There are different types of water treatments. These are as follows: (1) Sewage treatment processes: it includes single dwelling unit treatment processes (2) Municipal treatment processes: municipal sewage treatment systems carry out various steps involved. These steps are, namely, primary ( or mechanical ) treatment, secondary ( or biological ) treatment, and tertiary ( or final ) treatment.
As we know that the water generally gets contaminated with pathogenic microorganisms through intestinal discharges of man and animals (i.e., faecal contamination) and becomes an important source of water-borne diseases. It is, therefore, important that the water must be regularly analyzed to determine whether it is potable or polluted with faecal matter. Certain bacteria particularly Escherichia coli and related organisms called 'coliforms', faecal Streptococci (e.g., Streptococcus faecalis) and Clostridium perfringens normally inhabit the large intestine of humans and other animals and are frequently present in their faeces.