Physico-Chemical and Microbiological Assessment of Borehole and Tap Water in Nzérékoré (Republic of Guinea)

Abstract

The objective of this study is to assess the physico-chemical and microbiological quality of borehole and tap water consumed in the urban commune of Nzérékoré. The study was conducted from February 28 to October 13, 2024, and it is based on field surveys and laboratory analyses of 24 water samples from 14 boreholes and 10 randomly selected taps. Analyses were carried out in April, right at the start of the rainy season. We measured the fisico-chemical parameters (temperature, pH, electrical conductivity, turbidity, and total dissolved substances) in situ using a HI 9828 Hanna portable instrument. We measured the concentrations of chemical elements (aluminum, fluorine, chlorine, heavy metals, etc.) using titrimetry and atomic emission spectrometry. Bacterial contamination was determined by membrane filtration. The results show that the majority of borehole and tap water are compliant with WHO standards for concentrations of calcium, sodium, fluoride, carbonate, sulfate, phosphate and ammonium. However, anomalies were observed in temperature and, in some cases, pH, color, nitrates, iron and potassium. The pH of all water, whether from boreholes or taps, was acidic, with an average of 5.85 ± 0.048 for boreholes and 6.62 ± 0.42 for taps, which does not meet the standard of pH 6.5 - 8.5. Turbidity in tap water ranged from 0.01 to 10, with an average of 2.87 ± 0.58, and did not meet the WHO standard of 5 NTU in 20% of cases. Average levels of aluminum (0.664 ± 0.024 mg/l), lead (0.857 ± 0.06 mg/l), copper (3.139 ± 0.025 mg/l), and chromium (0.18 ± 0.034 mg/l) exceeded WHO standards of 0.2 mg/l, 0.01 mg/l, 2 mg/l, and 0.05 mg/l, respectively. Microbiological analyses show the absence of pathogenic germs in the tap water. However, one well is contaminated with thermotolerant coliforms and sulfur-reducing anaerobes (10 CFU/100 ml), while the WHO standard is 0 CFU/100 ml. The contamination of tap water with heavy metals and borehole water with fecal coliforms poses a health risk to the population. Urgent measures are needed to prevent the risk of waterborne diseases among consumers.