AWWA MTC53710

Enhancements to traditional system design practice are required if users are to fully capitalize on recentimprovements in both membrane and spiral-wound element technology. The common themes of theimprovements are lower net driving pressure and greater element productivity. This paper documents thebenefits of the latest low-pressure, high-flow technologies and explores their implications for the optimaldesign of new systems and upgrades to existing systems. A nanofiltration installation and a brackishreverse osmosis installation, operating at pressures as low as 50 psi (3 bar) and 175 psi (12 bar)respectively, are briefly described. The spiral-wound elements used in those systems incorporate large-diameterproduct water tubes for improved low-pressure operation. In view of the trend toward lowpressure and high productivity, consideration is given to the compelling advantages of inter-stage boost,permeate throttling, and hybrid membrane systems. Computer simulations of system performance areused to compare the benefits of some of those options. Finally, specific recommendations related toplumbing design are provided in acknowledgement of the fact that parasitic pressure losses represent anincreasingly significant energy expenditure as feed pressures decrease. Includes 6 references, tables, figures.