Investigation On Microbial Community Variation And Processing Performance Of Two-phase Integrated Sludge Thickening And Digestion Reactor (tistd)

There is many problems of conventional anaerobic treatment process such aslow load, long digestion time, higher investment costs and so on, so the development of new efficient and low consumption of sludge anaerobic process is very urgent. A new reactor called Thickening and Digestion Reactor with Two-phase Integrated (TISTD) was designed in this paper, is a new biological treatment process focusing on process changes rather than focusing on the transformation of the reactor structure, with good concentration of sludge digestion. To study the performance of the reactor operating under different loads and identify the optimal load conditions, the reactor indicators was detected during the stable operation. The results showed the thickening and digestation effects of the TISTD were separately better than conventional gravitational thickening tank and anaerobic digestor, and the optimal sludge dosage rate was 30%; To understand the mechanism ofthe microbial in reactor running under optimum dosage rate and the function bacteria which maintains the stable operation of reactor, the predominant strains of the TISTD reactor was isolated and cultured by conventional methods and studied by 16S rDNA sequence analysis under the mid-temperature; In addition, with the changes of sludge dosage rate, the gas production and other indicators was changed, which mainly due to microbial community structure within the reactor caused by a change. Groups of sludge samples were collected when the reactor was started-up, disordered and stably operated with 10%, 20% and 30%, respectively, and followed by DNA extraction, purification, 16S rDNA PCR amplification and temperature gradient gel electrophoresis(TGGE). All stages of the reactor community structure and ecological changes were researched and analyzed, and the dynamic relationship between the sludge dosage rate and the community structure of the reactor was revealed.The TISTD reactor was 110L in capacity, with design sludge dosage rate of 30%. To startup TISTD, the reactor used 10% sludge dosage rate under the condition of mid-temperature(33-37℃). Taken pH, alkalinity, VFA, gas production as monitoring indicators, the running performance were investigated during the reactor up and running with dosage rate of 20%, 30%, 40% and 50%, and the effect of sludge treatment were inspected in 20% and 30% of the dosing rate. The re sults show that the sludge organic matter decomposition rate and the rate of water content of influent sludge reached 65.09 percent and 92.09 percent respectively and the actual gas production achieved the highest when the TISTD reactor with the sludge dosage rate of 30% in the temperature conditions (33-37℃), which means sludge digestion and concentration were in good condition.When the reactor under the sludge dosage rate of 30% and on stable operation stages, the sludge microscopy of acid-phase of reactor revealed that various forms of amoeba, flagellates and ciliates, etc. The SEM photographs of the sludge in methane-phase show a variety of filamentous bacteria, rod-shaped bacteria, fungi, and larger spherical micelles bacteria. After isolation, cultivation and colonycounts in the anaerobic environment, the dominant strains were found to belongto Bacillus and Methanogenic bacteria by 16S rDNA sequence analysis and phylogenetic analysis, which may be function strains within the system.The bands belong to different load samples on TGGE patterns appeared numerous and significant changes, indicated that the reactor system contains a large number of microorganisms and a higher degree of diversity in the distribution to ensure the stable operation of the reactor, so that the TISTD has a strong resistance to shock load; The typical bands of TGGE pattern from different loads showing obvious differences revealed the community structure of the system occurred corresponding changes with the load of the reactor changed. Quantitative analysis by Quantity One software showed the similarity of each period sample is not high, indicating that the community structure of the reactor changed greatly under different loads. Typical band analysis showed that most of the significant bands of close relationship belongs to the genus of the uncultured strains.