Performance of materials used in seawater reverse osmosis plants

Abstract

Doha Reverse Osmosis Plant (DROP) has been in operation for more than 4 years. The plant consists of three different RO membrane configuration systems, each of which has its own materials requirements. Materials used for piping, pumps, valves and control systems were critically surveyed. A testing programme was initiated to generate data which will provide a sounder basis which these materials may be selected for use in reverse osmosis plants. A number of alloys were selected for the study to evaluate their behaviour in the various environments encountered in the reverse osmosis desalination plant. Corrosion performances and material behaviour were evaluated in terms of weight loss in the plant. Pitting and crevice susceptibility were assessed in the plant as well as by the electrochemical studies in the laboratory. A once-through pilot plant which could simulate most of the water conditions encountered in the reverse osmosis plant was constructed. Coupon weight losses of selected alloys are being determined under variables of PH, temperature and flow velocity. Preliminary work is still in progress. Results obtained from the programme, so far, appear from favour the use of high alloyed stainless steels in many area of reverse osmosis. plant. However, the economic incentive for extensive use of steel will depend on the results of long term studies current on the way.