Extending the operating temperature of biological phosphorus removal

Currently, enhanced biological phosphorus removal (EBPR) techniques in municipal wastewater-treatment plants (WWTPs) do not work well at temperatures above 25°C, which is common in warm countries. This limitation is expected to extend to more countries with the advent of global warming.

To “future-proof” phosphorus removal, scientists from the Singapore Center for Environmental Life Sciences Engineering (SCELSE; www.scelse.sg), Nanyang Technological University (NTU), Singapore and the National University of Singapore, have developed a technique that removes phosphorus from WWTPs at temperatures of 30–35°C. The method, described in a recent issue of Water Research, is based on the bacterial genus Candidatus Accumulibacter, which accumulate phosphorus from wastewater and store it as polyphosphate granules.

In the study, two laboratory-scale sequencing batch reactors (SBRs) were operated in parallel at 30°C and 35°C, respectively, for over 300 days. “Employing a slow-feeding strategy and sufficiently high carbon input into biological reactors, we effectively limited the carbon uptake rates of competing bacteria. This allowed Accumulibacter to flourish and benefited a stable and efficient process, representing basic conditions suitable for future full-scale treatment plants,” says NTU professor Stefan Wuertz, deputy center director of SCELSE, who led the study.

Unlike other P-removal methods, the SCELSE-developed method does not involve chemicals, such as iron and aluminum coagulants. These methods produce a large volume of inert sludge that needs to be treated and disposed of afterwards.