Evaluation of Performance and Microbial Community of NH4-N and NO3-N Bioreactors

Abstract

Nitrogen contamination of groundwater has become an increasingly serious issue affecting the quality of drinking water. An energy efficient and low cost drinking water treatment method involving two attached growth bioreactors were developed for both NH 4 -N removal and NO 3 -N removal. Continuous flow of the groundwater through the NH 4 -N bioreactor resulted in the removal of NH 4 -N by nitrification without any aeration. The efficiency of NH 4 -N removal was determined to be 70% in the laboratory and 95% in on-site trials. The higher efficiency of the on-site bioreactor resulted from the presence of various groups of local microorganisms (8 groups and 3 classes) which were cultivated from the on-site groundwater. The NO 3 -N bioreactor was capable of removing NO 3 -N from the groundwater efficiently by hydrogenotrophic denitrification at low H 2 supply rates. A high NO 3 -N removal efficiency of 98% was found in the bioreactors that used both local microorganisms and other microorganisms that were cultivated from a drinking water system. Although the microbial community present in both NO 3 -N bioreactors were different, the dominant bacterial taxonomic groups were found to be similar, i.e., Betaproteobacteria and Gammaproteobacteria. The NH 4 -N and NO 3 -N bioreactors are alternative methods with high efficiency and various microbial groups for nitrogencontaminated groundwater treatment.