Promotion Effect Of Biochar On Methanogenic Potential Recovery In An Acidified Anaerobic System

As a green solid waste treatment technology,anaerobic biological treatment technology has attracted wide attention in recent years because it advantages at area,energy consumption and sustainable.However,there are still many problems that limit the development of anaerobic fermentation and its large-scale application.Acid induced suppression is most important one of them.At present,To solve this problem,the main countermeasures at present are the addition of alkaline chemical reagents or the addition of highly active digested sludge,but these methods have some disadvantages such as high cost and insignificant effect.In order to explore a more economical and efficient acid suppression solution.In this study,biochar was applied to the recovery of methanogenic capacity in acidified methane fermentation system,based on the promotion of biochar to methane fermentation process.It aims to explore a more economic and efficient solution to acid suppression.This study firstly carried out the effect of biochar on the typical methane production process of typical volatile fatty acids(VFA).Based on the determination of the optimal preparation temperature of biochar,the feasibility of biochar for acidification recovery was explored.The biochar was put into the acidified methane fermentation system to verify the recovery of the methanogen activity in the fermentation system.Through the comparative analysis of microbial communities after acid inhibition and recovery,the mechanism of action of biochar to alleviate acid inhibition was explored.The main contents and results are as follows:(1)Biochar was prepared from sawdust at 300,500 and 700°C.The basic parameters of biochar prepared at different temperatures,such as yield,elemental composition,specific surface area,pH value,spectral characteristics,gain and loss electron capacity,were analyzed.The results show that the biochar prepared at 500°C has outstanding comprehensive performance and the largest direct interspecies electron transport(DIET)potential.(2)The feasibility of biochar on the recovery of acidified methane fermentation system was analyzed based on the influence of biochar on typical VFA methanation process.The results showed that biochar only promoted the interaction oxidation of butyric acid.The maximum methane production rate of biochar was 48% higher than that of blank control group at low VFA concentration(1000mg·COD/L).Biochar can promote the degradation of several VFAs,the delay time of methanogenesis is obviously shortened,the maximum methanogenesis rate is increased by 14.5%-30.2%,and the maximum methanogenesis potential is increased by about 8% with the increase of VFA concentration to 600mg·COD/L.The promotion is mainly due to the fact that the larger specific surface area of the biochar can provide the attached growth conditions for the microorganisms,help the microorganisms to quickly adapt to the high concentration VFA environment,and the promotion increases with the increase of the VFA concentration.(3)It was found that biochar was added to the co-fermentation reactor(VFA reached to 59.7g·COD/L)of acid-accumulating kitchen waste and sludge,the pH of the reactor increased rapidly from 6.7 to 7.3,which created the suitable alkaline conditions for methane fermentation.The accumulated VFA decreased significantly within 10 days.The effect of biochar on the recovery of actual acidified methane fermentation system was verified,which provided theoretical basis and technical support for the rapid recovery of anaerobic fermentation system after acidification.(4)The results of microbial community analysis showed that the abundance of Ruminococcus and Syntrophomonas in acidification was almost zero,and increased to 16.6% and 2.5% after recovery,both of which could accelerate the mutual oxidation process.The abundance of Methanosarcina in methanogenic archaea increased from 11.0% to 80.1%.The addition of biochar promotes microbial proliferation associated with direct interspecies electron transport.After the addition of biochar,the metabolism of methanogens in the system is changed from hydrogen to hydrogen and acetic acid,which accelerates the degradation of acetic acid.(5)The substrate was re-continuously added to the recovered reactor to verify the recovery of the activity of the methanogen in the fermentation system.The results show that the performance of the reactor is well restored,and stable and efficient operation can still be achieved without continuous supplementation of biochar.