COMPARISON BETWEEN THE EVALUATION OF BACTERIAL REGROWTH CAPABILITY INA TURBIDIMETER AND BIODEGRADABLE DISSOLVED ORGANIC-CARBON BIOREACTOR MEASUREMENTS IN WATER

In recent years, two different approaches to the study of biodegradabl e organic matter in distribution systems have been followed. The assim ilable organic carbon (AOC) indicates the portion of the dissolved org anic matter used by bacteria and converted to biomass, which is direct ly measured as total bacteria, active bacteria or colony-forming units and indirectly as ATP or increase in turbidity. In contrast, the biod egradable dissolved organic carbon (BDOC) is the portion of the dissol ved organic carbon that can be mineralized by heterotrophic microorgan isms, and it is measured as the difference between the inflow and the outflow of a bioreactor. In this study, at different steps in a water treatment plant, the bacterial regrowth capability was determined by t he AOC method that measures the maximum growth rate by using a compute rized Monitek turbidimeter. The BDOC was determined using a plug flow bioreactor. Measurements of colony-forming units and total organic car bon (TOC) evolution in a turbidimeter and of colony-forming units at t he inflow/outflow of the bioreactor were also performed, calculating a t all sampling points the coefficient yield (Y = cfu/Delta TOC) in bot h systems. The correlations between the results from the bioreactor an d turbidimeter have been calculated; a high correlation level was obse rved between BDOC values and all the other parameters, except for Y ca lculated from bacterial suspension measured in the turbidimeter.