Removal of Nitrate in River Water by Microorganisms in Saturated-Zone Soil: Laboratory-Scale Column Test

Aquifer recharge and recovery is a technology used to ensure a stable supply of clean water.During the process, river water is injected into a soil aquifer and stored.The stored water is then recovered and used to produce drinking water.It is important to understand quality improvement of the injected water while it is stored in the aquifer.In the present study, a lab-scale column reactor containing saturated-zone soil was employed to mimic an aquifer.The reactor was used to investigate microbial removal of nitrate that is a major inorganic contaminant detected in the Nakdong River.The reactor was introduced with river water that contained nitrate at concentrations (5.07, 6.81, 8.27, and 11.07 mg NO3 -/l) detected downstream of the Nakdong River in the past 2 years.The nitrate concentrations decreased during the introduced water is retained in the reactor.Effluent from the reactor contained 1.49 mg NO3 -/l or less and had an average pH of 7.98 regardless of the nitrate concentrations of the influent.However abiotic control reactor showed similar nitrate-concentrations in its influent and effluent.Considering the result of abiotic control, the decreased nitrate concentration observed in the test column suggested that microorganisms in saturated-zone soil removed nitrate in the river water introduced into the reactor.Results of this study will be used to better understand microbial improvement of water quality in aquifer recharge and recovery technology.