A Fully Integrated Membrane Operation for Sea Water and Brackish Water Desalination

Water scarcity already represents the major problem in many countries and is going to be - not far from today - worldwide significant. Considerable progresses have been reached by introducing pressure driven membrane operations as alternative to thermal desalination systems. Today, most of the new desalination plants are almost completely based on Reverse Osmosis, eventually integrated with Microfiltration and Nanofiltration for pre-treatment, with Nanofiltration in order to reduce bi-valent ions in the feed. The introduction of these technologies has already evidenced interesting cost reduction and operational flexibility. However, the growing of desalination processes as a solution to water shortage still requires further improvements: achievement of higher overall water recovery and productivity, additional cost reduction, implementation of strategies for brine disposal, better process flexibility with respect to the feed water composition and its level of acceptability, enhanced water quality for different potential end-users (ultrapure water, drinking water, agricultural and industrial water). Moreover, the strategy of process intensification - representing today on the most realistic answer to the request for a sustainable industrial growth - has to be extended to this industrial sector as has been already done in other cases. Fully integrated membrane operations, in principle, seems to offer interesting perspectives in this regards. In this work, authors discuss an energetic and exergetic analysis of an overall integrated membrane desalination introducing also appropriate and quantitative parameters for improvement in to the logic of process intensification (productivity, quality of fresh water, eco-environmental indicators). A cost analysis based on an output from the desalination plant of diversified water qualities as permeate, and crystals from the retentate is also provided.