The Energy Efficiency of Reverse Osmosis

Guest Bill Mitch says it’s no secret the world is running short of fresh water. As a civil and environmental engineer, he sees wastewater as a potential solution, if only we can eliminate the impurities. Mitch designs systems to remove toxic chemicals from wastewater to enable its reuse as a drinking water supply. It’s not easy, but it costs half as much as desalinating seawater, Mitch tells host Russ Altman on this episode of Stanford Engineering’s The Future of Everything podcast.

Show Notes & Chapters: The future of Wastewater

(00:00:05) Introduction

Russ introduces the podcast and guest, William Mitch, who discusses the future of wastewater treatment.

(00:00:38) Nitrogen in Wastewater Treatment

Russ and William kick off the conversation with an insightful discussion on the issues surrounding the nitrogen cycle in wastewater treatment. They discuss the nitrogen cycle, the role of nitrogen in wastewater treatment, and the challenges of removing it from wastewater, including the current technologies being used.

(00:02:28) The Basics of Wastewater Treatment

Mitch explains the fundamental process of wastewater treatment, highlighting the initial step of removing solids and the biological process of removing organic matter.

(00:07:35) Understanding Biochemical Oxygen Demand (BOD)

Mitch explains the concept of BOD, its importance in water treatment, and how technology has evolved to measure it.

(00:10:19) The Challenge of Nitrogen Removal

Discussion about the difficulties and processes involved in removing nitrogen from wastewater, focusing on the traditional and newer approaches.

(00:14:02) Energy Consumption in Wastewater Treatment

Mitch talks about the substantial energy demand involved in wastewater treatment, especially in the nitrogen removal process.

(00:17:32) Research on Nitrogen Removal

Mitch discusses his lab's research on a more energy-efficient process for nitrogen removal from wastewater, explaining the concept of anammox bacteria and their role in this process.

(00:20:49)  Phosphate Removal and Regulation

Mitch talks about the lack of regulatory pressure for phosphorus removal from water and its potential future implications.

(00:21:30) Public Acceptance of Wastewater Treatment Technologies

Russ probes into the public acceptance of wastewater technologies, specifically potable reuse of wastewater. William discusses the changes in public attitudes towards recycled water over the past decades, the importance of public relations campaigns and community education in shaping these attitudes, and the future of potable reuse facilities.

(00:24:39) The Quality of Potable Reuse Waters vs. Conventional Water Supplies

William discusses a recent study comparing the quality of water from potable reuse plants to conventional water supplies. He reveals that the treated waters were found to be of higher quality than surface waters and comparable in quality to groundwater supplies.

(00:27:00) Chlorinated Taste in Drinking Water

Russ asks William about the common chlorinated taste in drinking water. William explains the chemical reactions that lead to this taste and why it isn't necessarily a red flag for consumers.

(00:28:00) Future of Separate Infrastructures for Potable and Non-Potable Water

They wrap up the conversation discussing the possibility and implications of having separate infrastructures for potable water and water used for other purposes. William explains the logistical challenges and why many utilities are moving towards potable reuse.

(00:29:08) Conclusion

Russ concludes the episode, thanking William for his insights into the future of wastewater, and invites listeners to subscribe, rate, and review the podcast for future episodes.

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