Experimental Research On Microbial Diversity And Stability Of SUFR System

The spiral up-flow reactor(SUFR)is a new reaction system of wastewater treatment in which the spiral up-flow can better enhance gradient distributing of the substrate in the reactor, which provided relatively stable ecological niches for various microbes. Among these various microbes there grew some microorganisms that still could not been cultivated by tradition method.Based on the research of microbial culture, the low culturibility and recovery barrier of wastewater microorganisms was first systematically and fully analyzed in this paper, and a new method–"near-native pure culture"was created, which has speeded up the growth of some microbes to a certain extent (Patent of invention ZL 200410037037.8). By microbiologic and molecular biologic methods, through comprehensive separation, purification and identification of microbial populations, partial PAOs (Polyphosphate-accumulating organism) in SUFR system has been achieved in this study. Through dyeing test and phosphate uptake/release test, partial PAOs and non-PAOs populations were discovered. Some new PAOs species, which have seldom been reported in journals, were obtained from SUFR system, among which Tsukamurella spp. as a new species was identified primarily by 16S rRNA method. From the obtained results, poulation change, ecological factor impact and stable state were explored in this study. Especially, some ecological factors, include DO, pH value, low temperature (5 ~ 20℃), which affected the microbial community resulting in population change were researched. Through these researches, some microbial population dynamics and characteristics in SUFR were figured out, and a few hypotheses were validated. All these will provide a foundation for full understanding and better interpretation of SUFR system.This research was mainly carried out in the following several aspects:Near-native pure culture method was created, 34 bacteria were isolated from SUFR system, 21 bacteria were identified and studied primarily. Main PAOs population were Microbacterium oxydans, Bacillus spp., Tsukamurella spp. and Tsukamurella tyrosinosolvens and so on.It was found that only about 20% microorganisms may be cultured by conventional culture methods in SUFR system. The main reasons for low culturibility of microbes in SUFR system can be identified, such as crash of close cooperation of microbial populations, conflict between natural adaptability and a sudden change of nutrient, conflict between community dependence and isolated cultivated environment and sharply changed niches etc.Dyeing method was used to examine endocellular polymer of bacterium like PHB and Poly-P and what have been observed could be taken as evidence in PAO qualitative test. Together with phosphate uptake/release experiment, some strains, which included No.12, 22, 23, 29, 44, and 48, had obvious characteristics of PAOs. During phosphate uptake/release experiment, it was found that acetate was more effective than glucose as carbon source.Different DO in SUFR system heavily influenced the distribution of microbes. In all 34 kinds of obtained bacteria, most of them were isolated from anaerobic phase, and most are heterotrophic fermentation bacterium type. The genetic fingerprint presented a high degree of similarity in different DO phases. This phenomenon can be explained that DO mainly affected physiological activity of bacteria, many of them lived in viable but non-culturable (VBNC) state. The pH value of inlet water had a tremendous effect on the structure of microbial community in SUFR system, especially on PAOs/GAOs ratio. The low temperature also can influence bacteria structure, and the analysis indicated that microbial community changed into a simpler structure in SUFR system after experiencing low temperature, but the system still maintained a stable movement. After the higher temperature was resumed, the preponderant populations were recovered rapidly, and the system function was also strengthened subsequently.The research found and verified that after running a long time, abundant microbial diversity canbe achieved in SUFR system among which there were stable preponderant populations and apparently observed phenomenon of Denitrifying Dephosphatation. This phenomenon partially solved the problem of carbon source competition between denitrifying bacteria and PAOs. All these adbantages of SUFR system provided guarantee for its excellent capability of phosphorus and nitrogen removal and ecological stability.This research was sponsored by the National Natural Science Foundation of China "Research on an ideal fluid state urban wastewater biological treatment technology" (50378095) and the key teacher Foundation of Chongqing University(No. 716411045).