Human uses water for various purposes which include drinking, transportation, industrial and domestic use, irrigation in agriculture recreation, fisheries and waste disposal among others [1,2]. Microbes are an integral part of the water that is not only responsible for nutrient recycling in marine and freshwater environments but can also contribute to a variety of water-borne diseases [3,4].

Water quality is an index that determines the quality of water and comprises of physical, chemical hydrological and biological characteristics of water by which the user used in assessing the acceptability of water.

In Nigeria, the major problem facing is inadequate and safe drinking water. World Health Organization reported that about 80% of water-borne diseases are due to drinking contaminated water [5] and 3.1% of death are caused by improper hygiene and poor water quality [6]. Certain minerals are also toxic in water such as heavy metals. Although, some of the heavy metals such as Zinc, manganese, nickel and copper act as micro-nutrients at lower concentrations, become toxic at higher concentrations. Health risk due to heavy metal contamination of water through the soil has been reported [7-9].

The treated water produced by Sokoto state water co-operation could be contaminated by defective plumbing which causes the rush of water out of the pipe forming to pull mixed with sewage matters. The pulls eventually suck back through the burst pipe into the pipeline being distributed to various locations and collected as drinking water. The number of outbreaks that have been reported throughout the world demonstrates that transmission of pathogens by drinking water remains a significant cause of illnesses. Therefore, it is of paramount importance to assess the bacteriological standard of public water to improve sanitation and reduce the incidence of diseases transmission.

The main aim of this study is to make a comparative analysis of Sokoto State's main water production and other water resources at Sokoto State University. The objective is to determine physicochemical parameters and mineral contents of water samples. And also to enumerate, isolate and identify bacterial load from water samples.

Collection of Samples

The water samples were collected from two different sources namely: Sokoto State University water tank and Sokoto State water board production in a sterile bottle of 100ml capacity. From these two sources,3 samples were collected at three different locations. The samples were labeled and transported to the Microbiology laboratory of Sokoto state university for further analysis.

Ethical Approval/Consent

Ethical approval was obtained from Sokoto state water board, Sokoto state.

Physicochemical Analysis and Mineral Contents of the Water Sample

The samples were analyzed for their physicochemical qualities according to the standard procedure described by American Public Health Association, APHA [10]. The following parameters were determined; pH, Taste, Odor and Color, Turbidity and Total Dissolved Solids. Mineral contents in the water such as Cu, Pb, Ca, Zn and Fe were also determined using the same procedure.

Identification and Characterization of Isolated Bacteria

The microbiological analysis of the water sample was conducted according to the procedure described by Neboh et al. The bacteria isolates were characterized and identified based on their cultural, morphological, physiological and biochemical properties according to Holt et al. The tests employed in this study were motility, gas production, starch hydrolysis, citrate utilization test, indole test methyl red, Vogues-Proskauer, catalase, urease and sugar fermentation and gas production in addition to the macroscopic observations such were as color, shape, size elevation and the surface of the isolates.

Determination of Bacteria of the Coliform Groups

The sample container was vigorously shaken to distribute any deposited uniformly throughout the water sample. A test tube was then inoculated with 1ml of the sample and about 10ml of melted standard Nutrient agar was added to the sample in the test tube. The medium in the test tube was thoroughly mixed by the combination of rapid shake with circular movement lasting for 10 seconds. Then Durham tube was inserted in an inverted position. After incubation in the water bath, any presence of air bubbles in the tube after 48 hours, indicates the presence of bacteria or pathogenic organisms in the sample [11,12].

The Presumption Coliform (Multiple Tube Fermentation)

The medium used for the isolation of the coliform organism was lactose broth. Three rows of 3 tubes each in a test-tube rack were arranged. The tube in the first row
held 10 ml of double strength lactose broth while the tubes in the second and third row contain 5 ml of single–strength lactose broth, using a sterile pipette 10 ml of the sample was added to each of the three tubes containing the sample, 1 ml of the sample was added to each of the test tubes in sample two and 0.1 ml was added to each of the test tubes in sample three [11].

After gentle shaking, the tube test was incubated at 37°C for 24 hours. Each of these tubes contained sterile Durham tubes for indicating gas formation and was tightly plugged with sterile non-absorbent cotton wool. The tube showing acid (color changed to yellow) and gas formation was recorded as positive. Other tubes that did not show positive results were incubated and examine after another 24 hours [11,12]. Tubes that did not show acid and gas formation were discarded. From the same water sample, another inoculum was made on a nutrient agar plate to know other micro-organisms present in the water sample.

