Shuqaiq-II IWP is a combined RO water desalination and power plant facility. It operateswith an open intake that feeds the plant with 100,000 m3/h of raw water. The facility islocated 140 km north of Jizan, in a small bay where the run-off discharges of two wadisconverge. The run-off coming from the wadis are rich in alluvial sediments thatdramatically decrease the raw water quality at the intake point, causing periodicshutdowns of the plant and increasing the operational cost due to membrane replacement.Subsurface water intakes are an alternative for improving raw water quality, as theyprovide natural filtering of the feed water as it flows through the systems. In this type ofsystem water flow through the sediment matrix is induced and during the percolation,several physical, chemical and biological processes take place, cleaning the water fromparticulate matter, resulting in high quality feed water that can be directly sent to the ROprocess without any additional pretreatment.A full hydrogeological profile of the seabed needs to be performed in order to determinethe applicability of one of these systems in each particular location. In this study, 1 km ofbeach area at Shuqaiq-II IWP was surveyed. Ninety-one (91) samples from the shore and offshore sediments were collected and analyzed for hydraulic conductivity, porosity andgrain size distribution.The laboratory analysis showed that the construction of the seabed galleries wastechnically feasible, and the proposed intake system was design to meet the feed waterrequirements for the RO facility (530.000 m3/d). The preliminary design consists of 17cells in total, 16 of which will be in constant operation, and 1 alternate for whenevermaintenance is needed in one of the other cells. The seabed gallery design includes 5layers of sands with a total depth of 5 m. A detailed underdrain design methodology ispresented. The system would be operated at an infiltration rate of 10 m/d and an averagehydraulic retention time of 7h. Each cell will have an area of 3.500 m2 that will supply35.000 m3/d of feed water to each RO train.
展开▼
