Removing Two Pollutants With One Bacteria

A new strain of bacteria that can remove both nitrogen and phosphorus from sewage could reduce the electricity consumption of treatment plants by over 60 percent.

AsianScientist (Dec. 30, 2020) – A newly identified strain of bacteria that can simultaneously remove both nitrogen and phosphorus from sewage could make wastewater treatment simpler, cheaper and greener. These findings, by researchers from the National University of Singapore (NUS), have been published in Water Research.

Few of us consider what happens to what we flush down our toilets—until something goes awry with our plumbing. On a municipal level, sewage services are essential, and governments worldwide have imposed strict regulations on what can and cannot be discharged. Nitrogen—in the form of ammonia—and phosphorus from phosphates are present at high levels in sewage, making them the key pollutants that must be removed during the treatment process.

Currently, existing sewage treatment systems use separate reactors for removing nitrogen and phosphorous, with different conditions for different microbes. A single reactor can be used, but this makes the process inefficient because the different microbes in the same reactor will compete with one another for resources. This makes it difficult to maintain the delicate balance among the microbes, resulting in an overall lower efficiency.

Now, a team led by Associate Professor He Jianzhong has found a new strain of Thauera sp. bacteria that can tackle both nitrogen and phosphorus, greatly simplifying the sewage treatment process. Called SND5, the bacteria also circumvents the problem of nitrous oxide gas release by converting ammonia into harmless nitrogen gas instead.

The unique strain was discovered in a wastewater treatment plant in Singapore. When the NUS research team was carrying out routine monitoring, they observed an unexpected removal of nitrogen in the aerobic tanks, as well as better-than-expected phosphate removal despite the absence of known phosphorus-removing bacteria.

The researchers then took wastewater samples from a tank, isolated various strains of bacteria and tested each of them for their ability to remove nitrogen and phosphorus.

One of the strains, which appeared as sticky, creamy, light yellow blobs on the agar medium, surprised the researchers by its ability to remove both nitrogen and phosphorous from water. In fact, it did the job faster than the other microbes that were tested. The team sequenced its genes and compared them to related bacteria in a global database, establishing it to be a new strain.

Compared to conventional nitrogen removal processes of nitrification and denitrification, the lower oxygen demand of the newly identified microbe could help reduce electricity consumption at wastewater treatment plants by about 62 percent, He estimated.

“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,” He said.

Meanwhile, the researchers are looking to test their process at a larger scale and formulate a ‘soup’ of multiple microbes to boost SND5’s performance even further.

The article can be found at: Wang & He (2020) Complete Nitrogen Removal via Simultaneous Nitrification and Denitrification by a Novel Phosphate Accumulating Thauera sp. Strain SND5.


Source: National University of Singapore; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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