Effect Of Thermal Hydrolysis On Dewatering And Biodegradability Of Sludge And Its Mechanism

Nowadays,China has paid more and more attention to the disposal and treatment of sewage,and has built many sewage treatment plants.At the same time,sludge is also a by-product of sewage treatment.The sludge contains a lot of harmful substances,bacteria,organic and inorganic particles and colloids.If the sludge is not properly treated,it will cause serious pollution.After thermal hydrolysis,the dewatering and biodegradability of the sludge can be effectively improved,and the subsequent anaerobic digestion performance can be effectively promoted.This paper focuses on the effects of thermal hydrolysis on solid properties,dewatering performance and biodegradability of sludge,and the methanogenic properties of whole sludge,mud cake and filtrate after thermal hydrolysis.Thermal hydrolysis was carried out at different temperatures of 120,135,150,165,180,195 and 210 0 C and different times of 30,45,60 and 75 min.The TS,VS,SS and VSS of the sludge after thermal hydrolysis were found to decrease with increasing temperature and time,and the loss rates were 30.25%,39.10%,49.55%and 62.18,respectively.%.After the thermal hydrolysis of the sludge,the capillary water absorption time is reduced,the particle size distribution is reduced,and the sludge dewatering performance is effectively improved.Thermal hydrolysis effectively promotes the dissolution of proteins,sugars and VFAs in the sludge filtrate.The sugars are dissolved in a large amount at 150 0 C,and then gradually decomposed into VFAs.The proportion of sugars in COD is reduced from 17%to 5%.VFAs accumulate in the sludge filtrate,and the proportion of COD increases from 6.7%to 6.16.0%.The ratio of protein to COD is between 31%and 57%.When the protein is 150?180?,the protein concentration increases with temperature and time.When the temperature exceeds 180 0 C,the protein gradually decreases due to participation in the Maillard reaction.The reaction of organic matter during thermal hydrolysis was studied by means of GC-MS.A large number of heterocyclic compounds and aromatic compounds appear in the sludge after thermal hydrolysis,which improves the biodegradability of the sludge while thermal hydrolysis,and also brings more difficult-to-degrade organic matter to the subsequent anaerobic digestion.The biochemical methanogenic potential experiments of thermal hydrolysis filtrate,mud cake and full sludge were compared to compare the gas production performance of three different components.Results The anaerobic digestion gas production performance of the effluent,mud cake and full sludge reached the maximum values of 602.020 mL,281.59 mL and 572.28 mL at 180? for 60 min,150? for 75 min and 180?for 60 min,respectively.The performance of gas production is full sludge>filtrate>mud cake.The gas production performance of the filtrate gradually increases with the increase of the temperature and time of the thermal hydrolysis,and the gas production performance of the anaerobic digestion of the mud cake gradually decreases.The degradation rate of TCOD is as follows:filtrate>full sludge>mud cake.The RDA analysis showed that the protein was most correlated with the gas production performance of the sludge filtrate.