Recovery Mechanism Of Methane Production Performance From Stored Concentrated Anaerobic Sludge

Anaerobic digestion is an effective method for the utilization of biomass energy in China,which is faced with many problems for industrialization,and the rapid start-up of the new anaerobic reactor is one of them.New inoculum of anaerobic reactor can be obtained from the running of anaerobic reactor,but there are strong restrictions of time and space for this method.Nearby running anaerobic reactor and enough quantity anaerobic sludge is necessary,or transportation of sludge from other places will greatly increase the cost of anaerobic digestion,hindering the process of industrialization.It is time-consuming and inefficient to use animal manure and waste water to cultivate sludge.Therefore,the feasibility analysis is of practical significance for stored concentrated anaerobic sludge as the inoculum to realize rapid start-up of anaerobic reactor.First,the methanogenic activity of original sludge under different organic load(OLR)was studied.The results showed that the maximum methane yield and volumetric methane productivity of sweet potato vine(SPV)mono-digestion were 200.22 mL/g VSadded in wet anaerobic digestion and 12.20 Lmethane/Lworking volume in solid anaerobic digestion,respectively.In contrast with SPV mono-digestion,co-digestion with manure increased methane yield within the range of 14.34%-49.11%in different anaerobic digestion digesters.Synergistic effects were found in semi-solid anaerobic digestion and solid anaerobic digestion with each two mixing feedstock.The mathematical modified first order model was applied to estimate substrate biodegradability and methane production potential well with conversion constant ranged from 0.0003 to 0.0953 1/d,which indicated that co-digestion increased hydrolysis efficiency and metabolic activity.Secondly,the activity recovery performance of batch anaerobic digestion inoculumed with stored concentrated anaerobic sludge was studied.The results showed that the methanogenic activity of stored concentrated sludge decreased,the methanogenic activity of stored concentrated sludge reached 79.93%-90.39%of the original sludge.The cumulative methane yield in the second and third phase increased by 1.11%-29.97%and 3.33%-30.43%,respectively,compared to the original sludge.After three phases of the activation process,emerging time of the maximum daily methane yield of each treatment was advanced.The maximum daily methane production in the second phase is higher than that in the first phase,while the highest daily methane production in the third phase is higher than that in the first phase,and most treatment is slightly lower than the second phase.In terms of system stability,the anaerobic digestion system in three phases was stable and tended to be more stable.Moreover,addition of sweet potato to the digesters can improve the stability of the system.After a batch reaction,the methanogenic activity of stored concentrated anaerobic sludge can be largely recovered to achieve a rapid start-up.Finally,the methanogenic activity recovery performance of stored concentrated sludge and stored original sludge in different OLR batch reactor and continuous reactor was studied.In the start-up process,the biogas production of digester inoculumed by stored concentrated sludge is higher than that inoculumed by stored original sludge,while the cumulative methane yield is lower than that inoculumed by stored original sludge.Start-up processes under different OLR for stored concentrated sludge and stored original sludge were successful and reactors were able to run stablely and adapt to an operation load change.VFA accumulation and ammonia inhibition was not found in all the reactors,which could cause system instability and failure of digestion.Take biogas production in three continuous phases iinto consideration,the reactors under 10 g VS/L and 20 g VS/L were better than 5 g VS/L.No matter inoculated with the stored concentrated sludge or stored original sludge,the methane production of reactors started with 5 g VS/L OLR was relatively low and fluctuated,and the adaptability of those reactors were perfomed poor to adapt the load change.