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Abstract. To guarantee a good water quality at the customers tap, natural organic matter (NOM) should be (partly) removed during drinking water treatment. The objective of this research was to improve the biological stability of the produced water by incorporating anion exchange (IEX) for NOM removal. Different placement positions of IEX in the treatment lane (IEX positioned before coagulation, before ozonation or after slow sand filtration) and two IEX configurations (MIEX ® and fluidized IEX (FIX)) were compared on water quality as well as costs. For this purpose the pre-treatment plant at Loenderveen and production plant Weesperkarspel of Waternet were used as a case study. Both, MIEX ® and FIX were able to remove NOM (mainly the HS fraction) to a high extent. NOM removal can be done efficiently before ozonation and after slow sand filtration. The biological stability, in terms of assimilable organic carbon, biofilm formation rate and dissolved organic carbon, was improved by incorporating IEX for NOM removal. The operational costs were assumed to be directly dependent of the NOM removal rate and determined the difference between the IEX positions. The total costs for IEX for the three positions were approximately equal (0.0631 € m −3 ), however the savings on following treatment processes caused a cost reduction for the IEX positions before coagulation and before ozonation compared to IEX positioned after slow sand filtration. IEX positioned before ozonation was most cost effective and improved the biological stability of the treated water.

For drinking water treatment plants that do not use disinfectant residual in the distribution system, it is important to limit availability of easily biodegradable natural organic matter (NOM) fractions which could enhance bacterial regrowth in the distribution system. This can be achieved by optimising the removal of those fractions of interest during treatment; however, this requires a better understanding of the physical and chemical properties of these NOM components.Fluorescence excitation-emission matrix (EEM) and liquid chromatography with online organic carbon detection (LC-OCD) were used to characterize NOM in water samples from one of the two water treatment plants serving Amsterdam, The Netherlands. No disinfectant residual is applied in the distribution system. Fluorescence EEM and LC-OCD were used to track NOM fractions.Whereas fluorescence EEM shows the reduction of humic-like as well as protein-like fluorescence signatures, LC-OCD was able to quantify the changes in dissolved organic carbon (DOC) concentrations of five NOM fractions: humic substances, building blocks (hydrolysates of humics), biopolymers, low molecular weight acids and neutrals.

To guarantee a good water quality at the consumer’s tap, natural organic matter (NOM) should be (partly) removed during drinking water treatment. The objective of this research is to measure the effect of NOM removal by ion exchange on the biological stability of drinking water. Experiments were performed in two lanes of the pilot plant of Weesperkarspel in the Netherlands. The lanes consisted of ozonation, softening, biological activated carbon filtration and slow sand filtration. Ion exchange in fluidized form was used as pre-treatment in one lane and removed 50% of the dissolved organic carbon (DOC); the other lane was used as reference. Compared to the reference lane, the assimilable organic carbon (AOC) concentration of the finished water in the lane pretreated by ion exchange was 61% lower. The biofilm formation rate of the finished water was decreased with 70% to 2.0 pg ATP/cm2.day. The achieved concentration of AOC and the values of the biofilm formation rate with ion exchange pre-treatment showed that the biological stability of drinking water can be improved by extending a treatment plant with ion exchange, especially when ozonation is involved as disinfection and oxidation step.

The objective of this study was to evaluate the effects of the character and the removal of natural organic matter (NOM) on the formation of assimilable organic carbon (AOC) and brómate during ozone disinfection. Natural waters from two locations with different dissolved organic carbon (DOC) concentrations were tested, in addition, the DOC concentration of one of the natural waters was reduced either by ion exchange (lEX) or by granular activated carbon (GAC) filtration. The resulting four water types were tested in conventional pilot-scale ozone bubble column reactors and in a bench-scale plug flow reactor with dissolved ozone dosing. For the tested waters NOM fractions were determined with size exclusion chromatography using DOC and UVAí^ü detection. As expected, it was observed that for the same ozone dosages the CT is higher when NOM is removed by iEX or GAC compared to the situation without NOM removal.It is concluded that, for the waters tested, removal of the humic compounds with a molecular weight of approximately 1,000 g/mol by using IEX led to less AOC formation and less brómate formation as compared to the removal of humic compounds with a molecular weight of 300-500g/mol by using GAC. A, W, C. van der Helm eí al. Effects of NOM character and removal on ozonatbn Journal of Water Supply: Research and Technology-AQUA | 58.6 | 2009 WPK Co, /ocD SUVABB SUVAHS SUVAHS UVA UVA() drinking water treatment plant Weesperkarspei of Waternet concentration ot ozone in water (nig-03/l) conversion factor for calculation of the DOC concentration from the relative signal response of the OCD chromatogram measured with SEC-DOC (mg-C/l) conversion factor for the calculation of UVA254 from the relative signal response of the UVD chromatogram measured with SEC-DOC (l/m) first-order ozone decomposition rate (1/s) UVA254 decay rate (1/s) number of sampling points SUVA for building blocks fraction from SEC-DOC ((l/m)/(mg-C/l)) SUVA for humic substances fraction from SEC-DOC (l/m)/{mg-C/l) BB SUVA for the humic substances fraction and the building blocks fraction from SEC-DOC together ((l/m)/(mg-C/i)) hydraulic residence time (s) UVA254 in water (l/m) stable UVA254 after completion of the ozonation process (l/m) yield for ozone consumed per U VA254 decrease A, W. C, van der Helm er al. Effects of NOM character and removal on ozonation