FREE PRODUCT REMOVAL OF DIESEL-RANGE HYDROCARBONS USING A 3 STEP FLUSHING, EXTRACTION AND INFUSION PROCESS
James A. Jacobs
Platform Presentation
A three-step flushing, extraction and infusion process has been developed for removal of free product (hydrocarbons and chlorinated solvents). Flushing was performed at a former tank pit at a northern California site containing heavy oil-range hydrocarbons that were trapped beneath the saturated zone. Flushing uses a two-step flushing process which includes high-pressure air injection and biosolvent injection to thin and mobilize diesel-range or heavier hydrocarbons, which was measured up to 41 cm in height in one well on one site. The high-pressure air injection and biosolvents were used with dual phase extraction to recover both the heavy oil and the biosolvent.
At another site, biosolvent flushing was performed followed by a Supersaturated Water Injection (SWI) technology with carbon dioxide saturated water injection. SWI allowed for controlled mobilization of petroleum hydrocarbons into the water table for collection using dual phase extraction. SWI technology relies on water which is supersaturated with carbon dioxide using a mass transfer system. The saturated water is injected under high pressure into the former tank pit where carbon dioxide bubbles nucleate at the targeted area of the aquifer. The rising carbon dioxide bubbles contact with the submerged diesel-range hydrocarbons in the saturated zone and cause volatilization of the free product into the vapor phase and mobilization of NAPL trapped in the pores.
Several extraction wells and dozens of small-diameter reinjection ports were used to recirculate the carbon dioxide saturated water and provide a closely-spaced delivery and extraction system. The carbon dioxide is distributed by flowing water resulting in effective carbon dioxide distribution followed by heterogeneous bubble nucleation and continuous growth of gas bubbles in situ. A gas saturation front developed which expanded laterally and vertically towards the water table in the former underground tank pit. Diesel-range hydrocarbons mobilize to soil gas and are extracted with a dual phase extraction system. Case studies will be described. After the carbon dioxide SWI process, a similar SWI process using oxygen is used to flood the saturated remediation area with oxygen for enhanced bioremediation.
James Jacobs, P.G., C.H.G.
Environmental Bio-Systems, Inc.
707 View Point Road, Mill Valley, CA 94491; Tel: 415-381-5195;
jimjacobs@ebsinfo.com;
www.ebsinfo.com
