When it comes to slogans promoting sustainable water supply, “toilet to tap” is perhaps not the most appealing. I would imagine that for many people, the prospect that the water being used to flush people’s numbers ones and twos is then processed and fed into domestic water supplies would be enough to put you off your cup of coffee.
But such is the nature of the ongoing drought crisis in California, faucets in the state will soon be issuing water that comes from sewage treatment facilities. The state regulator recently approved a series of measures that will mean that some of the treated water that would have been released into rivers and other bodies of water will instead undergo additional processing and then be fed directly into the water supply network. This is not a new idea.
Multiple states across the southern and western United States have established facilities that produce reclaimed wastewater. These treat the discharge from buildings and industrial processes which is then used for irrigation and industry. Sydney, Australia has a separate recycled waste water supply in homes. This water can be used for watering gardens, flushing toilets, washing cars and laundry. Singapore has very limited supplies of freshwater and now recycles a significant fraction of its waste water. Most of that is used in industry but some is used to top up reservoirs that are used to supply drinking water facilities.
In that respect, all that California is doing is an additional step of treatment to make the water safe for human consumption. Again, this is not a new idea. Windhoek, the capital of Namibia, has been producing domestic drinking water from recycled waste water since 1968. The technology is well developed and there are no reasons that perfectly safe water could not be reliably produced. This could prove critical the next time California suffers another period of crippling drought.
But drinking toilet water. It’s not just that no process can be entirely safe, it’s the emotional barrier to the very idea. First about safety. Some Californians would be forgiven for being sceptical about water companies’ abilities to effectively treat waste water. Across the state over one million people are unable to access safe drinking water. Ironically, it is likely that additional processing and monitoring associated with waste water treatment would produce drinking water much safer than the water being pumped up from some underground deposits, because these deposits are becoming enriched with arsenic and other hazardous materials. These are issues that risk the health of Californians living in largely rural areas that do not have the money to do the required additional treatment. The sort of waste water treatment facilities that will very likely be deployed in the state will be for large urban areas with significant funds available.
Safety would be an issue if and when recycled drinking water systems are proposed in the UK. Given the atrocious track record of UK water companies dealing with sewage, you may be surprised to learn that the quality of UK drinking water really is first class. This situation is the result of a set of perverse incentives in which water companies face serious sanctions if they supply domestic water that is below very stringent guidelines, while suffering effectively no consequences for pumping million of litres of untreated waste into fragile aquatic ecosystems.
This then leaves the yuk factor. While we may dutifully sort out our tins, cardboard and bottles, doing our bit for recycling may not extend to drinking something that was not that long ago micturated by someone else. However, this is a strange way of looking at things because all water is recycled by nature of the hydrological cycle.
Each day hundreds of cubic miles of water are evaporated from the world’s oceans. This water vapour can travel hundreds and thousands of miles before condensing and falling as rain, snow, sleet or hail. This ends up in the surface waters of rivers and lakes, or below the surface in underground aquifers. Eventually it makes its way back to the oceans. This constant recycling of water means that some of the water you drink each day has been through countless other people. In fact, given the stability of water molecules, some of the water that comes out of your tap would have once been drunk and expelled from species now long extinct. The water you used to brew this morning’s cup of tea may have once been Tyrannosaurus rex pee.
Drinking someone, or something else’s waste water is what we all do, what all life has done for billions of years. We are just momentary stops in water’s endless cycle around the earth system. Recycling wastewater could, along with decreasing water loss from leaky pipes, help ensure safe drinking water for millions of people across the world. The issue here then, is not really where the water comes from, but the quality of its treatment before and after we drink it.
James Dyke is an associate professor in earth system science at Exeter University
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