Microcosm investigations of phthalate behaviour in sewage treatment biofilms

Discharge from sewage works has been shown to be an important source of phthalates into the environment which is of major concern because some are toxic, suspected endocrine disruptors and recalcitrant. Laboratory trickle filter microcosms (continuous and re-circulating flow) were constructed and operated to investigate the biodegradation and adsorption of phthalates and also to isolate phthalate degrading microorganisms. It was found that adsorption was critical for the removal of both DEP (77.5%) and DEHP (55.7%) in continuous flow microcosms. The proportion of phthalates removed by biodegradation in the continuous flow microcosms was estimated. Re-circulating flow microcosms improved the removal of DEHP compared to continuous flow microcosms. Microcosm biofilm used for an enrichment culture on phthalate media isolated a varied group of microbes including Gram negative and Gram positive bacteria, yeasts and fungi. Bacteria species with all the necessary enzymes to degrade phthalic acid were isolated.