RECONFIGURATION OF AN INDUSTRIAL WASTEWATER TREATMENT SYSTEM FOR PCB, PHENOL, ZINC, AND SUSPENDED SOLIDS REMOVAL AND INSTALLATION OF A BIOLOGICAL LEACHATE TREATMENT SYSTEM AT A FORMER VISCOSE RAYON PRODUCTION FACILITY

After the shutdown of a former viscose rayon fiber production facility, all impounded surface water and runoff (wastewater) from the site was deemed impacted, requiring the installation of continuous treatment prior to discharge to the river. Discharge criteria for the wastewater treatment plant (WWTP) outfall are specified in a Superfund Administrative Order and dictate compliance with limits for several heavy metals, total suspended solids (TSS), biochemical oxygen demand (BOD), phenol, polychlorinated biphenyls (PCBs) and pH. The influent wastewater is collected in several large surface impoundments, some of which contain large quantities of residual lime precipitation- neutralization sludge from a treatment facility that was used when the rayon plant was active. The influent constituents of concern include PCBs, zinc, phenol and suspended solids. Generally, these wastewater sources contain relatively low concentrations of organic contaminants (low BOD). Over time, the WWTP has been upgraded and retrofitted to improve system performance, to enhance stability and operability and to meet the demand of changing influent characteristics and flow rates. Currently, the WWTP is designed for a peak throughput of approximately 1.0 MGD; however, the plant tends to be operated as needed, based on weather conditions. A biological process was also installed following a large equalization basin to treat a relatively low flow rate (5-50 gpm) of concentrated leachate that is derived from several surface impoundments containing waste material produced by the viscose process itself. This leachate is contaminated with high levels of sulfide (HS−) and carbonaceous organic contaminants (BOD), presumed to be primarily soluble cellulose, and lower levels of phenol and carbon disulfide (CS2). The biological treatment system discharges treated effluent to the large surface impoundments for subsequent treatment through the WWTP with other site wastewater sources. Thus, the objectives of biological treatment include oxidation of reduced sulfur compounds to control ambient odor and CS2 emissions and removal of a portion of the readily biodegradable organic material to ensure that the final WWTP effluent BOD limit is achieved (in particular during dry conditions).