Impact of operations and cleaning on membrane fouling at a wastewater reclamation facility

- Coagulant addition reduced chemical cleaning frequency for older membranes.
- Cleaning with enzymatic detergents improved permeability regardless of membrane age.
- Both coagulant addition and chemical cleaning reversed fouling of older membranes.
- Chemical cleaning played greater role in reversing fouling of newer membranes.
- Coagulant and cleaning impacts on fouling were quantified using fouling indices.

Effects of operational changes on membrane fouling were evaluated for a wastewater reclamation facility. The focuses were on addition of a coagulant (ferric chloride) versus no addition and an accidental high chlorine (sodium hypochlorite) dose. Two membrane modules with different service ages, 3 years versus 9 months, were compared. Fouling rates ranged between 2 and 3 times higher during no ferric chloride addition. Chemical cleaning frequency was reduced by approximately 5 times during ferric chloride addition for older membranes, while it did not change for newer membranes. High chlorine dose had slightly improved membrane permeability for newer membrane, and reduced the transmembrane pressure (TMP) for both older and newer membranes. Chemical wash with enzymatic detergents substantially improved membrane permeability and reduced TMP for both older and newer membranes. Fouling index values indicated that coagulant addition had greater impact on performance recovery for older membranes than newer membranes. Successful and economical operation of membranes depends on fouling rate, which in this study was found to be a function of flux, membrane age, pretreatment, and cleaning type and frequency.