Treatment of reservoir water with a backwashable MF/UF spiral wound membrane

The paper presents results of a research project investigating newly developed spiral wound membranes that can be regularly backwashed with filtrate like capillary membranes. The modules were made of microfiltration or ultrafiltration membranes and may be applied for the treatment of surface waters. During a 3 year research project 5 membrane types were selected out of a variety of flat sheet MF/UF-membranes of different material and different pore size. The membrane elements were operated with untreated or pretreated water from a reservoir situated in the Northern Region of the Black Forest in Germany. The water quality showed fluctuating contents of turbid matter, algae and natural organic matter. During filtration of untreated reservoir water the permeability rapidly decreased whereby the degree of decrease was depending on the backwash conditions. It was surprisingly that the spiral wound membranes could be effectively backwashed with filtrate and that even air/water mixtures on the feed side during backwash had a positive effect on the permeability. The performance of these membranes was comparable to capillary membrane systems under defined conditions such that they ought to be considered in future applications.