Degradation of cefixime antibiotic by continuous flow ultraviolet-C persulfate based advanced oxidation process: Fresh and marine water matrices, antibacterial activity removal, and cost analysis

Abstract

Antibiotic pollutants in wastewater from freshwater and marine water based aquaculture farming are a serious concern as they may cause emergence and spreading of antibiotic resistant bacteria (ARB) into environment. Here we show, degradation of cefixime (CFX), an antibiotic pollutant, in freshwater, marine aquaculture water (1:1 freshwater and seawater mixture), and seawater by continuous flow ultraviolet-C/persulphate (CF-UVC/PS) system, with pseudo-first-order rate constant (k_obs) values of 0.5334 s⁻¹, 0.5080 s⁻¹, 0.4968 s⁻¹, respectively. Degradation of CFX was attributed to oxidation by sulfate radical anion (${SO}_4^{\bullet -}$) and hydroxyl radical (${HO}^{\bullet }$) generated via UVC activation of PS that was confirmed by electron spin resonance. Nitrite and dissolved organic carbon slightly reduced the degradation efficiency. Harmful bromate, and chlorate were not significantly formed in CF-UVC/PS system. Density function theory calculations predicted the susceptibility of 4N-6O bond and five and six membered rings of CFX toward electrophilic radical attack. Degradation byproducts were identified by high-resolution-mass-spectrometry, and predicted as nontoxic by ecological-structure–activity-relationship analysis, revealing detoxification. Further, antibacterial activity of CFX against Escherichia coli, and Bacillus subtilis, was removed after treatment by CF-UVC/PS system. Treatment cost was estimated to be about $ 0.332/m³. Additionally, a mixture of CFX, and other common antibiotics like ciprofloxacin (CIP), and sulfamethoxazole (SMZ) in aquaculture water was effectively treated by CF-UVC/PS system, with loss of antibacterial activity. Thus, the study highlights CF-UVC/PS system as a potential persulfate based advanced oxidation process for degradation of antibiotics in aquaculture wastewater that is needed to prevent the emergence of hazardous ARB.