Help Needed: Concentrations from Flow

[BradyD]

Hi All -

I hope this is posted in the correct place. I'm in the midst of studying for the PE, but there's one problem on the NCEES practice exam that I can't quite wrap my head around. I'm going to truncate it for fear of reprisal from NCEES. You are given 20,000 gpd of sludge flow, with 2% solids and 75% volatile. They somehow get 20,000 mg/L as the solids concentration out of the flow rate and solids percentage. Could anybody explain this leap in logic to me? It must be simple and I'm overthinking it, but I'm having trouble getting there.

Thanks!

 

[Compositepro]

Oh, that is funny. 2% is the same thing as 20,000 mg/L. I did have to think about it for a second, and that is what made it funny.

 

[ashtree]

Just to explain it better.

1% is equal to 1 part in 100. So 2% is two parts in 100. A litre of water weighs 1000000 milligrams. If you divide a million milligrams by 100 to get it into percentage terms you get 10000. So 1% is 10000 mg/l and 2% is 20000 mg/l. Hope this helps with the understanding.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[BradyD]

Thank you, that's a huge help!