Development of an ozonation process for degradation of polyaromatic hydrocarbons

Studies to develop an effective ozonation treatment for degradation of polyaromatic hydrocarbon (PAH) contaminants in solid matrices are reported. Tailings from the ARC/EPRI coal/oil agglomeration process for cleanup of contaminated soil from old Manufactured Gas Plants (MGP) were chosen for investigation. Treatment variables such as ozone concentration, hydrogen peroxide and other chemical oxidant addition, surfactant addition, pH, temperature and contact time were investigated to evaluate the effect on degradation of PAHs. Gravimetric and high pressure liquid chromatographic methods were used to monitor the concentration of PAHs. Treatment using 2.5% (w/w) ozone for two hours with the addition of 2 ppm Igepal CO-720 surfactant resulted in destruction of 59% of 2-, 3-, 4-, 5-, and 6-aromatic ring compounds in the agglomeration tailings. The addition of 2,000 ppm hydrogen peroxide (H2O2) further improved the ozonation treatment, resulting in 94% destruction of 2- to 6-aromatic ring compounds within 2 hours. The lowest residual PAH level achieved was 22 ppm. Pretreatment of the tailings with chemical oxidants other than H2O2 showed no further benefit. Variations in pH and temperature had marginal positive effects. Biological treatment of the ozone treated tailings showed promise in further reducing polynuclear aromatic hydrocarbons. Based on the laboratory results, preliminary costs for ozonation treatment were estimated to be $69 per ton. Process optimizations are proposed which could reduce the treatment cost to less than $20 per ton