Micro-bubbles enhanced breakage warning for hollow fiber membrane integrity with a low-cost real-time monitoring device.

A low-cost device was developed to monitor the integrity of hollow fiber membrane by real-time online detecting and measuring air bubbles in the permeate flow. When a breakage occurs in the fiber membrane system, air bubbles will find their ways to enter the permeate flow. The monitoring device consists of two pairs of platinum probes attached to a pipe, along which the permeate flows. Membrane's breakage was identified by the voltage changes between the two pairs of probes when air bubbles in the permeate touch them. There was no addition of any other chemicals or materials into the system that would jeopardize final products of the membrane process. Experimental results showed that the voltage signal changes before and after a breach of membrane were obvious in the normal operation conditions. The smallest diameter of the bubbles that can be detected by the monitoring device was 50 μm, which was captured and identified with a high-speed camera. Furthermore, the sensitivity of device with two pairs of probes improved by 5~9% over that with one pair of probes. Finally, cost of the proposed device was roughly estimated only about 70 US dollars and the detection result was highly consistent with that obtained with the prevailing particle counters of several thousand US dollars.