Study On Characterization Of Microbial Metabolism In A+OSA Excess Sludge Reduction Process

Activated sludge process is widely used in sewage biological treatment process, at the same time, the amount of excess sludge also triggered many ecological environment problems. An ideal approach was in-situ excess sludge minimization in the process of sewage treatment, coupled with less adverse effects on process performance and sludge characteristics. Oxic-settling-anaerobic(OSA) process which could result in good sludge reduction rate with a simple modification of conventional sewage treatment process and less power consumption has always been one of the focuses of current research. Since the sludge reduction mechanism of the OSA process still remains controversial, the process optimization control and practical application of the OSA process was restricted. However, the system interpretation of the microbial metabolism in the OSA process could not only obtain the direct evidence to the sludge reduction mechanism, but also may provide a theoretical reference for enhancement of sludge reduction rate and process optimization of A+OSA process. The activated sludge from anoxic-oxic-settling-anaerobic(A+OSA) is as the main studying object in this thesis, the microbial metabolism characteristics as well as its regular pattern are studied.The analysis of extracellular metabolites could investigate the microbial metabolic process. The result show that the component content of extracellular metabolites of microorganisms from the different reaction zone in A+OSA and AO systems and its variation are different significantly. The sludge microorganisms in the A+OSA processy strengthen its hydrolysis to dissolved cell substance under the condition of poor nutrition environmental and implicit growth occur correspondingly when return to the main reaction zone. Thus the utilization of the organic carbon is promoted. Due to the insertion of sludge holding tank, compared with the AO reference process, the environment of the A+OSA system result in the extracellular metabolites molecular distribution tend to smaller, at the same time, the proportion of small molecule substance also has a large degree of increase, thus makes the average molecular weight of EPS material components decrease in the system. The 3DEEM spectrogram show that large particle organic matter is decomposed into smaller pieces of material or aromatic ring cracking happened in the EPS samples from sludge reduction process. On the whole, the insertion of sludge holding tank, makes the molecular structure of EPS in the A+OSA system simplified, it is easier to microbial uptake and maintain metabolism of microbes under the condition of poor nutrition. All of these contribute to the sludge reduction effectiveness of the OSA system.The analysis of intracellular metabolite distribution with the technology of metabonomics could also investigate the microbial metabolic process. The result show that the main heterogeneity intracellular metabolite between the A+OSA process and AO process are organic acids, amino acids and the derivatives, parts of nucleic acid components and amines. The 3-Hydroxybutyrate and 2-Hydroxybutyrate used for synthesize energy storage compounds decrease in the A+OSA process is helpful to weaken endogenous metabolism and enhance cell lysis of reduced microorganisms.The increase of amino acids and the derivatives, parts of nucleic acid components and amines of microorganisms in the A+OSA process could prompt to withstand the unfavorable habitat in SHT. The analysis of intracellular metabolite and metabolic regulation on the EPS are verified mutually in this study, which interpreted the mechanism of microbial metabolism in the A+OSA process.In the current framework on the basis of the model ASM3,Using material balance theory, and through analysis of kinetic parameters of unique biological process, first proposed and established the sludge reduction and the reference SBR-ASM3-SMP model, and discusses the impact of SRT to water quality, active sludge, sludge accumulation of inert particles, etc. during the changes SRT. Found that SRT would bring greater impact on the nature of the sludge and water of sludge, the advantages of sludge reduction process lies in lower bH and longer SRT, which can maintain and even improve pollutant degradation rate while reducing sludge yield.