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Title: An evaluation of the factors controlling biodegradation of endocrine disrupting chemicals during wastewater treatment
Author: Koh, Yoong Keat Kelvin
ISNI:       0000 0000 7193 4450
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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Endocrine disrupting chemicals such as steroid estrogens and alkylphenol polyethoxylates entering the environment via regular domestic or industrial discharges have been demonstrated to cause feminization of aquatic organisms at trace levels. The presence of these compounds in surface waters has been primarily attributed to their incomplete removal in sewage treatment works and to degradation products generated from alkylphenolic compounds such as alkylphenols and short chain one to three ethoxy units, ethoxylates. This study investigates the factors controlling biodegradation of these chemicals in four sewage treatment works with various configurations of the biological treatment stage. Analytical methodologies for these endocrine disrupting compounds have been developed to allow accurate quantification at nanogram per litre concentrations in sewage matrices. Three activated sludge plants and one trickling filter work were examined. Temperature variation (±10°C) has no impact on the removal of estrogens with the exception of the conjugated estrone-3-sulphate. Removal efficiencies for most of these compounds were >90% at most of these works however the biochemical activity of the biomass was found to be 50-60% more efficient in the nitrifying/denitrifying plant (STW2) compared to the biological nutrient removal plant (STW3). The presence of an anaerobic zone in STW3 did not provide additional benefit in the removal of these compounds compared to a conventional nitrifying/denitrifying plant. The biochemical activity in the nitrifying only pilot-scale plant (STW4) was in between that of the nitrifying/denitrifying plant (STW2) and the biological nutrient removal plant (STW3). It was found that most of the alkylphenols in the final effluents did not exceed and complied with the proposed predicted no effect concentration (PNEC) values of 330 ng l-1 and 122 ng l-1 for nonylphenol and octylphenol respectively. However, concentrations of estrogens at all the works potentially fail to comply with the proposed Environment Agency PNEC value (E2 equivalent = 1 ng l-1).
Supervisor: Boobis, Alan ; Lester, John Sponsor: Anglian Water plc ; Severn Trent plc ; Thames Water ; United Utilities plc ; Yorkshire Water (Kelda Group plc)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral