This standard specifies the requirements for the design, materials, fabrication, and testing of settling tank (clarifier) equipment used in water treatment plants. It covers both circular and rectangular clarifiers, including their mechanical components like scraper mechanisms, drives, and launders.
Requirements for settling tank (clarifier equipment) for water treatment plant
Quick Reference Values
Typical Detention Period (Horizontal Flow)2 to 2.5 hours
Typical Surface Overflow Rate (Coagulation)20 to 40 m³/day/m²
Typical Weir Loading RateLess than 185 m³/day/m
Maximum Scraper Peripheral Speed3 m/min
Minimum Scraper Blade Thickness6 mm
Minimum Tank Bottom Slope8 percent (1 in 12)
Key Formulas
Surface Overflow Rate (SOR) = Flow Rate (Q) / Surface Area (A)
Detention Time (t) = Tank Volume (V) / Flow Rate (Q)
Practical Notes
Ensure precise coordination between civil (concrete tank) and mechanical (clarifier mechanism) drawings to avoid installation conflicts.
The selection of scraper drive torque is critical and must account for peak sludge loads to prevent stalling or failure.
Proper surface preparation and painting (as per Clause 8) are essential for the longevity of steel components in a corrosive environment.