Influence of Iron and Magnesium on Fouling Properties of Organic Matter Solution in Membrane Process

Organic matter has been identified as a significant type of foulant in membrane processes for water treatment. Its fouling tendency is highly affected by the presence of ions and inorganics. While the effects of ions addition on organic fouling have been extensively researched in the past, studies on the effect of positively-charged inorganics, such as Fe²⁺ and Mg²⁺, on organic fouling are limited. This study investigates the influence of Fe²⁺ and Mg²⁺ addition on fouling properties of the Suwannee River Organic Matter (SROM) solution in the MF process, with and without Ca²⁺ ions. Results showed that increasing the concentration of Fe²⁺ and Mg²⁺ from 0-5 mM promoted SROM fouling, and resulted in an increased flux decline up to 33% and 58%, respectively. Cake layer resistance became more dominant with the addition of Fe²⁺ and Mg²⁺, and was counted for more than 60% of the fouling. Mg²⁺, however, caused higher internal pore blocking, and facilitated the formation of a less permeable cake layer, compared to Fe²⁺. This was evident in the analysis of the cake layer properties and the visualization of the fouling layer. In all cases, SROM fouling with Fe²⁺ and Mg²⁺ worsened with the addition of Ca²⁺ ions. The results of the study indicated the importance of understanding the interaction between organic matter and Fe²⁺ and Mg²⁺, which would provide useful insights on their fouling mechanism and control.