I am Arup’s global skills leader for...
In many countries of the world, there is increasing demand placed on existing water supplies. As well as developing new supplies of water, there is much we can do to reduce the demand placed on our existing supplies.
For example, despite the vital role it plays in effective sanitation, the toilet hasn’t fundamentally changed since the Victorian era. In the UK, toilet flushing accounts for around 30% of household water use. That’s a lot of drinking quality water going down the pan.
So imagine combining ultra-efficient toilet designs with harvested rainwater and recycled water for flushing. Rather than relying on the mains water supply, this could be water sourced from community-scale networks. Just as distributed energy taps into local sources of heat or electricity, water reuse networks would tap into suitable sources of rainwater and treated wastewater and match them to demand for flushing and other purposes such as irrigation. You could flush your toilet with water piped from the local leisure centre, for example – saving both potable water and the energy used to treat it.
I think this approach could help safeguard the world’s valuable water resources and such a decentralised system could make it possible to supply remote communities and growing developing-world cities.
Like many good innovations it’s an evolution, not a revolution. It would complement, rather than replace existing water supply and wastewater infrastructure. But it would provide opportunities to save water, energy and money. It could even give traditional water utility companies the opportunity to develop networks outside their geographic areas and provide opportunities for new entrants in the water supply market.
The first step is assessing whether a proposed water reuse network (WReN) is viable, and Arup is working with University College London and other institutions on a tool to do this. However, finding non-potable water for flushing is only half the challenge; we also need a step change in toilet design.
Twenty-five years ago, toilets used up to nine litres of water to flush. Today’s dual flush toilets use six and four, with the option of a long or short flush. Arup is working with the inventor of an innovative toilet that uses a maximum of 1.5 litres per flush, thanks to air assistance. We’ve devised a universal connector so that it can be fitted to existing drainage systems and we’ve already installed a couple in our London offices to investigate their performance, especially the ability to convey waste through the drainage system effectively.
Reducing water use for toilet flushing may be a comparatively low priority in areas where water is relatively abundant. However, it will be vital for cities in Africa and Asia that are expected to experience rapid population growth.
According to Water Aid, there are currently 2.5 billion people without a toilet. I think the combination of ultra-efficient toilets and water reuse networks could help reduce that depressing statistic.