Effective removal of fluorescent microparticles as Cryptosporidium parvum surrogates in drinking water treatment by metallic membrane

The diarrhoea-causing parasitic protozoan Cryptosporidium parvum (C. parvum) cannot be efficiently removed by conventional drinking water treatment and poses a biological threat to public health. To ensure the biological safety, three kinds of metallic membranes, laminating metal mesh filter, non-woven metal filter and sintered metal fiber filter were employed to compare their properties. The results showed that the sintered membrane possessed the best filtration performance and lowest membrane resistance among three metallic membranes. Therefore, the sintered membrane was selected for subsequent experiments. Due to the low infectious dose of C. parvum and sophisticated detection methods, fluorescent particle tracers, Crypto-tracer-1, were chosen as a feasible surrogate was proposed to investigate the removal efficiency of sintered membrane for C. parvum. The results indicated that the tracer log removal value (LRV) ranged between 5.1 and 5.4 log10 under different filtration flux, which equivalently means that C. parvum could be completely removed and further tests are needed to confirm the results obtained using C. parvum. Furthermore, a pilot-scale study was performed for 10 weeks in full-scale drinking water treatment systems. The turbidity could be efficiently removed (outlet water of membrane was 0.08 +/- 0.04 NTU) and the average transmembrane pressure recovery rate was 84.6% after physical backwash. Fouling mechanism analysis indicated that the interaction energy between foulants and membrane material became stronger over time. The practical operation results showed that sintered membrane performed well in continuous operation for a long time and also had a good anti-pollution ability. These findings could facilitate application of metallic membrane in drinking water treatment.