Effect of physical, chemical and biological treatment on the removal of five pharmaceuticals from domestic wastewater in laboratory-scale reactors and full-scale plant
PhD ThesisPharmaceuticals and their metabolites are known to enter the environment from the
effluent of wastewater treatment plants. From statistical analysis on the usage of
pharmaceuticals, and their effects on the environment, five pharmaceuticals were
selected for this study (Metronidazole, Trimethoprim, Sulphamethoxazole,
Paracetamol and Ranitidine). Trace concentrations of pharmaceuticals were
determined using a sensitive analytical method, comprising solid phase extraction
(SPE) and liquid chromatography with a mass spectrometry detector (LC-
MS),operating in selected ion monitoring (SIM) mode. It was found that
Metronidazole, Trimethoprim, Sulphamethoxazole, Paracetamol and Ranitidine were
detected at the highest levels in the wastewater entering the Sulaibiya WWTP Kuwait,
with concentrations of up to 58 ng.L , 1814 ng.L , 1669 ng.L , 2086 ng.L and 2009
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ng.L , respectively. High removal efficiencies of these pharmaceuticals were found in
the Sulaibiya WWTP. One year study was conducted to investigate the occurrence,
persistence and fate of a range of these pharmaceuticals at different sampling points at
the Sulaibiya WWTP. The treatment processes consisted of screening, grit removal
and diffused air activated sludge treatment (primary and secondary treatment),
followed by microfiltration (MF), reverse osmosis (RO), and chlorine oxidation
(tertiary treatment). During primary and secondary treatment, Metronidazole,
Trimethoprim, Sulphamethoxazole, Paracetamol and Ranitidine were removed
efficiently with average removals efficiencies of 83.4%, 86.1%, 77.5%, 97.5% and
77.5%, respectively. The RO system lowered these pharmaceuticals further, giving
overall removal efficiencies of 97%, 99%, 99%, 100% and 100% for Metronidazole,
Trimethoprim, Sulphamethoxazole, Paracetamol and Ranitidine, respectively. All
selected pharmaceuticals were tested in laboratory scale reactors to assess their
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removal by chlorination and ozonation, and results showed that 10 mg.L of chlorine
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removed these pharmaceuticals better than 15 mg.L of ozone.
Lab-scale aerobic reactors (2 L), seeded with activated sludge inoculum from the
Sulaibiya WWTP and fed with different concentrations of pharmaceuticals (0.1, 1 and
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10 mg.L ), spiked individually into a synthetic wastewater showed that the TOC
could be removed efficiently without inhibition by these pharmaceuticals.
The fate of Metronidazole, Trimethoprim, Sulphamethoxazole, Paracetamol and
Ranitidine was investigated in a membrane bioreactors (MBR), and a sequencing
batch reactors (SBR), operating under strictly aerobic, and anoxic/aerobic conditions
at different concentrations of a pharmaceutical mixture (PM) of the same
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pharmaceuticals (1 µg.L , 1 mg.L and 10 mg.L ). The COD and TOC removal
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efficiency decreased when the PM concentration was increased to 10 mg.L . The
removal of Metronidazole and Trimethoprim was moderately effective, and similar in
all the reactors. Sulphamethoxazole and Paracetamol were removed efficiently, but
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this decreased when the PM was increased to 10 mg.L for most of the reactors,
whilst Ranitidine experienced high removal rates at all concentrations in all the
reactors.
Analysis of the microbial diversity in laboratory reactors treating pharmaceuticals
wastewater showed decreases in microbial community diversity when the PM
concentration was increased. Pure cultures of bacteria isolated on selected
pharmaceutical growth media were also detected in the microbial communities of
reactor sludge by performing polymerase chain reaction–denaturing gradient gel
electrophoresis (PCR-DGGE)