Gravity Sludge Thickener Sizing Calculator
Size municipal and industrial gravity sludge thickeners: calculate required tank surface area, circular diameter, solids flux loading (lb/ft²·day), and thickened underflow volume.
Sludge Feed Flow & Solids Concentration
Design Loading Criteria
Thickener Tank Sizing & Underflow Rate
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
What is the difference between solids flux loading and hydraulic overflow rate?
Solids loading rate (SLR, in lb/ft²·day or kg/m²·d) governs the area required to concentrate solids in the thickening zone at the tank bottom. Hydraulic overflow rate (HLR, in GPD/ft² or m/h) governs the clarification zone to ensure liquid velocities do not wash unsettled floc over the effluent weirs.
Why does Waste Activated Sludge (WAS) have a lower solids loading rate than primary sludge?
Waste activated sludge consists of low-density, highly hydrated biological flocs with poor settling characteristics. It typically tolerates solids loading rates of only 6 to 10 lb/ft²·day, compared to 20 to 30 lb/ft²·day for dense, fibrous primary sludge.
How does excessive retention time harm a gravity thickener?
If sludge remains in the thickener blanket too long (>24 hours), anaerobic bacteria decompose organic matter, generating methane and carbon dioxide gas bubbles. These bubbles attach to sludge flocs, causing them to float to the surface as unsightly scum that fouls effluent weirs.