Bacteriological and Physicochemical Characteristics of Kaptai Lake Water in Terms of Public Health Significance

Kaptai Lake (KL), which is one of the largest artificial freshwater lakes of South-east Asia, is located in the Rangamati district of Bangladesh and also the major dwelling place of the indigenous ethnic minorities. The lake water is consumed for drinking and other domestic purposes by the population living in islands within the lake without any intermediate purifying process. In the current study, the bacteriological, physicochemical and metal characteristics of the lake water have been measured to investigate the lake water quality regarding the health concerns in comparison with the limits set by WHO, USEPA and Bangladesh EQS. The heterotrophic plate count for the lake water samples were between ~75 and ~244 cfu mL -1 and was in compliance with the USEPA limit of 500 cfu mL -1 . However, the coliform count was in the range of 40.6 to 14017, and was above the standard limits set for drinking use. All the water samples also showed positive presence of Enterococcus spp., Salmonella spp., Pseudomonas spp. and Vibrio spp. The physicochemical analysis confirms that the water temperature (26-27 C), pH (7.5-7.8), electrical conductivity (108-113 µS cm -1 ), total dissolved solids (53-55 ppm), total hardness (42-43 ppm), total alkalinity (11-11.5 ppm), chloride (0.9-1.8 ppm) and dissolved oxygen (4.1-4.8 ppm) were within the limits of the guideline values. The concentrations (mg L -1 ) of toxic metal-species, e.g., lead (4.025-5.128), cadmium (0.008-0.020) and nickel (0.199-0.288) were found to be higher than the recommended regulatory limits, while the contents of copper (0.099-0.301), manganese (0.179-0.291) and zinc (1.989-2.278) were within the acceptable range. The findings from our work indicate that the water of KL is unsuitable for drinking use in terms of bacteriological and metal characteristics and might pose a long-term health risk to its consumers.