Long-term behaviour of UF membranes treating surface water

Since 1999 a UF plant with a mean throughput of 1.3 ML/d has been in operation treating surface water from a reservoir and springwater for drinking water supply. A three-year DVGW (German Water Works Association) research project accompanies the operation in order to gather data of the membranes' life time, their operational efficiency, the dependence of transmembrane pressure (TMP) on raw water quality (e.g. turbidity, particle count, concentrations of algae, natural organic matter) and the waste water demand. During operation TMP increased with increasing raw water turbidity and algae content and decreasing temperature as expected. Waste water demand has been minimised by decreasing the backwash frequency. A chemical cleaning showed not much effect with regard to TMP although waste water contained rather high amounts of suspended solids and dissolved organic matter. Bubble test for integrity showed that almost all membranes were still integral.