Effects Of Increasing Influent Solid Concentrations By Phases On Chicken Manure Anaerobic Digestion

The pollution of chicken manure?CM?has been increasing gradually with emission of CM annually.Anaerobic digestion process of CM can not only degrade the organic content,but also can recycle the bio-energy.High-solid anaerobic digestion of CM produces lower secondary pollution,consumes less energy and water,which can achieve high efficiency and has broader prospects.However,CM is high-nitrogen organic waste,including excessive amount of ammonia and organic acids can inhibit the anaerobic digestion process by exerting toxic effect on microbial activity,ammonia inhibition easily occurs when CM is disposed by high-solid anaerobic digestion,which results in stability declining of reactor performance.The stability process of high-solid CM anaerobic digestion is lacking.The characteristics of anaerobic digestion system was studied in the continuous stirring tank reactor?CSTR?by stepwise increasing influent solid concentrations in phases.Furthermore the biogas production,organic removal rate,p H,and the inhibitors of total ammonia nitrogen?TAN?,free ammonia nitrogen?FAN?and volatility fatty acids?VFA?were monitored to evaluate the effects of gradient solid concentrations on the anaerobic digestion of CM.The ammonia inhibition and recovery process were analyzed,moreover the effects of ammonia on the fermentation efficiency and process of anaerobic digestion?hydrolysis,acidogensis and methanogensis?were simulated by inhibition models,the sensitivity of hydrolysis,acidogensis and methanogensis to ammonia in unstable phases was revealed.The results of the present study were given below:?1?When the influent solid concentration increased from 2.10%to 7.24%,the volume biogas production rate had enhanced from 0.31 L·?L·d?^-1 to 0.96 L·?L·d?^-11 during the former four phases,the methane content stabilized on 60%,the efficiency of reactor performance augmented continuously,the stable performance achieved under 7.24%influent solid concentration,the performance of CSTR was at steady period.The kinetic relationship between influent solid concentrations and biogas production,influent solid concentrations and effluent solid concentrations was simulated by the kinetic models,the Modified Stover-Kincannon model was suitable to describe the effects of influent solid concentrations on the characteristics of CM anaerobic digestion,the maximum treatment ability of CSTR was predicted.In addition,when the total solid concentration was raised to 9.30%,TAN reached to3401 mg·L^-1,volume biogas production rate had decreased up to 0.21 L·?L·d?^-1,the obtained results indicated that the ammonia inhibition occurred,the performance of CSTR was at inhibition period.?2?In order to recover the CSTR performance,the influent solid concentration was adjusted to 6.22%,the TAN and VFA increased to 3967 mg·L^-11 and 4078 mg·L^-1 respectively,the performance of CSTR was still at inhibition period.Feeding ceased brought the performance of the CSTR in recovery period,volume biogas production rate and methane content recovered to 1.03 L·?L·d?^-1 and 63.9%respectively when influent solid concentration of 6.23%was fed into reactor,and the steady period of CSTR performance recurred,the tolerance of active sludge to TAN and VFA slightly enhanced.?3?Ammonia inhibition of high-solid CM anaerobic digestion at inhibition period revealed that sensitivities order of hydrolysis,acidogensis and methanogensis to ammonia were:methanogensis>hydrolysis>acidogensis.The overload leaded to the ammonia inhibition of phase 5,nevertheless,ammonia inhibition of phase 6 occurred on account of residual inhibitor and deteriorated sludge,the TAN and VFA during phase 5 was lower than during phase 6 under the same inhibition rate,the active sludge had been acclimated partly.