Development of novel cleaning techniques for nanofiltration (NF) membranes

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Project Background: Clean water is the foundation of life: the UN recently reported an expected increase in demand for water of 55% by 2050. The percentage of the global population living under water stressed conditions is, however, expected to rise from 1/3 to 2/3 by 2025, due to shortage and reduced quality of freshwater resources. This creates an urgent, unmet priority - ensuring the reliable and sustainable provision of clean water for everyone. To meet this target, improvement and development of new water treatment technologies are imperative, and this project takes an important step toward a solution involving membrane filtration.Nanofiltration membrane processes are increasingly popular as they supply high quality water, including drinking water, from many available water sources, as is the case in Scotland. A high pressure feed water is filtered through the membrane, producing permeate, i.e. clean water, whilst contaminants are retained on the feed side. Membranes are however known to foul due to an accumulation of contaminants on the membrane surface, leading to dangerously reduced quality and flow of permeated water, increased operational and energy costs and membrane life reduction. Chemical cleaning regimes, such as chlorination, are used to combat membrane fouling, but are inefficient and require process downtime. They can also modify the properties of the membrane, ultimately reducing its life. This project will assess novel cleaning techniques to remove fouling from NF membranes and compare them with current adopted ones. These will include the regular introduction of a burst of high salinity - a High Salinity Pulse (HSP) - into the input 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 fouling is efficiently removed from the surface. This cleaning technique will maintain water production quantity and quality at reduced costs and extend the usable lifespan of a membrane, having an immediate transformative effect on industries where NF membranes are used. These include the water, wastewater, aquaculture and food & drink industries. Key Research Questions:- Is HSP applicable to all types of NF configurations, i.e. tubular and spiral wound?- What are the optimal conditions for HSP and how do these depend on membrane type and fouling characteristics?- How does HSP cleaning and other developed cleaning regimes compare with current applied cleaning regimes?EPSRC remit and EPSRC priority area: Due to the current challenges presented in water management and provision, Goal 6 of the UN Sustainable Development Goals focuses in ensuring the reliable and sustainable provision of clean water for everyone. EPSRC has recently identified "Sustainable engineering solutions to provide water for all" as an Engineering Grand Challenge and Water Engineering research area in the Engineering theme is a priority growth area, in which this project fits perfectly. Water is an economically important area to the UK, and EPSRC has a considerable body of funded research in this theme. The current portfolio for Water Engineering comprises 37 grants of total value £47M.