RESIDUAL ALUMINIUM IONS IN WATER TREATED WITH 'ROCK ALUM' COAGULANTS

Abstract

Safe and clean water is one of the essential natural resources necessary for human existence. Demand for clean and safe water has dramatically increased with the increase in human population and industrial developments. In most developing countries, small-scale water consumers use coagulants obtained from commercial shops to treat drinking water obtained from rivers, lakes and bore holes to remove turbidity and other suspended particles. These coagulants are preferred due to their convenience in use, low cost and is widely available in local market. Examples of these coagulants include 'Rock Alum'. Previous studies hypothesized that use of aluminium-based coagulants leaves residual aluminium in water making it unsafe for human consumption. Effects of aluminium exposure include neurological disorders such as Alzheimer's disease, reduced intellectual capability, renal failure, and bone defects. This study focused on analysis of treated de-ionized, river and borehole water samples treated with variable masses of the coagulant ‘rock alum’ ranging from a maximum of 0.125 g to a minimum of 0.0125 g in 500 cm3 of water. The concentration of residual aluminium ions in treated water samples was determined using an Atomic Absorption Spectrometer. River water and borehole water samples were obtained from 3 different regions within central Kenya This study found that de-ionized water treated with 0.125 g and 0.0125g of coagulant in 500 cm3 of water reported concentration of residual aluminium at an average of 7.41 and 1.9 ppm respectively. Analysis of river and borehole water samples treated with 0.125 g of coagulant in 500 cm3 gave 4.23 and 3.47 ppm respectively. These concentrations are higher than 0.1 ppm which is the permissible limits the World HealthOrganisation (WHO) set for safe drinking water. These elevated levels are detrimental to consumers' health. These results provide important information to government bodies in charge of water provision and public health on the risks associated with water treated with commercial aluminium-based coagulants. This study recommends improvement in water treatment conditions to reduce residual aluminium ions.