Dual- and multi-media gravity or pressure filters — the conventional SWRO pre-treatment workhorse, cutting turbidity and silt density index ahead of the membranes.
SWRO Intake & Pre-Treatment for Desalination
Granular media filtration is the long-established first line of SWRO pre-treatment after screening and (where used) DAF. Coagulated seawater passes down through anthracite, sand and sometimes garnet, removing fine particulates so the reverse-osmosis membranes see a low-turbidity, low-SDI feed.
Coagulation, depth filtration and backwash
Coarse-to-fine depth filtration; the standard single-stage SWRO filter.
A third, denser layer sharpens removal and lowers SDI.
Two filtration stages for difficult or algae-laden seawater.
Pressure vessels for compact/skid plants; gravity for the largest flows.
Combined air and water backwash restores the bed efficiently.
Ferric coagulant upstream agglomerates fines for capture.
Typical engineering envelope
| Parameter | Typical | Notes |
|---|---|---|
| Filtration rate | 8–15 m/h | Dual / multi-media |
| Media bed depth | 0.8–1.5 m | Layered coarse-to-fine |
| Effluent turbidity | <0.1–0.2 NTU | To RO feed |
| SDI₁₅ | <3–4 | Often <3 after two stages |
| Coagulant | Ferric 1–5 mg/L Fe | Inline, upstream |
| Backwash | Air-scour + water | Periodic, automatic |
Continue across the SWRO intake & pre-treatment series
A companion stage of the SWRO pre-treatment train.
Read MoreA companion stage of the SWRO pre-treatment train.
Read MoreA companion stage of the SWRO pre-treatment train.
Read MoreA companion stage of the SWRO pre-treatment train.
Read MoreA companion stage of the SWRO pre-treatment train.
Read MoreThe intake-systems hub these stages belong to.
Read MoreDual / tri-media filtration applications.
Read MoreMedia and self-cleaning filtration across our range.
Read MoreDissolved air flotation for algae, HAB and oil removal.
Read MoreProtecting SWRO membranes from fouling and oxidants.
Read MoreOur desalination engineers design the complete intake and pre-treatment train — media filtration and every stage — to deliver a low-SDI, membrane-safe feed at minimum lifecycle cost.
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