Introduction

         Water is the most essential commodity for the survival of human beings next to oxygen. Nearly 71% of earth’s surface is covered with water but the availability of safe drinking water for consumption is becoming scarce (Malathy et al., 2017). In human body, water plays a central role in the regulation of nutrient transport, toxic waste removal, thermal regulation, digestion, organ functioning and metabolic activities (Kumar et al., 2013). However, if water is polluted it spreads diseases to a great number of people consuming it. World Health Organization (WHO) estimated about 1.1 billion people drink unsafe water globally; hence, perhaps water is the major route of massive outbreaks of pathogenic infections (Anbazhagi et al., 2007). India with more than 1.2 billion citizens suffers water shortage with its increasing population and economic growth, and lack of adequate infrastructure. Among various diseases caused due to contamination of drinking water, diarrhea is the third most common cause of death in children under the age group of five years and contributes to 13% of death killing 300,000 children every year in India (Bassani et al., 2010).

         Groundwater is an important source of drinking water and its quality may vary due to various factors such as discharges from sewage works and runoff from informal settlements and contamination by faecal waste of human and animal origins. Contaminated water may harbour infective and parasitic agents that can cause infectious diseases. Presence of these microorganisms could be detected by testing for the presence of Fecal coliforms (FC), the most commonly used bacterial indicator for fecal pollution and hence used to assess the microbiological quality of drinking water (Malathy et al., 2017). As per WHO standards, any microorganism known to be pathogenic or any bacteria indicative of fecal pollution should not be present in drinking water (Wright et al., 2004).

         Microorganism such as Micrococcus, Pseudomonas, Serratia, Flavobacterium, Chromobacterium, Acinetobacter and Alcaligenes are present naturally in water. Similarly soil bacteria such as Bacillus subtilis, B.megaterium, B. mycoides, Enterobacter aerogenes and E. cloacae may also be present in the water. Apart from these pathogenic microorganisms such as Escherichia coli, Enterococcus faecalis, Clostridium perfringens, Salmonella typhi, Vibrio cholerae, Proteus vulgaris, Zoogloea ramigera, Sphaerotilus natans, Haliscomenobacter hydrossis, Nostocoida limicola, Microthrix parvicella, Flexibacter, Microscilla and Nocardia may be present if the water is contaminated with faeces.

         Chennai one of the largest cities in India has two major rivers Cooum and Adyar connected by Buckingham Canal and has many lakes in and around Redhills, Poondi, Sholavaram, Chembarambakkam etc. Due to industrialization and urbanization almost all the freshwater bodies surrounding Chennai is polluted. Even the coast of the Chennai is also affected by the pollution carried by these rivers into the sea. Many studies have shown that the water around Chennai are affected by heavy metals, chemicals, organic and inorganic pollutants. Besides these there is also contamination due to sewage, household and commercial waste, and many more because of anthropogenic activity. Hence as a preliminary study, an attempt was made to determine the bacteriological quality of drinking water samples collected from North Chennai through random water sampling from various sources.

Materials and methods

         Water samples of 200ml from various sources such as sumps, borewells, metropipes, Water tanks and hand pumps were collected in sterile glass containers. Bacteriological examination was done by multiple tube fermentation tests using MacConkey’s broth to find the total or presumpive coliform count. Results of the test were expressed through most probable number (MPN) (Table 1) (Garg, 2003). The water samples (10 ml) from the bottles were aseptically transferred into three tubes containing 10 ml of double strength MacConkey’s broth and water samples (1 ml) into three tubes containing 10 ml of single strength MacConkey’s broth. Similarly, 0.1 ml of water sample was transferred into three tubes containing single strength MacConkey’s broth. All the tubes were incubated at 37°C for 48 hours and observed for colour change from red to yellow, indicator for the presence of pathogens and checked gas production which is considered as positive for the presence of fecal coliforms.

