Combined chemical oxidation and membrane filtration techniques applied to the removal of some selected pharmaceuticals from water systems

Abstract

The elimination of five selected pharmaceuticals (amoxicillin, hydrochlorothiazide, metoprolol, naproxen and phenacetin) dissolved in different water systems (two natural water matrices and a secondary effluent) was carried out by sequential processes constituted by membrane filtration and chemical oxidation stages. Different configurations of those two stages were applied. In a first group, a pretreatment consisting in a membrane filtration (ultrafiltration or nanofiltration) was conducted; and the permeate and retentate effluents produced were afterwards treated by chemical oxidation, using ozone or chlorine.

In a second group, the pretreatment consisted in a chemical oxidation stage (by using ozone, chlorine, O₃/H₂O₂, UV or UV/H₂O₂) followed by a nanofiltration process. The main objective of this set of experiments was the comparison of the efficiencies reached by using different systems and configurations in order to optimize the elimination of those pollutants from the selected water matrices. Results of removals and rejection coefficients for the five pharmaceuticals showed that the combined treatments involving UV radiation (254 nm monochromatic radiation during 30 min) followed by nanofiltration were very effective, with global removals over 80 % in most of the experiments. Ozonation (initial dose of 2.25 mg L⁻¹) followed by nanofiltration also showed high levels of efficiency, with removals over 70 % in the permeate stream generated in experiments carried out with natural waters. The opposite sequence, nanofiltration followed by ozonation, reached removals over 97 % in the natural waters by using an ozone dose of 2.25 mg L⁻¹; and over 90 % in the secondary effluent with an initial ozone dose of 3.75 mg L⁻¹.

Keywords:

• Pharmaceuticals
• chemical oxidation
• membrane filtration
• combined treatments
• removals
• rejection coefficients.

Acknowledgments

This research was supported by the Ministerio de Educación y Ciencia of Spain through the Projects CTQ 2010-14823 and CSD2006-00044.