Research On Process Of Direction Acids Rugulation And PHA Production Using Waste Carbon Resource

In the process of waste water treatment, a large amount of excess sludge was produced,which was rich in proteins, polysaccharides and other organic substances.How to combine social, economic and environmental benefits to maximize the use of sludge is the new direction of sludge treatment and resource utilization.In the process of sludge fermentation, large amounts of volatile fatty acids(VFAs) can be produced. Due to the use of VFAs in the process of coupling polyhydroxyalkanoates(PHA),sludge fermentation to produce VFAs becomes a heated topic. Since the proportion of odd-number and even-number in VFAs have a significant impact on the performance of PHA,the study on sludge fermentation for directional acids production is important. As a carbon source of waste generated in the production of biodiesel, the utilization of crude glycerol also caused extensive discussions.This study carried out the means of co-fermentation on sludge-glycerol.In the form of batch experiments, the research studied sludge-glycrine co-digestion.The study showed that a maximun total VFAs yield of sludge-glycerin codigestion was 694.87 mg COD/g VSS, which was 2.33 times to the contol experimental group-the sludge fermentation.When analyzing the VFAs composition, the result showed that the proportion of odd-numbered VFAs in codigestion systerm was highly improved,which was up to 65.41%, while the ratio is just 11.96% for sludge fermentation. To explore whether other carbon waste and sludge so-digestion has a similar effect on the total VFAs yield and the proportion of odd-numbered VFAs, the research studied sludge-glycerin and sludge-starch co-digestion. β-cyclodextrin(β-CD)is a kind of polysaccharide which can enhance the hydrolysis of sludge.The research studied different dosage of(β-CD) on the total VFAs yield.The result showed a maximum of VFAs yield 541.70 mg COD/g VSS, which is 2.04 times to the control group.The study analyzed the microbial community structure of batch experiments by terminal restriction fragment length polymorphism analysis(T-RFLP) technology.The result showed that the co-digestion can change the microbial community to some degree which β-cyclodextrin hardly have effects on the community structure.The study adopt a response surface design idea to realize the directional acids production.The p H,the dosage of β-cyclodextrin and the C/N were three variations in the response surface experiment.The result showed that the proportion of the odd-numbered VFAs can be regulated in the range of 15%~60%.Two mathematicalformula about the proportion of propionic acid and the odd-numbed VFAs were simulated,which met with Linear, Quatic pattern respectively.On the base of the response surface experiment,the study selected three diffrent conditions for semi-continuous flow reactor.In the final fermentation liquid,the proportion of the odd-numberd VFAs were 57%、48%、40% respectively.The T-RFLP showed that in the semi-continuous flow reactor,the microbial community structure made a change if the condition was different.In the end,a study of the synthesis of PHA were conducted with the fermentation liquid.The different components of VFAs have great influence on the constitute of PHA.Study showed that the odd-numbered VFAs were benifit to the synthesis of PHV and the even-numbered VFAs were the main source of PHB.The proportion of PHV generated from different VFAs composition were71.04% and 53.91% respectively.