In a clarifier, what will be collected if passages connecting stages are near the bottom?

In a clarifier, the design and placement of the connecting passages are crucial for effective separation of materials. When passages connecting the stages are positioned near the bottom, they facilitate the collection of lighter materials that tend to float, such as oil and other floatables.

This is due to the natural buoyancy of these substances, allowing them to rise to the surface of the clarifier. As the flow passes through these lower passages, the system can effectively capture and remove oil, grease, and other less dense contaminants that could otherwise interfere with the clarification process.

In contrast, other materials such as heavy solids are typically collected by mechanisms designed to trap them at the bottom of the clarifier, while wastewater flows through the system. Large debris is usually larger than what would escape from upper passages and would typically be removed prior to entering the clarifier stage. Hence, the positioning of these passages plays a significant role in what materials are collected, favoring the removal of floatable substances.