Removing nitrate from groundwater using innocuous oils: Water quality studies

Innocuous oil can be used to remove NO3 from flowing ground- water. Oil applied to soil columns becomes trapped in the matrix where it stimulates denitrification by providing a carbon source for microbial denitrifiers. In this study water was denitrified using up-flow reactors containing sand and vegetable oil. Effluent waters were evaluated before and after secondary treatment. Secondary reactors were aerated granular activated carbon (GAG) and sand filters. Denitrification reactors produced NO3-free water with high turbidity (19.2 NTU), chemical oxygen demand (62 mg/L), and total suspended solids (8 mg/L). The GAG-sand filters reduced turbidity to 2.5 NTU, chemical oxygen demand to 28 mg/L and suspended solids to 0.8 mg/L. Innocuous oil provides a simple method of NO3 removal. Application could involve the injection of oil around a well or the mixing of oil with sand and gravel to form a reactor for removing NO3. Also, oil injected into the ground might be used to contain a NO3 plume.