Reverse osmosis membrane element integrity evaluation using imperfection model

Abstract

The operational efficacy of membrane separation processes such as reverse osmosis (RO) and nanofiltration (NF) can be compromised by the lack of mechanical or chemical integrity of the membrane element. Currently, there are several methods applied to analyse membrane and membrane element integrity. However, given that most of them are somewhat inaccurate, expensive or time consuming, the motivation of this study was to implement a simple model-based evaluation method for a single element. The approach was built based on the solution-diffusion-imperfection model and its subsequent revised versions of this model. The models were fitted to experimental data obtained for three types of elements: new, damaged under controlled laboratory conditions and damaged during full scale operation. Based on the experimental results and the fitting of two model parameters, which are the leakage factor and the solute permeability, a criterion for diagnosis of the damage type was formulated. The results confirm the applicability of the modeling approaches. Finally, a decision tree is presented with the aim to help the plant operator to diagnose the type of damage the membrane element suffers.