Recovery of polyhydroxyalkanoate from activated sludge in an enhanced biological phosphorus removal bench-scale reactor

A sequencing batch reactor was used to study the possibility of harvesting polyhydroxyalkanoate (PHA) from enhanced biological phosphorus removal (EBPR) processes without compromising treatment quality. Because, in EBPR, the highest PHA concentrations are observed after exposure of the sludge to anaerobic conditions, PHA accumulation was evaluated with collection of waste activated sludge (WAS) at the end of the anaerobic stage, in addition to the traditional removal after the aerobic stage. The system achieved good phosphorus removal, regardless of the point of WAS collection. When sludge was harvested at the end of the anaerobic stage, the PHA content of the sludge ranged from 7 to 16 mg PHA/100 mg mixed liquor volatile suspended solids. Although this level of PHA production is below levels obtained with pure cultures, the demonstrated ability to harvest PHA, while simultaneously satisfying phosphorus removal in an EBPR process, is a key initial step towards of the use of wastewater treatment plants for PHA production.