SurfaceWater Treatment (SWT) Separator Range
Treat surface water runoff.
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Sizing, regulations, installation. Our team has been answering these questions for over 25 years.
Tanks Direct offers the Klargester AquaTreat range of water treatment separators help to reduce pollution in line with SuDS Mitigation Indices by removing metals, suspended solids, and hydrocarbons from surface water.
Our surface water treatment range is suitable for a wide range of SuDS schemes such as industrial estates, permitted sites, and roadways.
They are not considered oil separators according to EN 858-1 and must not be used in applications where full certification is required.
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Surface Water Treatment (SWT) Separator Range FAQs
What's the difference between an SWT separator and a full-retention oil separator?
An SWT (Surface Water Treatment) separator, such as the Klargester AquaTreat range, is designed to reduce pollutants like metals, suspended solids and hydrocarbons in line with SuDS Mitigation Indices. Unlike Class 1 or Class 2 separators tested to EN 858-1, they are not certified as oil separators and shouldn't be specified where full oil separation certification is a planning or Environment Agency requirement. Always check your discharge consent or drainage approval before selecting an SWT unit.
What size SWT separator do I need for my site?
Sizing depends on the contributing catchment area, surface type (roof, car park, road) and the local SuDS Mitigation Index requirement set by the LLFA or drainage engineer. As a rule of thumb, larger paved or trafficked areas with higher pollution risk need a bigger unit or a higher treatment stage. We're happy to talk through catchment figures with you, but final sizing should be confirmed against your site's drainage strategy or SuDS approval documentation.
Where are AquaTreat separators typically used?
They're commonly specified for industrial estates, permitted sites, car parks and roadways where surface water run-off needs treating before discharge to a watercourse or soakaway. They suit schemes needing to demonstrate compliance with SuDS Mitigation Indices rather than sites requiring full EN 858-1 oil separator certification. If your site handles fuel, chemicals or has a specific pollution risk, a certified oil separator is the more appropriate choice.
Do SWT separators need regular maintenance?
Yes — like any separator, silt, sediment and hydrocarbons will accumulate over time and reduce treatment efficiency if left unchecked. We'd recommend periodic inspection and desludging by a licensed waste carrier, with frequency depending on site pollution loading and local guidance. Keeping accurate maintenance records also helps demonstrate ongoing compliance with your SuDS approval.
Can an SWT separator be installed below ground and under traffic loading?
Most units in the AquaTreat range are designed for underground installation and can be specified with trafficked access covers for car park or roadway locations. Installation depth, groundwater conditions and loading class all affect the final chamber and cover spec, so it's worth confirming ground conditions before ordering. As with any underground tank, proper bedding, backfill and a level base are essential to avoid structural issues.
What should I check before ordering an SWT separator for a planning condition?
Check exactly what your planning condition or SuDS approval specifies — some authorities require a treatment train with a defined Mitigation Index, while others may insist on full oil separator certification to EN 858-1. Since AquaTreat separators are not certified oil separators, confirm with your drainage engineer or LLFA that this range satisfies your specific condition before you commit. Getting this confirmed early avoids costly re-specification later in the build programme.