Abstract
Surficial drainage features that allow periodic flash-flood discharges to the shallow marine environment cause operational problems for seawater reverse osmosis water treatment plants at Shuqaiq, Saudi Arabia. The facility at Shuqaiq was designed to produce 212,000,m
3
/day of fresh water and it has experienced operational difficulties. An investigation was conducted to assess the technical feasibility of developing a subsurface intake system that would improve the feedwater quality to this and other facilities. A seabed gallery system was found to be technically feasible to supply the required 530,000 m
3
/day inflow. The design contains nine cells, each yielding 66,250 m
3
/day with an infiltration rate of 10 m/day. The filter would have a hydraulic retention time of 7 h. Each cell contains five layers with the total filter bed thickness of 5 m. Design of the filter under-drain system was optimized to maintain an equal flow rate at the top of the filter.