In situ bioremediation of groundwater contaminated with petroleum constituents using oxygen release compounds (ORCs).

Over the past 5 years, the use of in situ biological remediation methods has gained acceptance for the biological degradation of petroleum hydrocarbons and chlorinated solvents in the groundwater. Application of slow-release compounds such as Oxygen Release Compound (ORC) and Hydrogen Releasing Compounds have been used routinely as remediation tools. This paper describes the implementation of an in situ bioremediation scheme to address the petroleum constituents in the groundwater at the site of a former gasoline station. Site investigations had indicated that groundwater beneath the site was contaminated with up to 34,300 microg/L benzene, toluene, ethylbenzene and xylenes (BTEX). The remedial scheme involved the installation of the four monitoring wells, monitoring and sampling of the wells and the application of ORCs into the Area of Concern (AOC). The results indicate that levels of petroleum constituents continue to be present in groundwater beneath the site after ORC injection. However, over time the levels of BTEX have significantly decreased. Kinetic study showed that the removal of BTEX fits a zero-order kinetic model for each monitoring well under enhanced oxidized conditions. The compound with the highest biodegradation rate constant was m,p-xylene in monitoring wells MW-2, MW-3 and MW-4.

Degradation of the pharmaceutical metronidazole via UV, Fenton and photo-Fenton processes.

Degradation rates and removal efficiencies of Metronidazole using UV, UV/H2O2, H2O2/Fe2+, and UV/H2O2/Fe2+ were studied in de-ionized water. The four different oxidation processes were compared for the removal kinetics of the antimicrobial pharmaceutical Metronidazole. It was found that the degradation of Metronidazole by UV and UV/H2O2 exhibited pseudo-first order reaction kinetics. By applying H2O2/Fe2+, and UV/H2O2/Fe2+ the degradation kinetics followed a second order behavior. The quantum yields for direct photolysis, measured at 254 nm and 200-400 nm, were 0.0033 and 0.0080 mol E(-1), respectively. Increasing the concentrations of hydrogen peroxide promoted the oxidation rate by UV/ H2O2. Adding more ferrous ions enhanced the oxidation rate for the H2O2/Fe2+ and UV/H2O2/Fe2+ processes. The major advantages and disadvantages of each process and the complexity of comparing the various advanced oxidation processes on an equal basis are discussed.