Microbiological evaluation of drinking water available in schools in Cruz das Almas, Brazil

Abstract

The current study assessed the drinkability of water in 25 schools in Cruz das Almas BA Brazil. Total coliforms, Escherichia coli, Enterococcus, mesophylls and psichrotrophic bacteria were evaluated, coupled with color, turbidity, free residual chlorine, dissolved oxygen and biochemical oxygen demands. Water samples were collected at four sites: the first tap within the supply network or within the alternative supply (first site), main reservoir (second site), kitchen water (third site) and drinking water troughs (fourth site). When the two assessment periods (during dry and wet seasons) were taken into account, contamination by total coliforms in approximately 65.3% of samples was detected, whilst E. coli and Enterococcus micro-organisms respectively occurred in 18.4 and 36.7% of samples. Counts of mesophyll microorganisms were greater during the dry period than during the rainy season. More than 34.7% of counts were above the legal limit. Although no apparent variation in color occurred, irregularity in turbidity and pH was detected in two schools. Inadequate rates for dissolved oxygen occurred in only two schools, during the dry period, whereas biochemical oxygen demand complied with legislation. Although, no coliform was extant in several samples, others had bacterial contamination requiring more efficacious practices for quality improvement. Results show that health risks in schools in Cruz das Almas may be solved by adequate water treatment, periodical cleaning of reservoirs and proper maintenance of taps and filters.