Normalization Method for Earlier Foulant Detection on A Reverse Osmosis Membrane Surface

Abstract

Operating Brackish Water Reverse Osmosis (BWRO) unit which a membrane technology in a water treatment system, operating parameters found to alter causing permeat flow and salt passage to shift, which leading to inaccurate evaluation of membrane condition.  The observed operating parameters must be standardized in order to discern between such typical events and performance variations owing to fouling or issues called Normalization. Among normalization parameters, the objective of this work is to evaluate RO membrane condition using Normalized Permeate Flow (NPF) method at constant recovery setup applied in an RO plant facility of a factory located in Cilegon, Banten, Indonesia. The NPF show distinguish result compared to actual permeate flow (Qpa). Qpa tends to stable or a slow deterioration at 7%, which leading inaccurate conclusion since Qpa is spot data. In contrast, NPF shows 27% drop of membrane performance since its first run until the end of running cycle and the membrane must be immediately clean. In conjunction with NPF, applied pressure (Pfa) tended to increase up to 23.7%. Such higher Pfa is required to solve the osmotic pressure on feed-brine surface of the membrane even with the same amount of product. The higher osmotic pressure is caused by foulant on the membrane surface even with constant raw water concentration. Chromatic Elemental Imaging^SM (CEI^SM) and Energy Dispersive Spectroscopy (EDS) analysis methods are used to understand type of foulant on the membrane surface. CEI detected a high weight percent of silicon as the primary foreign inorganic elements present on the membrane surface, while EDS analysis detected a layer of silicate at 40.22% wt. coated the membrane surface evenly.