That's a bit of an unknown. I've never heard of any mines...

That's a bit of an unknown. I've never heard of any mines putting their tailings through a filter press before but I'm sure that it does happen - its obviously a big filter press though. Too many unknowns at the moment to even take a guess - its not performing as expected but we don't know really in which way - not extracting enough of the water? If not why not - pressure problem, problem with the material, too much water? material caking the filters and refusing to unstick? They haven't really told us much about whatever the problem is.