The technology is ready, but is the world ready? The seismic shift toward water reuse will occur only as driving circumstances reach their tipping point.

Since San Francisco began exploring the possibilities of reusing water in 1932, the promise of conserving one of earth’s most precious resources has hovered around us tantalizingly. The idea of securing adequate water supply by reusing all or most of what we consume is appealing. No one can argue against its merits. The drivers that compel its consideration and adoption are growing. Yet, despite its great appeal, few corporations and individual households are adopting the concept. How do we move water reuse from interesting curiosity to a practice that is seen in every office, factory, farm, and home? How do we enable water reuse to become as widespread as waste recycling? There are five factors that could accelerate the adoption of water reuse, and this article highlights the opportunities available as well as the challenges that must be addressed if the potential of water reuse is to be realized.

Enhancing Climate Change And Drought Resilience

Nothing has been a more compelling driver for the adoption of water reuse than droughts. Climate change is making droughts more frequent and severe and extending the time it takes for affected areas to recover1. From states like California to Texas, water-vulnerable communities have had to embrace water conservation and reuse. In California, cities like San Francisco and Los Angeles have embraced and utilized indirect potable reuse. In Texas, direct potable reuse has been utilized in cities like Wichita Falls and Big Springs.

Cities in need of water will do whatever is necessary to get it — even if it means considering leading-edge options like direct potable reuse (DPR). The sustainability of water reuse is dependent on what happens afterward, when the drought subsides, and cheaper sources of drinking water become available again. Wichita Falls, TX, might offer a glimpse into how to handle such issues. At the height of its water crisis, officials set up a DPR system. When the drought subsided, they migrated to an indirect potable water reuse (IPR) system. This approach will potentially allow the city to move to less-expensive IPR options when the drivers for DPR are not present. Their example demonstrates that water reuse can be an essential part of a comprehensive strategy for tackling climate change and enhancing climate resiliency. During drought conditions, water reuse allows cities to tap into treated sewage for direct or indirect potable reuse. In coastal cities where climate change is leading to rising seawater levels and more frequent floods, increasing the risk of the inundation of freshwater sources with saltwater infiltration, water reuse will reduce the exposure of such cities to the unpredictable effects of climate change-related incidents that compromise water sourcing for drinking water.

Corporations And The Drive Toward Mitigating Environmental Risk

Over the last two decades, corporations have added a new risk to the growing list of uncertainties that they must hedge against — water-related branding and financial risk. Unlike general compliance risks that stem from the corporation’s ability to meet existing environmental regulations, water-related environmental risk is based on sustainability considerations and responsible corporate citizenship. It is related to how well a corporation is being a responsible steward of the water resources in its operational environment.

The introduction of the water footprint concept in 2002 by Arjen Hoekstra provided a quantifiable metric for how organizations impact water sustainability in their regions of operation. This meant that, for the first time, a metric was available for measuring the amount of water consumed and polluted to produce goods and services. This allows meaningful comparisons of water usage to be drawn between products, as well as within and across organizations. The result was that companies began to feel extensive pressure to define targets and set goals for managing their water footprint2.

There is scarcely an annual report from major corporations today that would not include water footprint metrics and goals. A 2004 paper analyzed3 the stock market impact of environmental performance and found that the announcement of environmental penalties caused a stock market response. While it would be cynical to say that all environmentally responsible actions from corporations have been driven by risk management and not a genuine interest in sustainability, the reality is that corporate interest in maintaining brand integrity and not compromising shareholder value increasingly plays a role in environmentally impactful activities such as water footprint reduction. But corporate self-interest and environmental sustainability don’t have to be mutually exclusive. For instance, there is a growing embrace of the fact that the stock market could be a powerful tool for enhancing sustainability4.

However, moving the needle on industrial water reuse must rely on more than just brand and valuation risk mitigation. Most of the economic activity in the world is not driven by companies that are listed on stock exchanges, whose business fortunes and brands can be impacted by shareholder behavior or influenced by the activities of sustainability-conscious institutional investors like mutual funds. It is unlisted, privately held small- and medium-sized enterprises that generate over 60 percent of all jobs. Until water reuse and recycling becomes a reasonable and sensible option for these firms, no substantial impact will be made. Their decisions will largely be driven by the economic value of water reuse. They will require compact, cost-effective solutions that can allow them to reuse some substantial part of their water and benefit extensively from being provided plug-and-play systems or operational service contracts that allow expert providers to manage the onsite water reuse platforms. If the cost of the service offers savings relative to the status quo, then these businesses will readily adopt water reuse solutions.

Differentiated Pricing Of Sewage vs. Water Treatment And The Impact Of More Stringent Regulations

In the mid-2000s, I was involved in a number of commercial water reuse projects in Brazil. These exciting and innovative projects were not taking place in New York, London, Spain, or Toronto, but in cities like Sao Paulo and Rio de Janeiro. The organization that I worked with at the time, a global industrial gas company, owned a water and wastewater contract operations firm that managed operations and sometimes engaged in self-funded design, build, and operate (DBO) water reuse projects.

The operations firm had a diverse portfolio of industrial and residential clients, the majority of which recycled their treated wastewater. The clients included high-rise residential buildings, a major television studio, several shopping malls, a tertiary institution, and an automobile firm. Why was water reuse thriving in Brazil while debates were still ongoing about its adoption in more developed economies? The driver was simple — sewage discharge costs were up to two to three times higher than drinking water treatment costs. At the time, Brazil had insufficient sewage treatment infrastructure and the higher charge for sewage discharge drove water reuse.

