Study on poly-hydroxyalkanoate (PHA) production in pilot scale continuous mode wastewater treatment system

Generation of poly-hydroxyalkanoates (PHAs) from milk and ice-cream processing wastewater was studied in a continuous mode reactor system at pilot scale. The integrated system comprised an anaerobic acidogenic reactor (AAR), a conventional activated sludge production reactor (ASPR) and a PHA synthesis reactor (PHAR) to induce PHA accumulation in the biomass which was finally harvested while treating the raw dairy wastewater to meet the disposal limits thereby reducing generation of disposable sludge. The PHA content in the PHA rich biomass was ∼43% of the sludge dry weight. Kinetics of both ASPR and PHAR were studied. The maximum PHA yield coefficient (Yspmax) with respect to COD degradation in the PHAR was derived as 0.25 kg PHA/kg of COD degraded. Similarly, the kinetic parameters i.e. Ks, μm, Yobs and kd of the ASPR were 37.16 mg/l COD, 0.97 d−1, 0.51 mg MLSS/mg COD and 0.049 d−1, respectively.