A Sewage Treatment Plant (STP) is designed to treat domestic and municipal wastewater to make it safe for reuse or discharge into the environment. The treatment process involves three major stages — Primary, Secondary, and Tertiary.

 Process Overview

• Primary Treatment:
  The sewage is held in a settling tank, allowing heavy solids to settle at the bottom while oil, grease, and lighter materials float to the top. These are removed for further processing.

• Secondary Treatment:
  The remaining liquid undergoes biological treatment, where microorganisms break down dissolved and suspended organic impurities.

• Tertiary Treatment:
  The treated water is chemically or physically disinfected (using chlorine or UV systems) to eliminate pathogens before being discharged or reused for gardening, flushing, or industrial purposes.