Characteristic Of Municipal Sludge Thermal Hydrolization And Anaerobic Digestion Process

Municipal sludge contains large amounts of organic matter,It is a key technology of realizing sludge resource utilization to improve sludge digestion performance by increasing anaerobic digestion efficiency.Sludge thermal hydrolysis can effectively remove sludge extracellular polymer and microbial cell wall,promote the release and hydrolysis of organic substances in cells.Thence,thermal hydrolysis combined with anaerobic fermentation is a effective way for realizing low organic matter sludge anaerobic digestion.The effect of sludge organics dissolution,dehydration and the stability of heavy metals were studied by thermal hydrolysis pretreatment.The thermal hydrolysis combined with anaerobic fermentation of methanogenic experiment was carried out by batch experiment and semi-continuous experiment.Further explorating methanogenic performance,dewatering performance and heavy metal stability performance as basis for anaerobic digestion resource utilization of low organic matter sludge.The dissolution of organic matter improved to a certain degree after the thermal hydrolysis.During high temperature heat treatment,increased temperature was beneficial to dissolution of soluble organics.During low temperature heat treatment,soluble organics increased with thermal hydrolysis time prolonged.Dewatering performance improved after sludge heat hydrolysis under 180 ? and deteriorated below this temperature.The stability of Cu?Pb?Cd and Cr were increased after thermal hydrolysis.Methane production was different because of different source.During batch anaerobic digestion,the effect of methane production was consistent with the dissolution of organic matter and the degradation of organic matter.Under the optimal conditions of 140 0C,the cumulative methane production reached 146.30 mL/(g·VS),and the VS,COD,total sugar and total protein degradation rates were 27.60%,29.03%,81.14%and 89.28%,respectively;At 180 'C5 the cumulative methane production reached 174.6 mL/(g·VS).After the heat treatment of sludge,the hydrolysis of COD,carbohydrates and proteins was significantly accelerated.The hydrolysis of organic matter was dominated by proteins,but the hydrolysis coefficient was not a determinant factor for the degradation of organic matter.Dewatering performance of sludge became better after anaerobic fermentation,and the stability of heavy metals in Cu,Zn,and Cd increased.During semi-continuous anaerobic fermentation,methane production was increasing with the residence time decrease.Thermophilic anaerobic fermentation produced more methane than mesophilic anaerobic fermentation correspondingly.The greater the hydrolysis constant,the better the methane production.When SRT was 20 days,the methane production at mesophilic anaerobic digestion reached 100?150 L/(VS·kg),the degradation rate of organic matter reached 18?25%,the hydrolysis constant was 0.62,and 150?250 L/(VS·kg),20?25%and 0.64,corresponding under thermophilic anaerobic digestion.Anaerobic fermentation of sludge was beneficial to the improvement of the stability of heavy metals and deterioration of dewatering.