Nanofiltration organics removal

Vickers J.C., Braghetta A., Hawkins R.A. (1997), Bench scale evaluation of microfiltration-nanofiltration for removal of particles and natural organic matter, Proc. ANX WA Membrane Technology Conference, New Orleans, Feb. 97, 369-387. 

W atson B.M., Hornburg C.D. (1989), Low energy membrane nanofiltration for removal of color, organics and hardness from drinking water supplies. Desalination, 72,11 22. 

A comparison between nanofiltration and pellet softening [combined with granular activated carbon (GAC) adsorption for organics removal] was made by Sombekke et al. (1997), based on a hfe-cycle analysis (LCA). Both treatment schemes were found to have a comparable impact, except that NF was advantageous for quality and health aspects. Other positive aspects for NF were the investments and costs, and the impact on the landscape. The main environmental impact for both alternatives is caused by the use of energy. The Water Supply Company of Overijssel (WMO), The Netherlands, decided to extend current treatment capacity with nanofiltration on the basis of this LCA. 

Nanofiltration (NF) pressure difference removal of small organics mono/divalention separation... 

Nanofiltration membranes usually have good rejections of organic compounds having molecular weights above 200—500 (114,115). NF provides the possibility of selective separation of certain organics from concentrated monovalent salt solutions such as NaCl. The most important nanofiltration membranes are composite membranes made by interfacial polymerization. Polyamides made from piperazine and aromatic acyl chlorides are examples of widely used nanofiltration membrane. Nanofiltration has been used in several commercial applications, among which are demineralization, oiganic removal, heavy-metal removal, and color removal (116). 

Schafer, A. I., A. G. Fane, and T. D. Waite, "Nanofiltration of Natural Organic Matter Removal, Fouling, and the Influence of Multivalent Ions," Desalination, 118 (1998). 

Membrane pretreatment includes microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF). Microfiltration and UF membrane processes can remove microbes and algae. However, the pores of MF and UF membranes are too large to remove the smaller, low-molecular weight organics that provide nutrients for microbes. As a result, MF and UF can remove microbes in the source water, but any microbes that are introduced downstream of these membranes will have nutrients to metabolize. Therefore, chlorination along with MF and UF is often recommended to minimize the potential for microbial fouling of RO membranes. The MF or UF membranes used should be chlorine resistant to tolerate chlorine treatment. It is suggested that chlorine be fed prior to the MF or UF membrane and then after the membrane (into the clearwell), with dechlorination just prior to the RO membranes. See Chapter 16.1 for additional discussion about MF and UF membranes for RO pretreatment. 

Micro-, ultra-, and nano-filtration can separate smaller particles using media with defined porous sizes (i.e., 10 1—1 pm in microfiltration, 10 2—10 pm in ultrafiltration, and 10 3— 10 2 pm in nanofiltration). Residual colloidal and suspended solids can be removed by microfiltration. Selected salts, most organic compounds, bacteria, protozoan cysts, oocysts and viruses are removed by nanofiltration, so that the treated water will be disinfected. This advanced filtration is used for the treatment of effluents for indirect potable reuse applications such as groundwater injection, water softening, decoloriza-tion, or removal of micropollution. 

Keck D. W. (1994) Removal of dissolved naffiral organic matter from a synthetic groundwater with nanofiltration. MS Thesis, Georgia Instimte of Technology, 65pp. 

In the mid-1990s, two spiral-wound nanofiltration plants were installed for the treatment of effluent from a paper mill. In both cases, the nanofiltration systems were installed to remove color, organic carbon, and dissolved solids from effluents for reuse or for further processing. Both plants had a very efficient pretreatment before the NF spiral-wound modules to prevent plugging of the filtration elements. For instance, the pretreatment included settling at several stages with chemicals, a sand filter, a backwashable screen filter, and a bag filter (5 pm) [106]. Neither of the plant is in operation today (P. Eriksson, personal communication, 2005). 

Afonso MD, Geraldes V, Rosa MJ, and De Pinho MN. Nanofiltration removal of chlorinated organic compounds from alkaline bleaching effluents in a pulp and paper plant. Wat. Res. 1992 26(12) 1639-1643. 

Eor water-treatment processes such as drinking water or potable water production, reverse osmosis (desalination), nanofiltration, and ultrafiltration are mainly used. In these processes often a microfiltration stage is implemented as the first cleaning stage for the removal of dissolved organic matter, colloids and particles from the source. 

Agbekodo K.M., Legube B., Dard S. (1996), Atrazine and simazine removal mechanisms by nanofiltration Influence of natural organic matter concentration. Water Research, 30,11,2535-2542. 

Alborzfar M., Jonsson G., Gron C. (1998), Removal of natiral organic matter from two types of humic ground waters by nanofiltration. Water Research, 32,10,2983-2994. 

Amy G.L., AUeman B.C., Cluff C.B. (1990), Removal of dissolved organic matter by nanofiltration. Journal of Environmental Engineering, 116,1, 200-205. 

KhowJ.H., Bernard I.A., RachwalA.J., Jefferies M., O Donnell J. (1997), Technical and economic feasibility of nanofiltration membranes for removal of metals and organics from potable water supplies,... 

This book, by Andrea Schafer, deals with the other important requirement in water treatment, the removal of natural organic matter (NOM). For many water sources NOM is a problem and must be removed to avoid the formation of trihalomethanes, by-products in the disinfection process. The Water Industry, wishing to use membranes, has a choice of options for NOM removal. This book provides valuable input to that choice. For applications with moderate to high NOM the choice could be Nanofiltration and for low or intermittent NOM the choice could be Micro- or Ultrafiltration with chemical coagulant as required. However the optimal choice remains a moot point, driven by costs and operational issues. 

Desalination, 118, Schafer, A.L Fane, A.G. Waite, T.D., Nanofiltration of Natural Organic Matter Removal, Fouling and the Influence of Multivalent Ions, 109-122, copyright 1998, with permission from Elsevier Science ... 

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