Synergetic Effects Of Biofilm Carriers And Membrane Separation On SCFAs Production Of Anaerobic Sludge Fermentation

The biological treatment capacity of urban wastewater nationally is increasing,and as a byproduct,the waste activated sludge(WAS)production is also increasing sharply.WAS is a special type of biomass,which is a research hotspot of resource recovery and re-utilization currently.In view of the low hydrolysis and acidification efficiency of anaerobic fermentation of WAS,the effects of biofilm carrier and membrane separation on short-chain fatty acids(SCFAs)production were studied in this dissertation.The results of tests on biofilm carriers type showed that biocarrier had significant effects on the anaerobic sludge fermentation process.After the addition of polyethylene plastics(PE)and polyurethane sponge(PUS)carrier,the concentration of soluble chemical oxygen demand(SCOD)and SCFAs increased to 1.7 times and 1.6 times of the original level,respectively,and the hydrolysis and acidification enzyme activities increased 1.2?2 times.The relative abundance of both Clostridium(belonging to Firmicutes phylum)and Bacteroidetes(belonging to Bacteroidetes phylum)that produce SCFAs have increased,while the relative abundance of ?-Proteobacteria(belonging to Proteobacteria phylum)that consume SCFAs has decreased.The addition of PE and PUS carriers improved the level of various metabolism function metabolism,especially the amino acids and carbohydrates metabolism levels.In contrast,the addition of GAC carrier seemed to inhibit the hydrolysis and acidification process of WAS,which might be due to the strong adsorption of SCOD on GAC.The dosage of PE carrier was optimized according to sludge disintegration solubilization,hydrolysis and acidification.Compared with the control test,the SCOD and SCFAs concentrations were much higher after the addition of 20% PE carrier,which was an optimal condition to promote the acid production from alkaline pretreated sludge,and it was economical and effective.The PE carrier obviously promoted the disintegration,solubilization and hydrolysis of sludge,especially the release of organic matter at the initial fermentation stage,but it had no significant effect on acidification.Separate and synergetic effects of 20% PE carrier and membrane separation on SCFAs production in an anaerobic fermentation reactor was studied,respectively.Results showed that PE carriers alone greatly promoted the sludge hydrolysis,and increased the SCOD and SCFAs by 1.33 times and 1.16 times,respectively.Microfiltration alone promoted the acidification of sludge,the concentration of SCOD and SCFAs increased 1.24 times and 1.27 times,respectively.After the PE carrier and membrane separation were both applied,the concentrations of SCOD and SCFAs in reactors were 2 times and 1.3 times higher than that in the separate operation mode,respectively.The analysis of microbial community structure showed that the addition of PE carrier was beneficial to the enrichment of hydrolytic bacteria,and increased the metabolic abundance of amino acids and carbohydrates,while membrane separation was beneficial to enrichment of acidified bacteria.The coupling of the PE carrier and membrane separation had a synergistic enhancement effect,and further improved the abundance of amino acids and carbohydrate metabolic function,which is the main reason for the increase in the production of SCFAs.After coupling with the PE carrier,the MBR membrane fouling has also been alleviated.