Analysis of microbial community structure and degradation of ammonia nitrogen in groundwater in cold regions.

Abstract

Nitrogen pollution exceeding the standard because of intensive farming and cropping systems has been a widespread problem in Northeast China. This study investigated the characteristics of functional microorganisms in groundwater in the Bang River farming area. Metagenomic sequencing was used to analyze microbial community structures and Canoco was applied to reveal the response relationship between the microbial community and water environmental factors and to identify changes in the microbial population in response to the addition of electronic donors NH4+-N, NO2--N, and NO3--N. The results showed that the dominant microorganisms in groundwater belong to the genera Exiguobacterium, Citrobacter, Acinetobacter, and Pseudomonas, which accounted for more than 40% of the total microbes in the study area. When combined with the results of a water chemical factor test, the dominant bacteria were found to be correlated with Fe2+, Mn2+, NH4+, NO3-, NO2-, HCO3-, DOC, and pH in the water. However, the microbial population changed after the addition of the electron donor, with the genera Pseudomonas, Serratia, Enterobacter, Azomonas, and Ewingella accounting for 97.06% of the total sequences. Indigenous nitrogen-degrading bacteria suitable for low temperature, low oxygen, and oligotrophic groundwater were screened out. The total removal efficiency of NH4+-N, NO2--N, and NO3--N in 120h was 90.83%, 75.04%, and 73.35%, respectively. According to the experimental results, the degradation reaction kinetics followed a pseudo-second-order equation. The results presented herein provide an important scientific basis for the microbial remediation of groundwater contaminated by ammonia.