Removal of pharmaceutical residue in municipal wastewater by DAF (dissolved air flotation)–MBR (membrane bioreactor) and ozone oxidation

Growing attention is given to pharmaceutical residue in the water environment. It is known that pharmaceuticals are able to survive from a series of wastewater treatment processes. Concerns regarding pharmaceutical residues are attributed to the fact that they are being detected in water and sediment environment ubiquitously. Pharmaceutical treatment using a series of wastewater treatment processes of the DAF (dissolved air flotation)–MBR (membrane bioreactor)–ozone oxidation was conducted in the study. DAF, without addition of coagulant, could remove COD_cr (chemical oxygen demand by Cr) up to over 70%, BOD 73%, SS 83%, T-N 55%, NH₄⁺ 23%, and T-P 65% in influent of municipal wastewater. Average removal rates of water quality parameters by the DAF–MBR system were very high, e.g. COD_cr 95.88%, BOD₅ 99.66%, COD_mn (chemical oxygen demand by Mn) 93.63%, T-N 69.75%, NH₄-N 98.46%, T-P 78.23%, and SS 99.51%, which satisfy effluent water quality standards. Despite the high removal rate of the wastewater treatment system, pharmaceuticals were eliminated to be about 50–99% by the MBR system, depending on specific pharmaceuticals. Ibuprofen was well removed by MBR system up to over 95%, while removal rate of bezafibrate ranged between 50 and 90%. With over 5 mg/l of ozone oxidation, most pharmaceuticals which survived the DAF–MBR process were removed completely or resulted in very low survival rate within the range of few micrograms per litre. However, some pharmaceuticals such as bezafibrate and naproxen tended to be resistant to ozone oxidation.