MICROFILTRATION AND ULTRAFILTRATION OF KARSTIC SPRING WATER

Karstic springs are characterized by their unsteady behaviour of quant itative and qualitative parameters. The irregular and unpredictable in creases of turbidity, natural organic matter (NOM), particles and solu tes require a flexible and reliable treatment to ensure save drinking water quality at any time. In this study, results of a microfiltration (MF) and an ultrafiltration (UF) pilot plant are presented based on 1 5 and 12 months on-site experience. The investigations were focused on the optimization of the operation conditions of the membranes (maximu m flux, dead-end mode, cross-flow mode) in order to guarantee drinking water production at any raw water quality. The results strongly suppo rt that MF performance is mainly influenced by submicron particles con tained in the raw water suspension at higher turbidity peaks and that UF membrane permeability is affected by NOM during storm weather event s. Additional quality problems in some springs caused by the presence of micropollutants (trichlorethene, tetrachlorethene, atrazine) gave r ise to experimentally assess the combination of powdered activated car bon (PAC) with membrane filtration. The adsorption characteristics of the solutes on different PACs were tested in laboratory and pilot scal e. In the on-site experiments, removal rates of 80-90% could be achiev ed by adopting the necessary contact time to the previously determined kinetic data. Additionally, NOM adsorption by PAC addition could subs tantially improve UF performance.