| Economic development has improved the living standard,but also increased the amount of food waste generated,which not only brought great pressure for the environmental protection,and also brought difficulty while the production of food waste is also accompanied by the disappearance of biomass,resulting in waste of resources.In the past,the treatment of food waste often lead to secondary pollution,thus affecting the environment.In order to be able to change the status,to achieve the green processing of food waste,the researchers developed an anaerobic digestion technology,that is,through microbial action,to promote the decomposition of the food waste,in order to achieve energy conversion,methane production,to promote biomass utilization efficiently.In this paper,the technology was studied in four problems:(1)Problem of the food waste,especially for the high oil content food waste;(2)Problem of the anaerobic digestion,especially for the continuous and stable operation;(3)Problem of the slurry treatment,especially for the environmental friendly solution;(4)Problem of the excess sludge treatment,especially for the improvement of biodegradability of excess sludge after pretreatment.Based on the experiment,the technological level was optimized.The pretreatment of high oil content substrate and the treatment of biogas slurry and excess sludge were carried out to further improve the biodegradability of food waste.While reducing the impact of the process itself on the environment,the process also improve the overall efficiency of the resources.The main work is as follows:1,In order to improve the degree of degradation of oil wastewater and increase the production of biogas,a biological-materialized pretreatment method is applied to anaerobic fermentation system.It was found that the introduction of oil-degrading bacteria could improve the efficiency of anaerobic fermentation of oil wastewater.The effects of ultrasonic and citric acid on the production of methane and the effect of improving the fermentation of oil wastewater were also studied.Experiments show that ultrasonic pretreatment can increase the initial stage of methane production,citric acid pretreatment can be in the subsequent stage of this higher methane production trend to maintain.The experimental results showed that the maximum methane yield was 1100 g/g VS,which was 2.8 times when the rate of oil-degrading bacteria was 9%,the ultrasonic time was 10 min and the citric acid concentration was 500 mg/L,The treatment can effectively promote the fermentation of oil wastewater.2,In order to solve the problems caused by acidification in the anaerobic digestion system,the paremeters were investigated.During the start period and continuous operation period,the alkalinity was chosen to be the key paremeter to evaluate the whole process.As a result,the alkalinity was sensitive enough to indicate the stability of the anaerobic digestion process.The organic loading rate of the process could be 12.9 kg/m3/d,methane content could be 70%,and methane production could be 0.54 m3/kg VS?Compare to the start period,the organic loading rate was improved by 1.9 times,and methane production was improved by 1.2 times,the process can operate continuously for over 270 days.3,In order to solve the anaerobic baffled reactor(ABR)low feed load,early compartment acidification serious,lack of late compartment substrate and other issues,the aerobic aeration device was added to the reactor.In accordance with the feed ratio of 6:2:2 and 6:3:1,respectively,for the feed to the reactor,and with the normal-feed for comparison.Experimental results show that,O/ABR at the influent COD of 4000-5000 mg/L,HRT was 48 h are the optimal conditions.For split-feed at 6:3:1,the average COD removal rate was 87%,indicates that the split ratio of 6:3:1 has an optimal community structure.However,the effluent still need to be furtherly treated.4,The effect of continuous stirring on the operation effect of MBR in membrane bioreactor was investigated by using the method of"stirring-aeration" instead of multi-membrane group.It was found that COD and ammonia nitrogen were removed in MBR with continuous stirring processing capacity is better than non-stirring.COD and ammonia nitrogen removal rate increased to 95%and 96%,respectively,effluent COD decreased to 40-60 mg/L,in line with national emission standards,the average processing capacity increased to 14.68 L/h*m2,3 times of the non-stirring,it was found that the continuous agitation of the sludge particles with larger specific surface area and more attachment sites,indicating that the activated sludge in a continuous stirring resulted in higher biological activity,for reducing the reactor area.It proved that MBR with continuous stirring has advantages in improving the efficiency of the reactor and reducing the cost of slurry treatment.5,Based on the synergetic effect of microwave and citrate,the microwave and sodium citrate coupling processes were introduced into the anaerobic digestion and pretreatment stage of the excess sludge.The degradation characteristics and productivity characteristics of the sludge were improved significantly.At the microwave power of 20 MJ/kg TS and sodium citrate concentration of 0.11 g/g TS,the biochemical methane capacity of the excess sludge reached 218.88 ml/g VS,which was 147.7%higher than that of the control.Microwave treatment was found to break the sludge structure,thereby improving the release of extracellular polymeric substances(EPS)and volatile fatty acids(VFAs).The treatment of sodium citrate further strengthened the breakage of tightly/loosely bound EPS.The results showed that the synergistic effect of microwave and citrate could improve the pretreatment effect of excess sludge and effectively improve the utilization of excess sludge. |
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