The Bacteriological Quality Assessment of Some Bottled Water Sold in Lagos Metropolis, Nigeria

FO Ogundipe,  FA Bamidele,  AO Adebayo Oyetoro,  OO Ogundipe

and OO Samuel

This study investigated the bacteriological quality of some bottle water sold in Lagos metropolis, Nigeria. A total of 30 bottled water samples were used in the study. The mean pH ranged from 5.95 to 8.30. All water samples were subjected to standard bacteriological tests such as heterotrophic plate count and coliform count and the multiple tube (MPN)  tests. The mean heterotrophic plate count ranged from 1.2 x10¹ to 2.5 x 10² cfu/mL while mean total coliform count ranged from 0.2 x 10¹ to 2.0 x 10²cfu/mL. The MPN/100mL of the samples ranged from < 3 to > 1100 coliforms/mL. Ninety nine (99) isolates were obtained and the completed test revealed the presence of Escherichia coli (3%) and Enterobacter species (97%). All the bottled water brands did not meet the standard stipulated by the Nigerian Industrial Standard for drinking water quality and the World Health Organization standard. This indicates that some of the bottled packaged water available in Lagos market may be unfit for human consumption due to their inability to meet up with the recommended standard by regulatory bodies in Nigeria. Effort needs to be intensified in the monitoring of activities in this rapidly expanding industry with a view to raising standards and ensuring safety of the populace.  

Introduction

Water is essential to life where it is very important for the composition and renewal of cells (Abera et al. 2011). Thus adequate supply of clean safe drinking water is required for the sustenance of life. The demand for safe drinking water in Nigeria is high, considering the inability of the government to provide adequate pipe-borne water to the populace.

Coliforms are the most common group of indicator organisms used in water quality monitoring. These organisms are representative of bacteria normally present in the intestinal tract of mammals including humans, so they provide an adequate index of faecal contamination of drinking water (Fewtrell and Bartram 2001). The coliform group comprises strains of the four genera of the intestinal group: Escherichia, Enterobacter, Klebsiella and Citrobacter. The number of Escherichia and Enterobacter cells remains much higher in the intestine compared to the remaining two (Stevens et al. 2003).

In terms of public health significance, E. coli has frequently been reported to be the causative agent of traveller's diarrhoea, urinary tract infections, haemorrhagic colitis, and haemolytic uraemic syndrome. Klebsiella pneumoniae is associated with pneumonia and upper respiratory tract infections. However, Enterobacter and Citrobacter species have also been previously reported as causes of cystitis, enteritis, pneumonia, diarrhoea, and food poisoning (Kistermann et al. 2002). Moreover, the presence of coliforms in drinking water could also indicate a breakdown of the treatment process.

The bacterial qualities of groundwater, pipe-borne water and other natural water supplies in Nigeria have been reported to be unsatisfactory, with coliform counts far exceeding the levels recommended by WHO ( Edema et al. 2001). The public health significance of water quality in Nigeria thus cannot be over emphasised. Many infectious diseases are transmitted by water through the fecal-oral route. Diseases contacted through drinking water kill about 5 million children annually and make 1/6th of the world population sick (WHO 2004).

It is known that packaged water in bottles or food grade polyethylene sachets designed for food processing, serves as a ready alternative for a growing population (Rompre et al. 2002). Bottled water, however, is being widely consumed even in countries where top quality municipal drinking water is provided (Copes et al. 2009). Bottled water includes natural mineral water and water drawn from springs and wells, but could also include purified water which is often treated municipal water (Ray 2005). In most developing countries including Nigeria, rivers, streams, wells and more recently boreholes serve as the main sources of water for drinking and domestic use.

Increases in population are however causing an increase in incidences of pollution of drinking water sources, which most often are from surface water that are likely to be polluted with domestic, industrial as well as agricultural waste (Dada 2009). Provision of safe drinking water is of major public health significance.The ever increasing demand for readily available water has led to the general perception that packaged water is safe for consumption (Adekunle et al. 2004), with bottled water being considered safer than sachet water by many. Thus the study was conducted to determine the pH and bacteriological quality of some popular brands of bottled water sold in Lagos State.

Materials and Methods

Sample Collection

Triplicates of ten (10) brands of bottled water were bought from ten different areas of Lagos, Nigeria. Samples were transported in cooling bags, labeled appropriately and taken to the laboratory where they were stored at 4^oC prior to analysis.

Determination of pH

The samples were allowed to cool to room temperature before all analyses were done. pH was immediately measured electrometrically with a glass electrode.

Heterotrophic Plate Count and Coliform Count

Each bottled water sample (0.1 mL) was aseptically inoculated into Nutrient Agar for heterotrophic plate count and MacConkey agar for coliform count according to Ibe and Okplenye (2005). All plates were inoculated in triplicate and incubated aerobically at 37^oC for 24 - 48 h.

