Chemical detoxification of dioxin-contaminated wastes using potassium polyethylene glycolate

Abstract A chemical destruction technique known as KPEG (potassium polyethylene glycolate) has been used successfully in the states of Montana and Washington to detoxify pentachlorophenol (PCP)-oil and spent solvent waste contaminated with dioxin. A mobile treatment unit, mounted on a 45-foot trailer, was employed to process 8,650 gallons of PCP wood-treating chemical waste at the Montana Pole site in Butte, Montana, in July 1986. This waste was generated as the oily phase of groundwater pumped from 21-foot deep recovery wells; after separation and decantation, approximately 3% PCP in light oil was obtained at the rate of 30 to 50 gallons per day. This site represents an inactive wood-treating facility located on a 20-acre, sloping, abandoned mining site, where contamination by dioxins (CDDs) and bibenzofurans (CDFs) has reached an adjacent creek, including groundwater and surface soil. The PCP-oil waste contained CDD/CDF homologs ranging from 147 ppb of tetra- to 83,923 ppb of octa-congeners and was processed in five batches, each batch comprising approximately 1,400 to 1,850 gallons of waste oil together with the KPEG reagent. The mixture was heated to 150dg and allowed to react for 90 minutes before cooling. The reaction conditions were not optimal, however, and were excessive based on results of earlier Wright State University brehm Laboratory parametric studies, but were considered a “safety measure” in light of the infancy of the process. The treated oil was then pumped from the reactor into a holding tank from which composite samples were removed and sent to the IT Corporation's analytical laboratory in Knoxville, Tennessee. No CDDs or CDFs were detected in the KPEG-treated oil at limits of detection in the parts per trillion (ppt) range. Subsequently, the equipment was transported to the EPA Superfund Western Processing site in Kent, Washington, where it also successfully processed, in September 1986, 7,550 gallons of spent solvent containing an oily waste with a high moisture content (28%) and total chlorides of 20.700 mg/l; the 2,3,7,8-TCDD content was 120 ppb. Bench-scale parametric studies were performed to determine optimum conditions under which to conduct field operations. Field reaction conditions, however, were less than optimal: 115dg for 12 hours. No 2,3,7,8-TCDD was found at a limit of detection of 0.3 ppb in any of the processed batches. Spent KPEG reagent was transported to the Chemical Waste Management PCB-permitted incinerator in Chicago for final disposition. The chemistry usedemploys two basic ingredients Potassium hydroxide and polyethylene glycol, which combine to form the reactive agent, KPEG. KPEG chemically removes chlorine atoms from the CDD molecule to form potassium chloride, thus rendering the dioxin molecule non-toxic. A battery of bioassay tests, conducted ai EPA laboratories in Research Triangle Park. North Carolina, and Duluth. Minnesota, was used to ascertain whether KPEG byproducts (a) bioaccumulated in ussues of organisms; (b) caused cell mutations; or (c) caused immediate harm to fish or mammals. There was no evidence that the byproducts were toxic in any of the tests performed. The KPEG process has therefore successfully destroyed CDDs and CDFs in waste PCP-oil. The processing cost in the Butte, Montana, decontamination field demonstration was less than 10% of the projected, estimated on-site incineration cost and amounted to $212,000. Additional parametric investigations are planned on the contaminated emulsions, groundwater, and soils at Montana Pole. The results of these studies will be reported later this year.