Characterization of the DOC in nanofiltration permeates of a tertiary effluent

In order to develop a feasible technology for a safe ground water recharge with treated waste water, quality and characteristics of four different nan ofiltration (NF) permeates were investigated for separation of organic cons tituents in the treated tertiary effluent. To avoid high fouling and scalin g potentials during the membrane process, we also used NF membranes with la rger pore size, and with a molecular weight cut-off (MWCO) in the range of several thousands g.mol(-1). Adsorption behavior on powdered activated carb on (PAC) of the dissolved organic carbon (DOC) permeating through these mem branes was significantly better than that of the feed waters (tertiary effl uent and microfiltered tertiary effluent). A numerical analysis of the adso rption isotherm data according to the Ideal Adsorbed Solution Theory (IAST) confirmed these results. Size exclusion chromatography (SEC) proved that t he reduction rate for adsorptive removal of DOC from NF permeates increases with decreasing molecular weight. In the feed water DOC adsorption on PAC is negatively influenced by humic substances (HS). As well as the adsorptiv e removal of DOC by PAC, soil aquifer treatment (SAT) showed similar DOC re moval rates in the low molecular range and therefore offers a promising opt ion by combining "large pore" NF-membrane filtration with conventional SAT for more effective DOC removal with the aim of an artificial ground water r echarge. (C) 2000 Elsevier Science Ltd. All rights reserved.