16.2.1 Water source (components, protection and condition)
As you know, the water supply source is the beginning of the drinking water system. Preventing source water contamination is the most effective means of preventing contaminants from reaching consumers. Source water protection also helps you to ensure the least expensive method is used for treatment of water. Hence, a sanitary survey should be designed to assess the control of contaminants and determine the reliability, quality, quantity and vulnerability of the source of water.
During a sanitary survey, you need to consider the terrain (the slope of the land), soil types, land cover, rainfall and runoff, and animals, which can all affect the water quality. In particular the potential sources of contamination by pathogens need to be assessed.
What pathogens might be a problem for water quality and what are the sources of those pathogens?
The pathogens are bacteria, protozoa, viruses and helminths. The primary source is human waste which gets into the water because of open defecation, discharge of sewage to water bodies, poorly sited latrines, etc.
In addition to contamination by pathogens from human body waste, there are many other human activities that can affect water quality. Runoff from barnyards and other areas where animals are kept will contain animal wastes and can cause significant problems. Farming activities can also lead to contamination from pesticides that may percolate into groundwater or wash off from fields into surface waters. Construction activities can result in large amounts of sediment being washed into rivers and streams.
Flooding is a natural event that may also be a source of contamination to sources of water supply. Surface runoff, which is a major contributor to flooding, can carry dirt, oil, pesticides, fertilisers and other contaminants that might be washed off from surrounding land.
16.2 Elements of a sanitary survey