Aluminum, the main ingreidient in Alum, dissolves in water with a PH below 6.0 and can be toxic. Yes, I would add the Hydrated lime to precipitate the aluminum out of the water column.

If you still have suspended clay in the water, the water will begin to cloud again rather quickly. Alum is a GCS (generally considered safe) chemical except again, when the water PH is below 6.0.

I would guess that you will need an additional 100-150# more Alum to get all the clay out. As I said in another post, the goal should be to remove ALL the suspended clay. The clarity or visibility in your water should be 18-30 inches, but due to zooplankton and phytoplankton....NEVER from clay.

EDIT:
How are you applying the Alum?

Last edited by Rainman; 10/09/10 08:15 PM.