Which is winning: desal, reuse, or cities?

Published April 6th, 2017

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Insight from Christopher Gasson, GWI publisher

Thanks to our new report on Desalination and Water Reuse, I now know the answers to two questions which have been bugging me for years. The first question is whether reuse is bigger or smaller than desal as a solution to water scarcity; and the second is which one is growing faster.

The problem is that reuse is a pretty nebulous market because it is so difficult to define, and as a result we have not maintained a solid data record of reuse plants in the way that we have followed the desalination market. We last published an inventory of the water reuse market in 2009, but we rather lost track of the market after that.

It turns out that one year later (in 2010), overall water reuse over took desalination in terms of new freshwater production added, and it has stayed ahead of desalination ever since on that measure (in value terms, desal is still worth more because the civil works and equipment are generally more elaborate).

The report also breaks down the reuse market into three categories: basic reuse, reuse with some kind of tertiary treatment (i.e. disinfection), and triple-barrier reuse (i.e. using ultrafiltration or microfiltration followed by reverse osmosis and either ultraviolet disinfection or ozonation). It seems that by 2013, reuse with tertiary treatment overtook desalination for the first time in terms of new freshwater production capacity added, and demand for reuse with tertiary treatment remains ahead of desalination (defined as creating freshwater from seawater and brackish water).

In 2015, at the nadir of the desal market, it was nearly overtaken by triple-barrier reuse. This is significant, because triple-barrier reuse is largely used as a solution to the same problems of urban water scarcity that desal is relied upon to solve. Basic reuse and tertiary-only reuse are largely used for agricultural and landscaping applications, which are not really important markets for desal. In the event, the recovery of the desal market since 2015 means that it has been gaining market share against triple-barrier reuse.

Looking forward to 2022, the total installed capacity of water reuse facilities could be more than twice the size of the total installed capacity of desalination, while tertiary reuse installed capacity will be 18% ahead of desalination, although the annual growth rate of new capacity added will be smaller for tertiary reuse than desalination.

Triple-barrier reuse is starting from a lower base, but it is expected to grow at nearly three times the rate of the desal market.

The cheapest alternative to both desal and reuse is conservation, and this is a growing priority across the world. However, in the longer term there is no avoiding supply-side solutions. My takeaway from the report is that in cities, the supply-side solution is converging on the same technology train: pre-treatment, reverse osmosis and post-treatment.

In the countryside, the solutions are much more constrained by economics: food prices won’t accommodate desal, nor major new water transfer schemes and dams. Further exploitation of groundwater is popular but not sustainable. If we see convergence towards a single water scarcity solution in the countryside, it will be towards greater water efficiency.

If you are interested in the report, you can order it here.