Influence of water type and pretreatment method on fouling and performance of an Al2O3 microfiltration membrane

The trans membrane pressure (TMP) increase due to fouling of an Al2O3 microfiltration (MF) membrane by particles and natural organic matter in different water types is studied. Removal of non-purgeable organic carbon (NPOC), turbidity and UV extinction by MF was found to be about < 10% for water with a very low turbidity (0.14 FNU). For water with a more representative turbidity (3.6–12 FNU) and varying NPOC level (3 or 15 mg/L), removal rates were comparable to literature values: 23% for NPOC and UV, and > 98% for turbidity. The TMP increase due to irreversible fouling is mostly determined by the presence of particles, whereas the amount of NPOC appears to be irrelevant. NPOC seems to be responsible for reversible fouling that can be removed by backwashing.The effect of pretreatment by anion exchange (AIEX) and coagulation on the performance and TMP increase due to fouling was investigated for Noardburgum lake water. The AIEX pretreatment removes > 80% of NPOC, turbidity and UV extinction.For both types of pretreatment reversible fouling is decreased, but irreversible fouling is increased. Especially the AIEX pretreatment leads to a TMP increase due to irreversible fouling, even though most of the NPOC and particles are removed and never reach the MF membrane.

► We compare fouling and performance of an Al2O3 MF membrane with three types of water.
► The TMP increase due to irreversible fouling is mostly determined by particles We also investigate the effect of anion exchange and coagulation as pretreatment.
► The AIEX pretreatment leads to a significant TMP increase due to irreversible fouling.
► Mass balance shows that up to 33% of the NPOC is not found; remains on membrane?