Seasonal effects on generation of particle-associated bacteria during distribution

In four successive studies at Jefferson City, Mo., seasonal temperature change has been observed to result in major changes in water treatment plant microbiological efficiency. The present study (1989) was directed at estimating the relative numbers of particles of potential health significance transmitted through the Jefferson City water distribution system during cold and warm water periods. In addition, the contribution of aftergrowth to the number of particles generated or recruited during distribution was estimated. Seasonal variations in turbidity, coliform, heterotrophic plate count organisms, total bacteria, planktonic bacteria, and particle-associated bacteria were observed in finished water and distribution system samples. Direct microscopic counting was used to enumerate the total number of particles larger than 3 mu m, as well as algal cells, long bacterial rods, activated carbon particles, and nematodes. All measurements confirmed the dominant effect of water temperature in influencing water treatment plant process efficiencies and the number of specific particles observed in the distributed drinking water. The results indicate that water treatment plant process efficiencies should be evaluated under low temperature conditions employing analytical techniques that are sufficiently sensitive to detect the impairment of removal of particles of potential health concern.