Evaluation of Drinking Water Biostability Using Biofilm Methods

A biofilm based, annular reactor method was developed and used to measure the biological regrowth potential of effluent water from various pilot treatment processes at the New York City Croton Lake Pilot Plant. A series of studies were carried out over the year-long study to collect bacterial growth and organic carbon biodegradation data for waters from six treatment options, including the raw source water. Quantitative and qualitative evaluations were made to determine the effects of filter media type, direct filtration, preozonation, and primary chlorination on the relative biostability of the produced waters compared to that of the original source water and water currently being distributed to consumers. In addition, results were compared to those obtained using traditional biodegradable organic material measuring methods such as assimilable organic carbon and biodegradable organic carbon. Quantitative biostability factors were developed that take into account both biological growth potential and biodegradability of the tested waters. Results from these studies were used to compare various piloted treatment processes and to assess pilot plant operation, design parameters, and seasonal source water quality.