Capillary nanofiltration (capNF) for drinking water treatment

High-pressure membranes are a frequently used means of achieving optimal water quality of drinking water from different sources. An example of these are reverse osmosis membranes, which are highly robust but also have their drawbacks. Because of the module design, these membranes are susceptible to fouling, and therefore require relatively extensive pre-treatment. The use of reverse osmosis membranes also requires a subsequent remineralisation. This project will investigate the potential of capillary nanofiltration as an alternative.

Capillary nanofiltration (capNF) is a new alternative membrane concept available on the market – the membrane technology of Pentair and NX filtration are examples. These membranes do not have many of the known drawbacks of reverse osmosis membranes, and, as long as desalination is not required, the capNF membranes are perfectly suitable. Given that drinking water treatment still has little experience with these new membranes, it is of interest to compare their performance with that of conventional state-of-the-art membranes.

Application in drinking water treatment

This project will develop an understanding of the extent to which capNF membranes are suited to the treatment of surface water for the production of drinking water. With a view to improving water quality, attention will focus on the removal of particles, pathogens, salts and organic (micro) pollutants, and on an improvement of the biological stability. The specific impact of capNF membrane fouling on the operational management will also be examined. In addition, the composition and disposal/treatment of the concentrate stream generated by the process will be studied.

Lastly, the position of the capNF membranes in the treatment process is important. The experience of Evides with these membranes in the improvement of the biological stability and other parameters shows that, because of their particular module design, they are very useful in the pre-treatment. The position of the membranes in the treatment determines the water quality improvement, operational management, and the composition and treatment of the concentrate stream.

Research outcomes

The experience gained with capNF membranes will be shared via a contact platform with the DPWE utilities concerned. This should help fine-tune the research questions. Depending on the priorities, this will lead to knowledge about water-quality improvement, operational management matters, the composition and treatment of concentrate streams from capNF in drinking water treatment, and a comparison of capNF with state-of-the-art membrane concepts.