RESEARCH ON GROUNDWATER NITRATE REDUCTION EFFICIENCY BASED ON METHANOTROPH AND FUNCTIONAL MICROORGANISMS
Pollutants in groundwater are complicated from many sources,and nitrate pollutants are one of them.In this study,a methanotroph-based biofilm reactor was established to find a remediation method with low consumption,high efficiency,and no secondary pollutants,by assaying nitrate reduction efficiency,functional microorganisms,and metabolic pathway.Results showed that the maximum nitrate removal rate reached 98.83%when nitrate nitrogen concentration in the influent was 10 mg/L.DOM component changes found that the dissolved organic matter primarily was a tryptophan-like protein.Macrogenomic analysis revealed that the dominant aerobic methanotrophs in this biofilm reactor were Methylocystis(5.25%)and Methylomonas(2.73%);the dominant anaerobic methanotrophs were Methylmirabilis(0.0016%),and Methanoperedens(0.0016%);and the dominant nitrate-reducing bacteria were mainly Lysobacter(9.72%),Opitutus(2.74%),and Hypomicrobium(2.01%).The KEGG database was annotated to identify microbial functions in the system,including 40 methane-metabolism-related functional genes and 19 nitrogen-metabolism-related functional genes,as well as 5 relatively complete methane metabolism pathways and 6 nitrogen metabolism pathways.Thus,methanogens could be proved with the capability of partial denitrification and good selectivity for nitrate.Relevant research results can provide technical support and a theoretical basis for the remediation of nitrate-contaminated groundwater.