Purple phototrophic bacteria granules under high and low upflow velocities

The application of granular biomass has enabled energy efficient, high-rate wastewater treatment systems. While initially designed for high-strength treatment, systems can also play a major role in resource recovery. This study focused on the formation purple phototrophic bacteria (PPB) during synthetic treatment. Liquid upflow velocity was applied as driving force granulation. Separate reactors were operated at either low (2-5m h?1) or high (6-9m velocities, with sludge retention times (SRTs) ranging from 5-15d. Reactors produced anaerobic, photo-granules within ~50d. volume index (SVI30) granules 10mL g?1 and average settling rates greater than 30m h?1, both metrics being similar to existing technologies. Granule sizes 2-3mm recorded, however particle size distribution bimodal large floc fraction (70-80% fraction). extracellular polymeric substance (EPS) alginate-like extract (ALE) contents those aerobic biomass. Fluorescence in-situ hybridisation (FISH) imaging identified PPB dispersed throughout very few methanogens an active core. Outer layer morphology substantially different two reactors. high-upflow reactor had outer Chromatiales inner Rhodobacteriales, while low-upflow lower abundances both, limited layering. According 16s gene sequencing, microbial community (40-70%), but dominated by (supporting FISH results), more diverse community. Methanogens seen only small amounts (?8%). crude protein content ~0.60gCP gVS?1 (~0.45gCP gTS?1), that other production growth rapid discrete suggests methods recovery using be diversified include