Technology International Incorporated 0f Virginia
US Navy

Ultrasonic Cleaning Of Membranes: Low-Energy Non-Invasive Method for Membrane Cleaning (Membrane Universal Ultrasonic Cleaning (MU2C))

Topic: N94-212; Low-Energy Non-Invasive Methods for Membrane Cleanin; August 4, 1995 through March 31, 1996

Contract: N61533-95-C-0098 Annapolis Detachment, Carderock Division; Naval Surface Warfare Center, Annapolis, MD 21402-5067

Mr. Frank Halsall

PI: Dr. Ali M. El-Nashar          

Project Team: Shane P. Babin, Dr. Jerry E. Lundstrom, and Abdo A. Husseiny

Publications

Ali M. El-Nashar, Shane P. Babin, Jerry E. Lundstrom, and Abdo A. Husseiny (March 1996). Ultrasonic Cleaning Of Membranes: Low-Energy Non-Invasive Method for Membrane Cleaning. Technology International Incorporated of Virginia Report TILA-NAV941-21201-96-3001; Contract # N61533-95-C-0098; Annapolis Detachment, Carderock Division, Naval Surface Warfare Center; Annapolis, MD

ABSTRACT

This Final Report addresses the outcome of the Phase I efforts, which involved investigation of the mechanisms of membrane fouling in wastewater applications; investigation of viable concepts to continually, and in a non-invasive manner, clean the membrane surface during processing; development of the ultrasonic technique; and planning for demonstration of the low energy non-invasive ultrasonic method for membrane cleaning on a bench-scale membrane-based wastewater treatment process.

A proof-of-concept (POC) test rig of the ultrasonic cleaning mechanism was designed and implemented for feasibility evaluation of the approach.  The test assembly was constructed by placing an ultrasonic probe on the feed side of a hollow fiber membrane module, near to the cross-flow outlet.  The membrane effective surface area is @ 1.8 m2 and the fibers are 200µm internal diameter and 40µm wall thickness.  Several experimental runs were made, in the POC test  on different water and wastewater streams, including navy graywater specifications composite mix of ship waste stream consisting of food service (galley), laundry, and washroom waste, which can be reproduced  in the laboratory.  Test runs were conducted first without the use of the ultrasonic cleaning device.  The test runs were repeated using the ultrasonic assembly.  The results of the POC tests showed that the most effective cleaning takes place in the portion of the module facing the ultrasonic probe throughout the test.  Based on these results, a bench-scale membrane-based wastewater treatment process will be rigged with the ultrasonic cleaning mechanism and proper redesign and modifications of the membrane modules will be made to demonstrate the capability of the low energy, non-invasive ultrasonic method for membrane cleaning and to prepare for transition to the Navy's Advanced Development Program.

Proper placement of multiple ultrasonic transducers to cover the whole volume of the membrane module, near the retentate outlet, with the emitted ultrasonic waves would deliver the desired cleaning to all the fibers exposed to the ultrasonic waves.  The results of the analysis of the test data demonstrated that the ultrasonic method has the potential of maintaining near initial membrane flux during the lifecycle of the process, and subsequently would decrease the size of a treatment system as a result of increased production per square foot of membrane surface area.

The ultrasonic cleaning of membranes will provide vast benefits to the numerous installations using membrane separation in the wastewater treatment, biomedical, and chemical industries as well as to wastewater/rawwater installations and skid-mounted units on commercial and Naval ships, on military bases; or on mobile platforms in the battlefield.  A substantial reduction in the life cycle cost can be achieved by savings in chemical and mechanical cleaning, reduction of the size of the pretreatment process, and enhancement of the productivity and efficiency of the membrane process.