The Effects of Humic Acid Fouling on the Performane of Polyamide Composite Reverse Osmosis Membranes

Abstract

An element of fully aromatic polyamide composite reverse osmosis membrane was taken from a desalination plant after being used for three years, and fouling behavior of the used membrane by Aldrich humic acid was investigated. It was found that the presence of Ca2+ significantly induced water flux decline for both virgin and used membranes. Additionally, compared to virgin membranes, more severe water flux decline was observed for used membranes which are coated with less amount of polyvinyl alcohol. Regarding the rejection of contaminants, the rejection of Cl- and NO3- gradually increased when the feed solution which contains Aldrich humic acid was treated; this trend was not observed for H3BO3. The analysis of experimental data using the solution-diffusion model which allows for the existence of unhindered advection through nano-scale imperfections showed that the increase in the Cl- and NO3- rejection was due to the clogging of nano-scale imperfections by Aldrich humic acid.

Keywords

• polyamide composite reverse osmosis membrane
• fouling
• humic acid
• solution-diffusion model
• advection