Polyhydroxyalkanoate (PHA) production in open mixed cultures using waste activated sludge as biomass

In this work, volatile fatty acids (VFAs) were used as a carbon source to assess the ability of bacteria present in waste activated sludge (WAS), as indigenous flora, to accumulate polyhydroxyalkanoates (PHA). Acetic acid and propionic acid were used both separately and in combination as feedstock, producing either homopolymer poly(3-hydroxybutyrate) (3PHB) and/or the co-polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(3HB-co-3HV). The overall potential to use waste activated sludge as biomass for production of valuable polymers was assessed, and a quality assessment of the as-produced polymers was run, with the extracted polymer being analyzed for properties such as thermal, microstructure and molecular weight. It was found that a blend of copolymers was typically produced, with thermal properties being similar to those reported elsewhere. The overall PHA cell content obtained was 0.29 gPHA gVSS^-1.