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Microbiological Evaluation of the Quality of Tap Water Distributed at Khartoum State



Sanaa O. Yagoub and Rawda Yousif Ahmed
 
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ABSTRACT

This study was aimed to evaluate the microbial quality of drinking water distributed at Khartoum state- the capital of the Sudan. Water distributed at piped system was investigated using two different standard methods (MPN and chromogenic media- based techniques), 47.5-90% showed positive isolation of bacteria. The results revealed isolation of faecal coliform (E. coli), coliform group (Klebsiella sp., Citrobacter sp., Enteriobacter sp.), some pathogenic and potential pathogenic bacteria (Staphylococcus aureus, Salmonella sp., Yersienia enteriocolitica, Proteus sp., Bacillus sp. and Pseudomonas aeruginosa) were isolated. Other bacteria with significant importance were detected. The quality of drinking water, types and number of isolated bacteria were evaluated and discussed according to seasons and locations.

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  How to cite this article:

Sanaa O. Yagoub and Rawda Yousif Ahmed, 2009. Microbiological Evaluation of the Quality of Tap Water Distributed at Khartoum State. Research Journal of Microbiology, 4: 355-360.

DOI: 10.3923/jm.2009.355.360

URL: https://scialert.net/abstract/?doi=jm.2009.355.360
 

INTRODUCTION

The microbiological quality of drinking water is a concern to consumers, water suppliers, regulators and public health authorities alike. The potential of drinking water to transport microbial pathogens to great numbers of people, causing subsequent illness is well documented in countries at all levels of economic development (Payment, 1997). Issac-Renton et al. (1996) mentioned that most sporadic cases of waterborne intestinal illness will not be detected or, if detected, may not be recognized as water related. Several researchers have attempted to estimate the total burden of waterborne disease world-wide. Hunter and Syed (2001) reported a total number of 1.2 million water related cases of illness. Hunter (1997) estimate that waterborne disease might account for one-third of the intestinal infections world-wide while Pruss et al. (2002) estimated that water, sanitation and hygiene was responsible for 4.0% of all deaths and 5.7% of the total disease burden occurring worldwide.

Human, livestock and wild animals are all sources of faecal contamination; in general human faecal wastes give rise to the highest risk of waterborne disease (Craun, 1996). Mieszkin et al. (2009) estimated the contamination of river by pig faeces. A wide spectrum of pathogenic agents can be found in water and monitoring for their presence on a routine basis is impractically. Traditionally microbial safety of drinking water has been confirmed by monitoring for absence of microorganisms of faecal origin (Le-Chevallier and Au, 2004). The same researchers added that safe drinking water is the result of careful evaluation of source water quality and variation and adequate, reliable treatment processes combined with performance monitoring to assure that treatment is within operating parameters.

The importance of quality changes in distribution is based upon evidence concerning the frequency and extends of known quality changes and their impact upon human health, a significant proportion of recognized piped drinking water-related disease outbreaks are related to quality deterioration in distribution (Cheryl et al., 2000). Piped distribution systems for drinking water are as important to the quality and safety of drinking water as the treatment itself. Water entering the distribution system must be microbiologically safe and ideally should be biologically stable. The distribution system itself must provide a secure barrier to post-treatment contamination as the water is transport to the user (Geldreich and Le-Chevallier, 1999).

Perkins et al. (2009) isolated potentially pathogenic bacteria from shower water and air of stem cell transport unit while Smith and Hill (2009) recovered Enteriococcus faecalis, Clostridium perferens spore and Cryptosporidium parvum oocyst from water by using MS2 bacteriophage. Muniesa et al. (2006), Mull and Hill (2009) illustrated the public health importance of the occurrence of E. coli 0157:H7 in water sources.

In this study detection of the coliform group was done with bacteriological isolation and identification of the bacteria presence in distributed water supplies.

MATERIALS AND METHODS

Area and Collection of Samples
This study was carried at Khartoum state (Khartoum, Omdurman and Khartoum North cities) from 2006-2008. Forty-tap water was collected monthly from four different locations from each Khartoum and Omdurman cities while thirty- tap water were collected monthly from three different locations at Khartoum North city. The collection was done for six months as winter (November, December and January) and summer (March, April and May).

Tap water were collected aseptically in sterile containers, transport in ice-boxes and examined within 2 h from collection at Microbiology laboratory, Department of Microbiology and Molecular Biology, Faculty of Science and Technology, El Neelain University, Khartoum, Sudan.

Microbiological Examination
Evaluation of the Quality of Tap Water
Treated water technique of the Most Probable Number (MPN) as describer by Rompré et al. (2002) was used, fifty milliliter of each water sample where added to 50 mL sterile double fold MacConkey broth culture medium with a Durham’s tube and 10 mL from the same sample where added to each of five tubes containing 10 mL MacConkey broth. All tubes were incubated at 37°C for 24 h. The occurrence of fermentation with acid and gas production indicated presence of coliform group. The presence of total coliform was confirmed using brilliant green lactose bile broth and the formation of gas in the tube within 48 h considered as positive.

Chromogenic media-based detection method using Colilert kits technique as described by Eckner (1998); APHA, AWWA, WEF (1998) were used for detection of the water quality. The colilert method based upon the sample turning yellow, indicting coliforms with β-galactosidase activity on the substrate ONPG. One hundred milliliter volume of water were added to the commercial dried indicator nutrients and incubated at 37°C for 24 h.

