To Dr. Robert Rubin of North Carolina, wastewater reuse is the obvious answer to the challenges caused by population growth, climate change and reduced resource availability. Grundfos met him for a talk about the status of wastewater reuse in the U.S. and globally.
Dr. Rubin, in short, what is the status of wastewater reuse as seen from a global perspective?
In a global perspective, wastewater reuse is a fledgling supply, but an important emerging source of supply. Only a very small portion of water is planned reuse – all water is returned to the water cycle and ultimately reused, but planned reuse is small. Legislation like California Title 22, the North Carolina 2U standards, EU standards and standards like those proposed as NSF 350 are helping raise the bar for reuse.
Which countries are pioneers and what are the major challenges?
Right now, I would say that the frontrunners are European countries, the U.S and Australia. As for the challenges, I think the biggest challenges are risk management in general along with the public perception of reused wastewater being disgusting or dangerous.
One of the important distinctions in wastewater reuse literature is the difference between centralized and decentralized reuse. Is there necessarily a conflict between the two?
No, centralized or decentralized are different approaches to management. A decentralized system allows recycle and reuse as close to potential users as possible and this reduces the energy required in a system. That can mean significant savings because the energy demands associated with moving water are quite significant. A centralized system, on the other hand, requires construction of reuse lines back to the community. A distributed or decentralized approach reduces the disruption necessary to supply water, and can mine water from a collection system and use it through small, appropriately sized systems.
For consulting engineers, what are the most important things to keep in mind when planning a wastewater reuse system?
Consulting engineers should start with rule requirements, then look at potential markets, then determine the level of treatment required for each of the markets. Then comes the design phase of obtaining permits, and the execution of the plan. That is a simplified version, but start by looking at rule requirements and potential markets... and remember, people are required to operate these systems; the personnel need skills in treatment, monitoring, etc. This might be a new skill set for operators.
What are the greatest perspectives about wastewater reuse?
The greatest challenge for us working with reuse is to create a vision where we cultivate building owners, operators, managers, and officials with an idea of how the future infrastructure of reuse can look. Often we cultivate the status quo, and that approach will not satisfy competing demands for high quality water resources in the future.
Dr. Robert Rubin is an Emeritus Professor in the Biological and Agricultural Engineering Department at North Carolina State University. He consults on water and solids management projects. From 1999 through 2005, Rubin served as a visiting scientist at the USEPA in Washington, D.C.