Rainwater and process wastewater may contain oil-derived substances (such as oils, petrol or grease), which pose a serious threat to the environment. However, there is a way to significantly reduce the risk of such problems occurring – the use of oil separators. These are devices that separate mineral suspended solids and oil-derived substances before the water enters the reservoir or sewage system.
Oil separators and how they work
Oil separators, or otherwise known as hydrocarbon separators, are used for treating rainwater and process wastewater. They are used for separating and storing accumulated and separated light liquids with a density no greater than 0.95 g/cm3.
Devices of this type take advantage of difference in density of hydrocarbons in relation to water. Hydrocarbons accumulate on the surface of wastewater, increase their volume and form a suspension which is then filtered out. Depending on the size of the catchment area and the type of facility, sedimentation, flotation or coalescence is used to achieve this purpose.
When choosing a particular model of oil separator, it is worth taking into account not only its features and specifics of operation, but also its suitability for the current needs. Selecting a device which ensures efficient filtration is a guarantee of adequate water treatment.
Coalescence separators – what are they and how do they work?
Coalescence separators are free-standing flow-through or in-soil devices for separating and storing light liquids or oils from wastewater. To increase efficiency, unlike conventional oil/water separators, they are additionally equipped with a coalescing insert.
Separators of this type isolate oil-derived pollutants in the separation part due to the gravitational phenomenon, further assisted by the coalescence phenomenon. As a result of sedimentation, suspension is settled and then filtered.
Larger oil particles float upwards thanks to the floatation phenomenon, and those that have been broken down several times by adsorption are deposited on the surface of the coalescing filter, combined into larger particles, and then float to the surface.
The treated water flows out of the separator through an outlet equipped with a float shut-off, which closes as soon as the accumulated oil substances overflow. This prevents contamination of the sewage system or the natural waters.
Coalescence separators are typically used for treating rainwater and snowmelt originating from roads, motorways, car parks, fuel distribution points, storage depots. They are also used for process water from car washes and garages.
Coalescence separators are used wherever there are lots of cars.
Lamella separators instead of coalescence separators?
How do lamella separators, frequently used instead of coalescence separators, work? In this type of device, rainwater is directed to the first part of the device, which is an inlet chamber with a deflector. This calms the flow and directs the effluent stream to the filtration chamber.
Separation of pollutants takes place during the flow of contaminated water through the specially constructed lamella sections.
Inserts contained in lamella separators force a multi-stream flow, which results in a reduction of the wastewater flow velocity. Oil-derived substances are then separated using the flotation and sedimentation processes.
The treated wastewater is then directed to an outlet chamber fitted with a lid, which prevents the contents of the separation chamber from overflowing into it when the wastewater is backpressured into the unit.
Oil separators with lamella insert can be used to treat rainwater run-off from industrial areas, municipal catchment areas, roads, car parks, forecourts and other paved areas.
What is the role of settling tanks?
Settling tanks are devices for treating wastewater of easily settling suspended solids with a density greater than 1 kg/dm3, which can provide further assistance for the operation of oil separators.
They work by releasing suspended solids when the flow is slowed down, which is achieved by increasing the surface area per unit of wastewater received.
Depending on the type of catchment area and the required level of wastewater treatment, two types of settling tanks are used: horizontal or vortex ones.
How do horizontal settling tanks work?
Horizontal settling tanks use the phenomenon of sedimentation for retaining suspended particles and solids. The efficiency of the device is additionally increased by the installed deflector.
How do vortex settling tanks work?
Vortex settling tanks are most often installed in urbanised areas, where it is recommended to use devices with high suspended solids removal efficiency and a small footprint.
This type of device uses centrifugal force, which aids the separation of fine suspended particles and improves the efficiency of separation at high hydraulic loads.
Additional support, as in the case of a horizontal settling tank, is provided by a deflector which ensures better distribution of wastewater over the surface of the device and reduces the so-called dead zones. Ecol-Unicon offers both single- and double-chamber devices of this type.
The full range of oil separators and the associated settling tanks can naturally be obtained from Ecol Unicon!