Abstract
Bio-electro-Fenton is emerging as an alternative technology for the efficient and cost-effective removal of refractory micropollutants. Though promising, there are still several challenges that limit its wide application, including acidic operating conditions (pH at 2–3), the addition of supporting electrolytes (e.g., Na2SO4), and the issue of iron sludge generation. To address these challenges, a novel hybrid persulfate-photo-bioelectrochemical (PPBEC) system is proposed to remove model micropollutants (carbamazepine and clorfibric acid), from secondary effluent at low persulfate (PS) dosage and neutral pH. The effect of crucial operating parameters on the process was studied, including input voltage, cathodic aeration velocity, and PS dose. Under optimal conditions (0.6 V, 0.005 mL min−1 mL−1 and 1 mM), the PPBEC system achieved approx. 0.56–1.71 times greater micropollutant removal with 93% lower energy consumption when compared to the individual processes (UV/PS and PBEC). The improved performance was attributed to a faster production of sulfate radicals by UV irradiation, hydrogen peroxide activation and single-electron reduction, and hydroxyl radicals generated by UV irradiation. Furthermore, the transformation products of carbamazepine and clorfibric acid were identified and the probable pathways are proposed. Finally, the ecotoxicity of the PPBEC treated effluent was assessed by using Vibrio Fischeri, which exhibited a non-toxic effect.
Highlights
In recent years, high levels of residual pharmaceuticals have been detected in municipal sewage due to the increasing global consumption of pharmaceuticals
The CBZ and clofibric acid (CA) concentrations and the corresponding transformation products during the PPBEC system were quantified by high-performance liquid chro matography (Agilent 1290 Infinity, USA, HPLC) system coupled with a tandem mass spectrometer (Agilent 6470 series, USA, MS/MS)
Our results show that both CBZ and CA were completely removed within 6 h by the PPBEC process, within the selected concentration range (Fig. 5)
Summary
High levels of residual pharmaceuticals have been detected in municipal sewage due to the increasing global consumption of pharmaceuticals. Bioelectrochemical process-based AOPs, in particular bio-electro-Fenton (BEF) process, have become a focal point of AOP research due to several advantages They inherit the advantage of the traditional electroFenton (EF) process that can efficiently treat high-concentration (mg L− 1 and even to g L− 1) pharmaceutical-containing wastewater through in situ production of OH (Eq (1)). Photocatalysis by UV irradiation to eliminate pharmaceuticals can be achieved through direct photol ysis, or by activation of the cathodic H2O2 generated in situ, to produce OH (Eq (3)) These processes can help to overcome the above mentioned drawbacks in the BEF system, including the requirement for pH adjustment and iron sludge generation. The PPBEC system was compared to the UV/PS process, the BEF process, and other AOPs such as the EF process, from the perspective of both removal efficiencies and economic cost
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