Microbially available organic carbon, phosphorus, and microbial growth in ozonated drinking water

Ozonation is a disinfection technique commonly used in the treatment of dri nking water. It destroys harmful microbes. but it also degrades organic mat ter in water, increasing the bioavailability of organic matter. Recently. i t was found that not only organic carbon bur also phosphorus can limit the microbial growth in drinking water, which contains high amount of organic m atter. We used a bioassay to analyze whether ozone could also increase the microbially available phosphorus (MAP) in drinking water, and whether MAP i n ozone-treated water was associated with the growth of heterotrophic micro bes. We found that both assimilable organic carbon and MAP concentrations w ere increased by ozone treatment. In ozonated water, microbial growth was m ainly limited by phosphorus. and even minor changes in MAP concentration dr amatically increased the growth potential of heterotrophic microbes. In thi s study, ozonation increased the MAP by 0.08-0.73 mug P/l, resulting in an increase of 80,000-730,000 CFU/ml in water samples, In contrast to MAP. the content of assimilable organic carbon (AOC(potential)) did not correlate w ith microbial growth. The results show that in water treatment not only AOC (potential) but also MAP should be considered as an important factor that c an limit microbial growth in drinking water. (C) 2001 Elsevier Science Ltd. All rights reserved.