Which process is primarily used to achieve biological treatment in wastewater?

Biological treatment in wastewater primarily relies on the process of aeration. This method enhances the activity of microorganisms that naturally occur in wastewater, allowing them to break down organic matter and pollutants. During aeration, air is introduced into the wastewater, which provides the oxygen necessary for aerobic bacteria to thrive. These bacteria metabolize organic compounds, converting them into carbon dioxide, water, and biomass, effectively reducing the concentration of harmful substances in the wastewater.

Aeration can take various forms, including activated sludge systems, extended aeration, and trickling filters. Each of these designs optimizes the conditions for microbial growth and activity, leading to efficient treatment of wastewater.

Other processes mentioned have different primary functions. For instance, filtration is typically used to remove solids and particulates from water but does not contribute to the biological degradation of pollutants. Sedimentation is a physical separation process where solids settle out of the liquid but does not intrinsically treat the wastewater biologically. Chlorination is mainly a disinfection method used after biological treatment to kill remaining pathogens in the effluent, but it does not contribute to breaking down organic matter. Therefore, aeration stands out as the correct choice for achieving biological treatment in wastewater.