Process optimization for PHA production by activated sludge using response surface methodology

A five-level-three factor central composite rotary design was employed to find out the interactive effects of three variables, i.e. static magnetic field intensity, concentration of NH3–N and initial pH on polyhydroxyalkanoates (PHA) production by activated sludge under the aerobic dynamic feeding (ADF) technique. Response surface methodology (RSM) was utilized for process optimization and a second-order polynomial equation was obtained by multiple regression analysis. A yield of 49.5% of dry cell weight (dcw) was achieved at optimized conditions, i.e. magnetic field 11 mT, NH3–N 4.8 mg l−1 (C:N = 60:1)and initial pH 9.0.