Abstract:
The objective of this study is two-fold, first to investigate the occurrence and fate of 20 selected pharmaceuticals and personal care products (PPCPs) and 13 drugs of abuse (DOAs) in a wastewater treatment plant of New Zealand for the period of one year; second, to design a novel photocatalytic treatment for the removal of selected PPCPs from wastewater. The samples were analysed by Triple Quadrupole Liquid Chromatograph Mass Spectrometer (LCMS/ MS) in both positive and negative Electrospray Ionization (ESI) mode. The results showed that all of the monitored PPCPs and 13 DOAs were detected in the wastewater influent. Nonsteroidal anti-inflammatory drugs (NSAIDs) and caffeine were predominant in the category of PPCPs, whereas ethyl sulfate, one of the metabolites of alcohol, was detected at the highest concentration in the wastewater influent. The average removal efficiency was found to be >99% for acetaminophen, caffeine, Tris (2-chloroethyl) phosphate (TCEP), naproxen, ibuprofen, morphine, ethyl sulfate, and hydroxycotinine and <50 % for trimethoprim, metoprolol, benzotriazole, methadone, and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP). The primary treatment was ineffective for the removal of PPCPs as well as DOAs. There were no significant differences in the removal efficiencies of PPCPs and DOAs through two secondary treatment units, membrane bioreactor (MBR) and Bardenpho. Monitored PPCPs and DOAs exhibited seasonal variations with PPCPs dominating in autumn and winter, whereas, DOAs’ concentrations were highest in summer. In the second phase of the study, photocatalytic removal of selected PPCPs using a novel conducting polymer, poly (3, 4-ethylenedioxythiophene) (PEDOT) was investigated. PEDOT showed >80% removal of metformin, an antidiabetic drug within 30 minutes of UV light irradiation. The photocatalytic study was extended to a mixture of seven PPCPs in ultrapure water and wastewater matrix. The results showed >99% removal of most of the PPCPs, whereas, the removal efficiency decreased in wastewater due to the presence of dissolved organic matter. The reaction mechanism was elucidated, and it was found that charge carriers and radicals, played an important role in degrading PPCPs from water. To demonstrate practicality, the PEDOT was immobilized on fiber mat through electrospinning; immobilized PEDOT again exhibited excellent removal (>90%) of metformin.
