The urban commune of Kankan “Nabaya” is located between 10˚23'05" north latitude and 9˚18'25" west longitude (Figure 1). It is bordered to the east by the rural commune of Balandou; to the west by the rural commune of Gbérédou Baranama; to the north by the rural commune of Karifamoriah, and to the south by the rural commune of Tinti Oulén ([14]). In terms of surface area, it is the second largest city in the Republic of Guinea after the capital Conakry and the largest in the region ([6]). Located in the Upper Guinea Region, it is the capital of the Kankan prefecture and covers an area of 334 km² with 504,325 inhabitants and 44 inhabitants per km². Its geographical position gives it the reputation of being a crossroads city in the sub-region ([11]).

Figure 1. Presentation of the area ([10]).

The city is crossed by the Milo River and watered by other tributaries such as Séngnè Dèbèkoro, Manfénda, Kokoudouni and Gboutouroun. The urban commune of Kankan is characterized by a morphology mainly influenced by the Milo River (tributary of the Niger) with significant population growth on both banks. The landscape is marked by plains and plateaus, with valleys and inland depressions ([2]). The climate is sub-Sudanese and is characterized by two alternating seasons: a dry season from November to April with very high and constant temperatures (averaging 30˚C) and a rainy season from May to October with rainfall varying between 1100 and 1800 m³ of water per year ([11]).

Water samples were collected from nine sites (Figure 2), taking into account the urban area, the representativeness of pollution sources, operational feasibility and use by local populations. The geographical coordinates of these different sampling sites are shown in Table 1 below ([10]).

The Kankan hydraulic laboratory, located in the energy district of the city of Kankan, served as the setting for these bacteriological analyses. This nationally accredited laboratory (REF N006/11/LARQEKK/DNH) provides reliable and compliant results for the analyses carried out within it.

Figure 2. Geographic coordinates of the different sampling sites ([10]).

Table 1. Geographic coordinates of the different sampling sites.

Samples were taken during the rainy season because pollution is very pronounced during this period due to runoff. Two water samples were taken at each site, with care taken to avoid any alteration or contamination of the samples ([10]). Sampling was carried out in two stages: while it was raining and when the rains became less frequent. Sterile 0.5 L bottles were used to transport the samples to the laboratory, where they were stored at 4˚C until bacteriological analysis. The analysis was carried out within a maximum of 12 hours after sample collection.

Bacteriological analysis is based on the detection of bacteria or test organisms. A total of 108 analyses were carried out, including 36 for total coliforms (TC), 36 for fecal coliforms (FC), and 36 for Escherichia coli (E. coli). For this analysis, the Petrifilm method was used to identify and determine the number of bacteria in the various samples taken. The petrifilm used is manufactured in the United States from American materials and imported by 3M. Microbiology petrifilm and 3M are registered trademarks. This method is a quick and easy technique for counting bacteria in food and environmental samples: it is the membrane filtration method. It uses ready-to-use plates that contain all the necessary nutrients and indicators, thus simplifying the process compared to traditional agar methods ([16]). The analysis requires equipment such as a syringe for collecting samples, a Petri dish to contain the sample to be analyzed, and an incubator where the analysis is carried out (Figure 3). The sample is inoculated onto the plate and then incubated at the appropriate temperature. The bacteria determined include Total Coliforms (TC); Fecal Coliforms (FC) and Escherichia coli at incubation temperatures of 37˚C, 44˚C, and 35˚C, respectively, and incubation times of 24 ± 2 hours. The incubation ranges depend on the resistance of each bacterium, i.e. the temperatures of the environment in which these bacteria can exist. The incubation limit of the plate is 0˚C to 100˚C.

Figure 3. Devices used: (a) Plate, (b) Incubator, (c) Petri dish, (d) Syringe.

The results in Table 2 and Figure 4 show that all the samples of these sites are polluted by the bacterium C.F, C.T. E. coli. The contamination is very high in these areas and the health risk is very pronounced. This high level of pollution may be due to various types of waste discarded by traders in these areas and probably by fecal matter, which presents a high risk of waterborne diseases such as cholera, dysentery, and typhoid ([15]). Although, the CF and CT values in the water samples from the Sogbè and Sénkéfara wells are low, the water still does not comply with the WHO standard, which specifies zero bacteria per 100mL of water sample.

Table 2. Bacteriological parameters of ordinary well water.

*Pop = Population.

Figure 4. Bacteriological parameters of ordinary well water.

The results presented in Table 3 and Figure 5 show that tap water samples from the Kabada and Dibida neighborhoods are heavily contaminated, which could cause a high risk of waterborne diseases such as typhoid, diarrhea, cholera ([5]). The particular pollution of tap water at the Sogbe market is explained by the fact that the water pipes in this area are constantly leaking, which encourages runoff infiltration and high contamination. In the Briqueterie neighborhood, although there is no direct fecal contamination, the water is slightly polluted and therefore needs to be monitored.

Table 3. Bacteriological parameters of tap water.

*Pop = Population.

Figure 5. Bacteriological parameters of tap water.

It should be noted that, tap water samples from the Sogbè neighborhood are heavily contaminated with fecal matter and E. coli, affecting water quality despite the absence of total coliforms ([4]).

Although the standard requires zero E. coli population/100 mL of water sample, it should be noted that all localities have at least one non-compliant parameter. The most critical cases are those of Kabada, Dibida, Sogbè, and Sénkéfara, with a count of 100 E. coli populations/100mL of water sample. The only area where there is no E. coli in the water samples is the Briqueterie neighborhood, but there is still C.T. that do not comply with the WHO standard for drinking water.

The results of the bacteriological parameters of the borehole water from the various sites are presented in Table 4andFigure 6.

Table 4. Bacteriological parameters of borehole water.

*Pop = Population.

Figure 6. Bacteriological parameters of borehole water.

These results show that water samples from the UJNK and CMIS boreholes comply with WHO standards and therefore pose no risk of contamination, while those from the Regional Hospital, Dibida Market, and Senkefara are slightly contaminated. However, analysis of the water sample from the Sogbè Market borehole shows that the water is heavily contaminated and could pose a real danger to human consumption ([7]). The Same result was obtained by Bah A et al., during the study of Ratoma borehole ([1]).

Table 5 and Figure 7 present the results of the bacteriological analysis of the water from the Milo River.

Table 5. Bacteriological parameters of Milo River water.

*Pop = Population.

Figure 7. Bacteriological parameters of Milo River water.

Based on these results, all points along the Milo River that were studied show very high levels of bacteriological contamination (Table 5 and Figure 7). This pollution is due to agricultural activities (chemical inputs) in the surrounding area. The WHO standard requires zero (0) coliforms and zero (0) E. colipopulation per 100 mL of water sample. It follows that this water poses a real danger to human consumption and should not be used without appropriate treatment.

In Table 6 are showing the comparative WHO standard and a complaint or noncompliant indicator for each parameter and site.

Table 6. Comparison between the WHO standard and the data obtained for each parameter and sampling site, and an indicator of compliance or non-compliance.

This table shows that all sampling sites are polluted, with the exception of the water at the briqueterie, UJNK, and CMIS sites. This high level of pollution is due to the proximity of some of these sites to markets and toilets. The pollution of Milo River is due to chemical inputs used by farmers. Aissatou Bah et al., 2024 made the same observation when studying the characteristics and qualities of borehole water in the municipality of Ratoma.