Coupling of waste water treatment with storage polymer production

Storage polymers in bacterial cells can be extracted and used as biodegradable thermoplastics. However, widespread applications have been limited by high production costs. In this study, activated sludge bacteria in a conventional waste water treatment system were induced, by controlling the carbon-nitrogen (C:N) ratio in the reactor liquor, to accumulate storage polymers. Specific polymer yield increased to a maximum of 0.374 g polymer/g cell when the C:N ratio was increased from from 24 to 144, whereas specific growth yield decreased with increasing C:N ratio. An optimum C:N ratio of 96 provided the highest overall polymer production yield of 0.093 g of polymer/g of carbonaceous substrate consumed, without significantly affecting the organic treatment efficiency in the waste water treatment system.