Isolation and Identification of Isolated Bacteria
Preparation of the media, isolation and identification of isolated bacteria were done according to Hawkey and Lewis (2004).

RESULTS

Number and Percentages of Positive Bacteria Growth
Out of one-hundred and twenty samples that collected at winter season from Khartoum city, 88 (73.3%) showed positive bacterial growth and 32 (26.7%) showed negative bacterial growth, at Omdurman city 57 (47.5%) showed positive bacterial growth with 63 (52.5%) negative for bacterial growth. Samples that collected from Khartoum North city, revealed (54.4%) and (45.6%) as positive and negative bacterial growth, respectively. The percentage of the positive bacterial growth in samples collected at winter season from Khartoum state showed 58.8% (Table 1).

In this Table 1 also it is clear that the positive bacterial growth at summer season was highest than winter season, it was 80, 90 and 80% at Khartoum, Odurman and Khartoum North, respectively.

Identification of Isolated Bacteria
Table 2 showed the number and percentage of isolated bacteria at Khartoum state cities. It is clear that Pseudomonas aureginosa was the dominant isolated organism with percentage of 24%. Klebsiella sp., Enteriobacter sp., Alkalagenes sp., Aeromonas sp., Proterus sp., Citrobacter sp. and E. coli were isolated as 9.7, 8.7, 8.7, 8.2, 7.7, 6.1 and 4.6%, respectively.


Table 1: Number and percentage of the positive and negative bacterial growth at samples collected from different cities of Khartoum state

Table 2: Types, number and percentages of bacteria isolated from tap water collected from Khartoum state

Table 3: Coliform and fecal pollution indicator bacteria isolated from water samples

Table 4: Number and percentage of pathogenic and potential pathogenic bacteria isolated from water collected from Khartoum state

Table 5: Bacteria with significant importance isolated from water collected from Khartoum State

Fecal pollution indicator organisms were isolated as 11.2% at winter and 2.6% at summer in Khartoum city, at Omdurman city they were isolated as 5.1 and 0.5% at winter and summer seasons, respectively, while in Khartoum North they were isolated as 7.1% at winter and 3.1% at summer (Table 3).

Isolation of Pathogenic and Potential Pathogenic Organisms
Salmonella sp., Yersina enterocolitica, Staphylococcus aureus, Listeria sp., Aeromonas sp., Proteus sp., Pseudomonas aeruginosa and other organisms were isolated as shown in Table 4. The percentage of isolation of the pathogenic and potential pathogenic organisms from water collected from Khartoum state at winter and summer was 16.8 and 5.6%, 6.6 and 3.6%, 14.3 and 1.0% at Khartoum, Omdurman and Khartoum North, respectively (Table 4). The percentage of isolation of these organisms from all samples collected from Khartoum state was 48%.

Table 5 showed that other bacteria of significant important were also isolated such as Aerococcus sp., Micrococcus sp., Flavibaccterium sp. Alkalegenes sp., Morgenella sp. and others.

DISCUSSION

Sanitary inspections are a key in the monitoring and surveillance of water supplies and are recommended by WHO. Outbreaks of disease from drinking water supplies often result from chance events. In this study it was clear that there is a problem in the tap water distributed at Khartoum state, sanitation condition is improper, the isolation of feacal pollution indicators might indicate inadequate treatment of water or post-treatment contamination and this confirm the fact that following abstraction and treatment water becomes a vulnerable and perishable product. It is vulnerable in that the integrity of systems used for the storage and distribution of water can be damage and contamination through ingress can occur. It is perishable in that microbial quality can deteriorate due to the bacteria remaining after treatment growing on residual nutrient in the water. The relationship between coliform compliance and outbreak occurrence is well documented by Craun et al. (1997) and Pruss et al. (2002).

Isolation of pathogenic and potentially pathogenic microorganisms such as Salmonella sp., Yersina enterocolitica, Staphylococcus aureus, Listeria sp., Aeromonas sp., Proteus sp. and Pseudomonas aeruginosa is of highly importance and indicated that tap water is unsafe. There is little epidemiological data on the endemic level of waterborne diseases and their aetiology. The association between many aetiological agents with a given route of exposure and their contribution to the total burden of disease is often uncertain. A significant proportion of recognized piped drinking water-related disease outbreaks are related to quality deterioration in distribution, these previously reported in developed and developing countries as mentioned by many authors (Leclerc et al., 2002).

It was clear that the quality of water is worse in summer comparing with winter; these might be due to the effect of the high temperature in enhancing the bacterial growth. The isolation of Pseudomonas aeruginosa and Areomonas sp. indicated water quality deterioration and that immuno-compromise people are in risk and suggested that there may be connection between the high cases of reported diarrhea and the isolated organisms.

This study concluded that water quality distributed at Khartoum state need more effort to limiting the numbers of organisms released into distribution systems and recommended that effective management and maintenance are required and the water suppliers need to have preventative and emergency response procedures in place to ensure safe water delivery in the event of variety circumstances.

ACKNOWLEDGMENT

This study was finance by Department of Scientific Research, Ministry of High Education. Sudan as a part of fund allocated to the first author for a project (2006-2008) for (Evaluation of Drinking water Quality at Khartoum State).

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