Degradation of diethyl phthalate in treated effluents from an MBR via advanced oxidation processes: Effects of nitrate on oxidation and a pilot‐scale AOP operation

Abstract

The major objective of this study was to delineate the oxidation of diethyl phthalate (DEP) in water, using bench‐scale UV/H₂O₂ and O₃/H₂O₂ processes, and to determine the effects of nitrate (NO₃ ⁻‐N, 5 mg L⁻¹) on this oxidation. The oxidation of DEP was also investigated through a pilot‐scale advanced oxidation process (AOP), into which a portion of the effluent from a pilot‐scale membrane bioreactor (MBR) plant was pumped. The bench‐scale operation showed that DEP could be oxidized via solely UV oxidation or O₃ oxidation. The adverse effect of nitrate on the DEP oxidation was remarkable in the UV/H₂O₂ process, and the nitrate clearly reduced its oxidation. The adverse effect of nitrate on O₃ oxidation was also observed. It was noted, however, that the nitrate clearly enhanced the DEP oxidation in the O₃/H₂O₂ process. A series of pilot‐scale AOP operations indicated that the addition of H₂O₂ enhanced DEP oxidation in both the UV/H₂O₂ and O₃/H₂O₂ processes. No noticeable adverse effect of nitrate was observed in the NO₃ ⁻‐N concentration of about 6.0 mg L⁻¹, which was naturally contained in the treatment stream. About 52% and 61% of the DEP were oxidized by each of these two oxidation processes in this pilot‐scale operation. Both the UV/H₂O₂ and O₃/H₂O₂ processes appeared to be desirable alternatives for DEP oxidation in treatment effluent streams.

Keywords:

• advanced oxidation processes (AOPs)
• diethyl phthalate (DEP)
• nitrate
• UV/H₂O₂ process
• UV/O₃ process

Acknowledgement

This research was financially supported by the Eco‐Star Project (contact no.: I² WaterTech 04‐4) of Korea's Ministry of Environment and the BK21 Program of Korea's Ministry of Education in Seoul, Republic of Korea.