Wastewater is what gets flushed down the toilet, rinsed down the drain, and produced by places such as factories, workplaces, and homes. Kartik Chandran at Columbia University is changing the perception of wastewater by treating it more efficiently and creating energy from resources found in it. "Human Water Cycle" is produced by NBC Learn in partnership with the National Science Foundation.
Human Water Cycle – Wastewater
ANNE THOMPSON reporting:
Wastewater. It's what gets flushed down the toilet, rinsed down the drain, and produced by places such as factories, workplaces, and homes. According to the U.S. Environmental Protection Agency, the average person uses about 100 gallons of water a day with almost all of it turning into some form of wastewater.
KARTIK CHANDRAN (Columbia University): Of the hundred gallons per capita per day of wastewater we produce, we are drinking about a gallon per day per capita. So essentially, wastewater is the one gallon of human waste produced per capita per day, diluted with 99 gallons of non-human waste.
THOMPSON: Because wastewater contains pollutants and contaminants, most communities send it to treatment plants to be processed. The water has to meet federal, state, and local standards before it's released back into the environment. Wastewater is one part of the human water cycle, which describes the many ways people interact with nature's hydrologic cycle to meet our needs for water, food, and energy. While water treatment plants are a necessary part of public health and environmental safety, they require a great deal of energy and resources to operate.
CHANDRAN: In the U.S., we devote about three to six percent of the national energy budget on the enterprise of clean water.
THOMPSON: Kartik Chandran is a professor of Earth and Environmental Engineering at Columbia University and funded by the National Science Foundation. He investigates new, more efficient ways to treat wastewater. Wastewater contains elements such as phosphorous, organic carbon and nitrogen, which are often removed during the treatment process.
CHANDRAN: Let's start with nitrogen. When we want to remove nitrogen from wastewater in addition to the organic carbon, the energy footprint of a wastewater treatment plant essentially doubles.
THOMPSON: At the Newtown Wastewater Treatment Plant in Brooklyn, New York, treating wastewater involves several steps. First, the system separates floating matter and solids from the water. The remaining sewage then enters an aeration tank.
JOHN PETITO (NYC DEP): What we do in aeration tanks is we supply oxygen to microorganisms that actually treat the sewage.
THOMPSON: Typical microbes for wastewater treatment require oxygen to degrade organic pollutants. The resulting sludge is further treated, and, in its final step, the water is disinfected. Chandran is trying to reduce the amount of energy used in this process. He uses a type of bacteria found in wastewater called anammox. These organisms don't need oxygen to remove nitrogen from wastewater. While traditional wastewater treatment often releases greenhouse gases, such as nitrous oxide and carbon dioxide, using anammox bacteria does not.
CHANDRAN: They allow us to remove nitrogen at far lower energy costs and chemical costs. Not just that, you would save sixty percent in terms of aeration costs if we use the anammox model for removing nitrogen.
THOMPSON: Chandran and his team are also looking at ways to use wastewater's abundant chemicals, nutrients and other resources to produce energy.
CHANDRAN: We have been able to convert the organic carbon and food waste in sewage sludge, in fecal sludge to biodiesel which is a liquid fuel, easily transported and easily used, directly used in diesel engines.
THOMPSON: The Newtown Wastewater Treatment Plant is already producing energy from organic material.
PETITO: The digesters are heated to about 95 degrees Fahrenheit. They act like the human body. They break down the organic material. And we provide no oxygen. And one of the products of the digestion process is methane gas.
THOMPSON: Methane gas is a common energy source.
PETITO: We are right now using a good portion of our digester gas to heat our boilers at our locations. The boilers are used for heating the environmental areas, the personnel areas, and they're also used to reheat the digesters.
THOMPSON: Chandran and his team are also finding additional uses for wastewater products. For example, they are using the organic carbon found in wastewater to develop bioplastics, and taking the phosphorous and nitrogen from wastewater for use in irrigation.
CHANDRAN: By linking the water sector, the energy sector, the food sector and a few other sectors, we are now able to address these challenges, not just one by one, individually in isolation, but together in conjunction. That's a very sustainable model.
THOMPSON: As Chandran and his team help make the human water cycle more energy-efficient, they are also helping us see wastewater not as waste, but as a precious resource.
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