Treatment of biorefractory organic compounds in wool scour effluent by hydroxyl radical oxidation

Wool scouring effluent that had been treated with chemical flocculation and aerobic biological treatment (Sirolan CFB effluent) was tertiary treated by hydroxyl radical oxidation to remove residual organic compounds. These compounds impart a high chemical oxygen demand of 500–3000 mg/L and dark colour. However, a H2O2/UV process was found to effectively treat the majority of residual compounds, with up to 75% COD, 85% total organic carbon, and 100% removal of colour (T480 nm) achieved. This was despite the effluent being strongly absorbing in the UV region, with a film thickness of 0.21 mm reducing T254 nm by 50%. Treatment was unaffected by pH over the range 3–9. H2O2/UV treatment increased the biodegradability of the effluent (5-day biochemical oxygen demand increased from <10 to 86 mg/L), but a combined chemical and biological process did not increase maximum COD removal or overall process efficiency. The tertiary treated effluent had a final COD in the range 125–750 mg/L, equating to a total COD removal from raw wool scour effluent of approximately 97.5%. This degree of treatment is sufficient for discharge in many, but not all, circumstances.