Comparison Of Escherichia Coli, Enterococci, And Sulfite-Reducing Anaerobes (Clostridia) As Faecal Contamination Indicators Of Water

Abstract

This study aimed at investigating the reliability of three microbial agents, namely: Escherichia coli, faecal enterococci and sulfite reducing, spore-forming anaerobes (clostridia, which are mainly Clostridium perfringens) as faecal contamination indicators of water in Sudan. Sixty samples of drinking water collected from ten different sites were examined for the counts of the three indicators during the summer (April – September) and winter (November – March) seasons. Forty Two samples of them were collected at drinking points (homes, schools, street Sebeels, universities, bottled, mosques and Mogran plant treated and untreated waters). The other eighteen samples were raw waters (Nile, hafeer and untreated waters) The water samples were also tested physically and chemically. The physical parameters measured were turbidity, electric conductivity (E.C) and temperature, whilst the chemical parameters tested were the pH and free and residual chlorine. Considering the totality of the samples, the turbidity ranged from 0.6 NTU (nephelometric turbidity units) to 11672 NTU during summer, but lower levels of turbidity ranging from 0.6 to 37.4 NTU were obtained during winter season. E.C. ranged from 11.9 to 453 μ/cm during summer and 117 to 502 μ/cm during winter. The temperature ranged from 20.0oC to 26.8oC during summer and 19.4oC to 24.1oC during winter. The pH values ranged from 6.7 to 8.2 during both seasons. Residual chlorine was not determined (because it is not expected) for about 40% of the samples. For the remaining 60% of the samples, iv during both summer and winter, the residual chlorine ranged from zero to 0.80 mg/l. Microbiological analysis was carried out to assay the total viable count (TVC) and total coliforms counts (TCC). The TVC ranged from 0.301 log10 to 5.913 log10 cfu/5ml and TCC ranged from 0.301 log10 to 3.990 log10 cfu/100ml, during summer. However, during winter TVC ranged from 0.301 log10 to 7.322 log10 cfu/5 ml, whilst TCC ranged from 0.301 log10 to 3.869 log10 cfu/100 ml during both seasons. All the samples were examined to assay the counts of Escherichia coli, faecal enterococci and sulfite-reducing, spore-forming anaerobes (clostridia). E. coli showed its reliability as faecal contamination indicator in 56.7% of the total samples, faecal enterococci showed its discriminative efficiency in 15.0% and Clostridium perfringens in 21.7%. The three indicators were at equal levels for 6.6% of the total samples. In addition, the presence of the three faecal indicators bacteria in ten samples, four human specimens two from sick persons and two from healthy persons, sewage water and five animals (donkey, goat, sheep, cow and pigeon) faeces were tested. The results revealed that all animals and human guts harbored the three indicators. In human (healthy and sick persons), TVC ranged from 1.8 × 1014 to 7.2 × 1016 cfu/g (on wet matter basis). In sewage sample TVC was 1.5×1010 cfu/ml, E. coli count was 1.3 × 103 cfu/g, enterococci count was 2.4 × 103 MPN/100 ml and Clostridium perfringens count was 4.5 × 102 cfu/ml. The three bacterial indicators were found in higher numbers in human samples than in sewage and animals samples.