Emulsion wastewater treatment by citrate enhanced UV/Fenton and combined with biological treatment

In the UV/Fenton process (UFP) treating artificial emulsion wastewater, the effects of citrate addition on the applicable pH range and effluent biodegradability were systematically investigated. In the citrate enhanced UV/Fenton process (CE-UFP), the applicable pH range was broadened to 4~8. When CE-UFP was carried out under 1.0 mM initial citrate concentration, the effluent BOD/COD ratio increased to 0.53, which is much higher than that of 0.32 with no citrate addition. When the effluent of CE-UFP and UFP were further separately treated with 8-hour biological treatment, the respective COD removal efficiencies were 78.7.0% and 96.0%. When 0~1.0 mM citrate was dosed at CE-UFP stage, the effluent COD after subsequent biological treatment may decrease from 293 mg/L to 48 mg/L, while no further decrease was observed with higher citrate dosage. All these results clearly indicate citrate can broaden the applicable pH range of UFP and enhance the biodegradability.