Veronica Garcia-Molina

Backwashing pressurized ultrafiltration using reverse osmosis brine in seawater desalination and its potential costs savings

This paper discusses the feasibility of using reverse osmosis concentrate to backwash ultrafiltration membranes in the seawater reverse osmosis desalination space. Brine is produced through DOW FILMTEC™ reverse osmosis elements and it backwashed every 90 min to DOW™ ultrafiltration membranes. A side-by-side validation is done for 15 d using two parallel ultrafiltration and reverse osmosis integrated systems. One line uses brine for backwashing, while the other uses conventional filtrated water. The optimization is proven to have the same cleaning efficiency than the conventional backwashing methods and no precipitation is observed in the fibers. An additional validation period that uses reverse osmosis brine during backwashes and only two backwash steps is also carried out successfully. These steps are the previously identified backwash top with air scour and forward flush. Fibers also show an excellent integrity after the whole experimental period. A model is built in order to analyze the backwash efficiency of the optimized conditions and the transmembrane pressure increases during the filtration cycle. The results show the same fouling tendency for the line operating with brine and the line operating with filtrated water. The efficiency of the ultrafiltration process is improved from 88 to 98% thanks to this optimization together with the previous researches. This represents filtrating 96 min extra per day and a reduction of 100% in the filtrated water used during backwashes. The chemical equivalent concentration is also optimized from 0.28 to 0.06 mg/L NaClO thanks to the adjustment of the chemically enhanced backwash frequency. This accounts for a 7.1% savings in the ultrafiltration step and for a 1.2% savings in the whole desalination process.

Optimizing seawater operating protocols for pressurized ultrafiltration based on advanced cleaning research

Abstract This paper is part of a global research project conducted by Dow Water & Process Solutions to optimize the efficiency of ultrafiltration processes. After an initial identification of the backwash as the key opportunity to increase the efficiency of the process, a study based on its optimization is developed. Main emphasis is given to the sequence and subsequent number of steps involved in the backwash. The ultimate goal is thus to increase the availability and recovery of the process while still attaining a high cleaning effect during the backwash. This optimization is done through the realization of various experiments using DOW™ Ultrafiltration SFP-2660 outside-in polyvinylidene difluoride (PVDF) membranes following an exhaustively planned factorial design of experiments. The factors being assessed are the steps normally performed during a backwash. These are the air scour (AS/D), the draining (D), the backwash top (BWT) with or without air scour, the backwash bottom (BWB) and the forward flush...

High-permeability FILMTEC™ SEAMAXX™ reverse osmosis elements: a success story in the Canary Islands

AbstractReverse osmosis (RO) has developed into one of the most commonly applied technologies for the reduction of the salt content of a feed stream. While it is a widely applied purification process, the market is continuously challenging suppliers for innovation to increase the economics and sustainability. This paper will review and analyse the field performance of Dow FILMTEC™ new high-flow/low-energy seawater reverse osmosis elements—SEAMAXX™. This new seawater RO membrane, which has the highest permeability currently available, is based on innovation related to membrane chemistry. SEAMAXX can be used to increase the recovery of an existing system or to decrease the energy consumption. In either case, the final cost of water is estimated to be between 10 and 15% lower compared to previously available state of the art RO elements. This paper will focus on three different cases studies where the expected performance of SEAMAXX has been validated. Two of these cases correspond to small-size and medium-s...

Long-term benefits of DOW FILMTEC™ RO membranes

Abstract Reverse osmosis (RO) is a widely accepted and applied process for the purification of a variety of raw water sources, especially when there is a need for removing the bulk of the dissolved salts and other impurities present in the feed streams. Since its first applications and references, the technology has progressively been refined and improved, up to the current mature status, where, even if innovations are still to come, a solid base frame exists already. This paper will review and analyze long-term operation data from medium and large-size projects, including two different seawater desalination plants examples. It will focus on the long-term stable and reliable performances of DOW FILMTEC™ RO elements, by comparing the expected performance to the current operation data, with special emphasis on the long life of elements, and thus low replacement rates. These two installations are of particular interest given the time they have been successfully producing the required amount of drinking water...