Aerobic production of activated sludge polyhydroxyalkanoates from nutrient deficient wastewaters.

It was found that aerobic strategies combined with multiple nutrient limitations produced greater quantities of polyhydroxyalkanoates (PHAs) than strategies relying on oxygen limitation (either microaerophilic or anaerobic/aerobic). This was true both for a synthetic wastewater composed of acetic and propionic acid, and also for a nutrient deficient industrial wastewater. PHA/substrate yields were shown to be comparable to axenic systems for many operating strategies analyzed, and it was found that PHA composition could be affected by process operational conditions. The molecular weight and melting point of the PHA produced were found to be in a desirable range with respect to material properties, which have not been well studied in the previous literature for mixed cultures (Salehizadeh and Van Loodsrecht, 2004). The effects of process staging, multiple treatment cycles, and inocula source were also addressed.