On Tuesday 12 July 2016 we had a televised discussion on the ‘Future of World’s Water’, still in the context of the Singapore International Water Week. Sri Jegarajah, Anchor/Correspondent CNBC moderated a fascinating exchange with fellow panellists Professor Asit Biswas (he contributed to this blog on several occasions),Venkatesh Kini, President, India and South West Asia, The Coca Cola Company, and Mike Burke, Chairman and CEO, AECOM, a professional and technical services firm positioned to design, build, finance and operate water/wastewater infrastructure assets around the world for public- and private-sector clients.
I was asked to say a few words on the following question: “Water is not like oil or coal which once used breaks down in different components and cannot be used. Water is a renewable resource, and thus conceptually it can be used, treated, reused and the cycle can continue indefinitely. Why then at present most cities and industries are not treating their wastewater and reusing it?”
Here are some thoughts that I presented, starting with some overall numbers to put things into context.
In 2010, 600 km3 of freshwater was withdrawn for domestic use and 800 km3 for industrial use. Meanwhile, according to UNEP, 330 km3 of municipal wastewater was generated globally.
So, we have a gap of some 1000km3 that appears to be disappearing. What is actually happening?
Let me start with industry. More than half of the water withdrawn is used for energy generation, for the cooling of power plants. This water evaporates, and thus disappears from the municipal water circle.
On the domestic side, much of the human intake of freshwater is used to cool us down. This evaporates as well. There is also evaporation from other domestic uses: the water used to water lawns and gardens is lost through evapotranspiration of plants.
You may say all this water comes back as rain, but the fact is that 80% of global rainfall happens over the oceans.
Now, it might be interesting to do a complete water accounting exercise. I have given just a few numbers to illustrate the orders of magnitude involved. It seems clear from these that that concept of an indefinite cycle through the re-use of wastewater does not really work.
Don’t get me wrong. Wastewater treatment for re-use remains an excellent and not yet sufficiently implemented idea. But we do need some degree of pragmatism here.
Moreover, only about 65 km3 of wastewater are actually collected and treated, a very small part of which is for re-use as drinking water. We re-use wastewater in our Nestlé factories – best in class are our zero-water factories for milk products. Cities re-use wastewater as well and on a much larger scale, the most sophisticated being Singapore, but there are other examples, such as Namibia for drinking water, or some cities in Peru which re-use wastewater for irrigation of urban parks. In the Californian Orange County, wastewater treated for re-use is pumped into underground aquifers (‘re-infiltration’), to be pumped up again as drinking water. This so-called ‘indirect potable use’ is intended to avoid negative reactions from users.
Obviously, all this does not go without a cost nor without the consumption of energy. In Orange County, to follow up on the example just cited, the treatment cost is 40 US cents per cubic metre of freshwater; this does not include the cost of wastewater collection, nor of the pre-treatment necessary (both are necessary for environmental and public health reasons), nor of the re-infiltration. Needless to say, if you can obtain natural groundwater, you may try to avoid this kind of cost.
Now, let me take my thinking one step further. If you only focus on household and industrial use of water, you are clearly ignoring the ‘elephant in the room’, namely agriculture, which accounts for more than 3,100 km3 of freshwater withdrawals every year. Almost all of this water is actually consumed through evapotranspiration of plants.
So, in my mind, we need to think comprehensively and include all uses of freshwater – that is, domestic, industrial and agricultural – and instead look to limit the withdrawals in a watershed to the amount of water that is naturally renewed (minus the environmental flows). This is what we postulated as a target for the UN Sustainable Development Goals agreed last year.
But this is not the case today. Increasingly, natural buffers on and below surface are being used. Take for example the frying Aral Sea, or many underground aquifers in India, China, Southern Europe, also in the US, from the Great Plains to California with rapidly falling water tables. And so, whenever a drought comes along, there is simply no buffer left for the dry period, and what is a crisis risks turning into a catastrophe.
In sum, we really are running out of water, despite the fact that water is considered a renewable resource. Wastewater re-use is without doubt a step in the right direction, but it is not always cost-effective, and with a current potential of 330 km3 annually, it is clearly not sufficient on its own to meet the water resource challenge. The gap from overuse is already some 800 km3 today, and it continues to grow every year. We must develop comprehensive strategies, watershed by watershed.
As ever, I would welcome comments, questions and further ideas.