Which treatment step in wastewater processing follows Preliminary Treatment?

The correct answer is Primary Treatment. In the wastewater treatment process, Preliminary Treatment is the first step, designed to remove large solids and debris from the wastewater, such as sticks, stones, and other materials that could damage equipment or hinder subsequent processes.

After this initial stage, the next step is Primary Treatment, which focuses on the physical separation of solids from the liquid wastewater. This step typically involves settling tanks or clarifiers where the heavier solids can settle to the bottom, forming sludge, while the lighter materials, including oils and greases, float to the top and are skimmed off. The goal of Primary Treatment is to reduce the overall organic load and suspended solids in the wastewater before it moves on to Secondary Treatment, where biological processes further reduce contaminants.

In contrast, Secondary Treatment involves biological processes to further break down organic matter, Tertiary Treatment refers to advanced treatment processes after Secondary Treatment aimed at achieving higher quality effluent, and Chlorination is a disinfection step typically performed to eliminate pathogens from treated wastewater before its discharge or reuse. Thus, the sequence and purpose of each step in wastewater treatment are essential for understanding how treated water is prepared for safe discharge into the environment.