Magnetic seeding coagulation (MSC) process has been used to accelerate flocs sedimentation with an applied magnetic field, offering large handling capacity and low energy consumption. The interactions of three typical Al species, aluminum chloride (AlCl₃), Al₁₃O₄(OH)₂₄⁷⁺ polymer (Al₁₃), and (AlO₄)₂Al₂₈(OH)₅₆¹⁸⁺ polymer (Al₃₀), with magnetic particles (MPs) were examined to clarify the MSC process. In traditional coagulation (TC) process, the aggregation of primary Al_a-dissolved organic matter (DOM) complexes with in-situ-formed polynuclear species generated a large average floc size (226 μm), which was proved to be efficient for DOC removal (52.6%). The weak connections between dissolved Al_a-DOM complexes and MPs led to the negligible changes of dissolved Al after seeding with MPs in AlCl₃. A significant interaction between MPs and Al₁₃ was observed, in which the MPs-Al₁₃-DOM complexes were proposed to be responsible for the significant improvement of DOC removal (from 47% to 52%) and residual total Al reduction (from 1.05 to 0.27 mg Al L⁻¹) with MPs addition. Al₃₀ produced a lower floc fractal dimension (D_f = 1.88) than AlCl₃ (2.08) and Al₁₃ (1.99) in the TC process, whereas its floc strength (70.9%) and floc recovery (38.5%) were higher than the others. Although more detached fragments were produced with MPs addition, the effective sedimentation of these fragments with the applied magnetic field led to the decrease of residual turbidity and colloidal Al in Al₃₀. The dependence of coagulation behavior to MPs and different Al species can be applied to guide the application of an effective MSC process.

Reverse osmosis (RO) membranes inevitably foul due to the accumulation of material on the membrane surface. Instead of trying to reduce membrane fouling by chemical modification of the membrane, a different approach was taken here based on adding a sacrificial coating of two polyelectrolytes onto the membrane. After membrane fouling, this coating was removed by flushing with a highly saline brine solution, and a new coating was regenerated in situ to provide a fresh protective layer (PL) on the membrane surface. The utility of this approach was demonstrated by conducting four consecutive dead-end filtration experiments using a model foulant (alginate, 200 ppm) in a synthetic brackish water (2,000 ppm NaCl). Brine removal and regeneration of the PL coating restored the water flux to an average of 97 ± 3% of its initial flux, compared to only 83 ± 3% for the pristine membrane. The average water flux for the PL coated membranes was 15.5 ± 0.6 L m-2 h-1 until the flux was decreased by 10% versus its initial flux, compared to 13.4 ± 0.5 L m-2 h-1 for the non-treated control. The use of a sacrificial PL coating could therefore provide a more sustainable approach for addressing RO membrane fouling.