What is pH

Water supplied to communities should be of acceptable level in terms of quality. Water quality can be assessed by the use of the water quality index (WQI). The use of indices is crucial in this era where water quality issues have raised health as well as legal concerns, both at local, national, and international levels. Water samples have to be collected, tested, and values for water quality index determined. It was initially proposed by Horton in 1965. There are several ways to calculate WQI, and this chapter gives formulae for different methods. Water quality indices differ from country to country. Some indices use three, six parameters, or even more than six parameters. Earlier methods to calculate the water quality indices did not capture microbial parameters, hence the reason for various methods. A recent method of calculating a WQI is based on fuzzy logic. Therefore, this chapter looks at the methods from all continents.