Step-feeding Biological Contact Oxidation Process and Its Microbial Community Structure for Treating Polluted River Water in the Dianchi Lake Watershed

摘要

The Dianchi Lake receives most of the pollution load from 29 rivers in the watershed.To control lake eutrophication,it is a cost-effective measure to split and purify some river flow in a bypass treatment system.A demonstration work of step-feeding biological contact oxidation process (SBCOP) with the treatment scale of 1000 m3/d for river water treatment was built and operated on the bank of Daqing River,the most seriously polluted river in the Dianchi Lake watershed.Experiments were carried out to determine the treatment efficiency of the SBCOP demonstration work,and the microbial community structures of biofilm and sludge in the SBCOP demonstration work were also analyzed by using denaturing gradient get electrophoresis (DGGE) technique to verify the treatment efficiency.The hydraulic retention time (HRT) was 4.75 h in the whole operation period.According to the influent qualities and climatic conditions,the step-feeding ratio (4∶3∶2 and 1∶1∶1) and air-water rate (3∶1 and 2∶1) were adjusted.The results showed that SBCOP demonstration work kept high removal efficiencies for COD and NH4+-N,and the average removal rates were 37.7％ and 32.9％ each; while the average removal rates of TN and TP were as low as 10.5％ and 13.7％ each.The microbial community structure experienced great changes during the whole operation,and the temporal change had more significant effect on microbial communities in treatment systems than spatial change.Biofilm,sludge,Spirogyra sp.,and duckweed were composed of a complex microcosm which could resist the environmental changes.When the influent was lake water,the DNA band numbers and Shannon-winner Indexes of microbial community got lower,possibly due to the shortage of substrate.The results of DNA sequencing indicated that the microorganisms with known sequences were mainly uncultured ones.The dominant microorganisms in the SBCOP demonstration work included Proteobacteria (α,ε,and γ-Proteobacteria),Bacteroides and unknown groups.Based on the sources in the NCBI database,all the dominant microorganisms are helpful to the purification of contaminants,and some of them are denitrifying bacterial strains.