[Purification Efficiency and Mechanism of Integrated Al Salt Floc-ultrafiltration Membrane Process]

Owing to the small land use and high pollutant removal efficiency, the integrated ultrafiltration (UF) membrane process has been gradually applied in water treatment. However, not only would the membrane surface be damaged by the commonly used granular adsorbents over time, but these types of adsorbents are expensive, such as nano zerovalent iron, carbon nanotubes, etc. To overcome these disadvantages, the loose Al-based flocs were directly injected into the membrane tank in the presence of humic acid and Miyun reservoir water. Results showed that severe membrane fouling was induced by HA alone, and the transmembrane pressure (TMP) significantly increased to 76.4 kPa after 12 d of operation. However, it dramatically decreased to 10.1 kPa after washing with tap water on day 13, indicating that the cake layer was the main fouling mechanism. The average HA removal efficiency was only 23.3% during filtration. In addition, the performance of the integrated flocs-membrane process could be influenced by floc dosage, injection frequency, and solution pH. The integrated membrane performed well with flocs (43.2 mmol·L^-1) continuously injected at pH 6.0 (aeration rate at 0.3 L·min^-1). The corresponding TMP only increased to 19.5 kPa after running for 12 d, which decreased to 5.6 kPa after washing with tap water on day 13. The average HA removal efficiency increased to 61.2%. Additionally, serious membrane fouling was also induced by Miyun reservoir alone. The TMP increased to 38.0 kPa on day 12, while it decreased to 3.8 kPa after washing with tap water on day 13. The cake layer was also the main fouling mechanism, and the average pollutant removal efficiency was only 7.5%. With floc continuously injected, however, the TMP only increased to 6.1 kPa on day 12. After washing with tap water, the TMP decreased to 2.3 kPa on day 13, and the average pollutant removal efficiency was as high as 58.6%. Based on the excellent membrane performance, the integrated membrane process exhibited potential application in drinking water treatment.