This Issue

Class Act

Class Act

Kohler’s innovative ways to treat wastewater in developing nations.


By Alexandra Pecci

Functioning bathrooms are taken for granted in the United States, but in many parts of the developing world, sanitation infrastructure is often patchy or nonexistent, and relieving oneself can be a matter of life and death.

“The basic problem is that all over the world there are hundreds of millions of people who don’t have access to a safe toilet,” says Rob Zimmerman, director of WASH (water, sanitation, and hygiene) and sustainability for Kohler, the Wisconsin-based plumbing fixture company and Platinum level member of the U.S. Green Building Council (USGBC). “The alternative is that people openly defecate.”

In many parts of the world, the familiar method of using water to transport waste through a sewer system to a treatment plant isn’t feasible because of lack of infrastructure. In places like India, for instance, flushing a toilet might discharge the human waste into an open channel or ditch outside the building instead of to a wastewater treatment facility. This leads to countless health, economic, and environmental problems, from spreading devastating infectious diseases to polluting water supplies.

“The question is, how do you create a gracious toileting experience—or even an acceptable toileting experience—in remote locations or rapidly urbanizing areas without infrastructure but millions and millions of people?” Zimmerman says. “Sanitation really affects all aspects of human development and economic development, so in places without proper sanitation, it’s clear a different model is needed.”


An estimated 62,000 million liters per day (MLD) of sewage is generated in urban areas, while the treatment capacity across India is only 23,277 MLD, or 37 percent of sewage generated, according to data released by the Indian government in December 2015.

That’s why Kohler is busy working on a different approach, one that doesn’t rely on plumbing infrastructure to deliver a clean, safe, bathroom experience. In India, the company is currently testing prototypes of a standalone Closed-Loop Advanced Sanitation System (CLASS), which is supported through a collaboration with the California Institute of Technology and a grant from the Bill & Melinda Gates Foundation through its Reinvent the Toilet Challenge.

CLASS is “a self-contained, turnkey wastewater treatment system in a box,” says Mike Luettgen, senior principal engineer for Kohler, who is leading the technical aspects of CLASS. The box in question is about six feet wide, nine feet long, and six feet high. It is connected to all the toilets in an apartment building, and powered using the local utility grid. Wastewater enters the box, gets treated until it’s safe, hygienic, and aesthetically acceptable, and is reused in the same toilets, over and over again.

Three prototypes of CLASS—a self-contained, turnkey wastewater treatment system in a box—were installed at apartment buildings in India in 2015.

Three prototypes of CLASS—a self-contained, turnkey wastewater treatment system in a box—were installed at apartment buildings in India in 2015.

So how does it work?

“That’s kind of where the magic comes in, I suppose,” Luettgen says. “We don’t like to think of it as magic, but good science.”

The system treats the water electrochemically: Water goes into an electrolysis cell, which breaks down the waste products in the water into compounds that off-gas, such as nitrogen and carbon dioxide. In addition, some of the chlorides that are naturally present in urine break down, become chlorine gas, and dissolve, disinfecting any bacteria that may still be in the water.

The box is designed to handle 20–25 people living in five or six apartments. Ideally, it would need to be stocked with water only once—rooftop water tanks are common in the developing world—since “people tend to bring more water into the restroom than they leave with, so to speak,” Luettgen says. If anything, excess water might need to be siphoned off occasionally.

Three prototypes were installed at apartment buildings in India in 2015. The team installed the systems in modern apartments that were already connected to large-scale water treatment plants that could act as backups should the systems fail or need to be taken offline.

“It’s still experimental,” Luettgen says. “We’re still working with prototypes, but we’re working with real people also, so we need to be careful about how much inconvenience we ask them to endure.”

Top: Rob Zimmerman is the director of WASH (water, sanitation, and hygiene) and sustainability for Kohler. Bottom: Mike Luettgen, the senior principal engineer for Kohler, is leading the technical aspects of the Closed-Loop Advanced Sanitation System (CLASS).

Top: Rob Zimmerman is the director of WASH (water, sanitation, and hygiene) and sustainability for Kohler. Bottom: Mike Luettgen, the senior principal engineer for Kohler, is leading the technical aspects of the Closed-Loop Advanced Sanitation System (CLASS).

Kohler has also partnered with a research firm to gather feedback from residents, which has so far been positive. “In an environment like India, where water is in short supply, droughts occur often, and water shortages are fairly frequent, they like the idea of reusing water,” Luettgen says.

But the Kohler team has also discovered that how things work in the lab isn’t always how they work in real life. “We’ve encountered many challenges we didn’t anticipate,” Luettgen says. “Things get flushed down toilets you might never imagine…Closed loop is ideal from a water standpoint, but it creates issues when people put things in there they shouldn’t.”

For instance, although toilet paper doesn’t create a problem because it breaks down easily, the Kohler team has discovered that some people in India often flush newspaper down the toilet. What’s needed next are devices to remove other items that get flushed along with water, human waste, and toilet paper.

Another issue is water quality: The source water in the test region is very mineral heavy, and although the CLASS electrolysis system is an extremely effective water softener, all those minerals are precipitating into the treatment tanks, leading to clogs. That’s why two of the three prototype systems are currently being rebuilt to deal with these issues. They should be back online within a couple of months. “That’s the point where it becomes grinding out one improvement after another,” Zimmerman says.

Its partner in making those improvements is Caltech, where the treatment technology was first developed. Kohler first became involved with Caltech’s work as an industry partner, bringing to life the technologies developed at the university. Now, Kohler is a Gates Foundation grantee itself for the CLASS project and has its own design team, but still collaborates with Caltech to troubleshoot problems unique to the Indian market, says Michael R. Hoffmann, Ph.D., Theodore Y. Wu Professor of Environmental Science at Caltech.

“I’m happy that Kohler got involved,” Hoffmann says. “They want to see a reasonable business in the future.”
Indeed, making CLASS economically viable is one of Kohler’s main goals, in addition to ensuring that the system works on a technical level.

“The idea is to develop a solution around which an economic ecosystem can develop and thrive,” Luettgen says.
That means everyone along the system’s entire value chain can make money on it—including the equipment manufacturers, installers, and maintenance workers—and still present a better and possibly cheaper alternative for the end user.

“If it’s done as a donation, charity or nonprofit, there’s a limit,” Zimmerman says. “If there’s a market where people can make a living from getting involved with this, then it actually has a chance at becoming scalable and becoming a new normal.”

To that end, the Kohler team also believes there are potential applications for CLASS in the developed world, too, which is why they’ll be talking about it this year at Greenbuild.

“It’s your own, onsite waste treatment system with water recycling, so you can’t get much greener than that,” Hoffmann agrees. “It’s pretty much as green as you can get.”