The NSFWQI, being used since long for the development
of standards, testing of products and certification services
in the area of public health, safety and protection of
the environment, calculates mathematically a single value
from the weightage computed for various parameters. The
index is rated from 0 to 100 to rate the water quality with
100 being the highest possible score representing excellent
water quality and 0 – 25 as the bad quality. Table 2
gives the index rating for different water quality classes