Impact of Temperature on Bacterial Growth and Survival in Drinking-Water Pipes

A study of a model drinking water distribution system, using previously used galvanized steel pipes, was carried out to evaluate the impact of temperature on the growth and survival of total coliform, E. coli and Heterotrophic Plate Count (HPC) bacteria for a maximum of 21 days residence time in the water phase in pipes and their respective glass control bottles. The study showed that for water temperatures of 15, 25 and 37oC, HPC bacteria initially increased in the first 2-4 days but much higher at 37oC after which the bacteria began to reduce in numbers. On the other hand, the decline in coliform and E. coli levels was observed after 24 h and this continued until no such bacteria were detected in the water phase. The oligotrophic nature of HPC bacteria allowed them to initially survive and grow in the nutrient-deficient environment, while the copiotrophic coliform and E. coli, which prefer nutritionally rich environments, began to die, hence the decline in their concentration. Whereas the decline in bacteria levels at lower temperatures of 15-25oC may be attributed to starvation and/or the temperature effect, those at ~37oC might have been significantly caused by the relatively higher temperature they were subjected to. The results, thus, established that higher water temperature was seen as important factor in reducing the survival of total coliform, E. coli and HPC bacteria in the water phase in drinking water pipes.