Statistical optimization of chemical cleaning conditions of reverse osmosis membrane process in forward osmosis testing set-up

Abstract

A chemical cleaning process is widely used to restore flux decline and solute rejection in membrane-based water treatment processes such as reverse osmosis (RO) process. In this study, the protocols for the chemical cleaning conditions in the RO process were optimized using a response surface methodology (RSM) for minimizing the experiment time and forward osmosis testing set-up, which can be operated with low or no hydraulic pressure, for reducing the usage of high hydraulic pressure pump. Fouled membranes were cleaned in accordance with the statistically designed conditions of various acid and alkaline agents with concentration, pH, and temperature as variables. Based on response surface plots, the chemical agent concentration was found to be the most influential factor to the membrane permeability. The optimum cleaning conditions obtained from RSM were 3% of the acid agent concentration at pH of 2.2 followed by 3% of the alkaline agent concentration at pH lower than 13. At these optimum conditions, the water flux was recovered about 86.1% with the salt rejection of 83.6%, compared with those of virgin membrane in RO process. Furthermore, this method could provide better understanding of the relationship among chemical cleaning agent concentration, pH, and temperature.