Micropollutant Rejection

Nano filtration (NF) is a relatively new process, though while the number of applications is growing rapidly, the transport mechanisms are still poorly understood (Raman et al. (1994)). NF shows a high selectivity between mono- and multivalent ions. Its popularity in water treatment stems from its softening abilities and high organics (and micropollutant) rejection. 

This brief overview illustrates the importance of operating conditions and the presence of natural organics on micropollutant rejection. Once again, solute-solute interactions are critical in the determination of removal of specific compounds. This highlights the importance of studying holistic systems, rather than single model compounds. 

Kimura K, Amy G, Drewes JE, Heberer T, Kim T-U, Watanabe Y (2003) Rejection of organic micropollutants (disinfection by-products, endocrine dismpting compounds, and pharmaceutically active compounds) by NF/RO membranes. J Membr Sci 227 113-121... 

Xu P, Drewes JE, Bellona C, Amy G, Kim T-U, Adam M, Heberer T (2005) Rejection of emerging organic micropollutants in nanofiltration-reverse osmosis membrane applications. 

Xu P., J.E. Drewes, C. BeUona, G. Amy, T-U. Kim, M. Adam, and T. Heherer (2005). Rejection of emerging organic micropollutants in nanohltration—reverse osmosis membrane apphcations. Water Environment Research 77 40-48. 

Membrane processes and membranes have changed significantly in recent years. The membrane characteristics required depend on the application as described in previous sections. NF represents an interesting trade-off between the high energy requirement RO and the low rejection UF. If waters are mrbid, but not coloured or polluted with micropollutants, MF is an attractive, low cost, option. Total treatment costs (capital and operating) in water treatment applications are summarised for the four processes in Table 3.3. 

Hofman J.A.M.H., Beerendonk E.F., Kruithof J.C. (1995), Modelling of the rejection of organic micropollutants by nanofiltration and reverse osmosis systems, Proc. AWWA Membrane Technology Conf, Reno, Nevada, Aug 95, 733-746. 

NanofUtration is used to purify a surface water that has been polluted with mainly three pesticid bentazone (10 (ig/l), lindane (14 xg/l) and dieldtin (17 ig/l). The membrane rejection for these micropollutants is 92%. 95% and 90%, respectively. 

Dudziak M, Bodzek M. Factors driving rejection of micropollutants (xenoestrogens and phytoestrogens) during reverse osmosis/nanofiltration treatment. Archit Civ Eng Environ 2010 1 95-102. 

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