A type of polyester called polyethylene terephthalate (PET) is used to make plastic bottles and containers for food, drink, and cosmetics. IN this manuscript, the focus will be on overview of PET manufacturing process and treatment plant of PET wastewater, and stoichiometry of microbial reactions in sequencing batch reactor (SBR) of PET wastewater treatment plant. PET is generally produced via two different routes: (i) Transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) to produce 2-hydroxyethylterephthalate (HET) (also called diglycol terephthalate, DGT) and methanol. The reaction of 2-hydroxyethyl terephthalate (HET) with a further ethylene glycol molecule leads to bis(2-hydroxyethyl) terephthalate (BHET), which in turn polycondensed to produce PET; and (ii) Direct esterification of purified terephthalic acid (TPA or PTA) with EG to produce DGT and water. The product from the first step is subjected to a further reaction stage known as polycondensation (PC) which produces PET of fibre-forming molecular weight. Wastewater treatment plant of PET involves the process of anaerobic digestion to break larger molecules tonon-toxic substances in the presence of microorganisms. Finally, a stoichiometric analysis is performed for microbial reactions taking place in SBR of PET wastewater treatment plant.