EMB ERJ 135 ER/LR
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Aircraft Equipment Problem Less Severe
Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
When conducting an ice system test in flight the test performed normally until we turned the system off. When turning the system off we the flight crew noticed a 'boom' sound; however didn't receive any ICAS notification or any other signs of abnormalities. The Flight Attendant called us to ask if we hear the same thing but she also reported the sound of a 'grinding noise.' She stated a passenger also told her they heard something abnormal and asked the Flight Attendant what it was. After getting this information I decided it was best to return to the airport of departure. We told ATC we needed to return to the airport. We landed safely and upon further inspection MX did state to us there was a broken bleed line that was causing all the noise and the initial boom.
On departure; the PIC and I initiated the ice detection test per the checklist and first flight of the day. We heard a boom noise as if somebody had dropped a case of water in the cabin. The flight attendant called us directly after and informed us of a loud grinding noise coming from underneath the floor of the aircraft. The PIC and I elected to return to [departure airport] where ample maintenance was present; and we were only on the departure. We returned safely with no further issues.
EMB-135 flight crew reported returning to departure airport after experiencing an anomaly in the anti-ice system.