Physically-assisted removal of organic fouling by osmotic backwashing coupled with chemical cleaning

Membrane filtration is a robust water treatment method against membrane fouling driven by natural organic matters for drinking water production and wastewater reclamation. Despite recent studies revealing that osmotic backwashing (OBW) can effectively remove organic fouling from the membrane, the mechanism of fouling removal and the supportive effect of OBW remains unexplored. Here, we performed a comparative analysis of chemical cleaning and OBW-assisted chemical cleaning to remove organic fouling from the reverse osmosis membrane. Natural organic matters such as humic acid, sodium alginate, and tannic acid were used as model foulants. Various in-situ monitoring and ex-situ characterization methods were used to evaluate direct and indirect effects on membrane cleaning. Using OBW increased the water permeability coefficient of the fouled membrane compared to using chemical cleaning solely, improving the water flux up to 10.8%. Notably, in-situ monitoring revealed that pore generation below the fouling layer readily dissociated the fouling layer and helped the cleaning agent encounter foulants rapidly. The characterization of the fouled membrane demonstrated that applying OBW before chemical cleaning could enhance the membrane cleaning efficiency.