Water Analysis : To determine the potability of water by MPN Test

AIM : To determine the potability of water by MPN Test

INTRODUCTION:

Water which receives animally & human which form a primary source of water borne disease. Direct testing procedures capable of detecting & quantifying the full spectrum of pathogens & identifying their source is time consuming process because of their variable occurrence, survival rate & origin; hence an indicator system has been identified as a best method for evaluating the microbiological quality of water.

A fecal coli form test is considered as most reliable test available for detesting  the presence of contamination of an intesting origin, the coli form group comprises all aerobic & facuttative an aerobic, gram –ve  non spirulating, rod shaped bacteria that ferment lactase with gas format within 48hrs at 35 ˚c.

REQUIREMENTS:

1. Single strength of sactose bile growth (10 ml) -10 test tube
2. Double strength of sactase bile growth (10 ml) - 5 test tube
3. Water sample
4. Sterile pipettes  
5. Mac Cankey broth

PROCEDURE:
 

-      Distribute 10ml single strength lactase broth each to test tubes.

-      Add 10ml of double strength lactase broth in each of test tubes.

-      Introduce the Durhalm’s wial in all test tubes & sterilize them at 121˚c for 15 min.

-      Inoculate 10ml of water sample to all double strength lactose broth tubes.(DSLB)

-      Inoculate 1ml water sample to each of 5 SSLB tubes & 0.1ml of water sample to remaining 5 SSLB tubes.

-        Incubate all the tubes at 37˚c for 24hrs.

-       If gas is formed in 24hrs indicate +ve test. If no gas is formed in 24 hrs, incubate for next 24 hrs. If no gas is formed even after 48 hrs of incubation test is –ve.

-        Count the no. of +ve tubes in each dilution.

-        Determine the MPN by Mc Cardy’s table.