FIELD APPLICATION OF REACTIVE TRANSPORT MODEL FOR NITRATE-BIOREMEDIATION USING FUMARATE IN GROUNDWATER SYSTEM

Groundwater of rural areas in Korea is often contaminated with nitrate exceeding drinking water standard of 10 mg/L (NO₃^--N), which caused harmful influence on human and livestock health. A composting facility in Gimje, Korea, where NO₃^--N concentration is 42 mg/L was selected for field-scale application site. The aim of this study is to simulate optimum design model of in-situ nitrate bioremediation system. The system has been developed to reduce high nitrate-nitrogen concentration in groundwater using slowly released encapsulated carbon source. Transport and reaction parameters for numerical modeling, such as dispersivity and first order degradation rate of nitrate by fumarate, were determined by column tests. First, groundwater modeling, using MODFLOW in GMS that is a commercial groundwater modeling software developed by AQUAVEO, was carried out to simulate the current groundwater flow condition, and the current distribution of NO₃^--N was also reproduced by MT3D. Fumarate was found to be an effective carbon source in terms of cost and nitrate reduction by the previous study. For reactive transport modeling of the bioremediation of nitrate using fumarate, the BTEX module of RT3D incorporated in GMS was adopted, where BTEX was replaced with fumarate as a carbon source. The numerical results showed that the optimal spacing of the wells, where encapsulated fumarate was released, would be 2 m and the optimal release concentration of fumarate would be 75 mg/L, which would reduce NO₃^—N down below drinking water standard and prevent contaminated groundwater from being by-passed between the injection wells. The field application of reactive transport model can be used as a tool for optimization of bioremediation system in nitrate-contaminated groundwater.