Tube settler coverage is the minimum required area tube settlers must cover to obtain the desired treatment. By nature of the shape, the calculations for circular clarifiers are a bit more complicated. However, the variables in the equation are standard measurements. To calculate in English units, all you need to know is basin flow in MGD, overflow rate in gpm/ft2, and clarifier diameter in ft.
Tank Diameter / 2 = Clarifier Radius
Pi * R2 = Clarifier AreaClarifier Area – Minimum Required Area = Uncovered Area
SqRt(Uncovered Area/Pi) = Uncovered RadiusClarifier Radius – Uncovered Radius = Tube Settler Coverage
Tube settler coverage is the width of the ring of tube settlers around the outer edge of the clarifier. We were recently asked to calculate the coverage for a customer. Here is the example:
6 MGD Basin Flow
2 gpm/ft2 Overflow Rate
103.5-ft Clarifier Diameter
(6 MGD) / (2 gpm/ft2) / (1440 min/day) = 2083.3 ft2 Minimum Required Area
(103.5 ft) / 2 = 51.75 ft Clarifier Radius
Pi * (51.75 ft)2 = 8,413.4 ft2 Clarifier Area
(8,413.4 ft2) – (2,083.3 ft2) = 6,330.1 ft2 Uncovered Area
SqRt[(6,330.1 ft2) / Pi] = 44.9 ft Uncovered Radius
(51.75 ft) – (44.9 ft) = 6.85 ft Tube Settler Coverage > Round up to 7 ft
This meets the Minimum Required Area as the 7-ft ring of tube settlers has a coverage area of 2,122.1 ft2.