Physico-chemical and bacteriological contamination of water from some supply wells in the Mandjou and Kano neighbourhoods, Djadombè sub-watershed, Bertoua, East Cameroon

The present research focused on the determination of the physical parameters and the biological contamination of water from four wells (MAP1, MAP2 KAN3, KAN4) at the Djadombè sub-watershed irrigating Mandjou and Kano neighbourhoods in the city of Bertoua. The Physical parameters were assessed at the Institute of Geological and Mining Research (IGMR) of Yaoundé, while the Centre Pasteur (CP) of Yaoundé analyzed the bacteriologic status of various water samples. The results showed that water is acidic. Low alkalinity (HCO-3) and low mineralization 35 EC 197 were recorded. The values of TDS and TSS did not exceeded WHO (2011) standards (1000 mg/L and 25-40 mg/L). Water is fresh without any salinity. The bacteriological examination revealed a strong bacterial contamination of the water. The microbial contamination concerns both fecal bacteria (E.coli, Intestinal Enterococci) and sufficiently pathogenic germs (vibrio cholerea, Salmonella ssp). The FS/FC 2 ratios led to the conclusion that the biological contaminations are human origin.


INTRODUCTION
Water is essential to life, but many people do not have access to clean and safe drinking water and many die of waterborne diseases.According to the WHO(2011), the mortality of water diseases exceeds 5 million people per year.From these, more than 50% are microbial intestinal infections, with cholera standing out in the first place (João, 2010).Developing countries such as Cameroon are experiencing rapid demographic change with the corollary of rapid uncontrolled urbanization.Under these conditions, the availability of quality water resources is becoming a real challenge for the public authorities who are unable to satisfy the population.Less than 40% of the population in Cameroon has access to clean drinking water (Tanawa et al., 2002, Kuitcha et al., 2008, Ndjama et al., 2008).Therefore, they are forced to turn to other sources of water supply such as domestic wells, private boreholes, or natural water points.Unfortunately, water from dubious sources can have a very high level of bacterial contamination (Katte et al., 2003;Tita et al. , 2009;Kuitcha et al., 2010).In the city of Bertoua, the population face this sad reality, which manifests itself in a very limited drinking water supply network coupled with untimely cuts.The Kano and Mandjou neighbourhoods along the Bertoua-Garoua Boulai national highway are characterized by a high human density and a significant presence of supply wells that serve as water points for the resident population and even for those in transit.Water is often consumed directly without further treatment.The purpose of this paper was to assess the biological contamination of water samples from four wells located on either side of the Bertoua-Garoua Boulai road in the Djadombè sub-watershed, covering the Kano and Mandjou.

Study area
The study area is in East Region from Lom and Djerem Division in the District of Bertoua 2. The area extends between 4°34'30'' North latitude and 13°41' 04''East longitude and covers an area of 100 Km 2 . It is influenced by both tropical and equatorial climates due to the presence of the Congo Forest.The district of Bertoua 2 has four seasons including two rainy seasons of unequal importance (March to June and September to October) and two dry seasons of unequal duration (July to August and September to October).Rainfall is abundant and humidity is constant (Gazel and Gérard, 1954).The peak of rainfall is usually in October when the rainfall reaches 265mm, the average annual rainfall is 1640mm, and the average temperature is 32°C.The soil cover of the study area is made up of two types ferritic and hydromorphic.Ferritic soils are the most abundant, they are developed on plutonometamorphic basement (Fig. 1).The soils are characterized by a thick profile formed by three levels from weathering process (Nkoumbou et al. , 2014 ;Ngnotué et al., 2000).In terms of hydrology, the study area belongs to Kadei River basin, 552 km long covering a surface area of 41,000 km 2 (Rakotondrabe et al., 2018).

METHODS
The work was carried out in two phases including field and laboratory works.

