Five different samples of water from Local Ganga River is collected and the microbial counts were compared with five samples of commercially available water according to IS 14543 to show whether the river water is fit for drinking or not.
Sample water 1-Local Ganga water.
Sample water2-Commercial water
2.5 litres of Ganga water was collected in a sterile container and was filtered through membrane filters and was further tested for the presence of the fourteen parameters for the testing of purity of package drinking water according to IS 14543.Same 2.5 litres of commercial water was made to undergo the same process for the comparative analysis.
Location of Sample 1- Local Ganga Water, Kolkata.
Location of Sample 2 – Kolkata.
Coliforms are found to be present per 250 ml of Ganga water when the filtered paper was allowed to stand on Lactose TTC agar plates by the presence of yellow colonies. The colonies were further transferred into a tryptone soy agar plate. The colonies showed oxidase positive test and also showed positive indole test in tryptophan broth. Further, gram staining showed the presence of gram negative rods showing the presence of E.coli whereas the plate showed no presence of colonies for the commercial water analysis.
Faecal Streptococci showed no presence when the filtered paper (from sample 1) was kept on Ethyl Violet Dextrose Agar (No dark red colonies even after 48 hrs incubation). They showed characteristic pink colonies on Mac Conkey agar (Incubated for 24 hrs). The plate remained clear for sample 2.
When 50 ml of sample water 1 was aseptically transferred to Differential Reinforced Clostridial medium (incubated for 44 hrs at 37 degrees), blackening due to reduction of sulphite and precipitation of FeS was seen which showed the presence of Sulphur Reducing Anaerobes. The tube remained clear for sample 2.
250 ml of sample water 1 was filtered 0.47 nm filter paper and transferred to 20 ml of Aspergine Proline Broth and incubated at 37 degrees for 48 hrs. There was presence of turbidity showing the presence of Pseudomonas aeruginosa after 44 hrs and then again inoculated to milk agar. They showed characteristic milk white colonies after 24 hrs incubation. The particular strain showed no florescence under UV light. The tube remained clear for sample 2.
250 ml of sample water 1 was filtered and the paper was transferred to 20 ml of salt medium and the conditions were made anaerobic using sterile paraffin oil. After overnight incubation, they were inoculated into Baird Parker medium where they showed greyish black colonies surrounded by a halozone and Nutrient agar where there were no characteristic colonies. Further Gram staining showed the presence of Gram positive cocci in grape like clusters confirming the presence of Staphylococcus aureus. But the strain did not show any coagulase activity. The tube containing salt medium remained clear for sample 2.
Another 250 ml of sample 1 and 2 passed filter paper was transferred to Yeast extract Dextrose Chloramphenicol Gentamycin agar medium plate. After 24 hrs, there was presence of yeast colonies and after 48 hrs, mould started appearing. The plate remained clear for sample 2.
Aerobic Microbial Count was also performed by using 1 ml of each sample 1 and 2 in 15 ml of plate count agar and the plates were maintained at two different temperatures, at 22 degrees and 37 degrees. The count was 170 CFU/ml for the plate maintained at 37 degrees (incubated for 24 hrs) and 248 CFU/ml for the plate maintained at 22 degrees (incubated for 72 hrs).
Another 250 ml of sample (1 and 2) passed filter paper was transferred to alkaline peptone water which showed turbidity on 24 hrs incubation. They were inoculated in a Thiosulphate citrate bile salt sucrose agar (TCBS) and Bile salt agar and incubated for 24 hrs for further confirmation. The TCBS plate shows yellow colonies and Bile salt agar shows characteristic colonies. For further confirmation the colonies show Gram negative character, motile, catalase and oxidase positive. They show yellow coloration in the Hugh-Leifson’s media and Negative TSI test. This confirms the presence of Vibrio cholera. The tube containing alkaline peptone water remained clear for sample 2.
Another 250 ml of sample (1 and 2) passed filter paper was transferred to Glucose salt Teepol broth which showed turbidity on 24 hrs incubation. They were inoculated in a Thiosulphate citrate bile salt sucrose agar (TCBS) and incubated for 24 hrs for further confirmation. The TCBS plate shows Round colonies with green/blue centres. For further confirmation the colonies show Gram negative character, motile, catalase and oxidase positive. They show yellow coloration in the Hugh-Leifson’s media and Negative TSI test. The culture shows negative VP test and growth in tryptone with 2% , 8% and 10% NaCl. This confirms the presence of Vibrio parahaemolyticus. The tube containing Glucose salt Teepol broth remained clear for sample 2.
Another 250 ml of sample (1 and 2) passed filter was transferred to Buffered Peptone water which showed turbidity after 24 hrs. They were transferred to Malachite green magnesium chloride medium and selenite cysteine medium which again shows turbidity. They were transferred to Brilliant green phenol red lactose agar (BGPRL) and Xylose lysine deoxycholate agar (XLDA). The BGPRL plate shows pink colonies and XLDA plate shows black colonies. The colonies show positive TSI test with the butt and slant turned black and negative urea sugar test. This confirmed the presence of Salmonella. The tube containing Glucose salt Teepol broth remained clear for sample 2.
There was no presence of colonies in Deoxycholate citrate agar. So there was no presence of Shigella per 250 ml of sample water (1 and 2).
Hence, local Ganga water in Kolkata is immensely polluted with several kinds of pathogens which is harmful to human health. E.coli might cause stomach upset. V. cholera causes cholera. The enterococci and many fecal Streptococci are normal flora of the gastrointestinal tract, where they are present at high concentrations. However, they can sometimes spread from the gastrointestinal tract and cause frank disease. Candidiasis is a fungal infection caused by yeasts that belong to the genus Candida. Pseudomonas aeruginosa infect damaged tissues or those with reduced immunity. The symptoms of such infections are generalized inflammation and sepsis. If such colonization occurs in critical body organs, such as the lungs, the urinary tract, and kidneys, the results can be fatal. Salmonella can cause typhoid. So Ganga water should be treated and purified before consumption.
Where the commercial packaged drinking water selected locally from various locations is found to be safe for human consumption.
Contributed by: Mr. Dipan Roy, Tech-in charge, Biological Division.