Study On Strengthening Anaerobic Digestion Of Lime Mud Filtrate

With the development of China's urbanization process and the improvement of environmental standards,the degree of treatment of sewage has been deepened,and the sewage sludge has also increased as a by-product of sewage treatment.Anaerobic digestion is a common treatment method for treating SS.After treatment,the utilization of organic matter in sludge is realized in the form of collecting biogas.In the anaerobic digestion process of SS,the overall reaction efficiency is low due to its slow hydrolysis.Therefore,before anaerobic digestion,the process of hydrolysis of sludge is often enhanced by pretreatment to improve the overall reaction efficiency.In this paper,the SS is pretreated by Lime Mud Filtrate(LMF)to explore its cracking effect on sludge and its impact on anaerobic digestion process.The purpose is to achieve comprehensive utilization of “double waste” through synergistic treatment.The main results of this paper is as follows:(1)The cracking effect of SS under LMF pretreatment.After soaking the sludge in LMF pH(8-11)for 48 hours,the results showed that the maximum increments of soluble total organic carbon(STOC)and soluble chemical oxygen demand(SCOD)in the test group were 27.0% and 91.7%,respectively,compared with the control group.With the increase of LMF pH,the VS of SS decreased from 53.0±0.2% to 45.6±0.2%.Therefore,LMF pretreatment could significouldtly improve the sludge cracking effect,accelerate the dissolution of organic substances,and effectively raise the hydrolysis efficiency.(2)Study on LMF enhanced sludge high temperature fermentation hydrogen production.Each group of the pretreated sludge was inoculated with an equal amount of anaerobic hydrogen producing bacteria,and then reacted at 55±1°C for 72 hours to carry out a hydrogen production test.The results showed that the group treated with LMF pH = 10 obtained the maximum hydrogen yield of 38.3 mL/gVS,which was 2.2 times that of the control group(without LMF).In addition,the maximum removal rate of SCOD in the end of hydrogen production could reach 39.1%.It indicated that the sludge could effectively promote the utilization of the organic substrate in the system after the pretreatment of LMF,thereby increasing the hydrogen yield.(3)Strengthening effect of LMF on high temperature anaerobic digestion of sludge.The pretreated sludge was inoculated with an equal amount of anaerobic bacteria under anaerobic digestion at 55±1°C.The results showed that the sludge treated by LMF could greatly shorten the anaerobic digestion time.The methane production is closely related to the pH of LMF during pretreatment.As the pH increased,the amount of gas produced showed a tendency to increase first and then decrease.After pH=9 pretreatment,the maximum cumulative gas production of the sludge was 1306.5 mL,and the methanogenic rate was 145.2 mL/gVS.At the same time,the removal rate of VS reached 25.0%,and the removal rate of COD reached 75.2%.However,when the pH of LMF was too low or greater than 9,the cumulative gas production of methane decreased,and the removal rate of organic matter also decreased to some extent.(4)The hydrogen production effect of LMF pretreated sludge at 35±1?.There were some differences in the reaction mechanism between mesophilic hydrogen-producing bacteria and thermophilic hydrogen producing bacteria,this experiment studied the anaerobic hydrogen production of the pretreated sludge at 35±1°C for 72 hours.The results showed that under the mesophilic degestion,the hydrogen production increases with the increase of the LMF pH value.When the pretreatment added pH=11,the hydrogen production reaches a maximum of 170.2 mL,and the hydrogen production rate is 18.9 mL/gVS.Compared with thermophilic degestion,the maximum hydrogen production rate(38.3 mL/gVS)was obviously reduced.(5)Study on medium temperature anaerobic digestion of LMF pretreated sludge.This experiment investigated the gas production of anaerobic digestion of inoculum methanogens and pretreated sludge at 35±1 °C.The results showed that with the increase of pretreatment pH(7~11),the cumulative gas production showed a trend of increasing first and then decreasing.When the pH of LMF = 9,the cumulative gas production reached a maximum of 1224.6 mL and the methanogenic rate was 136.1 mL/gVS.At this time,the removal rate of VS was 23.8%,and the removal rate of COD was 72.3%.(6)Economic benefit analysis showed that the highest methane yields could reach 145.2 mL/g VS and 136.1 mL/g VS under 55±1? and 35±1? anaerobic conditions,respectively.However,the medium-temperature anaerobic digestion process consumed less energy,and a more economical treatment could be obtained with comparable yields.In terms of economy and operability,LMF enhanced sludge anaerobic digestion is a potential integrated treatment method.