The need for a ‘Next Path’ on water

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Professor David Sedlak shared his views on the opportunities ahead for a new approach to water in his keynote presentation to the recent IWA Digital World Water Congress.

Professor David Sedlak, of UC Berkeley, sees that two fundamentally different approaches to water management have been adopted since the middle of the 20th century.

The first of these was during the post-Second World War 50-year spending spree, which saw an approach he refers to as the ‘Hard Path’. While it provided water for the ‘Great [economic] Acceleration’, Sedlak sees that we are now paying a steep price, with millions of people displaced and many valuable ecosystems on the brink of collapse. He argues that the Hard Path had lost its lustre by the end of the 20th century. He also sees that this era of abundant water made it possible for the subsequent approach he calls the ‘Soft Path’ to realise significant water efficiencies, allowing cities to meet their water growing needs in recent years without building new infrastructure.

But Sedlak cautions that the Soft Path may have peaked. There is no longer slack in the system. “The easy steps may no longer be available to us,” he says. As a result, water scarcity is a present threat, as a booming global population and more frequent droughts put cities under stress.

With tensions rising, Sedlak draws attention to the current and in some cases combative approach which pits public water supply against agriculture, power, and manufacturing. “The agricultural sector is not going to part with their water without a fight,” he notes. Recent crises such as those in Phoenix, Mexico City, Perth, Chennai, and Cape Town demonstrate the intensity and diversity of impacts which, he says, “the Soft Path alone may not be able to solve”.

The Next Path

Sedlak sees the need for what he calls the ‘Next Path’, and he warns that the water sector no longer has the luxury of adapting gradually. This new direction, which demands a radical change in how discussions about research, development, and implementation of new ideas are framed, will be catalysed by technology. He envisages the Next Path as a hybrid of what has gone before, but with a big difference in that he sees an opportunity “to access forms of water that we previously thought were unusable”.

Based on his experience as a member of the US National Alliance for Water Innovation (NAWI), Sedlak describes three themes fundamental to the Next Path.

Firstly, the IT revolution. David zeroes in on the true potential of ‘digital water’ that lies in the monitoring equipment and data algorithms which, he says, can “get more out of our existing infrastructure and possibly create small scale autonomous systems”.

Referring to fellow researchers in California, Sedlak notes how using advanced weather forecasting information, in place of 1960s era rule curves, expanded reservoir storage capacity by one third by better balancing flood risk with the ability to capture water. “The effective size of the infrastructure expands allowing existing assets to be used more effectively,” he says, adding that similar outcomes are also observed in existing stormwater infrastructure.

For Sedlak, such initial wins give a taste of what can be achieved by integrating streams of data, and he anticipates an opportunity for data streams to be shared with researchers to create ‘living laboratories’. He sees that the immediate challenge is to enable interoperability of data, recognising that embedded technology lasts for decades. “Each piece of equipment communicates with hardware and software that comes from a different era of computing,” he adds.

Sedlak’s second theme concerns mainstreaming brackish water and treated effluent as sources of water, and here he points to evidence from Israel, Australia, and Southern California. “Seawater desalination has matured to a point at which it’s often less expensive than other sources in water stressed cities,” he says, and he questions the slower uptake of projects making use of the same desal technology.

His sees that brine concentrate can be too expensive to treat using current Zero Liquid Discharge (ZLD) technologies if there are no simple disposal options, but that there is no shortage of ideas to solve this. These include using new types of 3D printable materials to replace ZLD concentrators, crystallisers, and polymeric membranes, as well as work to make low-tech methods of managing brine more efficient. As an example, Sedlak cites the work of researchers at the University of California, who have fully engineered the powerful evapotranspiration process of plants by using cellulose coated with sunlight-absorbing graphene oxide. This has the potential to reduce the size of evaporation ponds by two orders of magnitude. However, he makes it clear that, despite efforts to use recovered salt in the circular economy, its disposal remains the weakest link in the whole process.

Finally, Sedlak sees that combined advances in IT and modular water treatment technology can “realise the potential for safely operating small scale treatment and supply networks”.

This, he says, will enable more flexible decentralised systems in which individual are able to tailor the treatment.

Sedlak sees such options as exciting, but he also acknowledges that progress on non-grid and hybrid water supply treatment has been slow, in part because of public health risks. However, he urges the sector to consider the “electrifying technologies” that can solve this problem. He highlights their versatility and ability to “eliminate the need to replenish chemical reagents and remove waste from treatment facilities”, given their potential to produce disinfectants, oxidants, acids, and bases on site, as needed.

Recognising the speculative status of this technology, he enthusiastically highlights a project led by Ghent University researchers in which a householder “cannot only drink roof water, grey water, black water, or shallow groundwater, but they can also adjust the quality to suit their needs and their personal preferences, all of this facilitated by the reduced cost of desalination”.

A call to action

There are challenges ahead for accessing more diverse sources of water. “We’re going to have to pay more attention and be more systematic in our thinking about the effects of our use of water on other people and the downstream environment,” he says. “The other challenge with the Next Path is it has to make sense in all the different places where it’s going to be used. It has to work in arid and humid places; it has to make sense to people living in wealthy countries and poor countries; and it even has to work in urban and rural environments.”

“It’s a tall order. The Next Path that we’re about to embark on together isn’t going to be an easy one,” he adds. He sees a need to combine the old and new – at speed. “We have to learn the lessons from the Hard and Soft Path eras and embrace new technologies to make them work with our institutions and our existing water systems, all within a time of changing climate and changing ideas about what water systems are supposed to be delivering,” says. But, addressing the Congress audience, he is optimistic that the sector is able to respond: “I can think of no group better suited for taking on this challenge.”