Advantages of subsurface intakes for seawater reverse osmosis facilities

The use of subsurface intake systems for seawater reverse osmosis (SWRO) desalination plants significantly improves raw water quality, reduces chemical usage and environmental impact, decreases the carbon footprint, and reduces the cost of treated water to consumers.

These intakes include wells (vertical, angle, and radial type) and galleries, which can be located either on the beach or in the seabed.

Subsurface intakes act both as intakes and as part of the pretreatment system, by providing filtration and active biological treatment of the raw seawater.

This survey by a Saudi–US research team reports that recent investigations of the improvement in water quality made by subsurface intakes show lowering of the silt density index (SDI) by 75 to 90%, removal of nearly all algae, and removal of over 90% of bacteria.

It was also shown that subsurface intakes reduce concentrations of total organic carbon (TOC) and dissolved organic carbon (DOC), and result in the virtual elimination of biopolymers and polysaccharides that cause organic biofouling of membranes.

Economic analyses show that overall SWRO operating costs can be reduced by 5 to 30% by using subsurface intake systems.

Although capital costs can be slightly to significantly higher compared to open-ocean intake system costs, a preliminary life-cycle cost analysis shows significant cost saving over operating periods of 10 to 30 years.

Desalination, Volume 322, 1 August 2013, Pages 37–51.