Profiles and removal efficiency of polycyclic aromatic hydrocarbons by two different types of sewage treatment plants in Hong Kong

Yu Bon Man, Ka Lai CHOW, Zhang Cheng, Wing Yin Mo, Yung Hau Chan, James Chung Wah Lam, Frankie Tat Kwong Lau, Wing Cheong Fung, Ming Hung WONG*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

36 Citations (Scopus)


Sewage discharge could be a major source of polycyclic aromatic hydrocarbons (PAHs) in the coastal waters. Stonecutters Island and Shatin Sewage Treatment Works (SCISTW and STSTW) in Hong Kong, adopted chemically enhanced primary treatment and biological treatment, respectively. This study aimed at (1) determining the removal efficiencies of PAHs, (2) comparing the capabilities in removing PAHs, and (3) characterizing the profile of each individual PAHs, in the two sewage treatment plants (STPs). Quantification of 16 PAHs was conducted by a Gas Chromatography. The concentrations of total PAHs decreased gradually along the treatment processes (from 301 ± 255 and 307 ± 217 ng/L to 14.9 ± 12.1 and 63.3 ± 54.1 ng/L in STSTW and SCISTW, respectively). It was noted that STSTW was more capable in removing total PAHs than SCISTW with average total removal efficiency 94.4% ± 4.12% vs. 79.2% ± 7.48% (p < 0.05). The removal of PAHs was probably due to sorption in particular matter, confirmed by the higher distribution coefficient of individual and total PAHs in solid samples (dewatered sludge contained 92.5% and 74.7% of total PAHs in SCISTW and STSTW, respectively) than liquid samples (final effluent-total contained 7.53% and 25.3% of total PAHs in STSTW and SCISTW, respectively). Despite the impressive capability of STSTW and SCISTW in removing PAHs, there was still a considerable amount of total PAHs (1.85 and 39.3 kg/year, respectively for the two STPs) being discharged into Hong Kong coastal waters, which would be an environmental concern.

Original languageEnglish
Pages (from-to)196-206
Number of pages11
JournalJournal of Environmental Sciences
Publication statusPublished - 1 Mar 2017

Scopus Subject Areas

  • Environmental Engineering
  • Environmental Chemistry
  • Environmental Science(all)

User-Defined Keywords

  • PAHs
  • Removal efficiency
  • Sewage
  • Sewage treatment plants
  • Sludge


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