BiOsmoBackwash: a New Approach to Counter Biofouling in Membrane filtration

Clean drinking water is vital for human life. Water is also essential to agriculture, energy and manufacture. The United Nations recently reported an expected increase in demand for water of 55% by 2050. The reliable and sustainable provision of clean water for all is urgently needed worldwide, and is the focus of one of the Sustainable Development Goals established by the UN (Goal 6). In a scenario where conventional water resources are becoming increasingly insecure and contaminated, the development of new improved and resilient water treatment technologies is imperative to meet the UN's target. This proposal takes an important step towards a solution involving membrane filtration in water supply.
Nanofiltration (NF) and reverse osmosis (RO) membrane processes are increasingly popular as they supply high quality water, including drinking water, from any available water source. 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. Biofouling in particular, is caused by the accumulation, adhesion and growth of microorganisms 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 biofouling. These processes are inefficient and they require process downtime. They can also modify the properties of the membrane, ultimately reducing its life.
This project will demonstrate a simple, novel cleaning technique to prevent biofouling formation on NF and RO membranes. We will explore the regular introduction of a burst of high salinity - a High Salinity Pulse (HSP) - into the input feed flow of the membrane. The HSP causes a high osmotic pressure difference to occur between the feed and permeate sides of the membrane. As a consequence, the direction of water permeation through the membrane temporarily reverses, flowing from the permeate side to the feed side. The membrane is backwashed and adhered microorganisms removed from the surface, avoiding growth and subsequent biofilm formation. This will maintain water production quantity and quality at lower operational and energy costs and extend the usable lifespan of a membrane, having an immediate transformative effect on industries where NF and RO membranes are used, which include the water, wastewater, aquaculture and food & drink industries.

The development of novel technologies to improve NF and RO processes for clean water production, including drinking water, will have a far-reaching impact on society.
The Post-Doctoral Research Assistant (PDRA) employed in this project will benefit in many ways, gaining cross-disciplinary skills covering aspects of material science, engineering and biological sciences. The PDRA will develop specialist skills in advanced water treatment technology, which would be invaluable to the UK economy. Opportunities will also arise for public engagement and dissemination, where communication skills will be consolidated, as well as dissemination through publication of peer-reviewed journal papers, as detailed in Pathways to Impact and Academic Impact.
Improving water production processes and water quality will have a direct positive impact on UK public services, including water treatment companies such as Scottish Water, and the drinking water Regulators. The proposed cleaning method has many advantages which include: (1) maintaining production of high quality water, (2) reducing operational costs and energy requirements, (3) reducing the environmental footprint of presently adopted cleaning chemicals, and (4) increasing membrane life. Collaboration with these companies allows the UK to lead in this area, bringing economic competitiveness and potential for commercialization in the water sector. Water utility companies in the UK invest more than £10 billion in assets and services each year, employ 45,700 people, and create 86,000 indirect jobs. Approximately 400 specialist engineering companies generate revenues of £1.5 billion [1]. Other membrane end-users benefiting from the proposed cleaning method include the Oil & Gas, Food & Drink, Aquaculture and Dairy Industries. As a national example, Cameronbridge Diageo distillery in Scotland uses membrane technology for wastewater treatment and reuse [2].
This project will take a first step in fully understanding membrane fouling and developing efficient cleaning strategies to remove it. This is crucial knowledge for the development and design of novel membrane materials and modules carried out by polymer chemists, material scientists and engineers. Membrane manufacturers, which include Koch, Trisep and Xylem, current UK approved membrane suppliers, will have a vested interest. Further collaborations with these companies and membrane end-users will be sought for the longer term aim of improving membrane process operation.
The improvement of membrane process operation contributes to the goal of ensuring the sustainable and reliable provision of clean water for all human beings. To reach this goal, however, wider issues need to be influenced by the research community through engagement with policy-makers, governments, regulatory bodies, industry and stakeholders. Policy-makers and governments need evidence-based data from researchers to inform critical decisions regarding water planning, management and supply for the provision of clean water for everyone. This has obvious impacts on health, sanitation and wellbeing. It also ensures the wealth and economic development of the supplied regions, including geographical points which experience repeated shortages of freshwater and areas where seawater is the prevalent source of water, which could otherwise lose their inhabitants through migration or experience severe issues of water conflict. Illustrative cases include countries along the Mediterranean, such as Spain and Israel, as well as the UK where water shortage and population increase has seen the implementation of an RO desalination plant in Beckton to supply drinking water to London.
[1] UK Government, "Promotional material on water and treated water" (2015) - https://www.gov.uk/government/publications/water-and-treated-water/water-and-treated-water
[2] Diageo Presentation (2012) - http://www.slideshare.net/victorialambert/diageo-15385659