Study On The Strengthening Technology Of Anaerobic Digestion Of Domestic Sludge

In the traditional sludge anaerobic digestion process,there exist problem of low efficiency of hydrolysis rate and imbalance of C/N ratio in anaerobic digestion(AD) of WAS.Biological and physical pretreatment were applied to enhance the hydrolysis of organic matters in WAS. The C/N ratio was optimized and high quality inoculum was used to enhance anaerobic digestion biogas conversion rate.Some main results of the present research are obtained as following:The hydrolysis of sludge could be promoted by adding protease and cellulase enzymes. It was demonstrated that the optimal dosing of protease and cellulase were 60 mg·g-1TS and 20 mg·g-1TS, respectively, and the optimum reaction time and temperature were 4 h and 50℃, under which effluent SCOD of sludge hydrolysis increased by 12% and 28% respectively. The enzyme treated sludge under the anaerobic fermentation, and the gas production were 7.3% and 12.9% higher than the control, respectively.Different inoculum can affect the efficiency of anaerobic digestion of sludge.In the batch anaerobic digestion experiment, the specific biogas production of WAS enhanced by 9.5%,14.4%,27.5% with grease acclimated inoculum,food waste acclimated inoculum and cellulose acclimated inoculum, respectively, compared to the original strain,. Because of the maximum increase of anaerobic digestion efficiency of sludge, it is advisable to select the cellulose acclimated inoculum as the inoculum of anaerobic digestion of sludge.The CPAM can be put into the anaerobic bacteria in the sludge, which can separate the water from the anaerobic sludge by flocculation, and increase the concentration of the bacteria. It is demonstrated that the TS of anaerobic sludge rose to 2.14% and the rate of anaerobic sludge recovery(by COD) reached 80% with the CPAM addition of 100 ppm. The activity of anaerobic sludge was not inhibited with the CPAM added to 150 ppm.The combined ultrasonic and alkaline pretreatment can improve the dissolution of organic matter in the sludge, with the NH4-N,SCOD and VFAs in the sludge increasing 1 times, 74.1 times, 4.2 times, respectively. The methane yield can be increased by 20% after the combined ultrasonic and alkaline pretreatment.The cellulose acclimated inoculum can increase the methane yield by 6.4% in the continuous anaerobic digestion experiment.Spent mushroom substrate(SMS) could be used as supplementary carbon source for WAS. Biogas production of co-digestion of mixed WAS and pleurotus ostreatus SMS can increase 80.4% higher than each substrate fermented on its own. The unit VS biogas production rate of co-digestion of mixed WAS and pleurotus ostreatus SMS reached 264.0 ml/gVS. Biogas production of co-digestion of mixed WAS and pleurotus eryngii SMS can increase 84.4% higher than each substrate fermented on its own. The unit VS biogas production rate of co-digestion of mixed WAS and pleurotus eryngii SMS reached 298.4 ml/gVS。...