Are you happy to drink purified wastewater?

Water reuse membrane researchers Danny Harmsen (left) and Dirk Vries at KWR Water Research Institute, Nieuwegein, The Netherlands.

More and more people are coming to accept wastewater recycling as a way to produce clean water for drinking. That is according to a new survey from Cranfield University.

It is often assumed that the public will reject the use of wastewater as a source for drinking water due to the perceived ‘yuck’ factor. This can become a block to realising wastewater recycling projects, even in places where water scarcity is critical and the need for new sources is urgent.

However, the survey of 2,500 people reveals that people are more open to wastewater recycling than previously thought.

“Understanding the public perception of these kinds of solutions is only one part of the puzzle."

Heather Smith, Cranfield University

In the Netherlands, 75% of the respondents supported or strongly supported the use of recycled water for drinking, compared to 73% in Spain and 67% in the UK. Interestingly, there was higher support still for consuming food grown using recovered nutrients from wastewater than drinking recycled water - 75% in the Netherlands, 74% in the UK, and 85% in Spain.

Heather Smith, senior lecturer in water governance at Cranfield, said, “We looked at the drivers behind people's reactions, and there is a powerful influence from what we call social norms. Opinions on both recycled water and food were strongly affected by beliefs in their immediate networks.”

Researcher Heather Smith says people are strongly influenced by beliefs of people in their social networks.

Why reuse wastewater?

Historically, drinking water in the towns and cities of high-income countries has been extracted from groundwater or surface water, treated at specialised plants and distributed to homes and businesses via hundreds of kilometres of pipe. After use, it is eventually collected in sewage pipes as wastewater, taken to the treatment plant and finally deposited into rivers and the water environment.

This linear process is repeated time and time again, with the natural environment being impacted as treated wastewater is deposited upstream and raw water taken in for drinking water treatment downstream. However, technically speaking, there is no need to return wastewater to the water environment at all.

By adopting a circular approach, specialised processes can extract high quality water ready to feed directly into drinking water systems. This option is becoming increasingly important as populations grow and climate volatility also impacts on supplies.

Potable water reuse is a “realistic, practical and relatively climate independent source of drinking water.”

World Health Organisation

Other resources present in sewage and wastewater can also be reclaimed, including energy, and phosphorus, which can be used as agricultural fertiliser. Closing the loop in this way can reduce the total carbon and environmental footprint of wastewater and make its treatment and transport much more economical.

The World Health Organisation says potable water reuse is a “realistic, practical and relatively climate independent source of drinking water.” However, despite the positive benefits to water resilience and as part of a circular economy - where resources are kept in use for as long as possible to extract the maximum value - its introduction is still lagging.

In part, this is because of a disconnect in public understanding about the processes involved, but the Cranfield survey indicates that opinions are changing and those charged with managing our water systems may need to revisit their assumptions about how the public perceives wastewater reuse.

“An element in the acceptability of wastewater recycling relates to trust,” says Jos Frijns, team leader at KWR. “Trust in the water quality and personal experience but also trust in the organisations delivering the service.”

The survey undertaken by Cranfield was part of the European Union’s Horizon2020 NextGen collaboration, which aims to drive the circular economy through a wide range of water-embedded resources. KWR is the coordinating organisation behind NextGen.

“An element in the acceptability of wastewater recycling relates to trust.”

Jos Frijns, KWR

“In the Netherlands, there's high trust in governmental agencies related to environmental control and quality,” Frijns continues. “That helps in citizens trusting reuse initiatives, and that might be a much more important factor in improving acceptability than just informing and educating.

“Five years ago, in the Netherlands, the suggestion of the direct potable reuse of wastewater would have certainly been seen as a no-go. The water industry would say the general public wouldn’t want this. However, this mindset is now shifting.”

Trust in the organisations delivering the service is one element in the acceptability of wastewater recycling says Jos Frijns, KWR.

Results from the surveys are expected to be fed into long-term public engagement strategies for water recycling projects.

“This new understanding will help to ease the perception that the public is going to react badly to these types of schemes. However, there has to be a longer-term strategy of public engagement.

“Understanding the public perception of these kinds of solutions is only one part of the puzzle," added Smith

Who does potable water reuse?

Namibia: The oldest example of direct potable reuse (DPR) is in the city of Windhoek, Namibia, where the Goreangab plant produces purified water for 400,000 residents. The site was established in 1968 and has proven over the last 50 years that DPR can be more economical than indirect potable reuse, as it removes the need to manage discharge to receiving waters and raw water abstractions. The water is not treated again at a conventional water treatment plant; it goes directly to the distribution network – hence the name – direct potable reuse.

Texas, USA: El Paso Water is making history with one of the first direct-to-distribution projects in the USA. The US$100 million Advanced Water Purification Facility will be located in the arid Chihuahuan Desert on the municipality’s water campus. The facility will treat up to 190,000 cubic meters of secondary effluent from the Roberto R. Bustamante Wastewater Treatment Plant to produce high-quality purified water.

California, USA: One of the first US water authorities to deploy water reuse was the Orange County Water District (OCWD) with its flagship Groundwater Replenishment System. The award-winning three-stage process purifies treated wastewater before putting it back into the aquifer, creating a continual, sustainable water supply for 850,000 people. This is called indirect potable reuse as the water goes back to the aquifer before being extracted again for drinking water consumption.

Testing the water at Orange County's Groundwater Replenishment System. Image: OCWD.

Singapore: By branding reused water as NEWater and including it as part of its long-term water strategy, Singapore has also overcome one of the biggest challenges to implementing water reuse: public resistance. Singapore’s water agency, PUB, was inspired by the Orange County system and potable reuse has helped the city state to overcome a critical lack of natural water resources. Five NEWater plants now supply up to 40% of Singapore’s current water needs, planned to reach 55% by 2060. Again the Singapore project is an example of indirect potable reuse as the water is returned to a reservoir, before being retreated and consumed.

Public education was a big part of Singapore's strategy for water reuse. Image: PUB.

Additional information sourced from Qatium and Aquatech, with thanks to Tom Freyberg