Potential of UV/H₂O₂ oxidation for enhancing the biodegradability of municipal reverse osmosis concentrates Available to Purchase

UVC/H₂O₂ and VUV/H₂O₂ oxidation processes were evaluated for the degradation of organic pollutants in reverse osmosis concentrate (ROC) produced from a municipal secondary effluent. It was found that the oxidation by UVC/H₂O₂ and VUV/H₂O₂ processes could be described as a pseudo first-order reaction. For UVC increased oxidation occurred with increasing H₂O₂ dosage up to 2 mM above which improvement in oxidation performance decreased. At the same H₂O₂ dosage, VUV irradiation gave better overall oxidation performance. Compared with UVC/6 mM H₂O₂, VUV/2 mM H₂O₂ gave a greater rate of reduction of chemical oxygen demand, but a lower rate for reduction of dissolved organic carbon, suggesting that oxidation of organics by the two methods followed different pathways. The change of absorbance at 254 nm and fluorescence excitation emission matrix spectra of irradiated samples indicated that the large and complex compounds were fragmented rapidly by the ^•OH, resulting in rapid decolourisation. The biodegradability of the organics in the ROC was increased from 11% to 35% after 1 h treatment by UVC/3 mM H₂O₂, whereas a greater increase (41%) was obtained with VUV/2 mM H₂O_2. This increase in biodegradability indicates the potential for employing a subsequent biological treatment process.