Evaluation of drinking water biostability using biofilm methods

A biofilm based, annular reactor method was developed and used to measure t he biological regrowth potential of effluent water from various pilot treat ment processes at the New York City Croton Lake Pilot Plant. A series of st udies were carried out over the year-long study to collect bacterial growth and organic carbon biodegradation data for waters from six treatment optio ns, including the raw source water. Quantitative and qualitative evaluation s were made to determine the effects of filter media type, direct Filtratio n, preozonation, and primary chlorination on the relative biostability of t he produced waters compared to that of the original source water and water currently being distributed to consumers. In addition, results were compare d to those obtained using traditional biodegradable organic material measur ing methods such as assimilable organic carbon and biodegradable organic ca rbon. Quantitative biostability factors were developed that take into accou nt both biological growth potential and biodegradability of the tested wate rs. Results from these studies were used to compare various piloted treatme nt processes and to assess pilot plant operation, design parameters, and se asonal source water quality.