Dearc Sandeep, As we know, ...

Dearc Sandeep,

As we know, tube settlers are a cost-effective solution for drinking water and wastewater plants to increase treatment capacity, reduce new installation footprints, improve effluent water quality, and decrease operating costs.

Tube settler coverage is the minimum required area tube settlers must cover to obtain the desired treatment. 

To calculate in English units, all we need to know is 

basin flow in MGD, overflow rate in gpm/ft2, and clarifier diameter in ft. 

(# MGD) / (# gpm/ft2) / (1440 min/day) = Minimum Required Area 

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 

You get some more design calculation details here: http://www.edaenv.ca/_mndata/edaltd/uploaded_files/tube_settler.pdf

Or at Brentwood website - http://www.brentwoodindustries.com/resources/learning-center/water-wastewater/tube-settler-coverage-in-a-circular-clarifier/ 

Hope this info is useful, else you are suggested to POST an Question with more details.