Field Pilot Study of a Chemical Oxidation Process for Treatment of Industrial Waste Leachate

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Remediation efforts are ongoing at the Avtex Fibers Superfund Site in Front Royal, Virginia. As part of the future remediation of several surface impoundments used for viscose waste disposal during plant operation, it may be necessary to extract contaminated leachate and groundwater for ex-situ treatment and discharge to the Shenandoah River. This waste stream contains varying concentrations of sulfide (HS-), carbon disulfide (CS2), metals, COD and other contaminants as illustrated in Table 1. This work describes a field pilot study designed to support preliminary remedial design efforts for treatment of this waste.

Previous bench-scale treatability testing focused on the development of a cost-effective biological treatment process to oxidize the relatively high levels of reduced sulfur compounds in the viscose basin leachate. This testing demonstrated that direct biological treatment of the concentrated leachate streams would be impossible due to the high concentration and loading of HS- and CS2. Treatment by un-catalyzed alkaline pH hydrogen peroxide oxidation followed by biological treatment was identified as the most feasible and cost effective approach to meet the future permit limits for direct discharge. (Camper and Bott, 2006).

The objectives of the field pilot test conducted at the Avtex site during July-August 2006 were to develop process design criteria and to prove the effectiveness of un-catalyzed alkaline pH H2O2 oxidation of HS-, free CS2, CS2 associated with cellulose xanthate, and other reduced sulfur compounds present in the leachate and groundwater with minimal air emissions. For cost effectiveness, the chemical oxidation process was intended only to reduce the high concentrations of S2- and CS2, while minimizing reactions with organic carbon compounds (i.e. TOC or carbonaceous COD) in the leachate/groundwater stream to a level that would be successfully and consistently treated by a biological treatment system. Effluent H2O2 residual and temperature were also of concern because of the potentially detrimental effect on the downstream biological processes.

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