Three year operational experience of a spiral-wound SWRO system with a high fouling potential feed water

The refurbished SWRO plant of Eni Gela in Sicily has been working for 3 years at constant output and with low maintenance requirements. The plant consists of 4 trains, each with 74 pressure vessels and 6 elements per vessel, producing 4 x 4,200 m(3)/d permeate. The plant has required cleaning only twice within the last 34 months and is still producing permeate at lower pressure and substantially better quality than originally projected. The original plant fitted with HFF permeators had a history of problems due to fouling and was retrofitted with spiral wound elements in 2003. The retrofit element, FILMTEC (TM) SW30HR-320, was selected as it had the widest feed spacer commercially available in the market and was therefore specifically suited to water with known heavy fouling potential. In this paper the past and recent performance of the plant is discussed. Normalized data show the evolution of the performance on a weekly basis. It can be shown that both the normalized feed pressure and the salt concentration in the permeate are still lower than the projected design values after 3 years, respectively. The paper also discusses the factors which have contributed to this excellent performance, such as design and operation of the pretreatment, the RO section, and specific properties of the spiral-wound membrane element.