Aeration performance of immersed hollow-fiber membranes in a bentonite suspension

This paper discusses the aeration aspect of an ultrafiltration application involving immersed membranes creating an airlift pattern. The continuous aeration commonly used with immersed membranes to mitigate the effects of fouling was compared with several new aeration configurations. These new aeration configurations changed the local aeration intensity and aerated sequentially in different locations under hollow-fiber modules. The relative performances of each new aeration arrangement were evaluated against the continuous aeration in transient mode with a bentonite suspension.

New aeration methods were tested where the air is injected sequentially in different locations instead of being injected continuously. Alternating the injection of the air in different zones around the fiber bundles proved highly beneficial for the overall system performance. It is possible to significantly slow down the fouling kinetics using a cyclic aeration method in place of a continuous aeration mode. Improvements are function of the cycling frequency and the type of cycling put in place. The oscillating cassette has a very slight advantage over the inside-outside cycling. However, it seems much more attractive to use inside-outside cycling which is mechanically much simpler. By implementing an air cycling method, it is now possible to make more efficient use of the air to mitigate fouling and further reduce life- cycle costs. Immersed membranes like ZeeWeed® have been proven to produce higher quality effluents and to be an economical alternative to conventional treatments. Two air cycling methods have been tested that further increase their potential and confirm the connection between aeration conditions and performance.