The impact of chemical cleaning on separation efficiency and properties of reverse osmosis membrane

Abstract

One of most major concerns from both cost-effective and technical point of view in membrane process industry is membrane cleaning. The aim of the project was to investigate the variations in membrane surface properties and separation efficiency of reverse osmosis membrane.

Compativtive analysis have to be performed on four RO membrane before and after exposing the virgin membrane into chemical cleaning to identify and analysis the impact of the chemical cleaning on the performance of RO membrane. Commerical chemical cleaning used in this project were caustic and acidic cleaning agent. The project’s aim is the investigation of simulation software’s precision for the four membranes performance projection at different conditions of the feed water. The assessment of the membranes performance was done in the Innovation Cluster at pilot plant that was industrial in size. The main commercial elements used were the thin-film composite membranes with a spiral-wound of 8-inch polyamide. Ultrafiltration (UF) and seawater RO membrane pretreatment process was done for the red sea sourced feed water. A pressure vessel dimensioned at 8-inch was operated in conjunction with an individual element at 8 -20 m3/hr feed flow rate, with an 8 to 12 % recovery and an average 35,000-42,000 mg/L of total dissolved solids (TDS) composition for the feed water. To achieve the project’s aim in assessing the membranes, three phase experimental stages were completed. The membranes performance was assessed in terms of their water flux, salt rejection, boron rejection, bicarbonate rejection and permeate quality. In addition, the membrane surfaces were characterized after exposing the fresh membranes with a chemical cleaning reagent. The experimental results showed an increase in both permeate flow and salt passage for all studied elements. The changes in the membranes performance were systematically explained based on the changes in the charge density and chemical structure of the membranes surface. The experimental results showed that both the physical and chemical surface properties of the membranes do not significantly alter under standard industrial conditions. These results shed some light on the effects of chemical cleaning in a pilot-scale RO plant and improve our understanding to provide a potential research direction for cleaning methods of membranes.