Removal of selected pharmaceuticals and personal care products in wastewater treatment processes

Yi YANG

Research output: ThesisDoctoral Theses

Abstract

Pharmaceuticals and personal care products (PPCPs) are a group of emerging environmental disrupting contaminants. PPCPs and their residues are widely detected in surface water, groundwater, and sewage treatment plants (STPs) due to their universal consumption, low human metabolic capability, and improper disposal. STPs are known as one of the major sources of PPCPs released into the environment while activated sludge is the significant process of PPCPs removal. Therefore, this study aimed to investigate the recent tendency of selected PPCPs in waste water matrix, elimination routes in STPs and propose an innovative method to improve its removal efficiency. The major tasks were (1) to establish an appropriate, sensitive and repeatable analytical method to detect selected PPCPs concentrations in different units of STPs, (2) to investigate the eliminate mechanisms of PPCPs in activated sludge treatment process, (3) to determine the PPCPs adsorption behavior on rice husk-derived biochar, and (4) to study the transformation routes of PPCPs under different redox conditions. The appropriate, sensitive and repeatable analytical method with a low detection limit was established for trace analysis of PPCPs in different water matrixes via liquid-liquid extraction (LLE), solid-phase extraction (SPE), and gas chromatography-tandem mass spectrometry (GC-MS/MS). The method established in this study was accurate and could be applied to a different water body. PPCPs were detected at the ranges of 89–657 and 0–58 ng/L in STPs inlet and outlet, respectively. The concentrations of PPCPs in the same city by different treatment units varied by 1–2 orders of magnitude. The removal efficiency ranged from -5% to >97% of each unit of local STPs in Hong Kong. Biodegradation and adsorption were considered as dominant removal mechanisms for selected PPCPs at environment relevant concentrations under aerobic conditions. In particular, octocrylene (OC) was mainly removed by adsorption. N,N-Diethyl-3-methylbenzamide (DEET), benzophenone-3 (BP-3), homosalate (HMS), and triclosan were mainly removed by biodegradation process. The Biodegradation behavior of selected PPCPs under aerobic activated sludge can fit the first-order kinetics model well with the R2 ranged from 0.94 to 0.98. The consistent k1 ranged from 0.10 to 0.21. The adsorption of five PPCPs on rice husk-derived biochar performed well in Milli-Q water with all removal rate >80%. Therefore, the conclusion of the high potential of rice husk of adsorbed PPCPs could be drawn. Especially for BP-3, more than 99% has been adsorbed removed. Under different redox conditions, all target pollutants removal performance could have a positive response to the redox value increase. The pH and redox values showed a negative relationship with each other. The bacterial community was more active under the oxidation condition than that under the reduction condition. For triclosan, the oxidation condition may increase the formation of triclosan-methyl. The addition of rice husk derived biochar in activated sludge may increase the removal efficiency of PPCPs and decrease the PPCPs concentration in response to redox change. All rights reserved.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • The Education University of Hong Kong
Supervisors/Advisors
  • TSANG, Yiu Fai 曾耀輝, Supervisor
  • HO, Wing Kei 何詠基, Supervisor
  • SO, Wing Mui, Winnie 蘇詠梅, Supervisor
Publication statusPublished - 2019

Keywords

  • Wastewater treatment plants
  • PPCPs
  • Activated sludge
  • Biochar
  • Removal efficiency
  • Theses and Dissertations
  • Thesis (Ph.D.)--The Education University of Hong Kong, 2019.

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