Dear Aruna, I worked out my ...

Dear Aruna,

I worked out my own program that works very well. The theory behind it is the following:

- The flow of water along the lamellas has to be laminar, and I suggest a prudent Re number of less than 500. According to the profile of velocity in laminar flow, the velocity of the water is zero at the Surface of the lamellas. Hence the upflowing water is not sustaining the solids deposited on the Surface of the lamellas and the solids can slip downwards by gravity.

- The velocity of sedimentation of the solid particles is a function of the solid density and of the particle sizes. Normally the density of the solids is assumed 2,2 (sand). The particles size can be either analyzed or referred to statistics applicable for simila water. A typical statistic data is that 90% weight is of particles sized more than 30 microns.  The velocity can be calculated with the Stokes law (easy found in Internet)

-  The hold-up time inside the lamellas packing should be long enough the ensure that the particles (example larger than 30 microns) have time sufficient to sink from any part of water inside two lamellas down to the lamellas underneath, according to the calculated velocity

Please write to me privately to get a copy of my program