EXPERIMENTAL INVESTIGATIONS FOR TRAPPING OXYGEN GAS IN SATURATED POROUS-MEDIA FOR IN-SITU BIOREMEDIATION

Oxygen is often the rate-limiting factor in aerobic in situ bioremedia tion. This paper investigates the degree to which air or oxygen gas ca n be emplaced into the pore space of saturated porous media and provid e a significant mass of oxygen. Column experiments were performed to t est three emplacement methods: direct gas injection, injection of wate r supersaturated with gas, and injection of a hydrogen peroxide soluti on. The direct gas injection method fills 14-17% of the pore space wit h trapped gas. Water supersaturated with gas fills 18-27% of the pore space with a trapped gas phase, and hydrogen peroxide solution injecti ons emplaces trapped gas in 17-55% of the pore space. In addition to s upplying oxygen, gas entrapment causes a decrease in hydraulic conduct ivity which could be an advantage by decreasing the flow of contaminan ts offsite. The relative hydraulic conductivity of porous media with a trapped gas volume of 14-55% was 0.62-0.05.