The first physical barrier in a seawater intake and pre-treatment train — bar, band and drum screens that remove macro-debris and protect aquatic life while keeping downstream coagulation, flotation and membranes fouling-free.
How screening fits the full SWRO pre-treatment train.
The next stage — algae and colloid removal by flotation.
Full range of screens, traps and grit-removal equipment.
Depth filtration downstream of screening and flotation.
Removing what would otherwise blind filters, foul membranes and harm marine life
Coarse and fine screening is the gatekeeper of every seawater intake and industrial water-treatment train. Coarse bar screens with 20–50 mm clear openings intercept macro-debris — seaweed, timber, plastics and shellfish — that would otherwise damage pumps and block pipework. Fine band or drum screens with 1–6 mm apertures then remove smaller solids and exclude fish larvae and juvenile organisms before they enter the plant. Critically, screen design is governed by the through-screen velocity: keeping approach velocities below roughly 0.15 m/s minimises the impingement of organisms against the mesh and reduces entrainment of eggs and larvae through it, satisfying the environmental-protection requirements that increasingly shape intake permits. A correctly specified screening stage protects every downstream unit — coagulation, dissolved air flotation, media filtration and reverse-osmosis membranes — and is the cheapest place in the process to remove a kilogram of solids.
Matched to debris load, organism protection and hydraulic duty
Mechanically raked bar racks with 20–50 mm bar spacing capture large floating and suspended debris. Continuous chain or reciprocating rakes discharge screenings automatically, protecting intake pumps and culverts from blockage and impact damage.
Through-flow or dual-flow band screens with 1–6 mm mesh panels rotate continuously, spray-washing captured solids into a trough. Fish-friendly buckets and low-pressure wash systems return organisms to the source alive.
Rotating drum screens give a compact, high-area solution for fine straining where headroom is limited. Internal or external feed configurations suit both raw seawater intakes and recycled process streams.
Low approach velocities, wedge-wire passive screens and fish-return systems cut impingement and entrainment to meet marine consent limits — essential for open intakes feeding desalination plants.
Design rule of thumb: keep the through-screen velocity below 0.15 m/s for biological protection and limit head loss across a clean fine screen to 150–300 mm; size the wash-water system for the peak screenings load, not the average.
Seawater duty demands corrosion-resistant construction throughout. Screen frames and panels are specified in duplex or super-duplex stainless steel (UNS S32205 / S32750) or non-metallic composites, with sacrificial anodes or impressed-current cathodic protection on structural steelwork. Mesh panels use woven or wedge-wire elements selected for the target aperture and open area. Drives, bearings and spray-wash systems are rated for continuous marine service, and screenings handling — launders, compactors and skips — is sized for the site debris profile, which varies sharply with season, storms and harmful-algal-bloom events.
For industrial and municipal intakes the same principles apply at smaller scale: bar screens protect lift pumps, while fine screens upstream of dissolved air flotation and media filtration stabilise downstream loading and lengthen filter run times. Screening data — debris mass, particle-size distribution and seasonal variation — feeds directly into the pre-treatment train design and the membrane fouling forecast.
Explore the rest of the train
Ferric coagulation and dissolved air flotation for algae, colloid and TEP removal after screening.
Explore DAF SystemsGraded anthracite–sand–garnet depth filtration to drive SDI down ahead of the membranes.
Explore Multimedia FiltersAbsolute-rated guard filters — the final barrier immediately upstream of the RO feed pump.
Explore Cartridge FiltersSee how screening, flotation, filtration and RO combine into a complete SWRO process train.
Desalination OverviewOur engineers size screening, flotation and filtration as one integrated pre-treatment train.
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