production of APG was the highest;after ultrasonic pretreatment,the amount of surfactant was 0.8g/600ml,the initial pH value was 11,the fermentation time was 4 days,the fermentation temperature was 35?,and the maximum acid production was 1300mg COD/L without adding anaerobic bacteria;When anaerobic bacteria were added,the maximum acid yield was 3620 mg COD/L,which was three times higher than before,and the acetic acid content in VFAs was 3077 mg COD/L.Therefore,the optimum acid-producing conditions are adding anaerobic bacteria,surfactant APG,dosage of 0.8g/600ml,initial pH of 11,fermentation temperature of 35?.After fermentation under optimal conditions,the concentration of VSS in the remaining sludge decreased by 29.7%.and the water permeability was increased by 34 times compared with that after ultrasound.