On the cost effective bubble column photochemical reactor design. Identifying the influential parameters based on research on four priority pollutants

Chlorinated volatile organic compounds, e.g., chloroform (CF), carbontetrachloride (CTC), tri- and tetrachloroethylene (TCE and PCE) are pollutants commonly found in ground water and soil. Their oxidation in a novel, bubble column photochemical reactor, combining the mass transfer of pollutant from the gas phase followed by a free-OH radical reaction in a liquid phase is described mathematically and in terms of economic feasibility. The combined system eliminates the negative effects of direct oxidation in groundwater (reduced efficiency due to the presence of UV radiation absorbers and OH radical scavengers) and gas phase oxidations (production of stable reaction intermediates). For low initial concentrations of pollutant in a gas phase, reaction occurs mainly in the liquid phase (slow reaction regime). The absorption with reaction could be well predicted based on the ratio of the apparent rate constant of pollutant degradation to the volumetric mass transfer coefficient. The Electrical Energy per Order (EE/O) values depend mostly on the initial concentration of pollutant and hydrogen peroxide, as well as reactor radius. The levels of PCE and TCE in the order of 20 mg/L could be treated economically. However, the treatment of compounds with low affinity to OH radicals (CF and CTC) is economically unfavorable even for parts per billion level concentrations. This is an abstract of a paper presented at the 7th World Congress of Chemical Engineering (Glasgow, Scotland 7/10-14/2005).