Effect Of Hydrothermal Pretreatment On Anaerobic Digestion Performance Of Sludge

Municipal sludge is a kind of very complex heterogeneous micelle.If it is not treated properly,it will not only cause serious pollution to the environment,but also cause the waste of resources.Anaerobic digestion is a kind of sludge treatment technology which is used in China.However,the traditional anaerobic digestion technology has a long stay time,lower anaerobic rate and lower biogas production efficiency,which severely limits the development of this technology.The hydrothermal pretreatment could destroy the cell structure of sludge and promote the dissolution of organic matter in the sludge,which can effectively improve the anaerobic digestion rate of sludge and improve the anaerobic biogas production rate.In this study,the sludge was pretreated by the hydrothermal pretreatment,investigated the influence of sludge solid-liquid ratio,hydrothermal pretreatment time and temperature in the hydrothermal process on the dissolution of carbon nitrogen and phosphorus in sludge,and then the sludge would be proceed in anaerobic digestion.The best hydrothermal pretreatment conditions would be determined by the cumulative biogas production,at the same time,the effect of anaerobic digestion on the dissolution of carbon,nitrogen and phosphorus in sludge was studied.And the conditions of anaerobic digestion would be optimized by recycling the nitrogen and phosphorus of sludge and the solid-liquid phase processed in anaerobic digestion respectively,and ultimately determined the set of sludge treatment scheme.The main results are as follows:The hydrothermal pretreatment could promote the dissolution of carbon nitrogen and phosphorus in the sludge,the dissolution rate of VFAs,COD and total nitrogen increased with the increase of sludge solid-liquid ratio,and the dissolution rate of ammonia nitrogen decreased gradually.The dissolution rate of total phosphorus was largest 95.37%,when the sludge solid-liquid ratio was 10%.With the increase of hydrothermal time and hydrothermal temperature,the concentration of COD and total nitrogen would increased gradually,the VFAs,total phosphorus and phosphate would first increased and then decreased.The ammonia nitrogen concentration increased and the decreased with the increase of hydrothermal time,and it incteased with the increase of hydrothermal temperature.Under the different hydrothermal pretreatment conditions,the concentration of COD was decreased,the concentration of ammonianitrogen and total nitrogen was increased and the total phosphorus and phosphate was decreased after the anaerobic digestion.After the hydrothermal pretreatment,the anaerobic digestion efficiency of the sludge was improved and the cumulative biogas production increased.With increase of solid-liquid ratio of the sludge,the cumulative biogas production decreased and the biogas production efficiency decreased.The cumulative biogas production and the biogas production efficiency decreased with the increase of hydrothermal pretreatment time,and with the increase of hydrothermal pretreatment temperature,it increased first and then decreased.According to the situation of cumulative biogas production in anaerobic digestion,the best hydrothermal pretreatment conditions was chosen the solid-liquid ratio of sludge at 5%,and at the hydrothermal pretreatment temperature160? keeping 0.5h.The VS and TS removal rate in anaerobic digestion could be increased after hydrothermal pretreatment,and the content of methane in the biogas could be increased.After anaerobic digestion,the concentration of carbon and phosphorus was decreased,the concentration of nitrogen was increased.At the solid-liquid ratio of 10%,the degradation rate of TCOD and SCOD was 23.40% and 81.55%,respectively,the concentration of total nitrogen and ammonia increased most.At the solid-liquid of 5%,the total phosphorus and phosphate decreased most.When the hydrothermal time was1.0h,the degradation rate of TCOD and SCOD was 17.42% and 48.43%,respectively,the concentration of total nitrogen and ammonia increased most.When the hydrothermal time was 1.5h and 0.5h,the phosphate and total phosphorus decreased most.The hydrothermal temperature was 200 ?and 160?,the degradation rate of TCOD and SCOD was 39.86% and 60.24%,respectively.The concentration of ammonia and total nitrogen increased most when the hydrothermal temperature was160 ?.The phosphate and total phosphorus decreased most at the hydrothermal temperature was 200?.The anaerobic performance of sludge could be improved with the recovery of nitrogen and phosphorus in sludge after the hydrothermal pretreatment,at the same time the dissolution rate of total nitrogen and phosphate in anaerobic process could be improved.The cumulative biogas production increased by 11.25% after the removal of nitrogen and phosphate,while the daily biogas production efficiency was improved.The solid-liquid of the sludge was be separated after hydrothermal pretreatment,and then they was proceed in anaerobic digestion,respectively.The cumulative biogas production and the biogas production efficiency was improved,anaerobic digestion period can be shortened to 10-15 days.The cumulative biogas production in not solid-liquid separation was 1.3 times less than that of the liquid phase.