Factors affecting UV/persulfate treatment of phenacetin and its disinfection byproduct formation potential

Abstract

The pollution of aquatic bodies in the natural environment by pharmaceuticals has become a matter of increasing concern. In this study, we investigated the effects of the various influencing factors on the degradation of phenacetin (PNT) and its disinfection byproduct formation potentials (DBPFPs) by UV/persulfate (UV/PS) treatment. We first examined the effects of factors such as the PS concentration, pH, HCO3–, NO3–, NO2–, and natural organic matter (NOM) on the PNT degradation kinetics. The PNT degradation rate exhibited a positive correlation with the PS concentration. The PNT degradation rate was also pH-dependent, and it was highest under mild-alkalinity conditions. The presence of NO3–, NO2–, and NOM all inhibited PNT degradation, whereas HCO3– slightly accelerated PNT degradation. We next adopted LC/MS/MS to identify the degradation products of PNT, and the possible degradation pathways were proposed accordingly. The effects of UV/PS pretreatment on the DBPs from chlorination exhibit a close relationship with the abovementioned factors influencing the PNT degradation performance. Upon prolonging the pretreatment time and increasing the PS concentration, it was observed that trichloromethane (TCM) formation continuously decreased, while dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) exhibited patterns of increase and subsequent decrease in concentration. Mild alkalinity enhanced TCM formation and largely restrained DCAN and TCNM formation. Additionally, the presence of NOM enhanced TCM formation, while HCO3– hardly affected DBP formation. Meanwhile, NO2– profoundly affected the formation of TCNM. Therefore, these factors influencing PNT degradation by UV/PS should be carefully considered when integrating such technology as an alternative pretreatment for PNT-polluted water before disinfection.