Rainwater Harvesting

In the neighborhood where I grew up as a kid, many of the houses have metal barrels that collected water off the gutter from the roof to be used for bathing, washing and laundry. These days many facilities use the same principles to collect rainwater to augment their water supply from rooftops, land surfaces and rock catchments.

Commonly used systems are constructed of three principal components; namely, the catchment area, the collection device, and the conveyance system. Water is collected from the roof and stored in tanks or cisterns for the purpose. A separate plumbing system is installed to bring these to the point of use.

In the Philippines, where the average annual rainfall ranges from 965 to 4,064mm depending on the geography of the location, there is a high potential for water savings by collecting the rainwater. But just how safe is rainwater harvesting for domestic use? Proponents may sometimes present it as pure water condensed from the atmosphere and thus appropriate for use interchangeably with all freshwater requirements.

A research in South Africa using samples collected on eight occasions during the low- and high-rainfall periods (March to August 2012) conclusively showed a prevalence of virulence genes associated with pathogenic Escherichia Coli strains.

Thus, possible health risks (E. coli and other potentially dangerous bacteria that can accumulate in the tanks) associated with the consumption of harvested rainwater remains one of the major obstacles hampering its large-scale implementation. Current application is limited to toilets flush, dishwashing (if dishwasher machine sufficiently heats the water, otherwise limited to pre-rinsing), laundry, gardening / watering (but not for plants with fruits / vegetables that may be eaten raw