2.1
Field work The fieldwork involved the identification, description, and collection of water samples (Fig. 2).The sampling campaign was carried out during the month of June 2022, which marks the transition from the short to the long rainy seasons.The wells are hand-dug hydraulic structures with piezometric levels ranging from 5m (KAP4) to 9m (MAP1) and are generally protected (Fig. 3).Samples were collected using a bucket and string that had been washed three times with clean water.The water samples were collected in washed and labelled polyethylene bottles.The water samples for bacteriological analysis were carried into labelled sample bottles provided by the CP of Yaoundé.All vials were then packed Figure 1 : Geology of the study area in a cooler refrigerated at 2°C (Fig. 4).The sample codes correspond to different names assigned to the sampling wells (MAP1, MAP2, KAPA3 and KAPA4).A total of 12 water samples were collected with a ratio of 3 in each well.

pH
The pH value of the water varies from 4.818 (MAP1) to 6.192 (MAP) with an average of 5.349.This result shows that the water collected is acidic as the values obtained are not in line with standards of permissible pH of water at between 6.5 and 8.5.

Electrical Conductivity
The electrical conductivity of the water ranged from 35.3 (MAP1) to 197.1 (MAP2) with an average of 111.4.This parameter is closely related to the mineralization of the water.All the water samples examined are weakly mineralized, as the values obtained did not exceed the WHO(2011) target value (1500 µS/cm).

Alkalinity
The alkalinity ranges from 12.4620 (MAP1) to 134.41 (MAP2) with an average of 49.79.This parameter refers to the bicarbonate anions content.The values obtained in the water samples (MAP1, KAP3, KAP4) are low in comparison to WHO(2011) standards except the KAP2 in which the value obtained (134.41mg/L) is in accordance with WHO(2011) standards. .

Salinity
The water samples analyzed were not salty (value equal zero).This can be explained by the fact that the sampling area does not belong the marine environment.

TDS
The TDS of the water samples varied from 24.43 (MAP1) to 136.45 (MAP2) with an average of 77.137.These values agree with the WHO standard (1000mg/L).
3.1.6TSS Suspended solids vary from 1.8 (MAP1) to 2.15 (MAP2) with an average of 1.987.This parameter expresses whether the water is turbid or not.As the values obtained are below the range prescribed by the WHO standards (25-40 mg/ L), it can be deduced that the water examined are less turbid than those from watercourses.

3.2
Bacteriological parameters Nine varieties of microorganisms were detected (Revivable microoganisms at 36°C, Revivable microorganisms at 22°C, Coliforms, Escherichia Coli, Intestinal Enterococci, Spore of sulphite reducing microorganisms, Pseudomonas Aeruginosa, Salmonella ssp, Vibrio Cholerae) in water samples collected and examined at the CP in Cameroon.The interpretations were done based on the contextualized French standard JORF N°31 of 09/06 February 2007.The results obtained concern the detection (Tab.3),scanning (Tab.4) and evolution of the microorganisms (Fig. 4).The results obtained reveal the presence of all the microorganisms sought in the water samples analyzed, with the exception of salmonella ssp, which were not detected in the MAP1, KAP3 and KAP4 wells, and vibrio cholerae, which is totally absent in the water samples (MAP1, MAP2, KAP3 and KAP4).With regard to the number of microorganisms identified in the water samples, it is above the French standards (Tab.4) for each bacterium.These results show that the water is unfit for human consumption.Physico-chemical parameters The evolution of the physical parameters is recorded in Figure 5 above.The pH values show that the water is acidic.This acidity could be linked to the geological environment which is made of acidic plutonic and metamorphic rocks.The results obtained are like those reported by several authors who have examined surface waters in forest areas (Braun et al., 1998;Viers et al., 2000;Braun et al., 2012).Therefore, the alkalinity of the water samples is low for all wells except MAP2 (134.4mg/L) this could be linked to the recent input of pollutants that would neutralize the acidity.This is also observed in mining localities such as Bétaré-Oya (East Cameroon) where pH is generally basic.This basicity is due to oil spills or leakages from excavation machinery and transportation vehicles (Ahialy et al., 2000;Ibrahima et al., 2015).The EC shows that the water has low mineralization (Detay, 1993).These results reflect those obtained for water flowing in forest areas over plutonic and metamorphic rocks (Viers et al., 2000;Boeglin et al. , 2003, Braun et al., 2005).However, sample MAP1 shows a very high value of EC (197.1 µS/cm) which could be due to its great depth reaching the geological bedrock (Li et al., 2014;Mfonka et al., 2014).TSS and TDS show very low values because of the wells protection in stonework that avoids collection of various particles from surrounding area.Thus, in watercourses, TSS and TDS values are quite high, especially in forest areas (Sigha, 1994;Olivry, 1997, Braun et al., 2005, Ndam Ngoupayou et al. ,2016).The increase of TDS and TSS in mining areas may be linked to deforestation, dredging of river-beds, dumping of solid and liquid waste resulting from gold washing, high soil leaching and exposure during the raining season (Batancourt et al., 2005).The zero value of salinity is related to the non-marine environment to which belongs the study area.