Total Coliform Count

This was determined by using the three tube MPN test (Ibe and Okpelenye 2005). Presumptive test was performed by using Lactose broth. The first set of three tubes had sterile 10 mL double strength Lactose broth and the second and third set had 9 mL single strength broth. All the tubes contained Durham tubes before sterilisation. The three sets of tubes were inoculated with 10 mL, 1 mL and 0.1 mL of the water sample. Tubes were incubated at 37^oC for 24-48 h and examined for visible turbidity and carbon  dioxide gas production. Confirmation was carried out by sub culturing a loopful of culture from positive tubes onto MacConkey Agar. Thereafter, the completed test was done by streaking a loopful of isolate from the MacConkey agar plates on Eosin Methylene Blue Agar, plates were then incubated at 37^oC for 24-48 h. After the incubation period colonies that showed characteristics of coliforms were subcultured and subjected to Gram staining and biochemical tests using standard microbiological methods.

Results and Discussion

Microbiological examination of drinking water emphasises the assessment of the hygiene quality of the water supply. Coliform bacteria should not be detectable in treated water supplies but if found, suggests inadequate treatment, posttreatment contamination and presence of excessive nutrients (Copes et al. 2009).

Heterotrophic count measures a range of bacteria that are naturally present in the environment. The total bacterial counts for all the water samples were generally high. Table 1 showed that the counts were below standard for drinking water with a range of 12 to 250 cfu/mL. which exceeded the limit for drinking water. This high total heterotrophic count is indicative of the presence of high organic and dissolved salts in the water (EPA 2002). Therefore, the relatively high heterotrophic count was indicative of poor unhygienic handling and processing.

Presence of coliform indicates failure of treatment efficiency and integrity of the distribution system. All of the water samples examined in this study indicated counts for coliforms, hence all the bottled water brands failed to meet the WHO drinking water standard of zero coliforms per 100 mL (WHO 2006; NIS 2007). The lowest count obtained was 2 cfu/mL while the highest coliform count was 200 cfu/mL. The high coliform count obtained in the samples may be an indication that the water sources had faecal contamination (EPA 2003).

The most probable number (MPN) index (Table 2) showed that the bottled water samples had between <3 coliforms/mL to more than 1100 coliforms/mL. A total of ninety nine (99) isolates were obtained with the highest incidence of occurrence obtained for Enterobacter species (97%) followed by Escherichia coli (3%). Escherichia coli is significant in drinking water and is abundant in human and animal faeces. It is found in sewage, treated effluent and all natural water and soil subject to faecal contamination, whether from humans, wild life or agriculture. Enterobacter species are examples of non-fecal coliform and can be found in vegetation and soil which serve as sources by which the pathogens enter the water (Schlegel 2002). The British Standard Institute (BSI 1993) specifies that a count greater than 10⁴ is considered unsatisfactory for Enterobacter spp.

The pH of some water samples did not fall within the range (6.5-8.5) recommended by Nigerian Industrial Standard for drinking water quality (NIS 2007). The mean pH of the bottled water samples indicated that two of the brands recorded pHs below the recommended level. The highest pH obtained was 8.30 while the lowest was 5.95 as shown in Table 3. Although pH is an important water quality parameter and affects the aesthetic appearance and taste of water, it usually does not have direct impact on the health of the consumer.  However, drinking water with low pH can affect disinfection efficiency, thus may have an indirect effect on health while water with pH above 8.5 indicates that the water is hard (WHO 2006). Careful attention should be paid to pH control at all stages of water treatment to ensure satisfactory clarification and disinfection. 

Conclusions

Consumers usually perceive packaged drinking water as a healthier and safer alternative to tap water, however packaged water has been implicated as a source of outbreaks of typhoid and cholera (Osei et al. 2013).The bacteriological qualities of the examined bottled water were shown to fall below acceptable standards. The presence of indicator organisms in water for drinking is of public health significance considering the possibility of the presence of other bacteria, protozoa and enteric viruses that are implicated in gastro-intestinal waterborne diseases and the low infectious dose for these waterborne pathogens. Unlike municipal water which can be monitored and disinfected with residual chlorine still being effective, bottled water contains no residual chlorine, hence proper transport and storage is essential to preserve its microbiological integrity (Ray 2005). There is thus a great need to monitor the producers to ensure that they comply with appropriate standards. The regulatory bodies and ministries should exercise more stringent surveillance programs and awareness.

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FO Ogundipe, FA Bamidele  and OO Samuel are with the Department of Food Sciences, Yaba College of Technology, Lagos, Nigeria, and AO Adebayo Oyetoro and  OO Ogundipe are with the Department of Food Technology, Yaba College of Technology, Lagos, Nigeria.