Reporting in the journal Water Research on 15 October 2020, researchers from the National University of Singapore (NUS) have found a new strain of bacterium called Thauera sp. strain SND5 that could be used to remove nitrogen and phosphorus from sewage.

According to the research team, deploying the new bacterium in wastewater treatment would simplify the process and drive down associated costs, as well as reduce greenhouse gas emissions.

What makes the majority of existing sewage treatment systems inefficient and cumbersome is the need to have two separate reactors – one for removing nitrogen from the ammonia present in most sewage, and one for removing phosphorous from phosphates.

One-reactor solutions are, unfortunately, no better due to the fact that different microbes in the same reactor are forced to compete for resources, making it difficult to keep the overall system in balance and achieve satisfactory levels of efficiency.

The new bacterial strain was discovered when the research team was conducting routine monitoring at a wastewater treatment plant in Singapore. During the procedure, the plant’s aerobic tanks were found to be largely free of nitrogen and phosphorous, despite the absence of known bacteria that could have made it happen.

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An auspicious discovery of a new strain of bacterium could reduce sewage treatment costs and environmental impact. Image: Ivan Corvin via, CC0 Public Domain

After testing a number of different bacterial strains isolated from the wastewater, the team was able to identify the “culprit”. Once the genes of the bacterium were sequenced and compared to related bacteria in a global database, the team pronounced it a new strain.

Further testing showed that SND5 can not only remove both nitrogen and phosphorous at the same time, but also do it faster. In addition, the new bacterium is capable of converting ammonia into nitrogen gas, rather than nitrous oxide – a potent greenhouse gas released by some existing systems.

The team has calculated that using the new bacterium in wastewater treatment plants could reduce electric power usage by about 62%, thanks to its lower oxygen demand, as compared to current techniques.

“Population and economic growth have inevitably led to the production of more wastewater, so it is important to develop new technologies that cost less to operate and produce less waste overall – all while meeting treatment targets,” said project leader Associate Professor He Jianzhong.

The team is now looking for additional microbes that could further enhance SND5’s performance, and plans to conduct large-scale tests in the near future.


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