The effect of pH on organic carbon uptake and biological phosphorus removal by Tetrasphaera polyphosphate accumulating organisms

Tetrasphaera polyphosphate accumulating organisms (PAOs) have been found in greater abundance and may remove more P in full-scale enhanced biological phosphorus removal (EBPR) water resource recovery facilities (WRRF) worldwide than the more extensively studied Accumulibacter PAO. Understanding the effect that environmental conditions, such as pH, have on Tetrasphaera metabolisms is critical to understanding EBPR WRRF process upsets, achieving consistent low effluent P concentrations, and formulating optimization strategies. The objective of this study was to determine pH effects over the range from 5.5 to 8.5 on anaerobic amino acid uptake, P release, and cation release in a Tetrasphaera-enriched culture from a lab-scale sequencing batch reactor. Lower rates of carbon uptake and coupled P release were found in this study than in similar studies of Accumulibacter. Extracellular pH during carbon uptake was correlated to the change in pH, P release, and cation release, whereas carbon uptake and NH4-N release were not correlated to pH. The ratio of P released to carbon taken up was like other studies of Accumulibacter suggesting similar P release driven secondary transport mechanisms may be used by Tetrasphaera. The ability of Tetrasphaera PAOs to take up organic carbon over a wide range of pH conditions reinforces the idea that they may be more metabolically heterogeneous and adaptable to varied conditions than Accumulibacter. Optimization of EBPR WRRFs may benefit from strategies that support both a robust Accumulibacter and Tetrasphaera community.