Development of nanofiltration technology as a tool for concentration and partitioning of organic matters and separation of micropollutants

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Rejection characteristics of nanofiltration and reverse osmosis membranes were investigated in the applications of drinking water treatment of surface and/or underground water and in the applications of leachate treatment. Molecular weight cutoff sizes of commercially available membranes were determined by alcohols and by sugars. Some membranes with relatively low nominal desalination ratio showed more than 90% rejection of natural organic matters in the measurement of TOC.There was less correlation between rejection of organic matters and rejection of salts. This type of insignificant correlation was found in the case not only of surface water treatment but of underground water treatment and of leachate treatment. Bis phenol A, which is thought to be one of the endocrine disrupting chemicals showed lower rejection than the predicted value from the molecular weight rejection relationship obtained from sugar rejection. One of the actual leachate treatment facilities using high rejection reverse osmosis treatment was focused for the rejection characteristics survey. Salt rejections, organic matters rejection and micropollutants rejections were measured in that actual plant. A suction nanofiltration system was investigated using an immersed flat sheet nanofiltration module. Salt rejections were analyzed by using the well known solution diffusion model and the Extended Nernst Planck equations. Sulfate rejection was lower than the predicted value of the Extended Nernst Planck equation. The concentration polarization in membrane separation was calculated to be negligible in the case of small flux operation of immersed nanofiltration. In the arsenic contained ground water treatment, an affinity term was identified in the Extended Nernst Planck equation. A nanofiltration device connected with bicycle type manual pump was developed for the treatment of arsenic contained ground water treatment in Bangladesh.