Wastewater Treatment Plants

Photograph: A wastewater sedimentation tank

The aim of wastewater treatment is to discharge treated wastewater with minimal impact on the receiving watercourse (which will naturally have some turbidity and bacteriological activity). There are varying ways to achieve this, but normally the process is by screening out large particles before sedimentation and biological treatment. Sedimentation is very similar to the process at a water treatment works, where the wastewater flows through a tank slowly enough for solids to settle to the bottom as sludge. The effluent from this process goes through an oxidation stage (using filter beds or activated sludge in the presence of oxygen), where bacteria oxidize the organic matter. A final tertiary sedimentation process will remove the solids created during the biological process.