Time to rethink how we manage our water supply and urban drainage

Large networks of buried pipes. That is what we use to secure our water supply, urban hygiene, urban drainage, and control water pollution. While this centrally organised approach seemed like a good idea at the time of construction decades, or sometimes more than a century, ago, it may not be the smartest idea in the long run. Or so say dozens of water management researchers from around the world who gathered in the town of Monte Verita in Switzerland. Their discussion culminated in an article published last month in the journal ‘Environmental Science and Technology’ entitled Exploring the potential of non-grid, small-grid, and hybrid solutions. One of the authors is Dr Lisa Scholten of the Faculty of Civil Engineering and Geosciences.

Many of our water systems are unable to cope with rapid urbanisation, urban sprawl, eutrophication, climate change, resource scarcity, and aging infrastructure, or so you and your colleagues write. That’s quite a list of challenges. How worried should we be?

“I think the major problem is that we are failing to move beyond past paradigms that focus on meeting demand by transporting vast amounts of water over long distances rather than managing water cycles and demand locally. We use large amounts of drinking water to flush the toilet and in doing so discharge valuable resources and pollutants into rivers and the sea. That cannot go on. Water scarcity and pollution are already a rampant problem in many parts of the world. Climate change is bringing more periods of drought. At the same time, population growth and socio-economic changes are resulting in increased water demand. You can see the problem.”

The development towards small-scale and circular installations is at odds with the trend towards urbanisation. In the article though, you emphasise the need for this transition.

“Yes. More hybrid and decentralised solutions may be far better but are not usually considered. Water and sanitation systems usually undergo incremental changes rather than radical transformations because of socio-institutional lock-in effects.”

Why is decentralising better?

“In many instances hybrid or smaller-scale water and sanitation systems are promising alternatives because they can be made circular more easily. You waste less energy and materials pumping water over long distances. And you can even use biogas installations to produce energy and recover resources from waste water locally. Residual waste water can be filtered locally with membranes and wetlands. We also need circular systems to recuperate nutrients such as phosphorous. Now these nutrients are ending up in lakes and rivers and the ocean.

In many developing countries, a water supply and sanitary infrastructure has yet to get off the ground. They might do well to consider the whole portfolio of options, including off-grid or hybrid installations. In the Netherlands, we should do the same when addressing our large infrastructure replacement needs. Should we replace like for like and remain locked-into the centralised system or take the opportunity and transition towards an alternative infrastructure that may well be more future-proof? That greater diversity in water infrastructure systems is needed to address the diverse water issues around the globe is a hypothesis. This publication is only a start. More research will follow.”

What is a disadvantage of downscaling?

“What countries like the Netherlands have done very well is to ensure that the quality of the drinking water is of a high standard and that sewage is collected and treated to reduce the impact on the environment. Its whole water system has been optimised to do this reliably and at a low cost. Hybrid and decentralised systems still require further study and experimentation, optimisation and scaling to become equivalent alternatives.”