What happens after you flush the toilet is becoming a big deal. In a new article, published in the science journal Nature, researchers propose a paradigm-shifting change in the treatment of wastewater, a shift they say could have a dramatic global impact.

Arizona State University water treatment expert Bruce Rittmann and two colleagues outline ways to transition from conventional wastewater treatment, which removes contaminants and disposes of them, to advanced used-water resource-recovery methods that would be environmentally and economically advantageous.

In other words, your dirty water could be mined for useful and valuable resources — like nitrogen or phosphorus.

The technologies for doing this are being explored today, but challenges remain before they can be used on a large scale and meaningful way.

Rittmann, an engineering professor in ASU’s Ira A. Fulton Schools of Engineering and director of the Swette Center for Environmental Biotechnology in ASU’s Biodesign Institute talks about the new methods and what they can provide.

Question: These sound like very attractive and potentially useful technologies. Why aren’t they being implemented or at least developed further, now?

Answer: For decades, the conventional thinking was that anaerobic treatment processes are not efficient enough to treat domestic wastewater due to its low organic concentration and low temperature.

Also, conventional aerobic treatment (e.g., activated sludge) has served us well as a means of “treatment only.” Only in recent years have we begun to question the assumption that the only goal is “treatment.” Since conventional processes did their assigned task well and energy costs were relatively low (most of the time), we didn’t have the impetus to do anything different.

In the past 10 years or so, a pull to reduce energy and to limit the greenhouse gas costs of treatment has changed our perspective.

Combined with new materials (membranes and electrodes), we now have new tools to “push” development and to complement the “pull” of the desire to reduce energy and greenhouse gas impacts. The same reasoning exists for nutrient recovery — no “pull” until recently, and some new materials to give it a “push.”

Q: What are the environmental benefits of these technologies?

A: By shifting from energy negative to energy positive, the anaerobic technologies seriously reduce the greenhouse gas emissions of treatment. Recovering nutrients prevents their discharge into surface waters and thus minimizes the acceleration of aging and dead zones in our lakes, reservoirs and oceans.

Click here to read Part 2.