Iron oxidation coupled with biodegradation of organic contaminants in a simulated ground water system

Abstract

Aerobic degradation of hydrocarbon contaminants in anaerobic ground water would be enhanced by oxygenating the water. However, when a contaminated ground water contains high concentrations of reduced iron, competition for oxygen may occur. This study was designed to study this competition. The oxidation of iron and biodegradation of organics was studied in a 12 in X 2.5 in soil column by injecting either oxygen microbubbles or hydrogen peroxide into the soil matrix to provide a source of oxygen. The effluent concentrations of organic and inorganic constituents and the head losses were monitored after injecting oxygen.

First, iron oxidation alone was studied. Second, biodegradation of the organic compound was studied. Finally, the simultaneous iron oxidation and biodegradation of organic compound was carried out. The effect of different Fe2+ concentrations in water on the biodegradation of the organic contaminants was evaluated. It was intended to determine whether iron oxidation or biodegradation of organic compound would cause more plugging in soil. The oxidation efficiencies using oxygen microbubbles and peroxide were compared.

It was concluded that at high concentrations of Fe2+ in water, iron is rapidly oxidized utilizing most of the available oxygen. At low Fe2+ concentrations, biodegradation efficiency was high. Oxygen microbubbles were found to be slightly more effective than hydrogen peroxide in transferring oxygen to ground water and oxidizing iron or biodegrading organic contaminants. Soil plugging was found to occur regardless of the method of oxygen delivery. The use of coarse media removal system seemed to solve the problem.