Coffee Roaster Odor Removal

Have problem with the coffee odor coming out of the roaster exhaust. Previous managers installed a wet scrubber using zeolite as adsorping medium. Plain water is being used to scrub and recirculated. For two months, the odor seem controlled, but it's back again. Need suggestions to improve. Air flow is 6000 cfm; packed tower diameter is 3.1 meters; zeolite height inside is 2 meters with size of 6" irregular shapes at the bottom and smaller sizes at the top.

Have you tried adding a little caustic to your water? If your zeolite can handle the high pH, this should help with the odor. Also, you may be able to try activated carbon. In some cases (as in crushed coconut shells) the material cost can be downright negligible.