Oil traps

When dealing with urban runoff contaminated with oil, oil traps are an appropriate method of treating the water. For rainwater systems with very large water flows, traps have been developed which have a built-in lamellar construction which allows for the input of large amounts of water flows while the separated oil is held back.
Traps for rainwater are often constructed with circulation. In connection with minor rainfall, all of the rainwater will pass through the trap. In connection with heavy rainfall, the first runoff will pass through the trap. Usually, it is this part of the runoff that has the most oil in it, because the first rain to fall washes the surfaces clean. A sand trap should be installed before the oil trap.
Traps with circulation can therefore only be used in places without the combination of large amounts of oil and large flows of water.

Illustration: Teknologisk Institut