Storage of Backwash Water: During the backwash process, the filtration media is cleaned by reversing the flow of water. This process generates a large volume of backwash water containing suspended solids and impurities. The retention tank serves as a temporary storage reservoir for this backwash water.
Flow Equalization: After the backwash cycle, the system may experience an increased flow rate. The retention tank helps to dampen these flow fluctuations by acting as a buffer, ensuring a steady flow rate to the downstream treatment processes.
Sedimentation: As the backwash water is held in the retention tank, the suspended solids present in the water have time to settle. This allows for the removal of heavy particles by gravity settling before the water is discharged or recycled.
Chemical Addition: In some cases, the retention tank may be used as a point for chemical addition. Chemicals such as coagulants or flocculants can be introduced into the backwash water to enhance the removal of contaminants during the sedimentation process.
Sludge Accumulation and Removal: The settled solids and sludge generated during the backwash process accumulate at the bottom of the retention tank. This sludge can be periodically removed and disposed of appropriately, preventing it from entering the downstream treatment processes.
By performing these functions, the retention tank plays an important role in ensuring efficient filtration system operation, protecting downstream equipment, and improving overall water quality.