Molecular Screening for Enhanced Biological Phosphate Removal Organisms (EBPR) - getting a better grasp on a poorly understood group of microbes.
EBPR (Enhanced Biological Phosphate Removal) is a key part of phosphorus removal strategy along with tertiary coagulant/polymer treatment in final clarification. While we tend to discuss using either a biological phosphate removal or chemical precipitation approach, combining both technologies can improve effluent quality and save on costs as we don’t push either technology to its practical limits.
In both chemical and biological phosphate removal, we are fixing soluble phosphate into the floc and removing the floc from the water column. While many bacteria naturally store some phosphate, we are looking to provide conditions that promote the growth of bacteria that are “super phosphate” accumulators during aerobic growth. These bacteria store approximately 6x the phosphate of other wastewater bacteria inside their cells. We know cycling between anaerobic with soluble organics at the influent followed by aerobic oxidation sections promotes growth by taking advantage of the phosphate accumulator’s unique ecological niche. However, we don’t know much about the actual organisms.
The best organisms for EBPR are not cultured using standard microbiology techniques like a majority of bacteria present in nature. We tended to call many of these EBPR organisms “Candidatus acccumulibacter” – but we did not know much about them.
Using modern high throughput DNA based technologies including 16S and qPCR techniques, we are finally getting an idea to the actual organisms and their diversity in organisms best suited for EBPR. However, this process involves a learning curve. Key to discovering these organisms is finding a polyphosphate kinase (PPK1) gene to differentiate inside the group. But this is not the end to the research. Using 16S testing a group of researchers found 10 clades of EBPR organisms. Using the newer PPK1 qPCR on the 10 clades only covered 50% of the 16S identified group. So, the diversity is very high inside the EBPR group.
So what does this mean for wastewater engineers and operators? As we develop more molecular tools to isolate and determine which EBPR organisms are present, we can find ways to optimize the EBPR process by tracking DNA drift in response to operational changes or variation in influent makeup. This technology is in its infancy with respect to EBPR microbes, but will be a key part of lowering phosphate removal costs from wastewater.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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