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EFFECT OF OZONATED WATER ON THE ASSIMILABLE ORGANIC CARBON AND COLIFORM GROWTH RESPONSE VALUES AND ON PATHOGENIC BACTERIA SURVIVAL
Rajkowski, K. T. AND E W. Rice*. EFFECT OF OZONATED WATER ON THE ASSIMILABLE ORGANIC CARBON AND COLIFORM GROWTH RESPONSE VALUES AND ON PATHOGENIC BACTERIA SURVIVAL. Presented at International Association of Food Protection, Annual Meeting, Minneapolis, MN, 8/5-8/2001.
The assimilable organic carbon (AOC) and coliform growth response (CGR) are bioassays used to determine water quality. AOC and CGR are better indexes in determining whether water can support the growth of bacteria than biological oxygen demand (BOD). The AOC value of reconditioned wastewater increased after ozonation from 1176 to 1758 micro gC/L. When the ozonated wastewater was inoculated with Salmonella spp., the cell counts remained constant with a slight increase after 7 days, whereas the cell counts in the non-ozonated wastewater decreased after 7 days. Ozonated tap water (20 ppm) was used to wash alfalfa seeds for 20 min. There was little decrease in the total background counts from the ozonated washwater. After washing the washwater's AOC values increased six fold while the dissolved ozone decreased to undetectable levels. These increases are due to ozone's strong oxidizing ability to break down refractory, large molecular weight compounds forming smaller ones, which are readily used as nutrient sources for microorganisms. This same phenomenon was observed when using ozone in the treatment of drinking water. The increased nutrients would now become more readily available to any pathogenic microorganisms located on alfalfa seed surface as seen with the increase in inoculated levels of Salmonella in the ozonated wastewater. If the washing process using ozonated water is not followed by the recommended hypochlorite treatment, pathogen growth is still possible.