Newly Discovered Process Removes Nitrogen From Wastewater

Sept. 26, 2014

Wastewater is naturally high in nitrogen-based compounds such as ammonium that can fuel massive algae blooms, consuming the water’s oxygen and leaving behind “dead zones.”

To address this issue, most wastewater treatment facilities are required by law to convert ammonium to more benign forms of nitrogen before discharge. Yet today’s methods are expensive, requiring the constant addition of oxygen or heat, plus organic carbon.

Professor Peter Jaffe and colleagues in the Department of Civil and Environmental Engineering have discovered a new strategy for tackling ammonium that does not require the addition of oxygen, or aeration. It also works at temperatures as low as 48 degrees Fahrenheit and does not require the addition of organic carbon.

The approach involves using a bacterial strain recently identified as Acidimicrobiaceae A6 that the Jaffe team discovered in a New Jersey wetland. In a process known as “Feammox,” the bacteria — with help from iron — converts ammonium to a less harmful nitrogen compound called nitrite. The nitrite produced via Feammox can then be rapidly converted by another type of bacteria to nitrogen gas, which does not promote algae blooms.

Such a technology could be especially useful in regions near the Chesapeake Bay and the Gulf of Mexico, which are sites for notorious dead zones. Local governments in those areas are starting to require the conversion of ammonium to nitrogen gas prior to wastewater discharge, Jaffe said.

A water treatment process based on Feammox could lead to energy savings because it requires no aeration or heating.  The cost associated with providing iron to the bacteria could be overcome via a system that collects and recycles iron and by using scrap iron.

With funding from the National Science Foundation, the Jaffe team, which includes postdoctoral research associate Shan Huang, is now working on improving the efficiency of the Feammox process.

“This work arose out of our basic research on how nitrogen runoff from fertilized fields affects iron cycling and the transport of trace metals,” Jaffe said. “From this we have found a new pathway in the nitrogen cycle and are exploring ways to harness it for wastewater treatment.”