United States Environmental Protection Agency EPA/540/M5-92/009 September 1992 &EPA SUPERFUND INNOmTIVE TECHNOLOGY EVALUATION Emerging Technology Bulletin Electron Beam Treatment for Removal of Trichloroethylene and Tetrachloroethylene from Streams and Sludge* Florida International University and the University of Miami Technology Description: Irradiation of aqueous solutions with high-energy electrons results in the formation of the aqueous electron, e~aq, hydrogen radical, H-, and the hydroxyl radical, OH-. These reactive transient species initiate chemical reactions ca- pable of destroying organic compounds in aqueous solution, in most cases oxidizing them to carbon dioxide, water and salt. No sludge is formed and no pretreatment is necessary. The reaction by-products are non-toxic and thus this process represents a new technology for the restoration of contaminated water, soils and sediments. At one end of the system, an aqueous solution containing the hazardous organic chemical(s) is directed over a weir where it falls in a thin sheet (approximately 4 millimeters thick). At the other end of the system, a 1.5-million volt insulated core trans- former (ICT) electron accelerator generates electrons and accel- erates them to approximately 97% the speed of light. These * This is the first in a series of bulletins which will report results of research conducted through this cooperative agreement. accelerated electrons are propelled in a concentrated beam down a high-vacuum tube toward a scanner which scans the beam to a rectangular shape and directs it toward the aqueous solution which is flowing over the weir. It is at this point, when the electrons penetrate the waste stream, that treatment occurs. The studies have been conducted at 120 gal/min, and can be easily scaled up for larger applications (Figure 1). The process is essentially pH independent in the range 3-11. Waste Applicability: This process can treat complex mix- tures of hazardous chemicals in drinking water, groundwater, wastewater, and water containing up to 5% suspended solids. It can be utilized to remove various organic chemicals including chloroform, bromodichloromethane, dibromochloromethane, bromoform, carbon tetrachloride, TCE, PCE, frans-1,2- dichloroethene, c/s-1,2-dichloroethene, 1,1-dichloroethene, 1,2- dichloroethane, hexachloroethane, 1,1,1-trichloroethane, 1,1,2,2- tetrachloroethane, hexachloro-1,3-butadiene, methylene chloride, benzene, toluene, chlorobenzene, ethylbenzene, 1,2-dichloroben- Vault Exhaust Fan Window Exhaust Faif"' Step-up Transformei 5-Ton Crane V 'o\i 3i ie Regulator Capacitor Bank Influent Spreade Scanner 1.5MeV5 mAICT Electron Accelerate Treated Effluent Samplinq Area ICT Controls Influent Controls Vault Exhaust Duct Influent Line Figure 1. Elevation of the Electron Beam Research Facility, Miami, FL. ------- zene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, m-xylene, o-xy- lene, dieldrin, and phenol. Test Results: Several different experiments with electron beam irradiation of aqueous streams were conducted. These experi- ments had as their focus the effect of water quality, solute con- centration and irradiation dose on removal efficiency for TCE and PCE. To develop a more quantitative understanding of the factors that affect the removal efficiency of TCE and PCE from water by electron beam, experiments were designed that included the variables identified as important in the preliminary studies, i.e. total carbonate alkalinity, bicarbonate/carbonate ion speciation, solute concentration and the presence and absence of clay. The water used for the detailed experiments was potable water, and raw and secondary wastewaters. Potable water is delivered to the plant with a pH of approximately 9, and an alkalinity of 45 to 60 mg L1 as CaCO3. For these conditions the bicarbonate/carbonate ion speciation is 7.41 x 10'4M / 4.77 x 10~5 M, respectively. By lowering the pH of the water, using concentrated HCI, to pH 7, the speciation is altered to 6.98 x 10'4M / 4.93 x 10~7M. Additional HCI lowered the pH to 5 and essentially eliminated the carbonate alkalinity. To examine the effect of the addition of solids, kaolinite was added to give a concentration of 3% solids by weight. The addi- tion of kaolinite resulted in a lowering of pH of the solution to approximately 7, and therefore only pH 7 and 5 could be directly compared for the removal of TCE and PCE in the presence and absence of clay. In tests to compare the dose required to remove 99% of the TCE and PCE in three different quality waters at the lower and higher initial solute concentration, it was apparent that the removal of the TCE and PCE required a smaller dose in potable water than in either wastewaters. Although the quality of the three waters were quite different, there was not a large difference (< two-fold) in the removal efficiency between the three waters. The removal of PCE required a higher dose than TCE under equivalent conditions. This is consistent with the OH- reaction rate constants of the two compounds. More detailed studies were conducted at various TCE and PCE concentrations. The presence of suspended solids up to 3% had no significant effect on the removal of TCE or PCE when com- pared to solutions that had no clay. Solute concentration did not affect removal efficiency at the two lower concentrations studied. However, higher doses were required to achieve the same re- moval efficiency when the initial solute concentration approached 10 mg L1). Reaction by-products were determined for tests containing the highest concentrations of TCE and PCE. Aldehydes were found but were at concentrations which accounted for less than 1% of the total carbon. Formic acid accounted for up to 10% of the carbon in the TCE and PCE at low doses, but at the higher doses the percentage conversion resulted in no more than 5% of the initial solute carbon. The formation of chloroacetic acids in irradiated solutions of TCE was not observed. Chloride ion mass balances showed a complete conversion of organic chlorine to chloride ion. A paper detailing the results is available and has been submitted for publication. For Further Information: EPA Project Manager Franklin Alvarez Office of Research and Development 26 West Martin Luther King Drive Cincinnati, Oh 45268 (513) 569-7631 Technology Developer Contact: William J. Cooper Drinking Water Research Center VH 326 Florida International University Miami, FL 33199 (305) 348-3049 FAX (305) 348-3894 Charles N. Kurucz Departments of Management Science and Industrial Engineering University of Miami Coral Gables, FL 33134 (305) 284-6595 FAX (305) 284-2321 Thomas D. Waite High Voltage Environmental Applications, Inc. P.O. Box Miami, FL 33124 (305) 253-9143 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGES FEES PAID EPA PERMIT No. G-35 EPA/000/0-00/000 ------- |