Separators are devices designed to separate and retain petroleum derivatives as well as suspended minerals (sand, sludge) that rainwater and meltwater flowing from any kind of watershed may contain.
APPLICATION, DEPENDING ON SEPARATION TECHNOLOGY USED
It is important to choose the appropriate separation technology for petroleum derivatives depending on watershed type and device working conditions. When choosing the appropriate technology it is important to take the following aspects into consideration:
- watershed size
- protection of the device against potential storm flow
- the amount of suspended solids in wastewater
- separator’s sensitivity (protection zone, prohibited areas, etc.)
Design
Separators have watertight concrete body (chambers of Ø1000–3000 or a separated reservoir chamber) usually does not need extra load. Depending on the separator’s location cast iron or cast iron and concrete manholes classes A15, B125, C250 and D400 are used. In order to adjust the location of the separator slab to ground elevation there is an additional top element used made of concrete rings corresponding to the diameter of the separator’s body. When the sewer system is located deep in the ground, a reduction-slab and a chimney made of ID 1000 rings can be used. The inlet and outlet are located in the axis of the separator. It is also possible to deviate inlet and outlet axes (consult the catalogue for details) as well as connect several inlets.
A separator placed in a concrete tank with foundation on bearing soils up to 10 m below ground level does not need special foundation and does not need static calculations. Normally, excavation death is prepared using minimum 10 cm C8/10 (B10) concrete substructure or well-compacted layer of gravel or other course non-cohesive soil. Separators should have gravitation inflow. In case of need for wastewater pumping it is recommended that the pumping station is located after the separator. A separator must be located in a place providing access for a suction vehicle.
In order to reduce maintenance costs and improve ecological safety there is a possibility to connect a separator to alarm systems such as sediment level sensors, oil and overflow sensors. Regular monitoring of the device limits the necessity to physically control the device and shortens the reaction time of maintenance teams in case of a failure.
OPERATION
In high-efficiency coalescence separators the separation of petroleum derivatives takes place due to the phenomenon of gravitational separation of oil and water, which is enhanced by the phenomenon of coalescence. Mineral solids suspended in wastewater settle in the process of sedimentation and filtration in coalescent material. The construction of the separator slows down wastewater flow and at the same time forces its separation into wastewater stream with petroleum derivatives (stored in the separator) and water. Petroleum derivatives lighter than water come onto the surface where they accumulate forming a layer. Small droplets of mineral oil, which do not have sufficient buoyancy, form bigger drops when flowing through coalescent material (coalescence process) what makes their gravitational separation easy. Submerged outlet stops separated impurities from getting into the receiver.
ESK coalescent separator
ESK COALESCENCE SEPARATORS VERSIONS
Due to vast application of coalescence separators there are different versions available suited to individual needs resulting from installation conditions:
- ESK high-efficiency coalescence separator
- ESK-B high-efficiency coalescence separator with by-pass
- ESK-E high-efficiency coalescence separator with inflow closure.
The standard equipment of the device is a coalescence separation column together with wastewater outflow closure installation that activates when the limit of oil stored in the separator is reached. The task of a float valve at the outflow is to stop any accumulated petroleum derivatives from being flushed out into the outflow.
All design elements are characterised by high chemical resistance and mechanical durability. Inflow and outflow pipes inside an ESK-E separator are made of stainless steel (the device dedicated for energy industry).
Suspended Solids Separation – Cooperation of Coalescent Separators with a Settling Tank
Wastewater with suspended solids should be pretreated in a settling tank. A correctly designed settling tank should provide optimal treatment efficiency and sufficient storage capacity for suspended solids.
A settling tank can be a standalone device (Settling Tanks) or can be integrated with a coalescence separator where the settling tank is placed below the coalescence column – typically marked H (e.g. ESK-H, ESK-BH etc.). The purpose of such integrated system is to reduce the size of treatment installation, while providing high degree of treatment of petroleum derivatives and suspended solids. It is used mainly in highly urbanised areas.
Optionally, this device can be fitted with an alarm system (Monitoring System) or linked up to Bumerang, an intelligent rainwater management system.
ESK-H coalescence separator with settling tank
OS horizontal settling tank cooperating with ESK coalescence separator
Coalescence Separators in Overflow Systems with Regulators
Using regulators enables efficient protection of rainwater pretreatment facilities against their overload resulting from torrential rain inflows. Overflow systems designed by Ecol-Unicon are chosen individually and consist of:
- distribution chambers with a flow regulator adjusted to pretreatment devices throughput;
- a connecting chamber;
- external overflow of a diameter and gradient adjusted to accept maximum rainwater inflows.
In case of pretreatment systems before which a distribution chamber with a flow regulator and a by-pass pipe are installed it is important that the chamber is able to distribute the wastewater properly. Nominal flow from the watershed (Qnom) should be treated completely while in case of the maximum flow from the watershed (Qmax), the separator should be protected against hydraulic overload. An appropriately chosen flow regulator ensures that Qreg = Qnom at two points A and B.
The height of the bottom of a by-pass pipe (or the location of the top of overflow edge) should be at elevation of H ≥ HA, which ensures that the flow directed into pretreatment system is Qreg. With wastewater inflow, impoundage level rises to H = HB and the flow lower than Qreg, is directed thought the regulator, which protects the device against hydraulic overload. The flow higher than Qreg is directed into the by-pass pipeline.
