This blog is inspired by the recent Scientific American 60-second science feature on recycled drinking water (https://tinyurl.com/tdqftv7) and in a way continues from my previous blog about my research. In my last blog, the focus was on explaining the science and the methodology of the research without jargon and in a concise and straightforward manner. However, I did not divulge into specifics of the application of my research. Primarily, my research focuses on the use of membrane filters for the purification of wastewater to produce water suitable for potable reuse. As a researcher in the field of water reuse, I find myself very comfortable accepting the use of wastewater to provide clean drinking water. But when I listened to the podcast, the guest specifically pointed out that the disgust associated with the idea of recycled water is detrimental to the acceptance by general public. Now, I have always believed that the public needs to know what all goes into cleaning the wastewater to quality typically even better than regular drinking water. The logic goes like this; I accept the idea without disgust because I work with these processes and see them in action every day, and the visual changes to water as it passes through multiple barriers take away the disgust and add trust. So, I will use this blog as an opportunity to put a glimpse of the toilet to tap story and hopefully contribute to changing opinions of some if not all.

Before we dive into the original ‘toilet to tap’ story, we need to take a detour. It’s the story of de-facto reuse. There is joke among water professionals in Houston, ‘Every time you get a glass of water from the tap, you should thank the natives of Dallas for flushing their toilets.’ Essentially, the wastewater generated by Dallas is treated and then discharged into the Trinity River which is the primary source of drinking water in Houston. This is just one example of many such frameworks in existence.

With that out the way, let us talk about the actual ‘toilet to tap’. What is the idea? It is quite simple, (i) take the wastewater generated from toilets, kitchens, and other household uses, (ii) treat the wastewater using traditional processes in wastewater treatment plants (WWTPs), and (iii) take the treated effluent and further treat to drinking water standards. If we are to equate this process to the de-facto reuse, I mentioned. Basically we are replacing the natural processes after discharge in the river with more controlled and well-defined processes developed over years of research and practice.

Let’s talk about the processes involved. The reuse industry uses a critical term that in my view really defines our (water professionals) commitment to providing clean/safe drinking water to everyone. The term is ‘Multiple barrier approach’. You see, water treatment is a process designed to remove different types of contaminants from the water to make it safe for drinking. Now, to ensure the complete removal or more precisely removal to acceptable levels (as decided by EPA) we employ multiple treatment techniques, aka multiple barriers. Now, these techniques can be segregated into two, and to give more context let’s take example of football. We have the defense (making sure that contaminants cannot pass through, these are the filters), and we have the offense (going through the defense of the contaminants and scoring against them, in case of water treatment killing the contaminants, these are disinfection processes). So, the wastewater effluent, which let me remind you has already been treated in the WWTP, is subjected to a host of defensive and offensive techniques before it is deemed safe for drinking.

Now, it is essential to point out that the idea of water reuse is not new. Windhoek, capital city of Namibia has been producing drinking water from wastewater for half a century now. The plant in Windhoek was the first of its kind in the world. Singapore has been practicing this for well over a decade now. They have named it New water. It’s the psychologist’s way to counter the disgust arising from the term Toilet to tap. Many water professionals and water researchers are of the same view. Call it whatever, ‘new water’, ‘toilet to tap’, or something else; water reuse is the need of the hour.

The psychologist in the podcast pointed out that disgust is a powerful feeling and very hard to overcome, but thirst is even stronger. Every time this feeling of disgust stops you from accepting the idea of water reuse think of the thirstiest you were ever, and I am sure the disgust would be fast dissipating. And add to it the knowledge of multiple barrier approach to trust that the water you are drinking is clean and safe.

---Kunal Gupta
Kunal Gupta is a doctoral student in the Department of Civil and Environmental Engineering