WORCESTER — UMass ­Memorial Medical Center is canceling numerous surgeries at its Memorial Campus and shifting others to its University Campus after tests revealed contaminants in the hospital’s water lines and sterilization equipment, according to internal documents obtained by the Telegram & Gazette.

The sediment particles found in some water supply lines and equipment used to sterilize surgical instruments are thought to be the result of a major city water main break in mid-November that forced water service to be shut off to the entire city for about 12 hours.