Reduction in organic compound concentrations using well intakes for SWRO facilities in the Caribbean and the red sea of Saudi Arabia

Subsurface intake systems are generally believed to deliver higher quality of feed water compared to open-ocean intake systems. Some new research results are reported from several desalination plants; two plants located on the Red Sea and one on the Caribbean Sea. These facilities were assessed to compare the feedwater fouling potential of the open-ecean with the well intakes. A water quality assessment was constructed by quantifying the organics content fraction, transparent exopolymer particle (TEP) concentration, and microorganism (algae and bacteria) concentrations. The results were then used to evaluate the performance of the well intake system, which currently is not well documented. Sampling points at the plants include the seawater as background data representing the open-ocean feedwater and the well discharge representing the subsurface intake raw water. LCOCD analyses on the organic fractions showed complete removal of the biopolymer fraction in the well discharge compared to the seawater. Other defined fractions, including humic acid and low molecular weight compounds, are also reduced in the well water. Flow-cytometer measurements were used to quantify bacteria and algal clusters (Cyanobacteria, Prochlorococcus sp., and pico/nano plankton). It was found that seawater contained nearly 10⁵ cells/mL of algae and about 10⁶ cells/mL of bacteria. Interestingly, algae and bacteria exist at an insignificant number of cells in the well discharge, indicating a microbiologically stable water. In addition, the TEP, which generally is believed to be one of the precursors to membrane biofouling, was found reduced in the well discharge, indicating a lower fouling potential of water.