AWWA JAW54684

In parts of the world with severe water shortages, distribution mains may only supply water for a few hours each week, and householders must store the water in tanks on the rooftop or in a reservoir beneath the house. When these intermittent supplies are stored over a period of several days, water quality may rapidly deteriorate, creating a health risk to the consumer. A study conducted in Amman, Jordan, examined the extent and characteristics of microbial regrowth in different types of household storage tanks as well as the parameters influencing this regrowth. Study results showed that heterotrophic bacterial counts increased significantly from log 1.7 to log 5.2 and log 5.7 cfu/mL after water was stored for four and seven days. Microbial regrowth was dominated by Actinomycetes, Pseudomonas species, and Moraxella spp. The different materials of the household tanks (polyethylene, fiberglass, and cast iron) did not significantly influence the total bacterial count of the stored water. Temperature was the factor that most influenced microbial regrowth in household tanks. More research on this topic is needed, particularly to identify the most effective means of reducing the scale of regrowth. To reduce the public health hazard associated with drinking stored water (especially in hot climates), the authors propose various strategies including point-of-use devices, secondary chlorination in household tanks, and annual tank cleaning. Includes 21 references, tables, figures.