عنوان مقاله [English]
Many studies have been conducted on production of biodegradable polymers such as polyhydroxyalkanoates (PHAs) in overcoming the environmental problems due to the accumulation of synthetic plastics as waste materials and excessive activated sludge produced in municipal waste water treatment plants. In this study; the effect of magnetic field intensity of 5, 10, 15, 20, 25 and 50 milliTesla (mT) was investigated on the type and amount of monomers produced in the copolymer and PHA production in activated sludge and the results were compared simultaneously with the results of PHA production without the magnetic field (0 mT). The experimental procedure included the transfer of the activated sludge into the batch reactor, addition of sodium acetate, magnetic field generation by magnets, aeration for 30 h, sampling at definite timing, measurement of PHA by gas chromatography. In summary, this research indicated that, the maximum PHA content was produced at 20 mT which was equal to 0.75 g/L, whereas the lowest PHA content was observed at 50 mT (0.55 g/L). In addition, the magnetic field was influenced by the type and amount of monomer produced in PHA. The highest amount of valerate was observed at 50 mT, while this magnetic field decreased the amount of PHA (8.33%) compared to the control sample. Also, the maximum amount of butyrate monomer in the copolymer was observed at 5 and 20 mT, which were equal to 81% and 74 %. According to the results obtained, the mass percentage of valerate in the control sample and those exposed to magnetic field with negative effects was more than the mass percentage of butyrate; an indication of better copolymers on the basis of their mechanical properties.