It’s called wastewater—what gets flushed down the toilet and washed down the drain—but to Kartik Chandran wastewater is a precious resource. Most of the ‘waste’ is water that can be treated and reused. The rest? Nutrients ready to fertilize crops or be turned into methane to power homes, offices, and even sewage treatment plants. A professor of environmental engineering at Columbia University and a past MacArthur “genius” grant recipient, Chandran develops technologies to extract and maximize value from one of humanity’s most unlovely byproducts. Chandran’s work is helping to clean waterways from New York City to Rio de Janeiro. He will discuss some of his projects at a panel discussion Friday following the screening of a new film about Rio’s Guanabara Bay, a heavily-polluted estuary home to 16 million people.
Long Island Sound and the Hudson River used to be as filthy as Rio’s Guanabara Bay. What did it take for New York City to clean up its waterways?
Towns and cities began to build wastewater treatment plants after the U.S. Environmental Protection Agency passed the Clean Water Act in 1972, effectively banning the release of pollutants, including organic carbon and nutrients, into waterways. A sludge-dumping ban in 1988 put further pressure on municipalities to act. I’d expect Brazil and other developing countries to follow as the public becomes more environmentally conscious.
NYC has been a leader in restoring the health of its waterways. Wastewater treatment plants now remove almost all organic carbon from our waste before discharging it back into the environment. Many are now upgrading their systems to remove nitrogen and phosphorous as well. Overloading waterways with nutrients stimulates plant growth, lowering oxygen-levels in the water column, and harming fish and other aquatic life.
What will the next generation of treatment plants look like? What will they do better?
Future systems will clean wastewater to current standards or better while conserving energy and emitting less carbon dioxide and other greenhouse gases. Energy and chemicals recovered during the treatment process will help power the process. Ultimately, we are looking at installing smaller, distributed systems in regions without the capacity to lay a network of pipes.
The average American consumes 100 gallons of water per day. Are you also looking at ways to reduce water use?
We are experimenting with an approach called non-potable reuse to channel treated wastewater to flush toilets, clean laundry, irrigate crops, and provide heating and cooling for buildings—activities that consume most of our water. Cleaning wastewater to drinking water standards is not always necessary.
Describe your work in NYC.
We’ve worked with the city on energy-efficient nitrogen removal. Currently, we’re working at Brooklyn’s Newtown Creek Sewage Treatment Plant, among other facilities, to understand why some microbes are so good at digesting organic waste. At Columbia, we’re converting food waste into biodiesel, bioplastic, and fertilizers, for urban agriculture.
Where else have you worked?
I took a group of Columbia Engineering students to Rio last year to work with a local university to make a city treatment plant more efficient. I’ve also worked in rural Ghana, among other countries, to build systems that convert fecal sludge to energy and chemicals.
What upgrades are still needed in the United States?
We need to work on reliably removing nitrogen from sewage, and consuming less energy and chemicals during the treatment process. We’re getting there! Capturing runoff from farms and the built environment is a more difficult problem to address.
How did you choose this field?
Water quality is a global challenge. More than two billion people lack access to clean water and adequate sanitation. Environmental scientists and engineers need to find better solutions.
Favorite part of the documentary?
I was fascinated by the rich biodiversity that remains in Guanabara Bay. It inspires me to keep working to improve the health of water bodies around the world.
Urban Bay: Eyes Wide Open Under Rio de Janeiro’s Ocean, June 9, 1:30 pm-5pm, Davis Auditorium, Columbia University.
Top video credit: National Science Foundation (NSF) and NBC Learn