Separator system for light liquids SEPKO ST


The oil and hydrocarbons separator SEPKO ST is a treatment plant for light liquids (eg oil and petrol) for wastewater running off from paved surfaces such as squares, cars parks, underground garages, etc. or it can be used as part of treatment for industrial wastewater such as those discharged from car washes.
The line of SEPKO ST separators is engineered for a flow rate from 1.5 up to 30 l/s and include the sludge trap.
The system includes the trap for sludge, as provided in the EN 858, upstream of the oil-water separation zone dimensioned in function of different relationships relative to the nominal dimension of the separator for light liquids.


There are many human activities where oil products are used. In practice, it is impossible to avoid oil spills into the watercourses. A modern and effective oil separation technology is required to prevent the pollution of the environment. SEPKO ST oil/water separators are manufactured of all nominal sizes according to European standard EN 858-1 for water flow rates 1.5 to 150 l/s. As an option, integrated sludge trap may be supplied with the separator — all in one body. SEPKO ST contains no moving or wearing parts therefore it is very durable and requires little service. The separator is equipped with coalescing technology which has established itself as the most efficient gravitational oil separation material on the market. The coalescing media has also a high degree of resistance to plugging caused by dirt, sludge and biological growth.

Applications of oil/water separators:

  • rainwater run-off from petrol stations, parking areas, road terrain
  • process wastewater from car washes, industrial applications etc


Oily water influent enters into the separator tank under water surface through the inlet pipe (1). Water flows to the first primary settling section (2) where solids particles and bigger oil droplets are removed by gravity. Then water is directed through the coalescing media (3). As water passes horizontally through the pack of coalescing media the oil droplets rise vertically until they contact the material. By contacting the oleophilic surface, the oil particles are captured and they coalesce with other particles becoming larger. As the process continues, bigger oil droplets will be formed and driven upwards by gravity until they reach the water surface. As solid deposits accumulate on the coalescing media they increase in mass and eventually slough off to the bottom of the separator where they accumulate until disposal. This self-cleaning feature significantly reduces the frequency of cleaning of the coalescing media. Clean water after treatment is discharged through outlet pipe (5). SEPKO ST is equipped with an automatic closure device (4) which is calibrated to float on water and to sink in oil. This floating valve closes water outlet when the amount of accumulated oil on the water surface has reached the maximum level.



A body of SEPKO ST oil/water separator is manufactured from polyethylene by modern process of rotational moulding. The production method is ensuring the proper raw material composition, machine settings and optimised process parameters. Therefore all finished products are made with the highest quality and consistent accuracy. The automatic production is preventing from failures caused by human factor as well. Polyethylene material used for the production can be easily recycled reducing waste and environmental impact. Tanks made from PE are corrosion-proof, their smooth surfaces are ensuring the simple cleaning during servicing.


Technical Specifications

SEPKO ST provides a perfect load bearing capacity by keeping low weight of the product. The great stiffness of the separator body is achieved due to the advanced design and special ribbed structure. SEPKO ST is designed to withstand the heavy ground and groundwater loads without any significant deformations. The main advantage of the rigid body is that SEPKO ST may be installed in a significant depth from the ground surface without any additional concrete slabs or casings etc. Therefore the time and the cost of installation works of the separator are significantly reduced.

Features of the coalescing material:
Special oleophilic (oil attractive) polypropylene providing years of trouble free service.
Oil droplet‘s rising distance is reduced to 6 mm. The shorter distance means lesser rise time travelled to coalesce which will result in better removal rates.
Coalescing surface (approx. 450 m2/m3) is more than three times larger as other commonly used media.
Resistance against plugging by solid particles due to self cleaning design.
99,99+ % removal of free and dispersed oil regardless of micron size.

Gross dimension are shown in table as follow.

Vertical cylindrical
NS x 100
STORM BLACK CE 6/60066001601300148012201170180
NS x 200
STORM BLACK CE 1.5/6001.56001601300148012201170180
STORM BLACK CE 3/60036001601300148012201170185
Horizontal cylindrical
NS x 100
STORM BLACK CE 10/1000101000160169018302500115001430390
STORM BLACK CE 15/1500151500200143015154000214901420510
STORM BLACK CE 20/2000202000200169018304000214701400650
STORM BLACK CE 30/3000303000250169018302500 + 45002170014901020
NS x 120
STORM BLACK CE 6/120061200160143015152400112301160250
STORM BLACK CE 10/200010200016014301515400021230116480
STORM BLACK CE 15/3000153000200169018304000214701400590
STORM BLACK CE 20/4000204000200169018305500214701400810
STORM BLACK CE 30/6000306000250169018303500+45002145013801120
NS x 300
STORM BLACK CE 3/500035000160143015154000212501180430
STORM BLACK CE 6/500065000160169018304000215101440500
STORM BLACK CE 10/50001050001601690183045000215101440560
STORM BLACK CE 15/5000155000160169018305000214801470630

