Early discovery of RO membrane fouling and real-time monitoring of plant performance for optimizing cost of water

RO plant operators, end-users, membrane manufacturers and system suppliers have been facing two major problems since the advent of commercial membrane technology applications for water desalination utilizing reverse osmosis (RO) and other membrane processes: how to reliably monitor their membrane system performance and how to detect membrane fouling and scaling development in real time and before significant or irreversible loss of performance efficiency occurs, resulting in lower plant availability and significantly higher O&M costs. The current industry-standard performance analysis and evaluation technique is based on trending RO flux decline characteristics of membranes via normalizing system operating data in accordance with ASTM D-4516 standard method. This paper discusses the shortfalls of this technique, and introduces a practical new technology for measuring and monitoring membrane fouling and flux performance in real-time. The new Silent Alarm™ technology, designed as an early-warning system, allows the discovery of any fouling or scaling development on the RO membranes in the very early stages, thus providing a valuable tool for the plant operator to take immediate corrective measures before it is too late. Two major brackish and seawater Arabian Gulf RO plant case studies with and without a fouling history are discussed. This proven capability to monitor RO plant performance in real-time and measure the actual development of any membrane fouling or scaling very early on has a direct and dramatic positive impact on optimizing the total cost of desalinated water.

The membrane technology market around the globe is currently valued at over two billion US dollars a year with an annual growth rate of 10%. Water-scarce countries, as most countries in the Middle East and South Mediterranean region, will see a rise in the need for desalinated water capacity from 1.9 million m3/y a year to 14.9 million m3/y for the period from the year 2000 to 2025, an annual growth rate of 27%. This explosive growth in desalination, a great part of which will come from large-scale membrane plants, compels and mandates the need to address the critical problem of monitoring and evaluating membrane desalination plants performance, fouling development and operational cost-effectiveness. New mega-size sweater RO plants are already operating, coming on-line, or being designed or conceptualized for start-up in the new millennium, including new and refurbished plants of 50,000–130,000 m3/d capacity in Bahrain (Ad-Dur), Kuwait (Sulaibiya), Saudi Arabia (Al-Jubail, Jeddah and Yanbu), the United Arab Emirates (Fujairah), Tunisia (Djerba, Gabes and Zarzis), Malta (Pembroke), Trinidad (Point Lisas), and in the United States, Florida (Tampa Bay), Texas (Corpus Christie), Arizona (Scottsdale), and Southern California (5 SWRO plants for San Diego County). Reliable performance and availability of these plants, for example, at minimum operating and maintenance costs are mandatory. The recent fouling and performance problems at the new 25 MGD Tampa Bay Seawater RO Plant in Florida exemplifies the need for reliable monitoring technology if this and future mega plants are to succeed. The new Silent Alarm™ technology can provide these plants and many others a unique tool to help them achieve these objectives on a daily basis. More important, this proven capability to monitor RO, nanofiltration and other membrane-based plant performance characteristics in real-time, and discovering, not trending, the actual development of any membrane fouling or scaling before too late has a direct and dramatic positive impact on optimizing the total cost of desalinated water. Bibliography Al-Mansour, A.-H., 30 desalination plants produce 3 Mm3/day of drinking water. Arab Water World, 26(4) (2002) 42–43. ASTM D 4516-00 method, Standard Practice for Standardizing Reverse Osmosis Performance Data, American Society of Testing Materials, 2000 (revision). Brauns, E., Could fuzzy logic be the key to membrane fouling control. The International Desalination & Water Reuse Quarterly, 13(2) (2003) 18–24. Bremere, I., M. Kennedy, A. Stikker and J. Schippers, 12. Henley, M., Desalination — demand for more fresh water drives desalination in many nations, UltraPure Water, April (2003) 14–18. Metropolitan Water District Seeks Proposals on Desalting the Pacific Ocean, www.waterindustry.org, updated Dec 4, 2002. Pursley, K., Software warns of early membrane fouling, Industrial Water World™, Automation, 3(1) (2002) 13. Saad, M.A., Biofouling prevention in RO polymeric membrane systems. Desalination, 88 (1992) 85–105. Saad, M.A., Optimize water cost by early prediction of membrane system fouling trends, Proc. 1999 IDA World Congress on Desalination and Water Re-use, San Diego, CA, USA, Aug. 29–Sept. 3, 1999. Saad, M.A., Real-time membrane fouling monitoring — a case history, Proc. Water World™’s World Water Conference, Las Vegas, NV, USA, Dec. 10–13, 2001. Saad, M.A., New, real-time monitoring technology for desalination plants. Arab Water World, 26(1) (2002) 6–7. Saad, M.A., Manufacturer’s case study: smart software Texas Water Development Board, Demonstration seawater desalination project — Statement of Interest. Nov. 1, 2002.