钙离子对短期膜污染的影响

以处理生活污水的平板膜-生物反应器为依托,通过将进水调配成30、200和500 mg/L 3种不同的钙离子浓度,考察钙离子对短期膜污染的影响。结果表明,随着钙离子浓度的增加,TMP增长趋势变小,膜污染得到缓解;钙离子浓度为200 mg/L时,膜的渗透性最好,而过高的钙离子浓度并不利于降低膜污染。钙离子的投加强化了生物絮凝作用,可以降低SMP和LB-EPS的含量,主要通过降低外部阻力减缓膜污染;投加钙离子也可以增加絮体的大小,较大的絮体形成的泥饼有更好的过滤性,然而过高的钙离子浓度会使无机颗粒的量增加,造成平均粒径下降,将会加重内部污染,进而加剧膜污染。

Impacts of calcium ion on short-term membrane fouling

Impacts of calcium ion on membrane fouling were investigated in a flat-sheet membrane bioreactor(MBR) for domestic wastewater treatment by changing calcium concentration of influent to 30,200 and 500 mg/L.The results showed that the membrane fouling in terms of growth tendency of TMP was effectively controlled with the increase of calcium concentration,and the best permeability was achieved at calcium concentration of 200 mg/L.It was not benefit to reduce membrane fouling when the calcium concentration was much more than 200 mg/L,such as 500 mg/L.The increase of calcium ion can decrease the concentrations of SMP and LB-EPS by enhancing the bioflocculation,and reduce the external resistance due to the decrease of SMP and LB-EPS.The calcium ion can also increase the particle size of floc,and the larger floc size reduced the cake layer fouling.However,when the calcium concentration was much higher,the average size of floc would decrease due to the increase of the inorganic particle with less size,and then the membrane fouling was deteriorated because the inorganic particle would increase the internal resistance by blocking the membrane pore.