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Biological Fluidized‐Bed Treatment of Wastewater from Byproduct Coking Operations: Full‐Scale Case History

The Algoma Steel byproduct coke plant consists of three coke‐oven batteries capable of producing approximately 3 000 t/d of coke. The source of the primary process wastewater from the coke plant is the excess flushing liquor or weak ammonia liquor produced during initial cooling of coke‐oven gases. This raw liquor stream is directed to an ammonia still where ammonia is recovered through steam stripping. Wastewater is then directed to a biological treatment plant designed for phenolics removal. The biological treatment scheme used at Algoma is a fluidized‐bed reactor (FBR) system. Design of the system anticipated a median phenolic load of 1 117 kg/d (2 463 lb/d), consisting of a phenolics concentration of 1 012 mg/L in the wastewater and a flow of 46.1 m3/h (203 gpm). Nine days after start‐up, the FBRs were receiving more than 40 m3/h of wastewater containing 1 000 mg/L of phenolics and an approximately equal amount of clean mill water, added as dilution water for temperature control. Effluent from the system contained less than 5 mg/L phenolics. During a 6‐week performance assessment of the system, which began approximately 2 weeks after process start‐up, FBRs achieved more than 99% phenolics reduction based on diluted wastewater feed concentration. Approximately 5 weeks after process start‐up, thiocyanate in the effluent was reduced to less than 5 mg/L, representing approximately 95% removal based on diluted wastewater feed concentration. At this time the biomass concentration, measured as volatile solids, in the FBRs was greater than 15 g/L.