Bacterial Distribution And Organic Contaminants Degradation Effect Of Facultative Anaerobic Bacteria In Littoral Zone

Pollution of organic contaminants is a serious problem in the littoral zone of many eutrophic lakes in China and microbial degradation is a key part of organic contaminants degradation. Compared with aerobic degradation process, anaerobic degradation process could reduce the secondary pollution. Due to the complex oxygen environment of littoral zone, the facultative anaerobic bacteria that can survive both in aerobic and anaerobic conditions were the best choice. The present examination was to study bacterial vertical distribution and organic contaminants degradation effect of facultative anaerobic bacteria in sediments from littoral zone in Taihu Lake. The examination provided the necessary theoretical basis of its application in the littoral zone organic contaminants removal.Sediment cores were sampled from littoral zone in west coast of Taihu Lake, East Taihu Lake and Gonghu Lake, the vertical variation of bacteria population sizes, bacterial activities and the environmental impact factors in sediments were determined. The results showed that the sediment was anaerobic and acidic, the Eh had larger values in the surface than that in deeper layers while the pH showed the opposite trend. And the pH of sediment from littoral zone in Taihu Lake was decreasing gradually. The concentrations of TN and TOM showed a decrease trend with sediment depths and three electron acceptors showed the same trend. Sulfate concentrations were many folds higher than nitrate and Fe(Ⅲ) concentrations, sulfate was the most dominant electron acceptor. The aerobic and facultative anaerobic bacteria population sizes showed a decrease trend with sediment depths while the anaerobic bacteria population sizes increased firstly, then decreased. Compared with aerobic and anaerobic bacteria, the variances of facultative anaerobic bacteria population at different sediment depths were not obvious. The adaptability of facultative anaerobic bacteria to littoral zone was much better compared to that of aerobic bacteria and anaerobic bacteria. And the facultative anaerobic bacteria population sizes, electron acceptors, Eh and pH had a great impact on the bacteria activity.The respiration of screened facultative anaerobic bacteria was identified and the growth curve of FAG was drawn. The results showed that the dominant strains were facultative anaerobic bacteria. The growth curve of FAG indicated that the FAG grew rapidly, initiate retardation phase of the strain was8h, logistic phase was8～36h, stabilization phase appeared after36h and recession phase never appeared in88h.A facultative anaerobic bacteria community was inoculated to the sediment from littoral zone in Taihu Lake, the inoculation rate was1%,5%,10%,20%and50%(volume ratio), respectively. The organic contaminants removal rates were calculated and the bacterial population structure was measured during the biodegradation period. The results showed that the removal rate of TOC and TN in the treatment group which was inoculated with facultative anaerobic bacteria was much higher compared to that in the control group, and the most efficient degradation of TOC and TN was observed with the addition of facultative anaerobic bacteria at a volume ratio of10%. It was advised that the inoculum should be washed three times with sterile water before used in order to reduce the influence of organic carbon and nitrogen in inoculum. The facultative anaerobic bacteria population sizes and bacteria activity ETS value in the treatment group, which was inoculated the facultative anaerobic bacteria, were higher than those in the control group. The highest growth rate (at day0～1) of acultative anaerobic bacteria population sizes and the highest EST value (at day0) of bacteria were occurred with a volume ratio of10%. All in all, the volume ratio of10%is the best choice for organic contaminants degradation and the influence of bacterial population structure.