Résumé
Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops. The techniques usually followed in Asia and Africa arise from practices employed by ancient civilizations in these regions, and still serve as a major source of drinking water supply in rural areas. Of late, in Kerala (India), scientific methods are being increasingly employed for rainwater harvesting. But in some areas, for instance in Kannur district, where this study was conducted, the recommended scientific method is not followed properly, and high levels of nitrates (or nitrites) are said to be present, which can cause nitrate toxicity. This study mainly concentrates on the water quality analysis of rainwater harvesting area in Kannur district of Kerala. The following quality parameters were analyzed: pH, electrical conductivity, alkalinity, chloride, total dissolved solids (TDS), hardness, iron, ammonia, nitrate, nitrite, sulphate, and absorbed oxygen. It was found that most of these were within the prescribed international standards, but some parameters such as total dissolved solids (TDS), nitrate, nitrite and absorbed oxygen were quite high as compared to ground water. When the water was passed through commercially available filters, sand and gravel, or charcoal, the concentration of nitrate, nitrite, total dissolved solids and absorbed oxygen came down to acceptable levels, and the water satisfied all the drinking water quality standards, equivalent to the highest quality mineral water.