Bypass Separators

Bypass Separators treat all flows which are generated by rainfall rates of up to 6.5mm/hr. This in turn means it covers over 99% of all rainfall.
Flows which are above this rate are allowed to bypass the separator. These separators are used when it is believed there is an acceptable risk not to provide full treatment for high flows. This can be explained where there is low possibility of heavy rainfall and a large spillage occur at the same time.

Surface water drains normal discharge indirectly into underground waters or to a watercourse via a soakaway. Sometimes chemicals, suspended solids and oil can contaminate the surface water affecting the discharges. This can have a serious impact on the receiving water.

There are regulations put in place and agencies i.e the Environment Agency who have published guidance on surface water disposal. These offer a range of methods of dealing with pollution both at the source and the point of discharge from site. This is called end of pipe treatment.

Sometimes there are methods in which you may not need a bypass separator. When run-off is draining from car parks and non operational areas these are classed as low risk areas. Therefore a source control approach such as an infiltration trench or permeable surfaces. This maybe a suitable means of treatment.

You can also install oil separators on surface water drainage systems. This protects the receiving water from oil pollutants which can be present due to accidental spillage or minor leaks from vehicles.

There are 2 standard types of bypass separators.
Class 1 - which is suitable for removing small droplets of oil
Class 2 - Which are suitable for dealing with discharge where a lower quality requirement applies. For example where the effluent passes to foul sewer.

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