Question 9 of 19: Purposes of Equalization for Industrial Wastewater Treatment

Question 9: Purposes of Equalization for Industrial Wastewater Treatment (6 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

An equalization basin blends and stores flow ahead of treatment, and six basic purposes justify including one. (1) Hydraulic equalization — dampens flow-rate peaks so downstream unit processes can be sized for a steady average flow rather than a large instantaneous peak. (2) Load (concentration) equalization — smooths out swings in BOD/COD/SS concentration so a biological process sees a steadier, more treatable feed rather than alternating feast-and-famine conditions. (3) pH neutralization/buffering — blending an acidic batch discharge with an alkaline one (or with a steadier background flow) reduces or eliminates the chemical dosing that would otherwise be needed to neutralize each batch individually. (4) Shock-load / toxic-slug protection — dilutes an accidental or process-upset discharge of a toxic or high-strength batch before it reaches and potentially kills a biological treatment population. (5) Improved chemical dosing control — a steadier flow and load allow coagulant, neutralization or nutrient-addition chemical feed rates to be set and controlled far more precisely than against a constantly swinging raw waste stream. (6) Operational flexibility — provides storage volume to absorb a production shutdown, a batch dump timed outside normal operating hours, or planned downstream maintenance, so the treatment plant can be fed on its own schedule rather than the production line's.