Understanding Plain Sedimentation in Wastewater Treatment

Plain sedimentation is a physical process commonly used as a primary treatment step in wastewater treatment plants. Its main purpose is to remove settleable solids from the wastewater by gravity.

How Plain Sedimentation Affects Bacterial Load

While the primary goal of plain sedimentation is suspended solids removal, it also effectively removes a significant portion of the bacterial load. This is because a large number of bacteria in wastewater are attached to or associated with the suspended solid particles. When these particles settle down in the sedimentation tank, the bacteria attached to them are also removed.

The efficiency of bacterial removal through plain sedimentation depends on several factors, including:

• The nature and concentration of suspended solids.
• The settling characteristics of the solids.
• The design and operational efficiency of the sedimentation tank (detention time, flow velocity, etc.).

Percentage of Bacterial Load Removal by Plain Sedimentation

Studies and practical observations in wastewater treatment indicate that plain sedimentation can remove a considerable percentage of bacteria. While it doesn't remove all bacteria (as some are free-floating or dissolved), it significantly reduces the load.

Based on typical performance data for well-operated plain sedimentation tanks, the percentage of bacterial load removed is often cited as approximately 75%.

This removal efficiency is crucial because reducing the initial bacterial load makes subsequent treatment processes, such as biological treatment and disinfection, more effective and less resource-intensive.

Therefore, plain sedimentation plays an important role in reducing both suspended solids and associated bacterial contamination in wastewater before it undergoes further purification steps.