Evaluation of sudden and slow physical damage of ultrafiltration membrane based on pressure declination monitoring

To verify the effectiveness of pressure declination monitoring for assessing physical damage of ultrafiltration (UF) membrane, the changes of water qualities in UF permeate and the pressure declination behavior of the UF membrane were systematically investigated. Medical probe was used to induce the breakage points on UF membrane (the damage rate of single breakage point: A=5.46 × 10^-6). It was found that as damage percentage increased from 0 to 5A, the DOC and UV₂₅₄ in permeate only increased by 24% and 26%, respectively; although the permeate turbidity increased form 0.100 NTU to 0.290 NTU, the absolute value is still too low to reflect the degree of membrane damage properly. On the other hand, a sharp decreasing trend of the pressure inside the membrane fibers was observed for the damaged UF membrane even at the damage percentage of A, the pressure of 55 kPa was demonstrated to decrease to zero in only 66 s. Therefore, monitoring the pressure declination behavior can be considered as a fast, efficient and sensitive method for evaluating the damages on UF membrane. Furthermore, exposure tests showed that the contact of UF membrane with powdered activated carbon (PAC) in a short-term time (45 d) would not cause physical damage on the UF membrane, and the water quality of the UF permeate would be adversely affected by the short-term PAC contact.