a b s t r a c tDesalination of seawater and brackish water by reverse osmosis to produce potable and process water has been widely used. But the precipitation of low soluble salts is one of the major problems in RO plants operation. Several well-known techniques are used to protect membranes and antiscalant dosing is one of the most widespread. A wide range of reliable and efficient inhibitors have been developed but the trend of the last decade is creation environmentally friendly ("green") chemicals: phosphorus-free and biodegradable. A relative ability of industrial samples of four phosphorus-free polymers (polyaspartate (PASP); polyepoxysuccinate (PESA); polyacrylic acid sodium salt (PAAS); copolymer of maleic and acrylic acid (MA/AA)) and of three phosphonates (aminotris (methylenephosphonic acid), ATMP; phosphonobutane-1,2,4-tricarboxylic acid, PBTC; and AMINAT) to inhibit carbonate membrane fouling in the simulated Black Sea water under reverse osmosis (RO) conditions for the dosages ranging from 1 to 25 ppm is tested. The following ranking ATMP > HEDP > PESA (400 ÷ 1500 Da) ~ PASP (1000 ÷ 5000 Da) > PAAS (3000-5000 Da) ~ MA-AA is found. A comparison of this ranking with that one performed following the NACE Standard TM0374-2007 under static conditions confirmed results provided by NACE Protocol.
A B S T R AC TThe RO process is very attractive for providing high product quality through the removal of a number of contaminants like oil, detergents, organics, nitrates, ammonia, phosphates etc. However the main disadvantages of the modern RO techniques are connected with membrane fouling, concentrate fl ow and pretreatment that increase operational costs, complicate design and create problems of brine utilization. Often pretreatment costs even exceed reverse osmosis facilities costs. Now a number of successful attempts were undertaken to modify spiral wound membrane channels to limit fouling and scaling potential. As presented in a number of publications, elimination of the spacer mesh from the feed channels eliminates dead regions that provide scaling and fouling conditions whilst also reducing the risk of particle "trapping" and associated dramatic pressure increase. Introduction of a new "open channel" confi guration offers a new perspectives to escape fouling and development of novel techniques to treat water with high fouling potential (high suspended matter, organics and supersaturated solutions). This novel concept of spiral wound module with an "open channel" design is developed, fi eld-tested and introduced into practice. Fouling control is achieved due to the elimination of spacer and the implementation of an optimum hydraulic mode providing suffi cient cross fl ow velocities, fl ushings and cleanings. The main principles of high recoveries, low maintenance and zero discharge are ensured by concentration of brine through re-circulation by 50−100 times by volume. Several examples of water treatment fl ow diagrams are presented to demonstrate of zero concentrate fl ow discharge. Coagulated suspended matter after membrane fl ushes is collected, sedimented and fi nally dewatered. The concentrated solution containing salts and impurities together with the wet sludge constitutes no more than 1 percent of initial water in part due to high supersaturation values due to the strong stability of calcium carbonate solutions.
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