New bacterium can improve wastewater treatment

Article by Amanda Doyle

Associate Professor He Jianzhong and Research Fellow Wang Qingkun with a wastewater sample containing the new bacterium

A NEWLY-discovered bacterium strain could be used to remove nitrogen and phosphorous from sewage wastewater. The method is more environmentally friendly and cheaper than current wastewater treatment processes.

Nitrogen and phosphorous need to be removed during wastewater treatment as they risk polluting the environment. Nitrogen is present in ammonia in the wastewater and phosphorous is present in phosphates.

Conventional systems typically use different reactors to remove nitrogen and phosphorous, as different conditions are required for different microbes with separate aerobic and anoxic bioreactors for nitrification and denitrification. A single reactor can be used but the different microbes in the reactor will compete with each other making the process inefficient.

Researchers from the National University of Singapore (NUS), have discovered a new strain, called Thauera sp. strain SND5, in the Ulu Pandan Water Reclamation Plant in Singapore during routine monitoring. They discovered that nitrogen was unexpectedly being removed in aerobic tanks, as well as phosphate removal even with no known phosphate-removing bacteria. Using samples from the tank, they isolated the bacteria and found one that had the ability to remove both nitrogen and phosphorous from wastewater. After its genes were sequenced, it was discovered to be a new strain.

The bacterium can perform simultaneous nitrification and denitrification (SND) to remove nitrogen and it can also function as a denitrifying phosphate-accumulating organism (DPAO) to remove phosphorous.

The new method has a lower oxygen demand, reducing electricity costs by 62% compared to conventional nitrification and denitrification processes. Greenhouse gas emissions are also reduced, as the process only releases nitrogen gas, compared to the nitrous oxide released with conventional methods.

He Jianzhong, Associate Professor at the Department of Civil and Environmental Engineering at NUS, said: “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."

The researchers are currently working on boosting the performance of the microbe and testing the process at a larger scale.

Water Research

Article by Amanda Doyle

Staff Reporter, The Chemical Engineer

Recent Editions

Catch up on the latest news, views and jobs from The Chemical Engineer. Below are the four latest issues. View a wider selection of the archive from within the Magazine section of this site.