Fouling is the most significant problem encountered with the use of membranes in many liquid separation processes such as water treatment. The I/UCRC for Membrane Applied Science and Technology at the University of Colorado (EEC-0120725) adapted ultrasonic time-domain reflectometry (UTDR) as an analytical tool to monitor noninvasively the condition of membrane modules during operation. UTDR provides real-time information about membrane fouling and the progress of the subsequent cleaning process. This technique minimizes the use of chemical cleaning agents and enables the modules to be placed back on-line as quickly as possible. A U.S. patent has been issued for this technology, and the development of a commercial version of the fouling and cleaning meter is in progress.