Gold Coast Desalination Plant - Intake
General description
The Gold Coast seawater intake is a 5.8 m diameter cylindrical structure positioned on the seabed 20 m below sea level, 1400 m offshore. The pheriphery of the structure is fitted with copper nickel bars spaced 140mm apart. The seawater intake is connected to the onshore facility through a 2800 mm diameter concrete tunnel.
The intake has a capacity of 320ML/d with a tunnel depth that extends to 70m below sea level. The flow of water into the intake has a velocity three times lower than recommended by California Coastal Commission (0.05 m/s to 0.15 m/s). A vertical cap allows fish to move more easily against horizontal flows and with 140 mm bars allows fish to swim freely.
Pump
Any chemical treatment
The seawater is shock-dosed at the intake with sodium hypochlorite at intervals of one to two weeks to eliminate biological growth in the system. Sodium bisulphite is injected into the filtered seawater to neutralise residual chlorine in the seawater and prevent membrane damage from the sodium hypochlorite.