Water treatment with membranes in Scotland: what affects their performance, and how to improve their lifespan?

Mankind cannot survive without potable water. Despite this, our potable water resources are becoming more polluted due to human activity (e.g., mining, industry and agriculture), rendering them unfit for consumption. Additionally, water scarcity is becoming more common with over 1/3 of the world’s population living in water stressed countries. This figure is predicted to increase to 2/3 by 2025. In order to guarantee our survival, processes that allow obtaining clean potable water are crucial.

Nanofiltration (NF) membrane processes are increasingly popular as they supply high quality water, including drinking water, from water resources of varied quality. This process is commonly used in Scotland and Scandinavian countries, treating freshwater from lakes and reservoirs in order to produce drinking water. Membranes are however known to foul due to an accumulation of contaminants on the membrane surface which reduce quality and flow of permeated water, increasing operational and energy costs and reducing membrane life. Current cleaning regimes, which are mostly chemical based, are inefficient and they require process downtime. They can also modify the properties of the membrane, ultimately reducing its life.

This project will assess and identify what parameters affect the disparity observed in membrane lifetime in water treatment in Scotland (between 3 to 15 years). These parameters will include quality of water resources, operational parameters during membrane filtration (crossflow velocity, flux), as well as cleaning regimes employed to clean the fouled membranes, with the aim to modify the process and prolong membrane lifetime.

This project will also assess novel cleaning techniques to remove fouling from NF membranes and compare them with currently adopted practice. These will include a regular introduction of a burst of high salinity – a High Salinity Pulse (HSP) – into the feed flow of the membrane. The HSP insertion creates a high osmotic pressure difference between the feed and permeate sides of the membrane. As a result, the direction of water permeation through the membrane temporarily reverses, flowing from the permeate side to the feed side. Consequently, the membrane is backwashed and membrane foulants are removed from the surface. This cleaning technique has the potential to maintain water production quantity and quality at reduced costs and extend the usable lifespan of a membrane.

This PhD project will be carried out in collaboration with Scottish Water and will include pilot scale tests at a Scottish Water Treatment Plant.

Entry Requirements:
The research is rewarding and challenging, so applicants should have (or be close to obtaining) a 1st class or 2:1 honours degree (or equivalent) in Chemistry, Chemical Engineering, Civil and Environmental Engineering, or a related subject.

For more details and to apply, please go to:
https://eng.ed.ac.uk/studying/postgraduate/research/phd/water-treatment-membranes-scotland-what-affects-their-performance