How water conservation can affect the reliability of recycling

161004-F-XX000-011For years, I have been reading about the need to conserve water – to use lesser water to brush, bathe, wash and irrigate plants. I have also read a great deal on the need to recycle water – how used water from toilets can be reused for gardening, how used water from washing machines can be reused to clean floors and so on. In Singapore, where I live, NEWater has become such an important source of water that during the prolonged dry spell of 2014, rationing of water to citizens was avoided mainly thanks to the facilities for recycled water. Singapore has also gone out of the way to change the paradigm by referring to wastewater as “used water”.

But, somewhere at the back of my mind, I wondered what would happen to the supply of recycled water if people began to concertedly conserve so much that they produced lesser wastewater and consequently there was not enough water to recycle.  

A recent study at the University of California, Riverside has addressed exactly this question in a paper titled “The implications of drought and water conservation on the reuse of municipal wastewater: Recognizing impacts and identifying mitigation possibilities” which appeared in the online journal Water Research, published by the International Water Association. A press release by the university says with reference to the study’s findings that “indoor residential conservation can have unintended consequences in places where systems of wastewater reuse have already been implemented diminishing both the quantity and quality of influent available for treatment.”

“You often hear it never stops raining at a wastewater treatment plant, meaning the influent from households will continue to flow regardless of whether we’re in a drought or not,” said Kurt Schwabe, professor of environmental economics and policy one of the authors of the paper. “It may be true that it will continue to ‘rain,’ but the quantity of flow can be severely impacted by drought and indoor conservation efforts, which has implications for the reliability of the system, especially when it comes to downstream or end users of the treated wastewater.”

In other words, when people take fewer showers, flush less frequently and adopt other water-saving measures, there is a problem of reliability of supply in water recycling plants and it is “pervasive in linked systems of wastewater reuse”.

To make it worse, when flows of used water decrease, the concentration of salts and pollutants increase making it harder for plants that are not designed to handle the elevated levels of total dissolved solids, nitrogen and carbon.

However, Professor Schwabe indicates that it is not correct to conclude that conservation efforts must be reduced during drought. “Our solution is based on a system of blending water,” explains Prof Schwabe. “Traditionally, wastewater facilities have operated by the principle that all the influent is treated to the fullest extent possible. But depending on the sort of demand and regulations a treatment plant confronts for its effluent, managers may have the opportunity to be creative and achieve a much less costly outcome by treating only a portion of the influent with the most advanced technology and blending this with the remaining influent that has been treated but with a less advanced and thus lower-cost process.”

The professor has highlighted a “central tenet of economics: that there’s a cost with every action we take”. He says their results are intended to illustrate how different drought mitigation actions are related so agencies can plan, communicate, and coordinate in the most informed and cost-effective manner possible.

Once again, it is proven that there are more dimensions to a problem than are commonly appreciated. Penetrating into the limits and complexities of a problem requires a  different kind of thinking. The world needs to cultivate multi-dimensional thinkers.


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