Microbial safety of Lake Nabugabo water for recreation

Abstract

The study was carried out between November 2013 and May 2014, it aimed at assessing the suitability of Lake Nabugabo water for recreation. Faecal microbial indicator contaminants and physic-chemical characteristics of Lake Nabugabo were determined at two beaches (Sand Beach and Holiday Center). Water samples were collected monthly covering the last weekend of each month (Friday – Sunday) at near and offshore spots within recreation at near and offshore spots within recreational zones at the beaches in the morning and afternoon. Water samples were collected, handled and tested according to APHA (1998) for microbial and physic-chemical parameters. Data was analyzed using student t-tests and correlation analysis at 95% confidence level. Results were; total coliform (10.5 – 13.8CFU/100mls) at Sand beach and (11.7 -15.8CFU/100mls) at Holiday Center, faecal coliform (10-11.4CFU/100mls) at Sand beach and (10-12.5CFU/100mls) at Holiday Center, Escherichia coli (0-2.63CFU/100mls). Electrical conductivity (27-32.6uS/cm), pH (7.1), turbidity (12.6-26NTU), total dissolved solids (13.2-15.4mg/1), average colour value (10.3Pt-Co), alkalinity (29.3mg/1), hardness (CaCO3) (32.5mg/!), total nitrogen (averagely 1.3mg/1), ammonium-N (averagely 0.6mg/1), nitrates (averagely 0.05mg/1), total phosphorus (average 0.8mg/10, orthophosphates (0.02mg/1), iron (0.2-0.3mg/1), calcium (1.2-1.8mg/1), magnesium (0.4-0.6mg/1), sodium (1.2-2mg/1) and potassium (1.8-2.6mg/1). Total coliforms and faecal streptococci showed a significant linear correlation with TSS (r = 0.9, p = 0.04). There were strong positive correlations between some physic-chemical parameters for example turbidity and pH (r = 0.9, p = 0.01), hardness and colour (r = 0.9, p < 0.01), total phosphorus and colour (r = 1, p < 0.01). A two sample student t-test showed no significant difference in microbial counts at the two beaches. Microbial counts obtained in the recreational zones were higher than those obtained in non-recreational zones of Lake Nabugabo but lower than known recreational water standards. Results indicate low microbial contamination and average physic-chemical parameters implying that Lake Nabugabo does not pose major problems for recreation at the moment. There is therefore need for regular monitoring of water quality changes in order to detect contaminants early for appropriate management.