基于压力衰减的超滤膜急性与慢性物理破损评价

为验证超滤膜物理破损压力衰减监测的有效性,对破损后膜出水水质的变化和膜内压力的衰减情况进行系统考察.借助医用探针在超滤膜上制造破损点(单个扎孔破损率A=5.46×10-6),发现随着破损率由0增加到5A,超滤膜出水的UV254和DOC仅分别增加24%和26%;出水浊度由0.100 NTU增加到0.290 NTU,但绝对值依然很低,难以反映超滤膜破损的程度.超滤膜急性物理破损时,膜内压力则呈现出急剧下降的趋势,即便破损率仅为1A时,55 k Pa的压力仅66 s就降至零点.因此,以压力衰减监测作为超滤膜物理破损的一种快速、高效、灵敏的评价方法是行之有效的.接触实验表明,粉末炭与超滤膜的短期接触(45 d)不会造成超滤膜的慢性物理破损,不会影响出水水质.

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.