Chris.
I need to corrrect myself a bit in my previous post. I did a bit more research. GAC works by adsorption (not absorption) as well as does GFO. GAC is highly porous, whereas GFO is not. Adsorption (phosophate binding) by GFO takes place on the surface, and adsorption by GAC takes place on the surface and also inside the pores of the GAC.
The reason you want flow thru with GAC is you need to be able to force flow thru the GAC so the inside the pores of the GAC are able to adsorb the organics, whereas the fluidised state of the GFO maximizes surface contact with phosphate for surface binding.
Dave
