Field experience with a 20,000 m3/d integrated membrane seawater desalination plant in Cyprus

Abstract

The desalination plant in Moni (Cyprus) is designed, built and operated by Nirosoft Industries Ltd. together with SubSea Infrastructure Ltd. The plant is a fully integrated membrane system using ultrafiltration (UF) membranes as pretreatment for sea water reverse osmosis (SWRO) membranes. The UF system consists of twelve racks with a total number of 792 DOWTM ultrafiltration modules; the SWRO system is a single pass design in three trains with 1,953 DOW FILMTECTM1 elements. It was started up in December 2008, only nine months after signing the contract. Since then it supplies 20,000 m3/d of potable water with less than 360 mg/l TDS and less than 1 mg/l boron to Limassol city and surroundings. This is a mobile plant, and the equipment can be removed to an alternate location or placed onto a barge at the end of the contractual period, which is the end of 2011. In order to optimize operational costs the operating conditions of the UF plant have been adjusted during the first months. The average transmembrane pressure (TMP) ranges at around 0.8 bar, and the consumption of acid, caustic and chlorine for chemical enhanced backwash (CEB) has been minimized. A cleaning-in-place (CIP) has not been required since the start-up in December 2008. The RO plant reliably achieves the required permeate flow at a recovery of 43–44% and feed pressure of 65–69 bar. Salt and boron rejection values have been better than predicted. The pressure drop has always been below 1 bar. The characteristics and the performance of the integrated membrane system, and the experiences during start-up and the first 1½ years of operation will be discussed in detail in this paper.