Vortex Separator — StormWater Solutions

Vortex Separator is a hydrodynamic stormwater treatment device that uses induced rotational flow to remove sediment, silt, oil and floatable debris from surface water run-off before discharge to sewer or watercourse. Vortex separators are widely used as a pre-treatment step in SuDS schemes treating highway and industrial run-off.

How a vortex separator works

Stormwater enters tangentially into a cylindrical chamber, creating a slow vortex flow. The rotational motion drives heavier solids — sand, silt and grit — outward and down to a sediment storage zone at the base of the unit. Lighter floatable material rises to the surface where it is retained behind a baffle. Treated water exits centrally near the top of the chamber.

The process is purely passive: no power, moving parts or chemicals are needed. Performance is measured against CIRIA C753 treatment performance targets, with most well-designed units achieving 60–80% removal of total suspended solids over typical UK rainfall conditions.

Treatment performance and applications

Vortex separators are most effective at removing sediment particles down to around 50 microns. They are particularly suited to sites where particulate pollution dominates the load — highway run-off, motorway service areas, lorry parks, fuel forecourts and industrial sites.

• Highway run-off — removal of brake-wear particulates, tyre fragments and road grit before discharge.
• Industrial yards — pre-treatment ahead of attenuation tanks or biofilters.
• Forecourts and lorry parks — combined with downstream oil-water separators where hydrocarbons are a concern.
• SuDS treatment train — first treatment stage before swales, wetlands or infiltration components.

Sizing and standards

Vortex separators are sized on the design treatment flow rate, normally taken as the run-off from a 1-in-1-year or 1-in-2-year storm rather than the peak attenuation flow. Sizing per The SuDS Manual (C753) and the manufacturer’s water-treatment performance data is normal. Larger units treat up to 1,000+ litres per second; compact units handle 5–100 l/s for small developments.

Maintenance — sediment removal by vacuum tanker every 12 to 24 months — is essential to sustained performance and should be programmed into the site operational plan from day one.

Related ViaCon solutions

ViaCon supplies vortex separators and the wider ViaCon Storm Solutions treatment train. See our flood control systems and the full stormwater solutions range. Related glossary entries: attenuation tank, SuDS and stormwater management.

Frequently asked questions about vortex separator

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