Confirmatory Test

All the positive presumptive tubes are those that released gas at the end of 24 hours incubation at 37°C and were utilized in the confirmatory test for coliform organisms. The positive tubes were sub-cultured into plates of eosin methylene blue agar and were incubated for 24 hours at 37°C, for confirmation of the presence of coliform organisms. The plates were examined for typical coliform colonies. Colonies were button-like in appearance and should be surrounded by a greenish metallic sheen, flat with dark too black centers [12].

Completed Test

The completed test was performed with the colonies obtained from the confirmed test that show the characteristics of Escherichia coli each selected colony was inoculated into tubes of lactose broth and also streaked on nutrient agar slant and the tubes was then incubated for 24 hours to 48 hours 35-37°C. The presence of gas and acid in the broth and stained slide showing non-sporing bacilli coliforms indicates the presence of Escherichia coli [12].

Detection of Faecal Streptococci

One (1 ml) of the water sample was stored in a refrigerator for three days and various volume of the water samples from the presumptive tubes that showed the positive reaction was inoculated into Azide agar plate and incubated for 48 hours at 37°C colonies from those plates was inoculated into Azide blood agar and was incubated at 37°C for 24 hours. The colonies which showed lysis on the blood incorporated into the medium was examined by subjecting them to Gram staining and biochemical test like catalase test oxidize test etc. [13].

Detection of Escherichia coli 

The media used for this test is lactose broth from the positive tube of a presumptive test, 1 ml was collected from each sample and inoculated in a fresh lactose broth in the test tube and then inoculated for 24 hours.

Statistical Analysis

The valuesare presented as mean and compared with a standardized value of heavy metals and physicochemical parameters in water set by the World Health Organization [14] and Nigeria Standard for drinking water quality (2015).

The results of the physicochemical properties of the water samples obtained from the Sokoto state university water plant and the Sokoto State Water Board were presented in Table 1. The results revealed that the three water samples obtained at Sokoto State University (SSU) had a pH range between 6.6-7.2, also the sample obtained at Sokoto State Water Board (SSW) had a pH of 7.0. The conductivity of the water samples showed that SSUW1 had the highest conductivity value (196.25) and SSUW3 with the least conductivity value of (24.5). Also, total dissolved solid measurement of the water samples showed that SSWI and SSW2 had the highest total dissolved solid (17.83 mg/l) and SSUW3 and SSWB3 with the lowest value of (0.1 mg/l).

Table 1: Physicochemical properties of the water samples from three locations of Sokoto State University and Sokoto State Water Board

Key: NSDWQ*MPL-Nigerian Standard for Drinking Water Quality Maximum Permissible Level. Unobj: Unobjitionable, SSUW: Sokoto State University water, SSWB: Sokoto State Water Board, TDS: Total Dissolved Soli

Table 2 showed the result of the mineral content from the water sample. The Metallic elements analyzed were calcium, zinc, copper, iron and lead. The result shows that 
the value of iron (Fe) obtained ranged between 0.1 to 0.14 mg/L while the range of values for Lead (Pb) was between 0.001 to 0.14 mg/L.

Table 2: Concentration of Mineral Content (mg/L) in water samples from three locations of Sokoto State University and Sokoto State Water Board

Keys: NP: No value is proposed, *Level is above acceptable limit, SSUW: Sokoto State University water, SSWB: Sokoto State Water Board

The result presented in Table 3 shows the Most Probable Number (MPN) and Total Bacteria count (cfu/ml) which indicates that samples of water obtained at Sokoto State University and those obtained at Sokoto State Water Board were all found to be turbid (showed the presence of growth) and sample SSWB2 had the highest mean plate count (3.0×10⁶ cfu/ml), followed by SSUW3 with 2.7×10⁶ cfu/ml and sample SSUW1 had the least mean plate count (5.0×10³ cfu/ml).

Table 3: MPN and Total Bacteria Count of the Water Samples

Keys: SSUW: Sokoto State University water, SSWB: Sokoto State Water Board

Table 4 present the morphological and biochemical characteristics of bacterial isolates from water samples which include; Staphylococcus aureus, Streptococcus spp., Bacillus spp., Micrococcus spp. and Klebsiella spp.

