Structure-Function And Manganese Metabolic Mechanisms Analysis Of Manganese Oxidizing Bacteria In Biological Fixed And Removal Of Manganese Process

High concentration Fe²⁺ and Mn²⁺ in the groundwater has a serious impact on industry and living. Excessive Fe²⁺ and Mn²⁺ can make water appear color, and can easily lead to various diseases. Thus, Mn²⁺ and Fe²⁺ content in the groundwater are strictly limited in many countries. As a result, biological fixed and removal of manganese process came into being. Mature and stable microbial manganese-oxidizing microbial system would benefit to promote the stability, chemical and biological capability, as well as to improve the tolerance of filter and to achieve quickly start-up of the water-treatment systems. Therefore, it is necessary to have a comprehensive understanding on manganese oxidizing bacterial physiological ecology, enzymatic properties, and further construct high efficient manganese oxidizing functional flora.DGGE and SSCP techniques were applied to analysis the structure and function of manganese oxidizing microorganisms in typical bio-fixed and removal of manganese process; and manganese-oxidizing bacteria with high exoenzyme activity was isolated to construct highly efficient manganese-oxidizing flora, which was used to bioaugment the biofilter column when treating with groundwater containing Fe²⁺ and Mn²⁺. Microbial community's structure in different filter bed and the relationship between them were discussed to reveal the mechanism of bio- removal of manganese further.Study on the microbial communities structure and functional status of manganese oxidizing bacteria in biological fixed and removal of manganese process showed that dissolved oxygen and Fe²⁺-Mn²⁺-ion were important factors to the formation of microbial community structure. Microbial community structure was simple in 20cm⁶0cm depth of filter with high Fe²⁺ and low Mn²⁺, and there were only six operational taxonomic units (OTUs). Flavobacterium sp·and Zoogloea sp·were the dominant manganese populations. There were 21 OTUs in 80cm depth of the filter, and Crenothrix sp·,Zoogloea sp·were the dominant one. Zoogloea sp·was the permanent flora in biological filter, and has widely niche, which plays an important role on the stability of the biological filter. In high Fe²⁺ and Mn²⁺ filter, the diversity of microbial community was poor, and there was no obvious microbial community succession. Fe²⁺ oxidizing bacteria, Gallionella and Ferribacterium, were functional populations, while Zoogloea exist in different depth of filter was the main manganese-oxidizing Flora. In high Mn²⁺ content filter with little Fe²⁺, the diversity of microbial community was richest, and obvious microbial community succession could be observed. Exiguobacterium sp·, which had widely niche and could be adapted to different water quality conditions of ferromanganese, was dominant flora within 40cm depth of filter. Exiguobacterium sp·played an important role in the stability of biofilter. Determination of functional bacteria in different manganese removal water plant would provide theory supports to the process control and the application to the immobilized bioaugmentation technique.18 strains of manganese oxidizing bacteria with high exoenzyme activity were isolated from three waterplants. 16S rDNA identification results showed that all bacteria belonged to eight genera, namely Pseudomonas, Exiguobacterium, Bacillus, Chryseobacterium, Sphingobacterium, Klebsiella, Burkholderia and Delftia. Chryseobacterium sp·MS601, Sphingobacterium sp·MS604 and Chryseobacterium sp·MSB-4 were selected to constructing manganese oxidizing flora and the result showed the optimal porperation was 3:2:1. When treating groundwater with 12mg/L Fe²⁺ and 5.6mg/L Mn²⁺, Mn²⁺ removal rate was 95.96%, while Fe²⁺ removal rate was 97.28%. Immobilized micro-organisms filtration column experiments showed that effluent Mn²⁺ up to national standard after the bacteria inoculated. Microorganisms worked at 17d after incubalation, and the effluent Mn²⁺ in the 300mm of bilfilter reach standard at 44d. With the filtration rate increasing gradually to 8m/h, the effluent Mn²⁺ in the 900mm of bilfilter was still in trace, and the filter columns showed a greater potential and capacity of manganese removal. Sulfuricurvum, Sphingobacterium, Exiguobacterium, Flavobacterium, Clonothrix, Crenothrix made up of microbial ecosystems in steady-state of biofilter. Compared to the control, the immobilized micro-organisms accelerated the stability of reactor, and enhanced the biological and chemical capacity of filter; make the quick start-up of biological manganese removal column come to be true.Microbial oxidizing bacteria were main functional parts in biological filter and the removal of Mn²⁺ is a procedure of adsorption-oxidation involved in cellular enzyme induction and repression. Exoenzyme reaches strong enzyme activity when the temperature was at 10¹5℃, and pH was neutral partial alkaline conditions. Fe²⁺, Al³⁺ and Mg²⁺ take as a catalytic role on manganese oxidoreductase, and Fe²⁺ is the most obvious one; Cu²⁺ and Zn²⁺ have selectivity on different strains'enzyme activity; Hg²⁺ plays non-catalytic role on most of bacteria, but significantly inhibited enzyme activity of Exiguobacterium sp·MB4. The use of Mn²⁺ for manganese-oxidizing bacteria is not only a way of physiological detoxification but also a way of energy reserves. The oxidation of Mn²⁺ is a result of multi-enzyme system working together, and single enzyme had a little (or a little) impact on Mn²⁺. Therefore, it's a more feasibility method to use immobilized bioaugmentation technology or multi-enzyme preparation to strengthening the effectiveness of manganese removal in the process.