Nitrogen Clean Up: A Triple Win.

Reducing nitrogen pollution from wastewater treatment plants could be a triple win for business as well the environment, concluded a study published in Environmental Science & Technology.

Adding additional purification technologies to the existing infrastructure of wastewater treatment plants could have three benefits: lower energy usage; less water pollution; and fewer greenhouse gas emissions. Economic benefits could be realized as well if treatment plants used nitrogen removal to earn credits for greenhouse gas removal.

"Our study shows that there's a win-win-win situation out there waiting to be realized," said James Wang of the National Oceanic and Atmospheric Administration's Air Resources Laboratory, and lead author of the paper, in a Columbia University press release.

"The creation of an emissions trading market could provide the needed incentive for wastewater treatment plants to adopt technologies that would reduce climate pollution, help clean up our waterways, and even save energy and money," said Wang.

Wastewater treatments plants in the the United States alone could earn up to $600 million in emissions credits, as well as reduce their electricity bills by $100 million, said the study.

"As wastewater permits on wastewater treatment plants become more and more restrictive, the resultant increased capital and operating costs can pose quite a burden to utilities and municipalities," said Kartik Chandran, associate professor of earth and environmental engineering at Columbia University and a co-author of the study.

"Our study shows that, if the reduced emissions associated with well-designed and operated biological nitrogen removal operations can be used to earn CO2 credits, then this could be a big benefit both for the utilities from a cost perspective and for the environment from water quality and air quality perspective,” Chandran said.

Excessive nitrogen in the water system contributes to the “dead zone” found at the mouth of the Mississippi and other rivers. The nitrogen acts as fertilizer for algae which then die and provide a buffet for bacteria that consume oxygen in the process, reducing the level of oxygen available in the water column for other life forms, such as fish.

Nitrogen also contributes to climate change. Nitrous oxide (N2O) is a greenhouse gas 300 times more potent than carbon dioxide.

"Recent N2O monitoring studies conducted by Columbia Engineering and research groups across the globe have found that meeting wastewater treatment objectives actually decreases biogenic N2O emissions," said Chandran. "So designing and adopting better process technologies for improving water quality could actually have a significant impact on reduced N2O emissions."

Chandran's research focused on using a biological means of removing nitrogen, a technique known as sustainable water sanitation and hygiene. He is also working to develop a system that would use the nitrogen removed from the water to produce energy.