Removing Pharmaceuticals and Personal Care Products from Urine with Waterless Urinal Sealants
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Authors
Thapa, Utsav
Issue Date
2021
Type
Dissertation
Language
Keywords
emerging contaminants , partitioning , source separation , toilet , urine diversion
Alternative Title
Abstract
Pharmaceuticals and personal care products (PPCPs) after their therapeutic use and regular use, are released in wastewater, often poorly treated in wastewater treatment plants (WWTPs), and finally discharged in rivers, streams, or lakes. PPCPs are designed to interact with the tissues of humans and animals, and it is likely that they may also influence aquatic organisms. Thus, these compounds are bioactive, and they have potential toxicological and hazardous effects on ecological systems and environments. Majority of the PPCPs are discharged through domestic sewage, which are excreted via human urine and feces. Therefore, this dissertation focused on removing PPCPs from the urine using waterless urinal sealant fluids.At first, I investigated the potential for waterless urinal sealant fluids to remove pharmaceuticals from urine. 1H-NMR, FTIR, and GC/MS characterization of the sealant fluids indicated that they are mostly composed of aliphatic compounds. Removal of ethinyl estradiol was >40% for two of the three sealant fluids during simulated urination to a urinal cartridge, but removal of seven other compounds with greater hydrophilicity was <30%. At equilibrium with Milli-Q water, ≥89% partitioning to the sealant phase was observed for three compounds with log Kow (log Dow) >3.5. At equilibrium with synthetic urine, removal ranged widely from 2% to 100%. I increased the hydraulic retention time (HRT) 100-fold over that of typical male urination and found removal of specific hydrophobic compounds increased, indicating that both hydrophobicity and kinetics control removal. I also monitored two in-use waterless urinals for three-week and samples were collected to measure the concentrations of nine PPCPs. I developed a method to quantify PPCPs in the sealant phase with liquid/liquid extraction (LLE) and centrifugation, and liquid chromatography-tandem mass spectrometry quantification. The developed method resulted in 85 ±33% and 77 ±34% recovery of nine PPCPs from two sealant fluids. Six of nine PPCPs were present in the sealant samples; caffeine and diphenhydramine were present at the greatest mass concentrations, from 111 µg/ L to 241 µg/L and from 8 µg/ L to 64 µg/L, respectively. Carbamazepine, fluoxetine, sulfamethoxazole, and trimethoprim were also present at concentrations above the detection limit in at least one sample. Results showed that most PPCPs were likely too low to impact wastewater and environmental pharmaceutical loading measurably. I further focused on determining how waterless urinal cartridge design may improve upon pharmaceutical removal from urine. A model compound, benzalkonium chloride, with increasing alkyl chain length (C8 to C16) was selected to systematically investigate the effects of hydraulic retention time (HRT), urine/sealant interfacial area, and hydrophobicity on removal. During simulated urination, removal of BAC ranged from 0% to 97% for two investigated sealants and a trend of increasing removal with increasing alkyl chain length was observed. Increasing HRT did not generally increase removal over a wide range of retention times, which agrees with our previous research and indicates that an increase in sealant volume alone will not substantially increase pharmaceutical removal. An increase in sealant/urine interfacial area was generated by sonication of the sealant fluid during simulated urination and removal of BAC was strongly correlated with interfacial area. When the same experiment was performed with eight pharmaceuticals, removal fell into two groups: A) those which were removed to a greater extent by increasing sealant/urine interfacial area and B) those which were removed poorly independent of interfacial area. Those which were removed poorly tended to be ionized at the pH of the synthetic urine. Thus, removal is strongly controlled by the hydrophobicity of the compound, which is not possible to control, but also by ionization and urine/sealant interfacial area which may be controlled through pH adjustment and cartridge engineering, respectfully.