SWRO feed water quality improvement using subsurface intakes in

Water quality sampling and analysis conducted at four global locations, along the shorelines of the Arabian Sea, the Red Sea, the Mediterranean Sea, and the Caribbean Sea, demonstrated that subsurface intakes (wells) provide a robust degree of feed water treatment close to that provided by energy-intensive, conventional pretreatment systems. SDI values were reduced in virtually all cases to below 3. In vertical wells, from 70 to 100% of the TEP and 50% of the TOC and DOC found in natural seawater were removed in the aquifer. Reduction in the concentration of the organic fractions was selective based on molecular weight with the biopolymers nearly fully removed. Humic substances, building blocks, and light organic substances were removed at lesser percentages. Site geology was not the predominant factor affecting the removal efficiency, but the length of the flow path from the sea to the wells and the hydraulic retention time appear to be most significant. A comparison between vertical wells, a tunnel intake system, and a horizontal drain system at Alicante, Spain, demonstrated that the vertical wells performed best followed by the tunnel system, and the horizontal drain system which showed a breakthrough of algae and a very high organic carbon concentration. © 2014 Elsevier B.V. All rights reserved.

Water quality investigations conducted at four geographic sites, along the shores of the Arabian Sea, Red Sea, Mediterranean Sea, and Caribbean Sea, with differing geologies, show that well intakes to SWRO plants provide a robust water treatment system similar to that provided by multiple process pretreatment trains in SWRO facilities using openocean intakes. Conventional vertical well intake systems showed elimination of the algae and a high percentage of the bacteria reduction for the seawater between the shoreline and the well. Bacterial removal rates were as high as 99.3%, which is higher than what many SWRO pretreatment processes currently achieve when treating feed water from open intakes. TOC and DOC removal was roughly 50% or greater of the concentration in the natural seawater at each site. It was found that the removal of the NOM fractions was selective with the highest Fig. 9. Comparison of bacterial and TEP concentrations in the natural seawater and selected vertical wells at Alicante.