‘Wastewater’ equals a water opportunity wasted; in some parts of the world, direct potable reuse is a real solution to water deficiencies
Since the National WateReuse Symposium took place in September, there have been several conversations surrounding the titanic shifts that have taken place in the water reuse sector over the past five years. As part of our ongoing Economics of Water blog series, here are five themes that indicate how water reuse is evolving.
We will write more in depth about these themes throughout 2018.
Theme 1: The conversation is all about potable reuse.
When I attended this conference five years ago, potable reuse was a side conversation. Now, most the conference focuses on potable reuse. Direct potable reuse (DPR)—where water is purified and sent immediately back for use as drinking water—is in the spotlight and now considered an inevitable part of our collective future.
Stantec team members touring a wastewater treatment facility. In the United States, 15,000 wastewater treatment plants discharge wastewater. "Wastewater” equals a water opportunity wasted.
Some of the symposium presentations showed how DPR is being developed or explored in California, Florida, Ohio, Texas, and South Africa. Currently, South Africa is positioned to be a leader in DPR, as the country has faced severe droughts and is turning to DPR as one part of the solution. Its neighbor, Namibia, has provided global leadership in DPR for decades and has 50 years of potable reuse implementation experience in the City of Windhoek. On the other hand, in the United States, 15,000 wastewater treatment plants discharge wastewater. “Wastewater” equals a water opportunity wasted. There is an opportunity here to capture a portion of this wastewater and purify it until it is safe for use as drinking water.
Theme 2: Potable reuse is all about demonstrating purity and protection of public health.
It’s clear that the No. 1 objective of the water industry is to protect public health. Quantifying what that means with respect to water reuse is in the spotlight at conferences, such as the WateReuse Symposium, with some exciting presentations focusing on quantitative microbial risk assessment (QMRA). One risk assessment presentation at this year’s symposium pointed out that DPR water is safer than de facto potable reuse—where wastewater discharges are located upstream of drinking water uptakes. The truth is: there is very little evidence that supports storing water in a reservoir or river inherently improves water quality—conditions are site specific.
Allegra da Silva touring the West Basin Edward C. Little Plant in California, which makes five different types of “designer” waters,” including water that is so ultra-pure—beyond drinking water purity—that it can be used in high pressure boilers.
Theme 3: Potable reuse regulation is a hot-button issue.
There is significant debate within the US water reuse industry of whether it would be helpful for the U.S. Environmental Protection Agency to provide DPR guidance, given that it is currently up to each state’s authority to come up with their own guidance and regulation for all forms of water reuse. As states proceed down this path, we may end up with two related issues in the US.
First, within each state the quality between water produced for DPR under state rules and water produced via de facto potable reuse under the federal Safe Drinking Water Act could start to differ. States could end up with a two-tiered system where different communities receive different water quality, with DPR water likely being of higher quality than de facto potable reuse. The industry may have a hard time reconciling what is “safe enough” for different communities.
Secondly, those inconsistencies would be reflected on a national level—with water produced for DPR varying due to a patchwork of state requirements. How will this affect the public’s long-term confidence in authorities’ ability to protect public health and safety if a unified standard cannot be created across states?
The Stantec-conducted Reno-Stead Water Reclamation Facility Ozone-BAC technology demonstration project for the City of Reno that utilized an advanced treatment process train consisting of membrane filtration, ozonation, and biological activated carbon (BAC) to treat wastewater for potential indirect potable reuse applications.
Theme 4: Demonstrating purity has two fronts—real-time online sensors and predictive analytics.
To prove the purity of water for DPR, research in online sensors is working toward the goal of verifying the quality of the water in real-time, all the time. Since the technology isn’t yet available to measure pathogenic microorganisms in real-time, the industry’s brightest minds are also looking at how we can use machine learning to predict microbial water quality, based on other types of present-day sensors.
These intelligent platforms are helping us explore the complex relationships in standard water quality parameters, with the goal of predicting “faults” and process upsets at least before failure occurs. Current approaches can predict failure up to two weeks prior to them happening.
Theme 5: Much of the actual work going on in the US is in harnessing the untapped potential of non-potable reuse.
Despite all the buzz around potable reuse, advocates for water reuse are charging ahead with a variety of untapped, low hanging fruit—non-potable reuse projects to help diversify communities’ water supply portfolios. This work rarely is showcased in international symposia because it is already well-established, but it’s important to remember how much opportunity there remains in non-potable reuse.
These five themes barely skim the surface on the conversations surrounding water reuse. The water industry is clearly moving full steam ahead via research and pilot tests to see how we can better use the resources available to us today.
As someone who has seen the topic of potable reuse grow and change in the last five years alone, I’m excited to see the advancement and shift towards some of the fruit at the top of the tree—projects that explore how we make the best use the water already in our systems.
The Economics of Water blog series brings together Stantec experts to discuss the key technologies and innovations impacting the future of water infrastructure, water funding, and the value of water. You can read more from our ongoing series here.
Dr. Allegra da Silva has more than a decade of experience in drinking water, wastewater and water reuse, as well as more than almost 20 years of experience working on international collaborations. Dr. da Silva specializes in water reuse, including treatment technology evaluation, policy framework development, feasibility studies, and research design and execution.