Synthesis Of PHAs Using Carbon Source From Alkaline Fermentation Of Sludge Coupled With Potassium Perbisulfate Compound Salt

Polyhydroxyalkanoate(PHA)is an environmentally friendly "green material",but the relatively high cost of carbon sources limits the commercial application of PHA.Short Chain Fatty Acids(SCFAs)produced by alkaline fermentation of sludge can be used to synthesize PHA,reduce the production cost of PHA,and realize resource utilization and reduction of sludge.However,alkaline fermentation of sludge has problems such as long fermentation time and limit carbon source.Peroxymonosulfate(PMS)is a new type of active oxygen disinfectant that integrates safety,environmental protection and high efficiency,which can promote the fragmentation of sludge particles and increase the acid production of sludge.PMS with alkaline fermentation of surplus sludge can increase the acid production of sludge and short the fermentation time.The study of PMS synergistically with alkaline fermentation to obtain SCFAs to synthesize PHA is of great significance for the promotion and application of industry and commerce and the sustainable development of resources and environment.To study the feasibility of PMS with residual sludge alkaline fermentation to obtain carbon source to synthesize PHA,and to investigate the PHA production performance and microbial community structure of the enrichment reactor under the two substrates of simulated pH10 fermentation broth and simulated pH10+PMS fermentation broth.Compared the performance of PHA production under the two groups of substrates in batch synthesis experiments;analyzed the effects of aeration under the optimal substrate and different feeding times on the synthesis of PHA;explored the actual pH10+PMS performance of PHA production under fermentation broth,the conclusions obtained are as follows:(1)The simulated pH10 fermentation broth and simulated pH10+PMS fermentation broth have two carbon sources on the enrichment reactor for PHA production performance.The study shows that the maximum synthesis of PHA when the simulated pH10 fermentation broth and simulated pH10+PMS fermentation broth are carbon sources are respectively 10.61 wt%,12.22wt%(accounting for the proportion of exploitable suspended solids,namely VSS),and the synthesis of poly-3-hydroxybutyrate(PHB)under the two carbon sources is higher than that of poly-3-hydroxyvalerate(PHV)synthetic volume.(2)Simulation pH10 fermentation broth and simulated pH10+PMS fermentation broth have two carbon sources on the synthesis stage of PHA production performance.The research shows that the order of carbon source for maximum synthesis of PHA is: simulated pH10+PMS fermentation broth>simulated pH10 fermentation broth.They are 52.53 wt% and 48.84 wt%,respectively;PHB and PHV have the same changing law with PHA,and the synthesis of PHB under different carbon sources is higher than that of PHV.(3)Sampling was taken from the SBR reactor at the enrichment stage when the simulated pH10 fermentation broth and simulated pH10+PMS fermentation broth were used as carbon sources,and the microbial community structure was analyzed,and the results showed : At the phylum level,the Proteobacteria in the two samples were the dominant phyla,accounting for72.09% in the pH10 fermentation broth group and 82.93% in the pH10+PMS fermentation broth group.At the class level,the α-Proteobacteria accounted for the largest proportion in the two groups of samples,and the β-Proteobacteria,γ-Proteobacteria and δ-Proteobacteria accounted for a significant increase in the pH10+PMS fermentation broth group.At the genus level,the synthesis of functional flora closely related to PHA synthesis in the pH10+PMS fermentation broth group has increased.Among them,Paracoccus accounted for 23.45%,Dauer accounted for 7.62%,and Methylobacterium The genus is 3.98%.Comprehensive analysis showed that the use of pH10+PMS fermentation broth as a carbon source to enrich PHA,the bacterial flora related to the synthesis of PHA was enriched,and the proportion of other bacterial communities was reduced accordingly,making the system more conducive to the synthesis of PHA.(4)Using simulated pH10+PMS fermentation broth as carbon source without adding nitrogen and phosphorus,the effects of aeration in the synthesis stage and different feeding times on the performance of PHA production were investigated.The results show that the synthesis of PHA is in the aeration rate.It reached the maximum at 1.6 L/min,which was 67.30wt%;the PHA synthesis amount was the maximum under three feeds,which was 83.01 wt%.(5)The struvite precipitation method was used to investigate the removal effect of Mg/P and pH on ammonia nitrogen and phosphate.The best conditions obtained were: pH=10,Mg/P=2.4.Under these conditions,the phosphate removal rate was 88.09 %,the removal rate of ammonia nitrogen was 71.98 %.(6)When the sludge fermentation broth with nitrogen and phosphorus removed was used as the substrate,the maximum PHA content of the mixed flora in the PHA synthesis stage was only 31.98 wt%,which was due to the large amount of dissolved organic matter(DOM)in the actual sludge fermentation broth.