The influence of membrane and water properties on fouling during ultrafiltration

Membrane techniques are an alternative for classical processes of water treatment. However, one of their main drawbacks is that their capacity and membrane lifetime are limited by the phenomenon termed fouling. Natural organic matter (NOM) has been reported as the main foulant during water ultrafiltration. The character of NOM fouling depends on many factors. The results of the study on the effect of water properties such as pH, kind of foulant and ionic strength on the extent of membrane fouling are discussed in this article. Membranes used in the experiment vary in contact angle. Unified Modified Fouling Index (UMFI) was used to describe the intensity of fouling during ultrafiltration. The investigations was made with the use of the Ultrafiltration Cell Millipore CDS10 System. The device was equipped with flat sheet membranes and was operated in the dead-end mode. The study showed that the increase of ionic strength and pH resulted in the decrease of fouling. It was also found that the most severe fouling was caused by humic substances, followed by polysaccharides (dextrans) and the lowest fouling rate was observed for the mixture of humic substances and polysaccharides. Membrane hydrophobicity and pore size distribution had also a significant impact on fouling in case of low ionic strength waters.