Autopsy of an old reverse osmosis membrane from Cap Djenet seawater desalination plant: case study of Algeria

Abstract

In Algeria, as many other southern Mediterranean countries, the water’s resources remain limited. Today there is an increasing demand of drinking water and water requirements for irrigation and industry. Therefore, if we consider the saline water potential along the 1600Km coast, using reverse osomosis R.O process, the seawater desalination has been promoted such as an efficient alternative to provide security for drinking water. However, scaling and fouling are the most serious problems in the efficient operation of reverse osmosis systems and may leads to a loss of membrane performance then the necessary to replace the membranes. Therefore, in order to prolong its life and reduce the costs of producing drinking water, it is necessary to study the phenomenon of wear of the membrane using chemical analysis and membrane autopsy to analyze reverse osmosis fouling elements. Our work investigates phenomenon of wear of the membrane of the Cap Djenet seawater desalination plant. We focus on reverse osmosis membrane autopsy including an exhaustive study of the surface of the membrane and of the food-rejection spacer. We carried out several techniques including a chemical and microbiological analysis of the deposit which covered the surface of the membrane, tests to determine chemical oxidation (Fujiwara test), Tests with Scanning Electron Microscopy (SEM) with elemental analysis by X-ray Dispersive Energy (EDX) to study the atomic composition of fouling and an analysis of Fourier Transform Infrared (FTIR-ATR). The results obtained from the different analyses carried out on the autopsied elements indicate that the membrane from 1st position shows a high presence of fouling.  The fouling on membranes show mainly characteristics: a mixture of protein derivatives related to biofilm, sodium chloride, iron, aluminosilicates and other elements commonly detected on sea water membrane fouling were identified. Due to the presence of fouling, membrane from first position showed a lower permeate flux than reference values. Considering these results, a review of plant pre-treatment and disinfection should be carried out in order to avoid the presence of the fouling components identified during the autopsy.