Table 4: Morphological biochemical characterization of the isolated bacteria

Keys: +: Positive, -: Negative, Lac: Lactose, Suc: Sucrose, Glu: Glucose, SSUW: Sokoto State University water, SSWB: Sokoto State Water Board, H₂S: Hydrogen Sulphide gas, MR: Methyl red, Voge’s Proskeur, Indo: Indole, Cat: Catalase, Oxi: Oxidase

The physicochemical properties of water from various sources investigated include pH, conductivity, Total Dissolved Solids (TDS), odour, taste and colour. The pH values recorded were ranging from 6.5-7.2 which is in agreement with the requirements for drinking water as per the guidelines of the World Health Organization [15] and the Nigerian Standard for Drinking Water Quality Maximum Permissible Level. This finding conforms with Yahaya et al. [16] who reported pH value 6.36-6.93 of the water sample at Sokoto state university. The water samples were tasteless, odourless and colourless which are the physicals features of normal healthy water. This is in line with the World Health Organization [15].

In this study, Table 2 revealed five elements, consisting of heavy metals copper (Cu), lead (Pb), calcium (Ca), Zinc (Zn) and iron (Fe) were detected. Iron (Fe) had the highest concentration (1.49) mg/L than the recommended value of WHO [15] for drinking water. As for copper, the value is within the allowable WHO limit, while as for lead only the SWB1 sample is within the range but the rest of the sample is above the WHO allowable limit. The high concentration of iron (Fe) is mainly influenced by Geological settings and hydrogeology of the area, which is in agreement with the findings of Yahaya et al. [16] and Bello et al. [17] found high level of iron (Fe) in water samples obtained from kware lake and Sokoto state university respectively. 

The results show that sample SSWB2 had the highest mean plate count (3.0×10⁶ cfu/ml), followed by SSUW3 with 2.7×10⁶ cfu/ml and sample SSUW1 had the least mean plate count (5.0×10³ cfu/ml) on Table 3. These indicate that the water sample obtained in the Sokoto State water board had high bacterial load count than those samples of water collected from Sokoto State University Tanks. It may be due to high total microbial loads in the environment corresponding to the high presence of organic compounds, primarily from human and animal activities. Thus, the relatively high bacterial loads in the water samples could be attributed to contamination from surface runoff laden with environmental residues of humans, animals and plants. Such waste-laden water has been reported to percolate and contaminate underground water bodies [18,19]. The bacterial load of the water sample obtained in this study was lower than those reported in other communities in Nigeria such as from Eyaen Community Area in Edo State [20] and Ile-Oluji community in Ondo State [21]. It is also agreement Adefusisoye et al. [22] who reported Total mean bacteria ranging from 2.79-9.66×10⁸ from wells water. But relatively similar to reports from Ijebu-Ode in Ogun State [23] and Auta Balefi Community in Nasarawa State [24]. 

The bacterial isolates identified include; Staphylococcus aureus, Streptococcus sp., Bacillus spp., Micrococcus sp. and Klebsiella sp. The presence of fecal coliforms such as Klebsiella sp. is of public health importance because; they indicate recent pollution of water bodies by human/animal fecal wastes and sewage [14,18]. A basic observation at the study location was that the majority of the indigenes lack good toilet facilities and sewage systems and thus use any available bush or space around their residence to defecate and dump sewage. Such unhealthy practices could be one of the major reasons why the entire water samples displayed positive reactions to coliform analysis. The presence of Streptococcus sp., Staphylococcus sp. and Micrococcus sp. are also worth noting because, they have been reported to cause diverse human ailments [14].

The findings from the present study revealed that pH values for the six samples met the WHO standard. Chemical parameters like calcium, zinc copper, iron and lead were detected the level and quality of microbial isolates in this study were above the WHO standard for microbial loads. It’s therefore suggested that some of the Sokoto State water Board and Sokoto State University water tanks are not safe for drinking. Bacteria including S. aureus, Bacillus sp., Micrococcus sp., Streptococcus sp. and Klebsiella sp. were identified, thus making the water unsafe for drinking.

Recommendations

Government and other stakeholders need to take some appropriate steps that would ensure that drinking water sources available for the community are rendered safe. Regular monitoring to ensure conformity to World Health Organization standards and to assure the public of the portability of their water is necessary. Tests should be carried out regularly at short intervals which are of more value than detailed test mode occasionally. Moreover, general awareness on simple water treatment such as boiling, regular disinfection, cleaning of the borehole and proper disposal of sewage.

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