Scientists at the Singapore Center for Environmental Science Engineering (SCELSE), Nanyang Technological University Singapore (NTU Singapore) and the National University of Singapore have developed a method to remove phosphorus from wastewater at higher temperatures than is possible with existing methods, using bacteria. to store the chemical.
Modern phosphorus removal methods do not work well at temperatures above 25 degrees Celsius, which is now the case in warm countries. It is expected that this will spread to more countries with the onset of global warming.
Due to the presence of diverse microbial communities in reclamation plants in Singapore, SCELSE’s bacteria-based innovation will thus help “future-proof” the removal of the chemical. Scientists have demonstrated that it effectively removes phosphorus from wastewater at temperatures of 30 and 35 degrees Celsius.
A genus of bacteria called Candidatus Accumulibacter is harmless to humans and the environment and removes phosphate from wastewater and stores it internally as polyphosphate granules. Scientists say their method can be used in laboratory reactors and full-scale sewage treatment plants.
Removing phosphorus from wastewater before discharging it into freshwater bodies is important because its presence can lead to algal blooms, which are rapid increases in algal populations. Algal blooms severely reduce oxygen levels in natural waters as the algae die, and sometimes lead to the release of high levels of toxins, killing the organisms that live in the waters it affects. In Singapore, wastewater is treated at reclamation plants located near coastal areas before being discharged into the sea.
Unlike other methods, the method for removing phosphorus from wastewater developed by SCELSE does not involve chemicals such as iron and aluminum coagulants. These methods produce a large volume of inert sludge, which must then be treated and disposed of.
Bacteria-based technology expands temperature range of enhanced biological removal of phosphorus up to 35 degrees Celsius. This would help “promising” phosphorus removal, as other methods using biological approaches only work at lower temperatures and will be less effective as temperatures around the world are expected to rise due to global warming.
The results of the study were published in the journal Water research in June.
NTU Professor Stefan Würz, deputy director of the SCELSE Center who led the research, said: “We have shown that phosphorus can be removed sustainably at Singapore’s reclamation plants, even as we expect further global water temperatures to rise. By using a slow-feed strategy and sufficiently high carbon input to the bioreactors, we effectively limited the rate of carbon uptake by competing bacteria. This allowed Accumulibacter to flourish and contributed to a stable and efficient process, providing the basic conditions suitable for future full-scale sewage treatment plants. This will help Singapore and other countries experiencing high water temperatures to prepare for the effects of climate change.”
Co-author Dr Rohan Williams, Head of Integrative Analysis at SCELSE, said: “We found that the Accumulibacter strains in the reactors were closely related to strains commonly found in temperate systems, suggesting that the chosen strategy was successful in maintaining the required microdiversity. for a stable process.” He is also a Senior Research Fellow at the Institute of Life Sciences at the National University of Singapore.
Dr Guanglei Qiu, a former SCELSE researcher who was also a co-author of the study, said: “The operation of biological reactors side-by-side at different temperatures has provided clues to understanding the mechanisms and underlying changes in the microbial community.” He is currently an associate professor at South China University of Technology.
The innovation developed by SCELSE reflects NTU’s commitment to mitigating our impact on the environment, one of humanity’s four grand challenges that the University aims to address through its NTU 2025 Strategic Plan.
To start the process, the researchers enriched the bacteria from the sewage in experimental reactors at a temperature of 30 to 35 degrees Celsius, while making sure that the pH was roughly neutral. After a six-hour cycle, the bacteria completely absorbed the phosphorus.
During more than 300 days of testing in laboratory conditions, they found that there was a consistent removal of phosphorus, coping with daily infusions of fresh sewage containing this element.
The scientists will conduct further research to further improve the effectiveness of their method. They are also going to use bacteria to capture and store phosphorus, which some experts believe could run out globally within 50 to 100 years.
Professor Wurtz added: “Almost all the phosphorus that farmers use today and that we eat comes from several sources of phosphorite, mainly in the USA, China and Morocco. Our solution can not only help the future of biological phosphorus removal, but also to retain the element and then re-introduce it into agricultural systems.”
Guanglei Qiu et al., Preparedness for Global Warming: The Potential for Enhanced Biological Phosphorus Removal at 35 °C, Water research (2022). DOI: 10.1016/j.wateres.2022.118301
Courtesy of Nanyang Technological University, Singapore
Citation: ‘Future-proof’ method using bacteria to remove phosphorus from wastewater (2022, July 13) Retrieved July 13, 2022, from https://phys.org/news/2022-07-future-proof-method -bacteria-phosphorus-wastewater .html
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