USE OF VEGETABLE OIL TO REMOVE NITRATE FROM FLOWING GROUNDWATER

Abstract

This study investigated the use of vegetable oil to cleanse nitrate from groundwater. The hypothesis on which the study was based was that oil trapped in the soil matrix would form an immobile organic zone through which water flows; nitrate in the water would be removed as microbial denitrifiers utilized the oil as a carbon source. Laboratory studies show that the procedure has merit. Both corn and soybean oil rapidly stimulated native bacteria to remove nitrate from water in static anaerobic bioreactors. Soybean oil/water mixtures ranging from 0.8 to 12.5% oil in water were tested and all were effective at supporting denitrification. Also, denitrification occurred rapidly at nitrate concentrations up to 2000 ppm NO3-N. In addition to studies with static bioreactors, soil column studies were conducted. Soybean oil injected into 2.5 × 34 cm columns containing aquifer matrix or sand removed nitrate from flowing water. Flow rates of up to 600 mL/day were successful. Innocuous vegetable oil may provide the basis for a simple and inexpensive method of nitrate removal from contaminated groundwater.