Table 1: Determination of most probable numbers by multiple tube test (Garg, 2003)

Results and Discussions

          The water samples for the test were inoculated and incubated in respective MacConkey broth tubes and looked for acid and gas production. The number of tubes with acid and gas production for each volume of water added i.e. 10 ml, 1 ml and 0.1 ml (each volume in 3 tubes) were noted and the results obtained were compared to the probability table (Table 1). Of the 10 water samples from different sources tested only three samples, one from hand pump and two from borewell, were showing MPN values < 3 implying that they were fit for consumption. The bore water is ground water that is accessed by drilling into the underground aquifers and pumped to the surface. These bore wells are confined or deep aquifers, which are usually covered by more than 20 meters of rock or clay which act as natural filter preventing microbial contamination. Similarly hand pumps are unconfined and shallow aquifers, which are not protected by thick layers of rock or clay as they are present closer to the surface and are susceptible to both chemical and microbiological contamination. Each sample of hand pump and bore water were recorded with MPN of 23 implying they were mildly contaminated by microorganisms. Similarly tank water filled with borewater from the same region had MPN value of 23. The microbial contamination in these regions may be due to the leachate of sewages and other contaminants.

          Three water samples were collected, two from metro water taps and one from metro water tank, for microbial quality testing. These are supplied from the water reserves around the city after proper treatments for drinking. The MPN values determined for the various samples are listed in Table 2. The microbial load was high such as MPN value of 240 for metro water collected from tap at East cemetery road, MPN of 1100 for water collected from somuchetty street and highest MPN index of > 1100 at metro water tank at MC road. The water tank constantly receives the treated water which is then transferred through taps to the public for drinking. The water tanks are not cleaned regularly and there is continuous supply of water to the tanks as the water is spent. Depending on the source of the water received each time’ the microbial load gets varied but it records the highest MPN value. Meanwhile in taps the scenario is almost same as the water which is stored in the tanks is distributed through them everyday hence the microbial load here also varies. The other possible ways to the get contamination is through break or leak of drinking water pipes, mixing of sewage into the source, waste dumped near water reservoirs, poor water sanitization procedures or improper maintenance of water bodies and supply systems etc.

         It is clear that 70% of the fresh water source is contaminated by microorganisms. The water supplied by the corporation is highly contaminated and it is the responsibility of the corporation board to provide safe drinking water to the community. There should be standards set for adequate chlorination and safe distribution of water from the storage point to the receiving end. The safety standards should be checked regularly and updated according to the needs of the situation to prevent outbreaks of enteric diseases. Use of non-corrosive pipelines; replacing broken pipelines at earliest, pluging the leakages etc. for avoiding contamination would ensure safe delivery of water. This preliminary study reveals that the water available to the public is of low quality and they should be educated about the spread of water borne diseases and its control measure through awareness programmes. Only a part of the city was covered for the study and extensive studies are required to do a complete assessment of bacteriological quality of water for the entire Chennai.

Table 2: MPN values of water samples collected

References

Anbazhagi, M., Loganathan, D., Tamilselvan, S., Jayabalou, R., Kamatchiammal, S. and Kumar, R. (2007). Cryptosporidium oocysts in drinking water supply of Chennai City, southern India. CLEAN–Soil, Air, Water 35(2): 167-171.

Bassani, D. G., Kumar, R., Awasthi, S., Morris, S. K. and Paul, V. K. (2010). Causes of neonatal and child mortality in India: a nationally representative mortality survey. The Lancet 376(9755): 1853-1860.

Garg, F. C., 2003. Experimental Microbiology, First ed. Satish Kumar Jain for CBS Publishers & Distributors, New Delhi.

Kumar, D., Malik, S., Madan, M., Pandey, A. and Asthana, A. K. (2013). Bacteriological analysis of drinking water by MPN method in a tertiary care hospital and adjoining area Western UP, India. J Environ Sci 4: 17-22.

Malathy, B. R., Sajeev, S. K., Thamphy, S., Guruvayurappan, K. and P, S. A. (2017). Bacteriological Analysis of Drinking Water by MPN Method from Chennai, India. Journal of Environment Science, Toxicology and Food Technology 11(7): 57-64.

Wright, J., Gundry, S. and Conroy, R. (2004). Household drinking water in developing countries: a systematic review of microbiological contamination between source and point‐of‐use. Tropical medicine & international health 9(1): 106-117.