Removal of 17β estradiol and fluoranthene by nanofiltration and ultrafiltration

With the recent emergence of endocrine disrupting compounds as an important potable drinking water and reclaimed wastewater quality issue, the removal of two estrogenic compounds (17β-estradiol and fluoranthene) by nanofiltration and ultrafiltration membranes was investigated. A less hydrophobic organic compound model species [parachlorobenzoic acid (PCBA)] was tested. 17β-estradiol (E2), fluoranthene, and PCBA were applied to the membrane in the presence and absence of natural organic matter (NOM). Both batch adsorption and dead-end stirred-cell filtration experiments indicated that adsorption is an important mechanism for transport/removal of relatively hydrophobic compounds, and is related to the octanol-water partition coefficient (K_OW) values. All filtration measurements were performed approximately the same permeate flow rate in order to minimize artifacts from concentration polarization varied with different hydrodynamic operating conditions at the membrane interface. The percent removal by dead-end stirred-cell filtration ranged from 10 to >95% depending upon membrane pore size/hydrophobicity and presence/absence of NOM at an initial concentration ranging from 0.1 to 0.5 μM. Additional batch adsorption experiments with radio-label (³H) E2 at lower concentrations ranging 0.025 to 5 nM showed that E2 removal due to adsorption was independent of its initial concentration. Adsorption occurs both on the membrane surface and interior membrane pore surfaces. However, adsorption was insignificant for PCBA (log K _OW=2.7), but removal presumably occurred due to electrostatic exclusion. Partition coefficients (log K) of 0.44 to 4.86 measured in this study increased with log K_OW and membrane pore size.