Research On Enhancement Of Waste Activated Sludge Hydrolysis In WWTPs Using Lysozyme And Alkyl Polyglycoside

The waste activated sludge contains many reusable resources and hazardous substances.Inappropriate treatment methods will not only cause loss of resources,but also cause secondary pollution.Therefore,it is practically significant to explore reasonable and effective sludge disposal methods.Anaerobic digestion is one of the most promising methods in sludge treatment,however,hydrolysis is the rate limiting step of it.Therefore,the basic of effective sludge treatment method is to improve hydrolysis efficiency.At present,it has been proved that lysozyme and alkyl polyglycoside alone can promote sludge hydrolysis.Nonetheless,the effect is limited,and the intensive reaserch on the relationship between microbial community structure and hydrolysis efficiency is lacking.In this study,the writer uses the the solubilization of alkyl polyglycosides to solve the problem of insufficient dispersion of sludge particles and low utilization efficiency of lysozyme under the action of lysozyme alone.In this paper,the enhancement of waste activated sludge hydrolysis in WWTPs using lysozyme and alkyl polyglycosides were investigated,and the optimal dosage and reaction condition were determined.In addition,the study also uses molecular biology techniques to analyze the microbial community structure under different conditions,and attempts to explore the effect of alkyl polyglycosides on sludge hydrolysis through the perspective of microorganisms.Studies have shown that alkyl polyglycosides promotes the effect of lysozyme on sludge hydrolysis,and the SCOD,polysaccharide and protein in the combination system increase respectly with the increase of alkyl polyglycoside dosage.When the dosage of alkyl polyglycosides reaches 0.3g/g DS,the difference between the SCOD concentration in the combined system and the SCOD concentration in the lysozyme alone and the alkylpolyglycoside alone at 2h reaches the maximum,and the maximum difference of SCOD is 693.87 mg/L.In that condition,the sludge reduction ratio reaches 17.84%.In addition,the alkyl polyglycoside shows a great promotion effect on the prolongation of lysozyme.Compared with the action time of lysozyme alone,the sustainable action time of sludge hydrolysis under combined system increased from 150 min to 6h.Different pH has different effects on promoting sludge hydrolysis in the combination system.The effect is strongest when the combination system is in the strong alkali condition.Besides,the alkali environment can improve the excess sludge reduction retio and prolong the decay period.When pH=11,the difference of SCOD concentration between the combination system and lysozyme& alkyl polyglycoside alone system at 2h reaches the maximum,which is 1318.87mg/L.The sludge reduction ratio improves when the combination system is in the strong alkali condition.When the pH=11,the reduction ratio is 26.23%,which is 132.08% higher than that under acidic condition(pH=4).Increasing the temperature can increase the hydrolysis effect and sludge reduction ratio of the combination system.When the temperature is 35 ℃,the SCOD difference between the combination system and lysozyme&alkyl polyglycoside alone system is maximized.And the polysaccharide and protein also shows the similar changes as SCOD.The enhancement of sludge hydrolysis is strongest at that time.After comprehensive consideration,the optimal reaction conditions are: 0.3g/gDS alkyl polyglycoside,pH=11 and Temperature=35℃.Even if the combined system is in the 25℃,the SCOD concentration of it at 2h is higher than the sum of SCOD concentration of lysozyme& alkyl polyglycoside alone system in the 45℃,which shows that combination system has much stronger effect on sludge hydrolysis.While in the combination system,the microbial diversity of the sludge is decreased,the relative content of the acid-producing bacteria such as Escherichia and Citrobacter are increased,indicating that the combined system is much more conducive to acid accumulation than the alone action system.pH and temperature have a great impact on the structure of the flora.Under acidic conditions,acid-resistant bacteria such as Burkella are main bacteria.Under alkaline conditions,acid-producing bacteria such as Bacillus and Clostridium are dominant bacteria.From the analysis of the microbe community of the sludge at different pH,when the pH=11,the relative content of the acid-producing bacteria in the combined system can reach 74.91%,and the acid production under neutral conditions and pH=4.The relative contents of the gas bacteria were 62.23% and 40.38%,respectively.The effect of temperature on the flora structure is mainly reflected in the fact that the dominant bacteria in the sludge are Bacillus and Clostridium at 25℃,however,the sludge is mainly composed of heat-resistant actinobacteria with excellent hydrolysis and acid production capacity at 45℃.