Optimal production of polyhydroxyalkanoates in activated sludge biomass

Polyhydroxyalkanoates (PHAs) have been recognized as good candidates for bi odegradable plastics, but their high price compared with conventional plast ics has limited their use. In this study, activated sludge microorganisms f rom a conventional wastewater treatment process were induced, by controllin g the carbon:nitrogen (C:N) ratio in the reactor liquor, to accumulate PHAs . In addition, an intermittent nitrogen feeding program was established to optimize the volumetric PHA productivity in a wastewater treatment process. The optimal overall polymer production yield of 0.111 g of polymer/g of ca rbonaceous substrate consumed was achieved under a C:N ratio of 96:1. by fe eding nitrogen in the reactor liquor once every four cycles. At the same ti me, the amount of excess sludge generated from the wastewater treatment pro cess was reduced by 22.9%.