NOTE: The data are not binding and may change without notice

Letters shown in illustrations and in tables have the following meanings:

NS – nominal flow (NS)
ST – sludge trap volume
DN – nominal inlet and outlet diameter
D – diameter (vertical or horizontal)
A – total height (extension excluded)
L – total length (horizontal cylindrical tank)
n – number of manholes
A1 – inlet pipe height
A2 – outlet pipe height
W – weight (manhole excluded)

For further information and tailor made solutions, please contact technical office.

The servicing of SEPKO ST oil/water separator is very simple; it does not require much labour and material costs. Main servicing procedures are:

  • extraction and disposal of accumulated oil and sludge by means of vacuum truck,
  • cleaning of the coalescing modules from solids using high pressure cleaner.

The design of the modules allows convenient lifting off the tank and washing out of the 4 sides.
After the proper cleaning 100 % functionality is returned to the oil/water separator.
SEPKO ST does not contain any replacement filters which should be disposed of as hazardous waste.

The separator is provided in the REINFORCED version or in the EXTRA version for greater strength in case of the presence of ground water or for the most demanding solutions.

Sizing of sludge trap.

According to EN858-2 standard, separator systems shall incorporate a sludge trap either as separate unit or as an integral part of the separator.
The sludge trap is always included in a storm water runoff treatment plant SEPKO ST (except the model SEPKO ST 30/6000)
In most models the sludge trap is integrated in the same tank with oil separator.
The volume of the sludge trap can be determined as given in the table below:

Volume of sludge trapQuantity of sludgeApplication
NS 100/fd a)SmallProcessing wastewater with defined small sludge volume Catchment basins on petrol tank areas
NS 200/fd b)MediumPetrol stations, vehicle parking lots, garages
NS 300/fd c)HighCarwash, truck wash places

a: Not for separators NS ≤10, except for covered car parks.
b: Minimum volume of sludge trap 600 liters.
c: Minimum volume of sludge trap 5000 liters.

fd is the mass density factor defined by the EN 858-2 in ‘Appendix A, and depends on the density of the lighter fluid to be separated and combination of separation light liquids.


Separator Alarms.

SEPKO ST oil separators can be equipped with alarm system for automated and remote monitoring of accumulated oil, sludge or liquid levels. Alarm allows the operator time to take corrective action ensuring the safe and economic operation of separators. The system is preventing oil passing through the separator and polluting watercourses which may result in expensive fines and clean up costs. Timely removal of accumulated sludge and oil from reduces the servicing costs of separator. There are two models of separator alarms. The alarm model UTA is fitted with one probe for monitoring the oil layer. The alarm model IP65 can be equipped with up to 3 probes for warning of excessive levels of oil, sludge and liquid within. The standard version of the alarm is mains powered. Battery or solar powered alarms can be supplied upon request. Options: beacon, sounder, GSM alarm notification. The alarm units are ATEX approved (Baseefa 08ATEX0110/1).

Bypass systems.

Bypass systems can be used when it is considered an acceptable risk not to provide full treatment for high flows, e.g. where only small spillages may occur and the risk of spillage is small. The system is dividing the peak rainwater flow in case of heavy rain. Only 1/3rd (in some cases even less) of the average maximum rainfall flow is directed to the oil/water separator, and the excess flow goes via bypass. Considerable investment cuts may be obtained by using bypass system, in comparison with conventional full retention treatment systems. The bypass system allows employing of smaller and more cost-efficient oil/water separators. According to the environmental studies the biggest part of oil and other pollutants is washed off in the beginning of the shower while the complete rainwater flow is treated by the oil/water separator. Therefore, although only a part of the peak flow is being processed, the bypass system is ensuring a very efficient oil removal.



SEPKO ST separators were successfully testes and approved according to provisions of European standard EN 858-1. The testing of treatment efficiency, i.e. determination of nominal size of the separator, water tightness and stiffness of the tank were performed by the independent authorities.
After treatment with SEPKO ST the residual hydrocarbon content in water of less than 5 mg/I is achieved. This effluent value is mandatory for oil/water separators of Class I acc ording to the standard EN 858-1. Based on the test results separators were granted with CE mark. Our oil/water separators comply with the standards of Russian Federation as well. Appropriate certificates issued by the Russian authorities are in our possession. AZU Water is available to develop solutions tailored to the particular needs of the customer.