Drinkable Water Stored in Hot Climates: Interactions among Water Quality Parameters

Abstract

The lack of water mostly in the arid regions of the world has triggered water users to store water in different container materials. The situation is more pronounced in countries having epileptic power supply since pumping of groundwater whenever needed could not be guaranteed due to poor power supply. However, most water users bothered not about the quality of the water during storage. Hence, this paper investigated the chemistry of stored water especially in the arid regions which are usually known to have high solar heating during the dry season. In order to achieve this aim, two sources of potable water (tap and borehole water) were stored in twelve water storage containers (six for each water source) for a period of six weeks. The containers include black plastic tank, blue plastic tank, green plastic tank, coated steel metal tank, uncoated steel metal tank and clay pot. However, the water quality parameters examined were temperature, colour, total solids, dissolved oxygen (DO), chlorine content, pH, total hardness, and total heterotrophic bacteria (THB) which were all analyzed at a sampling frequency of seven days interval. Results showed that the colour of both water sources stored in uncoated steel metal tanks stretched from 5 TCU – 20 TCU, which indicates that the colour of water stored in these tanks were above the limit set by WHO (15 TCU) during certain period of storage. Similarly, values/concentrations of pH and THB in all the storage containers were found to exceed the limits set by WHO standard during certain periods (weeks) of retention for both water sources. This is because the pH value ranged from 5.8 - 8.7 while THB concentration ranged from 2.0×102 CFU/100ml - 1.56×104 CFU/100ml which are contrary to their allowable permissible limits (6.5 - 8.5 and 0.00 CFU/100ml - 1.0×104 CFU/100ml respectively). Nevertheless, the remaining water quality parameters were within the WHO permissible limits in all the storage vessels during the retention period. Hence, it was concluded that most water quality parameters of potable water stored in hygienic condition remain fresh during the first week of storage thereafter, the quality cannot be guaranteed