Biodegradation of styrene in a recirculation reactor using immobilized activated sludge

The performance of immobilized cells in the biological treatment of hazardous waste was investigated using a recirculating flow reactor in batch mode. A mixed culture activated sludge from a municipal waste water treatment plant was immobilized in calcium alginate gel, The bio-oxidation ability of these microbes towards a model toxin (styrene) was studied under closed system using dilute H2O2 solution as an oxygen source. The process parameters studied were as follows: Effect of flow rate of recycle stream, Effect of biomass loading, Effect of spiking concentration of styrene, and Flow pattern and average residence time within the reactor. Dissolved oxygen concentration was monitored by a Clark type dissolved oxygen probe and also by an oxygen electrode. Biodegradation rates of styrene with two different oxygen sources, air and H2O2, were determined and compared. Abiotic losses of styrene were taken into account. It was found that biodegradation was the primary removal mechanism when H2O2 was used as oxygen source, whereas stripping was the primary removal mechanism in the case of sir, considerable adsorption of styrene on the alginate was observed initially, but all the styrene desorbed to the bulk slowly and biodegraded finally