Full Description

The objectives of this study were to identify foulants and to investigate fouling mechanismsassociated with the nanofiltration (NF) membrane for a pilot unit fed with conventionally treated water and conventionallytreated ozonated water during spring and fall seasons. Generally, membrane fouling depends on acombination of physicochemical and hydrodynamic conditions. This study focused on the effects ofbulk natural organic matter (NOM) type, NOM concentration, and ozonation on the membrane fouling. Other factors that affectfouling such as membrane material, solution chemistry (pH, ionic strength), and operating parameters(transmembrane pressure and cross-flow velocity) were maintained constant during the test period.Pilot scale fouling experiments were carried out with four NF200 (DOW Filmtec, Minneapolis)membrane elements (two series of two stages) fed with sand filtered water (SFW, without ozonation) andsand filtered and ozonated water (SFOW, with ozonation). The 2ndstage membranes were not subjected to analysis due to the relatively lesser degree of fouling compared to1st stage membranes even though feed concentration was higher for the 2nd stage. The operating conditionsprovided a system pressure of 5-15 bar, a recovery of 12%, a pH of 6.9 (with sulfuric acid addition),antiscalant addition of 2.1 g/m3 (blend of polycarboxylate and phosphonic acid). Three month periodtests were conducted during two seasons (spring and fall, 2001). Feed water samples were characterized according to dissolved organic carbon (DOC) andUVA254 by a total organic carbon analyzer (TOC 800, Sievers) and a UV-visiblespectrophotometer (UV-160A UV/Visible Spectrophotometer, Shimadzu) with a 1 cm quartz cell,respectively. NOM fractionation was performed by XAD-8/-4 resin adsorption. The concentrations ofmajor cations and anions were measured using a Liberty-Series II ICP-AES Spectrometer (Varian, TX) anda Dionex ion chromatograph with an auto sampler (with an IonPac AS-SC column). A DS-130 (AKASHI,Japan) scanning electron microscope (SEM) was used to determine the deposit morphology offouled membranes. An energy dispersive spectrophotometer (EDS, EDAX PV9900, PHILIPS) wasalso used to characterize inorganic foulants on the membrane surface. To identify the functional groups offoulants, spectra were collected with a Nicolect 752 Attenuated total reflection-Fourier transform infrared(ATR-FTIR) spectrophotometer using a KBr pellet or membrane specimens. Includes 19 references, tables, figures.

Product Details

Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 12File Size: 1 file , 1 MB