Characteristics And Efficiency Of Thermophilic Anaerobic Hydrolysis And Acidification Of Low-organic Carbon Sludge In Wastewater Treatment Plant

Sewage treatment process produces large amounts of sludge.Improper disposal of sludge will cause environmental problem.Reduction,reuse and recycle are the main research directions in sludge treatment and disposal.Waste activated sludge contains large amounts of organic matter.Hydrolysis and acidification of waste activated sludge can produce volatile fatty acid,while reduce the amount of sludge.Volatile fatty acids can be used as carbon source for nitrogen and phosphorus removal.As a raw material,volatile fatty acids also can be used to synthesize polyhydroxyalkanoates.In this paper,hydrolysis and acidification performance of thermophilic anaerobic fermentation of low organic carbon sludge was investigated.To improve the efficiency of thermophilic hydrolysis and acidification of low organic carbon sludge,the sludge hydrolysis and acidification performance of sludge was analyzed and compared under different fermentation temperature,the effects of the change of sludge retention time(SRT)and sludge concentration were investigated.In addition,characteristics of thermophilic anaerobic hydrolysis and acidification under different electron acceptors shocking conditions was examined.Conclusions were obtained as follows:(1)Temperature had a significant influence on the hydrolysis of proteins,carbohydrates and VFAs.The soluble protein,carbohydrate and VFAs were improved significantly at high temperature.With fermentation temperature increasing from 35°C to 55°C,VSS removal rate increased from 12.98% to 22.31% during the short term fermentation experiment,VSS removal rate increased from 13.59% to 22.92% during the semi-continuous fermentation experiment.The methanogenic bacteria inhibitor can suppress the consumption of SCOD and VFAs and increased their accumulation.(2)Increasing the sludge loading rate of semi-continuous reactor improved the efficiency of anaerobic hydrolysis and acidification.Experimental results showed that the increase of sludge concentration and the decrease of SRT in a pertinent range benefited the hydrolysis of sludge and the accumulation of VFAs,high sludge concentration increased the treatment efficiency and reduced the volume of reactor.Lower SRT and higher sludge concentration enhanced soluble chemical oxygen demand production,and the feasibility of nitrogen and phosphorus recovery depending on the nature of waste activated sludge.SS of 20 g/L and SRT of 2 d were the optimalconditions for the production of VFAs.(3)Under short term aeration shocking conditions,efficiency of anaerobic hydrolysis and acidification was enhanced significantly,with the VSS reduction percentage of 40% compared to 31% without shocking effect.Short term aeration increases the yield of COD,the concentration of COD increased nearly twice times compared with the anaerobic group.A short time aeration(10 min)enhanced protease activity compared with the anaerobic group,more protease enzymes were released into the solution.