Scum Pumping Hydraulics

[Aguatanta]

I'm designing a secondary clarifier scum pumping system. We're looking at submersible choppers, so a reasonably good estimate of headloss is important.

I have a good understanding of sludge pumping but cannot find much info on scum pumping. I've looked through M&E and Sanks and have found no guidance on scum pumping, specifically an estimate of % solids. My plan is to develop system curves assuming lowest TDH as if pumping water and highest TDH as if pumping liquid with 10% solids.

Any advice on this?

 

[stanier]

Use a progressive cavity pump and then fluid properties will have a lower impact. Use a slow running model (larger size) so it doesnt fail and cost a fortune in spares. Motor should be large enough to start a fluid with a high yield stress or has plugged.

If you need to macerate before the pump then this could be a separate unit. It owuld also tend to emulsify the oils and fats.