Feb 01, 2021

Nanofiltration Targets Water Quality & Scarcity Issues

This article originally appeared in the Jan/Feb 2021 issue of WQP as "Driven by Sustainability"

nx filtration direct nanofiltration
Hollow fiber nanofiltration is a proprietary technology that applies an alternative chemistry approach with water-based polyelectrolytes to make very stable, cross-linked complexes on a supporting membrane.

The Netherlands has experienced consecutive years of drought. In 2018, record shortages of rainfall were measured, and in 2020, the spring and summer were amongst the 5% driest years since 1906. As a result, groundwater levels are under pressure. Especially in the eastern part of the country that lies above sea level, these droughts have been most prevalent. In this part of the country, the production of drinking water is traditionally reliant on groundwater. Hollow fiber nanofiltration membrane concepts may offer a simple, sustainable and cost-effective solution to this problem.

Approximately 60% of the total drinking water production in the Netherlands is reliant on groundwater with the remainder being based on surface water coming merely from the European rivers Rhine and Meuse. Especially in the higher eastern part of the country, where these rivers do not flow, groundwater is the key source for drinking water. Because of the extended periods of drought over the last years, groundwater levels have not been replenished with sufficient rainfall. Amongst others, this is resulting in damage to the precious natural environment and also causing various issues for the agriculture sector.

Drinking water companies have been exploring various options to deal with this problem. One of the measures has been to convince households and industries to moderate their water consumption during periods of drought. Drinking water companies are also investigating the construction of long pipelines to transport water from rivers to replenish groundwater levels in the eastern part of the country. However, a more straightforward, cost efficient and sustainable solution could be at hand, as is currently being demonstrated by Dutch membrane specialist NX Filtration. 

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Low-Fouling Hollow Fiber Nanofiltration Technology As a Solution

To showcase its hollow fiber nanofiltration technology in the Netherlands, NX Filtration installed a demo-unit at the Twentekanaal, a local canal that has long been considered too contaminated for the production of drinking water. This demo-unit demonstrates the effectiveness of nanofiltration membranes in removing pharmaceuticals, pesticides, microplastics, per- and polyfluoroalkyl (PFAS) and other contaminations from the water.

Hollow fiber nanofiltration is a proprietary technology that applies an alternative chemistry approach with water-based polyelectrolytes to make stable, cross-linked complexes on a supporting membrane. This method enables precise and controlled rejection and flux properties of the membrane. 

Traditional methodologies for water treatment include combined ultrafiltration and reverse osmosis or spiral wound nanofiltration schemes. Compared to these methodologies, hollow fiber nanofiltration membranes offer various important advantages. They typically operate in a low-pressure regime with reduced energy use, avoid the use of chemicals in pre-treatment and enable a one-step filtration approach with a smaller footprint. Depending on the requirements and feedwater, this also results in significant cost savings versus traditional filtration methods.

At the Twentekanaal demo-unit, the simple one-step nanofiltration process now produces drinking water quality at a demonstration scale. This technology is not only suitable for fully automated decentral applications but can easily be scaled-up to a larger industrial or municipal installations as is already being applied in various municipal plants across Asia. Remote areas in Vietnam, Philippines and Indonesia are already being supplied with clean drinking water produced from polluted surface water with nanofiltration membranes.

Global Access to Clean & Affordable Water

The water scarcity and quality issues in the Netherlands do not stand in themselves. Two out of seven people globally do not have daily access to clean, drinkable water, and 50% of the world’s population will live in water stressed areas by 2025. A key component in addressing these issues is the treatment and reuse of wastewater in which nanofiltration technology can play an important role. Reusing water often provides an economically more viable solution compared to, for example, seawater desalination.

Wastewater comes with two important challenges. First, there is an environmental issue. 80% of the world’s wastewater flows back in nature without being treated. For the 20% that is being treated prior to environmental discharge, we typically fail to remove the ever increasing problems with medicine residues and other micropollutants. 95% of medicine waste reaches nature through sewerage system today, which effects all aquatic life and also human health. Secondly, there is a missed opportunity to recycle treated wastewater for e.g. industrial or agricultural applications or even as source for drinking water. For example, today, only 2% of treated wastewater in the EU is being reused.

Hollow fiber nanofiltration membranes can address both issues. Membranes are capable of removing micropollutants, like medicine residues, endocrine disruptors, pesticides, viruses, micro- and nanoplastics, anti-biotic resistant bacteria and color from wastewater streams, such that these pollutants do not end up in the environment. Removal of all sorts of micropollutants is such that wastewater can easily be reused for all forms of industrial and municipal applications and even for drinking water.

Two key benefits of hollow fiber nanofiltration stand out in this context. First, contrary to, for example, reverse osmosis, hollow fiber nanofiltration does leave in all useful minerals that are a desirable part of our drinking water. Secondly, the hollow fiber nanofiltration process does not require pre-treatment with chemicals or UF, making it a simple, compact and sustainable solution.

“With this demonstration in the Netherlands, we prove the viability of using a difficult surface water from the Twentekanaal for the production of drinking or process water,” said Michiel Staatsen, CEO for NX Filtration. “Applying this on a larger scale, as we already do at several locations around the world, could prevent a further decline of groundwater levels and restore balance. Nanofiltration membranes are also capable of using wastewater streams for the production of drinking or process water. As industrial companies have willingly been adopting this concept, driven by cost savings as well as sustainability goals, we also anticipate a wider adoption of nanofiltration membranes on the municipal level, especially due to their retention capabilities on micropollutants.” 

About the author

Erik Roesink is founder for NX Filtration and Michiel Staatsen is CEO for NX Filtration. Roesink can be reached at [email protected] and Staatsen can be reached at [email protected]

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