Sulfamethoxazole removal in membrane-photocatalytic reactor system - experimentation and modelling.

In this study, the efficacy of membrane-photocatalytic reactor (MPR) in sulfamethoxazole (SMX) removal was explored at a fixed initial SMX concentration, i.e. 100 mg/L. A supported catalyst, i.e. TiO2 on granular activated carbon (GAC-TiO2), was used for MPR experiments. The SMX removal efficiency of the MPR was investigated under a range of hydraulic retention time (i.e. HRT from 51 to 152.5 min) and TiO2 catalyst dosage (55-50 mg/L). A maximum SMX removal efficiency of 83.6% was observed under 220 mg/L catalyst dosage and 80 min HRT. The increase in catalyst dosage from 55 to 550 mg/L has increased the transmembrane pressure of the reactor from 9.8 to 22.2 kPa. A multiple non-linear regression model was developed based on the experimental data and its significance was analyzed using two-way ANOVA. Based on the model, the optimal HRT and catalyst dosage for complete SMX removal (100%) were found out. The comparison of photocatalytic degradation experiments with sorption experiments conducted earlier revealed that SMX removal in the MPR was mainly by photocatalytic degradation and not by adsorption onto GAC-TiO2 catalyst. However, the performance of MPR in removing other emerging pollutants from real-time wastewaters could be explored before its field-scale application.

Sulfamethoxazole in poultry wastewater: Identification, treatability and degradation pathway determination in a membrane-photocatalytic slurry reactor.

The presence of sulfamethoxazole (SMX) in a real-time poultry wastewater was identified via HPLC analysis. Subsequently, SMX removal from the poultry wastewater was investigated using a continuous-mode membrane-photocatalytic slurry reactor (MPSR). The real-time poultry wastewater was found to have an SMX concentration of 0-2.3 mg L(-1). A granular activated carbon supported TiO2 (GAC-TiO2) was synthesized, characterized and used in MPSR experiments. The optimal MPSR condition, i.e., HRT ∼ 125 min and catalyst dosage 529.3 mg L(-1), for complete SMX removal was found out using unconstrained optimization technique. Under the optimized condition, the effect of SMX concentration on MPSR performance was investigated by synthetic addition of SMX (i.e., 1, 25, 50, 75 and 100 mg L(-1)) into the wastewater. Interestingly, complete removals of total volatile solids (TVS), biochemical oxygen demand (BOD) and SMX were observed under all SMX concentrations investigated. However, a decline in SMX removal rate and proportionate increase in transmembrane-pressure (TMP) were observed when the SMX concentration was increased to higher levels. In the MPSR, the SMX mineralization was through one of the following degradation pathways: (i) fragmentation of the isoxazole ring and (ii) the elimination of methyl and amide moieties followed by the formation of phenyl sulfinate ion. These results show that the continuous-mode MPSR has great potential in the removal for SMX contaminated real-time poultry wastewater and similar organic micropollutants from wastewater.