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Gateway Center Water Treatment Plant, Los Angeles: Controlled Hydrogen Peroxide Treatment of Hydrogen Sulfide and VOC Affected Groundwater

Groundwater affected by hydrogen sulfide and volatile organic compounds (VOCs) was removed during a temporary construction dewatering project. Treatment was required to reduce the total sulfide and VOC concentrations prior to discharge to the Los Angeles River. Hydrogen peroxide and sodium hydroxide were added to oxidize the sulfide to sulfate at pH=9.2 in the first reaction vessel. A prototype hydrogen peroxide control system (Perox 20) was implemented to minimize the amount of hydrogen peroxide used. This was the first application of its kind in the world. The largest commercially available UV-Oxidation system was specified for organics destruction in combination with a backup carbon adsorption system for UV system maintenance, or in the event of a UV system failure. The chemical oxidation of hydrogen sulfide was successful throughout the duration (to date) of treatment plant operation. The UV-Oxidation system was successful at meeting the discharge limits at low organic loading rates, however, activated carbon was implemented at higher organic loading rates. The operation of the various components of the treatment plant with respect to the oxidation of hydrogen sulfide and dissolved VOCs (benzene) are addressed in the paper.