Feasibility of Gallery Intake Systems for Seawater Reverse Osmosis Facilities along the Northern Red Sea Coast of Saudi Arabia

摘要

The Kingdom of Saudi Arabia is dependent on desalination of seawater to provide newwater supplies for the future. Desalination is expensive and it is very important to reducethe cost and lower the energy consumption. Most seawater reverse osmosis facilities useopen-ocean intakes, which require extensive pre-treatment processes to removeparticulate and biological materials that cause operating problems. An alternative intakeis the subsurface system which utilizes the concept of riverbank filtration using wells orgalleries and provides natural filtration to improve the quality of feedwater before itenters the desalination plant. This reduces operating cost and lowers energy consumption.Research was focused on evaluating gallery-type intakes (beach and seabed galleries)that could be used along the Northern Red Sea shoreline to provide a better qualityfeedwater for desalination. The geological characteristics of the visited sites werefavorable for the development of seabed filter systems (offshore), but not for beachgallery intakes. The low wave energy along the shoreline and the presence of mud orrocky coasts made beach galleries infeasible. One of the potentially favorable sites for aseabed filter was located in the nearshore area at King Abdullah Economic City (KAEC).This site has a predominantly sandy offshore bottom with shallow water depths, and alow tide range. In addition, the bottom is always covered with water and contains softlimestone unit below the sand mantle that could be easy excavated to facilitate the construction of a seabed filter. About 50 sediment samples were collected from the siteand laboratory measurements were performed on them. Grain size distribution, porosityand hydraulic conductivity measurements were performed on the sediment samples. Inaddition, six statistical methods were used to estimate the hydraulic conductivity values.Based on results of lab measurements, field observations, tide ranges and sediment types,it is concluded that the geological conditions and characteristics of KAEC site arefeasible for design and construction of a seabed filtration system. A conservativelydesigned cell with dimensions of 100 by 50 m would produce about 25,000 m3/day offiltered seawater and seven cells could support a 60,000 m3/day (permeate) seawater RO plant.