A critical evaluation of the ozone/UV technology for treatment of water contaminated with organic pollutants

The performance of the ozone/UV technology was evaluated for treatment of water contaminated with organic pollutants. During photoozonation the concentrations of specific organic pollutants in water were reduced due to a combination of stripping and conversion to other organic compounds. In many cases the rates of removal of the specific organics were much higher than the rates of removal of TOG, and while the compound of interest was removed, complete mineralization (conversion to H2O , CO2, or simple salts) did not occur. In addition, introduction of ozone /UV was shown to reduce the overall rates of removal of TOG for volatile organics in water, when compared to stripping alone. This phenomenon was demonstrated for 1,2-DGA, acrylonitryle, MEK, and 2 chloroethyl vinyl ether. PGE, TGA, and TGE were stripped during residence times of less than 3 minutes. The tests with 2 chlorophenol were inconclusive, while the removal rates of TOG associated with bis (2-chloroethyl) ether, bis (2-chloroisopropyl) ether, and phenol were enhanced when ozone/UV were present. While the ozone/UV technology may be applied to remove certain organics from contaminated water, this study raises several concerns that need to be more fully evaluated: 1) parent compounds are in many cases transformed into unknown decomposition products which may or may not be toxic, 2) long residence times are required to assure total mineralization of these unknown compounds, 3) stripping without photoozonation may be more efficient for removal of certain volatile compounds, than the combination of ozone/UV/stripping. Further research needs to be conducted on the decomposition products of typical organic compounds to assure that the technology is a viable one, and resulting in a decrease in toxicity.