“USE OF SONICATION/ACOUSTIC CAVITATION WITH ADVANCED OXIDANTS TO TREAT PETROLEUM HYDROCARBONS-CONTAMINATED SURFACE WATERS AND GROUNDWATERS” by

Groundwater is one of our most valuable natural resource. More than 50% of the U.S. population depends on groundwater for domestic use and more than 95% of the rural population is dependent on groundwater. A major portion of industries and agriculture use groundwater. These numbers suggest that the personal and economic health of the nation is dependent on groundwater. Contamination of groundwater is a major cause of concern because of its negative implications in terms of public health and economics. The largest source of groundwater contamination involves underground storage tanks (U.S.T). As of September 30, 2006, EPA reported more than 460,000 [U.S. EPA, 2006] confirmed releases from underground storage tanks. The majority of underground storage tanks contain gasoline, diesel, and other petroleum products, which are the most frequently found contaminants in groundwater. One of the most dangerous chemicals found in petroleum products are a group of chemicals known as BTEX. The BTEX group consists of benzene, toluene, ethylbenzene, and xylene. Benzene, a member of the BTEX group found in groundwater contaminated with petroleum products, is a known carcinogen. Toluene, ethylbenzene, and xylenes as well as methyl-tert-butyl ether (MTBE) are toxic chemicals, and their presence in drinking water represents a grave danger to public health. This concern has resulted in considerable research into development of technologies to remove hazardous contaminants such as petroleum hydrocarbons from groundwater. Many advanced water purification techniques including vapor stripping/carbon adsorption, biological treatment, and advanced oxidation processes, have been applied to remove these contaminants from groundwater. All these technologies have their advantages and disadvantages in terms of their practical applications, costs, and process efficiencies. An innovative technology (sonication as an advanced oxidation process) was tested to remove volatile organic compounds, such as petroleum hydrocarbons, from solution. Sonication is an application of ultrasound processes. Ultrasound has been used for a variety of different applications including plastic welding, emulsification, medical imaging, and atomization of particles. Sonication as a new advanced treatment process promotes the ultrasonic destruction of organic compounds. Most previous attempts in this field rely on the chemical consequences of ultrasound for water and groundwater treatment. Different than previous studies, this study investigated the effect of ultrasound for destruction of BTEX compounds. This research project investigated the removal of petroleum hydrocarbons from groundwater using air sparging in combination with sonication. Experiments were performed to optimize the air flow rate for efficient and economical air sparging. Groundwater contaminated with petroleum hydrocarbons was subjected to air sparging treatment alone, sonication treatment alone, and air sparging combined with sonication treatment. Results are presented from the operation of the three systems (sonication alone, air sparging alone, and combined sonication + air sparging). Analysis of the results shows air sparging (vapor stripping) combined with sonication system performed best among the three systems tested. Air sparging combined with sonication removed in excess of 90% of the benzene, toluene, ethyl benzene, and o-xylene (BTEX) contaminants from groundwater. It is expected that bioremediation after the combination of air sparging and sonication treatment will further improve the system performance. The research described in this final report addresses the technological and economic complexities associated with groundwater remediation. Using sonication-based technology, groundwater treatment is expected to be considerably cheaper, quicker, and a more efficient process. The following describe some benefits of the integrated air sparging/sonication technology. Treatment is performed in-situ thus avoiding having to deal with technical, economical, and legal problems associated with handling or disposal of contaminated water and sludge;