Combination of lauroyl arginate ethyl and nisin for biofouling control in reverse osmosis processes

Lauroyl arginate ethyl (LAE) is a non-oxidizing biocide effective in controlling biofouling in reverse osmosis (RO) processes. However, the operating concentrations of LAE should be lowered to reduce the possible adsorption of LAE onto RO membranes and to reduce operational costs. This study investigated combinations of LAE with another non-oxidizing biocide, nisin, to overcome such practical limitation of LAE in a bench-scale RO unit operated with full recirculation with the model bacteria Staphylococcus aureus ATCC6538 and Pseudomonas aeruginosa PA14. Several combinations of LAE and nisin (e.g. 1 mg/L LAE + 2 mg/L nisin) were more effective in killing bacteria than LAE or nisin treatment alone, possibly due to permeability synergy. Furthermore, in a bench-scale RO unit operated with full recirculation and model bacteria, flux declines were more effectively moderated by dosing LAE and nisin together compared with the dosing of LAE or nisin alone. LAE dosing alone showed rapid flux decline in the early operational period, while nisin dosing alone demonstrated the lowest flux at the end of the operation. In conclusion, combinations of LAE and nisin appear more effective to mitigate biofouling developed on membranes than LAE or nisin alone.