Flocculation–cross-flow microfiltration hybrid system for natural organic matter (NOM) removal using hematite as a flocculent

This study investigates the performance of CFMF process with flocculation pretreatment for NOM removal using hematite as a flocculent. Spiral flocculator consists of rapid mixing and slow mixing units. The presence of rapid mixing prior to slow mixing enhances removal performance of the treatment system. The maximum dissolved organic carbon (DOC) removal of 60% was achieved using hematite in membrane hybrid system. CFMF with spiral flocculator pretreatment was able to reduce internal clogging of the membrane, thereby improving the removal performances. The effluent turbidity was found to be less than 1 NTU for the membrane hybrid system. Smaller membrane pore size (0.1 µm) lead to higher DOC and turbidity removal compared to larger pore size (0.65 µm) studied. For the same amount of coagulant concentration and membrane pore size humic acids were easier to be removed compared to fulvic fraction.

The ability of NOM removal by hematite using flocculation–cross-flow microfiltration hybrid system was studied. Predetermined organic, hematite and calcium chloride concentrations were used for the study. The presence of spiral flocculation system (rapid mixing and then slow mixing) with CFMF achieved a DOC removal of about 60%. The turbidity removal performance and flux development was favorable. The absence of rapid mixing prior to slow mixing reduced the DOC removal efficiency. Recycling the retentate gave higher DOC and turbidity removals compared to system without retentate recycle. Smaller pore size had greater removal performance compared to larger pore size membranes under the given experimental conditions. The effluent turbidity was below 1 NTU for with CFMF hybrid system under the study conditions adopted. For the same amount of coagulant concentration and membrane pore size, humic acids were easier to be removed compared to fulvic fraction. The experimental results were found to be promising in the use of hematite with flocculation CFMF hybrid system for NOM removal. Further studies on the effect of different