Reusing water was the economically sensible thing to do. The treated wastewater was used for flushing toilets, watering lawns, and doing factory washdowns. The conditions were right for leveraging innovative technologies like membrane filtration, pure oxygen-based aeration, and advanced oxidation with ozone for ensuring the safety of the reused water while also keeping treatment costs low. The first commercial-scale membrane bioreactor (MBR) and advanced oxidation projects I was ever involved with were deployed for water reuse applications during this time in Brazil.

There is a trend emerging in the U.S., Europe, and even China that might drive the disparity in water and sewage treatment costs to the extent that water reuse starts becoming more economically viable. This is the emergence of more stringent sewage treatment regulations, especially regarding the control of nutrients like nitrogen and phosphorus. As communities in the mid-Atlantic and northeastern U.S. are starting to find out, meeting low-nutrient limits requires the use of advanced technologies like MBRs, tertiary filtration systems, moving bed bioreactors, granular sludge reactors, and specialized bacteria (e.g., anammox). This adds costs — a lot of it — to sewage treatment. Using these technologies also implies that the quality of the treated water is higher and that the “water quality gap” to make the water of reusable standard is much lower. When regulations begin to address compounds of emerging concern that are present in trace amounts in the treated sewage, treatment costs will inevitably increase and water reuse will likely naturally emerge as a viable option to pursue for holistic water management.

Reduction Of The Cost Of Water Management At The Household Level

Although the water that goes to homes is called “drinking” or “potable” water, less than 1 percent of it is drunk or put into a pot for cooking. The remaining 99 percent of the “drinking” water is used for activities like washing clothes and dishes, watering lawns, flushing toilets, and bathing.

There are significant opportunities for reusing a lot of the water used in the household. However, the cost of treating the water and reusing it could be prohibitive. The challenge of small-scale commercial and household treatment systems is scale. Water usage at the household level is about 200 gpd — at 50 gallons per capita for a household of four persons. A household water reuse system must be able to recover water from shower systems, faucets, clothes, and dishwasher systems and treat the water so it can be used for things like toilet flushing, car washing, or lawn irrigation. For economic reasons, microbial treatment systems would offer the most viable options. At a minimum, biologically mediated household treatment systems would have to be sized at a volume which is one to five times the total daily water usage capacity to ensure there is sufficient holding time for the treatment. They must be capable of removing solids, separating fats and oils from the water, and eliminating pathogenic bacteria. Since toilet flushes with fecal matter will likely be excluded from the reuse streams, the wastes will be diluted and not very amenable to anaerobic treatment, so aerobic methods will be needed. Lacking the depth needed to ensure that efficiencies for oxygen transfer are at the 15 to 20 percent level found in municipal treatment plants, they must incorporate novel gas transfer technologies. Meeting all these goals might require filtration systems that are in the micro- or ultrafiltration range — small enough to ensure that microbes don’t break through, providing disinfection-grade treatment without the use of chemicals. The technologies exist, and what is now needed are innovators that will find novel ways of integrating them for viable deployment at the household level, as well as developers who will reimagine household water piping and sourcing from drinking water and reuse options.

Managing Utility Revenue Reduction Due To Water Reuse

As more water reuse occurs, less water will be demanded from or treated by utilities. In essence, the volume of water that utilities can charge to cover their costs would be reduced. Most utilities are not profit-making entities, so their rates reflect the bare minimum costs required to maintain drinking water and sewage treatment infrastructure. Regardless of how much water flows through the pipes, pump stations must still be run, and sewer lines must still be maintained. Wastewater treatment plants must still have sufficient capacity to treat sewage that will likely be severely reduced in terms of overall flow, but still have almost as much organic content as was contained in the higher flows prior to the wide-scale adoption of water reuse. A municipality’s treatment costs will not reduce proportionally with flow. The most likely outcome will be that utilities will need to increase the costs of drinking water and sewage treatment as water reuse becomes more mainstream. In fact, it is possible that many aspects of utility asset management might become even more expensive as water reuse gathers pace. For instance, less water flowing through sewer systems would imply that the retention time of more concentrated sewage in the lines will increase. The resulting effect will be that sewer lines will have more septic conditions, odors will increase, fugitive methane emissions will rise, and corrosion problems will be higher. Unless and until we accept the reality that the operating environment for utilities will change along with the mainstreaming water reuse, we might find ourselves in a situation where the water and sewage utilities end up becoming one of the major impediments to the wide-scale adoption of water reuse.

References

1https://www.dailymail.co.uk/sciencetech/article-4792908/Study-findsdroughts-frequent-severe.html
2 https://en.wikipedia.org/wiki/Water_footprint.
3 Lorraine et al (2004. An analysis of the stock market impact of environmental performance information. Accounting Forum. https://www.sciencedirect.com/science/article/pii/S0155998204000031
4 Siobhan Cleary. http://unepinquiry.org/wp-content/uploads/2015/12/Stock_Exchanges_and_Sustainability.pdf

About The Author

Malcolm Fabiyi, PhD, is COO and VP of operations for Drylet LLC. He is a chemical engineer and holds degrees from Cambridge University (PhD), University of Lagos (BSc), and University of Chicago Booth School of Business (MBA). Dr. Fabiyi has over 20 years of experience in the water industry and specializes in the development and commercialization of innovative technologies for water treatment and solids management. He writes extensively on water-related issues.

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