This paper presents the results of tests of fabric filter wet scrubber and electrostatic precipitator wet scrubber environmental control configurations from the EPRI 2.5 MW (e) Integrated Environmental Control Pilot Plant (IECPP). Higher particulate penetration from the ESP limited SO2 removal by restricting the pH control point; this occurred when the limestone scrubber was operated under closed loop water management conditions. The presence of aluminum and fluoride was identified as the cause of these operating problems. The aluminum is probably leached from the ash; fluoride is scrubbed from the flue gas. These control and removal problems could be avoided by (1) operating under open loop water management, (2) using lime rather than limestone or (3) reducing particulate penetration to the scrubber.