What is secondary treatment in wastewater treatment?

Secondary treatment refers to the biological processes used to remove dissolved and suspended organic matter from wastewater. During this stage, microorganisms, such as bacteria, decompose organic pollutants present in the water. This process is essential because it significantly reduces the biochemical oxygen demand (BOD) and helps to improve the quality of the effluent before it is discharged or further treated.

The biological aspect of secondary treatment typically involves aeration tanks where air is pumped into the wastewater to encourage the growth of aerobic bacteria. These bacteria consume the organic pollutants, turning them into biomass (bacterial matter) and reducing the amount of harmful substances in the water. After this treatment, various methods, such as settling tanks, are used to separate the biomass from the treated water.

This biological focus distinguishes secondary treatment from other methods utilized in wastewater treatment, highlighting its key role in providing a natural way to treat and clean wastewater effectively.