Natural organic matter removal by ion exchange at different positions in the drinking water treatment lane
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 drinking water quality, including biological stability, 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) are 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. NOM removal can be done efficiently before ozonation and after slow sand filtration; it was found that the position in the treatment lane did not influence the NOM removal capacity. The operational costs were assumed to be directly dependent of the NOM removal rate and determined the difference between the IEX positions. The operational costs for IEX positioned before coagulation were higher than for IEX positioned after slow sand filtration, however the savings on following treatment processes caused a cost reduction compared to IEX positioned after slow sand filtration. IEX positioned before coagulation or ozonation were most cost effective and produced the highest water quality.