May 2009, Vol. 21, No.5

Research Notes

A New Method for Monitoring Bacteria Health

Researchers at Purdue University (West Lafayette, Ind.) have developed a new technique to monitor the health of a bacterium critical to wastewater treatment facilities. Using sensors, the researchers continuously monitor changes in chemistry related to the bacterium’s health for immediate results, according to a university news release.

Receiving immediate results from monitoring could make it possible to tell when bacteria will stop processing waste and correct the problem before toxins are released into waterways, according to Eric McLamore, a postdoctoral research associate at the university.

The new technique is notable in that it does not damage or destroy biofilms during testing, the news release says.

“It’s important to monitor intact living specimens to obtain accurate data, and our approach is both noninvasive and a real-time technique,” said Marshall Porterfield, an associate professor of agricultural and biological engineering at Purdue.

The researchers studied the bacterium Nitrosomonas europaea, which converts ammonia from human wastes and fertilizer into nitrites that are broken down by other bacteria into nitrogen gas, the news release says. Sensor data show how well the bacteria are absorbing ions from the wastes. The flux sensor measures ammonia and nitrite to reveal how many ions are being transported in and out of the biofilm each minute.

“When bacterial biofilms are poisoned, sick, and stressed, they start to release ions, including potassium and calcium, which is an early warning signal,” Porterfield said.

Detecting these signals can alert wastewater professionals when their systems have a problem that requires remediation. The sensor probe moves back and forth every 3 seconds in a method called self-referencing, enabling the device to capture data in two locations. This method compares the difference between measurements taken in two positions with the same sensor, thereby increasing the accuracy and immediacy of results. The self-referencing technique is noninvasive and capable of sensing changes in biologically active analyte flux as small as 10 fmol/cm²•s, according to the news release.

The sensor used in the study has never been used to measure biofilm ammonia and nitrate flux, McLamore explained. “Self-referencing has been used in other applications but never in environmental studies,” he said. The technique can be used to monitor “many compounds that exist in liquids,” he added.

©2009 Water Environment Federation. All rights reserved.