Biological processes have the potential to remove pollutants that may be ineffectively removed water supplies generally require extenby conventional treatment, such as biodegradable organics, synthetic organic compounds, sive treatment because of the direct ammonia, nitrate, iron, and manganese. Biooxidation of organic matter and ammonia input of pollution and eutrophication. decreases available substrates for microbial regrowth in distribution systems, reduces tastes Conventional water treatment employs and odors, and decreases the amount of precursor available to form disinfection by-products. physicochemical processes that are most Biological removal of certain contaminants could extend the service time or capacity of effective for removing particulate matter, subsequent physicochemical processes. In US water treatment, the practice is often to impair hardness, taste and odors, and pathor preclude development of biological activity by prechlorination, rigorous scouring of filter ogens.z A typical treatment train includes media, and frequent backwashing of granular activated carbon. Practical experience in Europe coagulation, flocculation, sedimentation, with media containing microbial activity has been favorable. filtration, and disinfection. 82 RESEARCH ANI) TECHNOLOGY JUIJRNAL AWWA