4.2
Biological parameters The content of digestible microorganisms in water sample (Revivable microorganisms at 36°C, Revivable microorganisms at 22°C, Coliforms, Escherichia Coli, Intestinal Enterococci, Spore of sulphite reducing microorganisms, Pseudomonas Aeruginosa) shows an overflow for each type of microorganism (Tab.4).Bacteriological examination of water sample which is usually carried out is to estimate the level of faecal pollution and the presence of other pathogenic organisms that could be hazardous to man and animals (Raji et al. , 2015).Bacteria in the intestines of vertebrates have majorly been used as indicators of faecal pollution.Total coliforms, faecal coliforms, and faecal streptococci have all been used as pollution indicators (Isobe et al. , 2002;Park et al. , 2006).The results obtained are like those of many authors who studied the biological contamination of water in Cameroon (Nola et al. , 2006;Djeukom et al. , 2003;Tita et al. , 2009;Kuicha et al. , 2010).Since the routine basic microbiological analysis of drinking water regards the assaying the presence of Escherichia coli and the quantification of enterococci (João, 2010), the FC/FS ratio is used to examine the origin of faecal coliforms and streptococci (Borego and Romeo, 1982).The result of FC/FS ratio (Tab.5)indicates that the contamination is caused by human origin.
Table 5: Origin of bacterial contamination of wells (Borego and Romeo, 1982) 5.0 CONCLUSIONS The physical parameters (pH, EC, TDS, TSS, alkalinity, salinity) indicated that the water samples were acidic trend but not salty.They are weakly mineralized and less turbid.However, the water was highly contaminated with bacteria.The omnipresence of bacteria indicates faecal contamination (E.coli, Intestinal Enterococci) as well as other pathogenic germs (vibrio cholerea, Salmonella ssp).This shows a very high risk of the occurrence of water-borne diseases in these neighborhoods where the populations use the water drawn from the wells for consumption and domestic purposes.The level of bacterial contamination is high, and human has been identified as the main cause for this contamination.A solution to this situation would be for local authorities to organize the population into hygiene committees who are responsible for the protection and maintenance of the wells and their surroundings.
The laboratory work aimed to determine the physico-chemical parameters (Hydrogen potential, pH ; Electrical Conductivity, EC ; alkalinity, salinity, Total Dissolved Solid,TDS and Total Suspended Solid, TSS).The physical parameters were assessed by the IGMR of Cameroon.The results of physico-chemical parameters were interpreted based on WHO (2011) standards.The bacteriological analyses were carried out by the CP of Yaoundé.The French standards (Tab.1) were used to interpret all the results.

Figure
Figure 2 : Sampling map

Figure
Figure 5: Evolution of physical parameters in the wells 4.0 DISCUSSION 4.1Physico-chemical parameters The evolution of the physical parameters is recorded in Figure5above.The pH values show that the water is acidic.This acidity could be linked to the geological environment which is made of acidic plutonic and metamorphic rocks.The results obtained are like those reported by

Table 3 :
Detection of the presence of microorganisms in the water samples

Table 4 :
Enumeration of microorganisms in the waters samp