Full-Scale Results from a Biofilm Carrier Process Treating Wastewater from an Ethylene Glycol Reclamation Facility

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The Consolidated Recycling Co., Inc. (CRCI) reclaims between 5 and 6 million gallons of previously used ethylene glycol from spent antifreeze every year. The distillation process generates ethylene glycol contaminated wastewater which must be treated prior to discharge to the municipal wastewater treatment plant. CRCI upgraded the existing facility in 2005 with a biofilm carrier treatment system, an aerobic process employing fluidized carriers. Laboratory testing was first conducted to evaluate the treatability of the CRCI wastewater and to determine full-scale design parameters. Laboratory-scale testing indicated that removal rates greater than 16-18 gCOD/m2/d were achievable using biofilm carriers and the results of the testing provided the design basis for the full-scale installation.

The full-scale biofilm carrier system was seeded with sludge from an onsite aeration pond, and the effluent SCOD concentration was reduced to below 400 mg/L almost immediately following initiation of flow. The influent flow to the bioreactor was increased to 80% of the design flowrate, while maintaining effluent targets, within 40 days of start-up. The system has been operating for over one year and has reliably produced effluent COD concentrations below the required levels of 550 mg/L. Effluent concentrations of phenol have consistently been maintained below 0.6 mg/L.

The results from this study demonstrated that an aerobic biofilm carrier process provided a robust treatment solution for wastewater generated from an ethylene glycol reclamation facility. The system required minimal operator intervention and has produced high quality effluent since initiation of flow. The finding suggested that biofilm carrier processes provide an economically viable alternative to discharging glycols to municipal wastewater treatment plants.

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