Improvement of the resolution in direct membrane integrity test by controlling solution surface tension

Membrane-based treatment technologies have been introduced as a promising tool for the removal of water-borne pathogens. To ensure successful application of membrane processes, the integrity of the membrane system should be maintained. Related with evaluation of the membrane integrity, USEPA guidance recommends pressure-based membrane integrity (MIT). Based on the bubble point theory, the ability of detecting smallest integrity breakage during the MIT is defined as "Resolution". However, the response to remarkably small breach demands significantly high initial test pressure of the pressure decay test. In this study, the surface tension of the test liquid was controlled to improve the resolution without increasing the corresponding test pressure. Three common chemicals were chosen to control the solution surface tension. It is concluded that 0.1 M of the citric acid can decrease the initial test pressure significantly for the same pore size. Subsequently, the improvement of the resolution with controlled surface tension was confirmed by the results of pressure decay test and marker test.