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Clogged filter press cloths

Q: In our plastics reclaiming plant, we use high density salt water solutions to separate plastic by specific gravity. These solutions have higher viscosities than water. Some "dirt" always comes in with the plastic feedstock and ends up contaminating the fluids. We are concentrating the dirt in a clarifier (with polymer flocculant) and then filtering the clarifier bottoms to recover the fluid. The problem occurs when the recessed plate type filter press cloths tend to "slime" causing high delta P, low flow rates and wet cakes. We have tried adding diatomaceous earth, lime and perlite as "body feed" to improve permeability with limited success. Do you have any suggestions?

A: Here are my suggestions:

1. Try another more forgiving cloth.
2. Use an initial precoat to condition the cloths prior to filtration.
3. Control the polymer dose so it doesn't overdose and cause sliminess. Maybe even switch to a different polymer.
4. Try using rice hull ash filter aid.
5. Switch press to membrane plates.