The water or liquid carried waste from an industrial process. These wastes may result from any process or activity of industry, manufacture, trade or business. The wastewater from industries varies so greatly in both flow and pollutional strength. So, it is impossible to assign fixed values to their constituents. In general, industrial wastewater may contain suspended, colloidal and dissolved (mineral and organic) solids. In addition, they may be either excessively acid or alkaline and may contain high or low concentrations of colored matter. These wastes may contain inert, organic or toxic materials and possibly pathogenic bacteria. It may be necessary to treat the wastes prior to release to the municipal system or it is necessary to a fully treatment when the wastes will be discharged directly to surface or ground waters.
The major aim of wastewater treatment is to remove as much of the suspended solids as possible before the remaining water, called effluent, is discharged back to the environment. As solid material decays, it uses up oxygen, which is needed by the plants and animals living in the water.
The main aim of the treatment is to reduce the contaminants to acceptable levels to make the water safe for discharge back into the environment and which can be used for secondary purpose.