Vfas Bio-production From Waste Activated Sludge Fermentation Stimulated By Brewing Wastes Carbon/Nitrogen Conditioning: Key Technology And Mechanism Research

Because of the gradually strengthened intensity of sewage treatment and the large increasement of sewage treatment plant quantity,the production yeild of waste activity sludge(WAS)was inevitably increased.In order to achieve the recycling of WAS and reduce the secondary pollution at the same time,more cost-efficient and benign alternatives and strategies are needed.Sludge anaerobic digestion was one of effective ways to achieve the reduction and recycling of WAS.However,C/N ratio in WAS was low.In order to solve a series of problems resulting from low C/N ratio in anaerobic fermentation,additional carbon resources should be added into the digestion system.Combined with the development of the vinegar and wine industry in Shanxi,brewing waste was considered as C/N conditioning carbon in laboratory research of this study.Firstly,different experiment were conducted using vinegar residue(VR)pretreated by different methods to study the improvement of sludge fermentation performance and volatile fatty acids(VFAs)yields.And then vinegar residue(VR),stillage(S)and soy sauce residue(SSR)using preferable pretreatment method were used as conditioning carbon to do the same research.Secondly,the diversity and structure variance of microbial community in the systems were analyzed using high-throughput sequencing.The study may provide reference information for simultaneous recycling of WAS and brewing wastes.Major conclusions were listed below:1.Three typical pretreatments,Ammonium hydroxide(AH),sulfuric acids(SA)and thermal assisted alkaline(TA),all can remove the lignin of VR,break hydrogen bound and produce swelling effect in VR.However,the degree of effect was different to some extent.Biological availability of pretreated VR was increased,which was beneficial to the subsequent degradation in the fermentation process.2.Co-fermentation results showed that the concentration of protein and hydrolysis enzyme activity was enhanced after adding pretreated VR in the system,which implied that pretreated VR can promote degradation of protein in WAS and further improve fermentation performance of acids production.Thermal assisted alkaline(TA)pretreatment had better promotion effect of fermentation performance of acids production than ammonium hydroxide(AH)and sulfuric acids(SA)pretreatment.The maximum concentration of VFAs in TA test achieved 3105 ± 35 mg COD/L which was 2.9 times as much as Control test.However,it was only 1885 ± 159?1561 ± 168 mg COD/L in AH and SA test,respectively.3.Component analysis results showed that C2~C3 carbon was the main components recovered from WAS when maximal VFAs concentration was achieved.The summed ratio of HAc and HPr was respectively 84.5% and 79.1% in AH and SA test,which were both higher than that in TA test.That was to say,TA pretreated VR can greatly enhance VFAs production,while the summed ratio of HAc and HPr was lower than that in AH and SA test.4.As for fermentation performance of acids production,TA was superior pretreatment for VR.TA can also be used as pretreatment for S and SSR in that three kinds of brewing wastes were similar in component.Test results using different brewing wastes as additional carbon showed that SSR can lead to 4517 ± 367 mg COD/L of maximal VFAs,which was 4.2 times of that in the Control test.However,there was little difference of maximal VFAs in VR and S test,which were respectively 3105 ± 35 and 3144 ± 69 mg COD/L.C2~C3 carbon were similarly main components in all VFAs.Compared with Control test,summed concentration of HAc and HPr in VR,S and SSR tests were respectively 2077?2253?3308 mg COD/L,which respectively improved 2.9-fold?3.2-fold and 6.2-fold.SSR were the best brewing waste for VFAs production and C2~C3 carbon recovery.5.The essential reason of acids production enhancement of brewing waste was the variance of microbical community.Pyrosequencing analysis was conducted in order to figure out the characteristics of variance.Diversity indexes,such as Shannon and Simpson index indicated that the diversity of co-fermentation system was reduced after adding VR,S and SSR.Of course,the diversity of sample in SSR test was the lowest.In other words,adding brewing waste into fermentation system was beneficial to accumulate functional microbial community and consequently accelerated production of VFAs.6.Taxonomic classification of pyrosequences at the phylum,class and genus levels were analyzed,which indicated that the microbial community structure was indeed changed.The content of Clostridia closely related with hydrolysis enzyme and VFAs production was enhanced in samples of co-fermentation test,with highest content in sample of SSR test.Other functional microbial community also increased to some extent,which indicated that dominant genus changed.The content of typical functional genus,such as Acetoanaerobium?Proteiniclasticum?Levilinea?Cloacibacillus?Petrimonas increased a lot,which explained the acceleration in production of VFAs.Different increasement implied that different kind of brewing waste would affect microbial community in the system and further affect the efficiency of acids production.