Results with the EPRI 2.5 MW (e) Integrated Environmental Control Pilot Plant (IECPP) compare the influence of particulate penetration on scrubber waste production and properties. Tests compared a fabric filter/wet scrubber and ESP/wet scrubber, the latter operated to simulate 1979 NSPS, 1971 NSPS, and pre-NSPS units. Tests were conducted with low sulfur coal at 400 ppm; flue gas spiking could be used to increase SO2 to 2000 ppm. Scrubber waste was dewatered in a thickener and vacuum belt filter (to 55% solids content), and fixed with fly ash.