Light liquid separator
A light liquid separator system (also known colloquially as an oil separator , petrol separator or mineral oil separator ) is a waste water treatment system in the form of a basin in which light liquids (e.g. oils ) are separated by floating and retaining them on a baffle . The contaminated sewage flows under the baffle, whereby light liquids and oil droplets float up and cannot pass the baffle. The term “oil separator” is also used colloquially for oil mist separators (e.g. for the oil separator in a car ).
function
The operating principle of the oil separator is based on the difficult miscibility of oil (or gasoline) and water and the difference in density between these organic components and water, i.e. H. the specifically lighter organic phase floats and collects on the water surface. The light liquids separated in this way in the oil separator can then be sucked off and disposed of. A cleaning performance of 100 mg / l residual content is possible.
Coalescence separator
Coalescence separators are a further development of conventional gasoline separators. The effect of these systems is based on the principle of coalescence , i.e. H. the confluence of small oil particles to form large oil droplets is encouraged. This means that even the smallest oil droplets can float up and be separated according to the principle of gravity. A cleaning performance of up to 5 mg / l is achieved.
Vortex separator
The vortex separator combines the functions of the coalescence separator, lamella separator and sedimentation basin. The wastewater entering tangentially is guided in a spiral system. Oils and oil droplets can float due to their lower density compared to water. The large, spiral-shaped surface coated with an oil-absorbing material composite on the inner wall serves as a coalescing surface. The oils collect in the center of the spiral and can be removed from the surface. The solids are forced outwards by the circulation, separated from the oil and sink to the bottom. They can be drained or pumped out of the funnel-shaped bottom of the vortex separator.
system
A separator system consists of a sludge trap, the separator and the sampling.
The sludge trap is a basin, the size of which is specified in the standard. The minimum volume is 600 liters. Usual sizes are 650 liters (up to NS 3), 2500 liters (from NS 3) and 5000 liters. Today, the sludge trap must have a coating, a closed cover and a baffle plate in the inlet so that the water in the sludge trap can calm down and the sludge settles.
Then the separator unit follows. In order to prevent the uncontrolled leakage of oils through the drainage of the separator (if too large a quantity of separated oil is reached), it is necessary that a float in the separator mechanically closes the drainage of the separator before this specific amount of separated oil is reached. This automatism is referred to as automatic completion . The float is tared to the density of the expected light liquids (for example 0.85 g / cm³). Older gasoline separators without this device are no longer permitted today.
In addition, the separator system should have an elevation compared to the lowest inlet point. If this is not the case, a warning system must be installed in consultation with the lower water authority.
However, the standard now generally prescribes a warning system for new systems. This warning system consists of a control unit and two probes, a probe for the build-up (see elevation) and a probe for measuring the oil layer thickness. The warning message is output via a lamp and a warning tone. All system parts that are fastened in the separator must be explosion-proof and have ATEX approval.
The system must be able to hold back the light liquid that occurs in the event of an accident.
A separator system achieves the highest cleaning performance in a so-called "SBKP" system. A combination with a coalescence separator with an upstream gasoline separator .
A separator especially suitable for large wastewater flows is the " API oil separator ". It is a device designed to separate large amounts of oil and dissolved solids from wastewater from (petro) chemical and other industrial plants.
A sampling shaft is to be provided behind the separator unit . Sampling devices in the form of a suction hose are no longer permitted today. The sampling shaft is similar to a sewer shaft, but has a downward gradient in the channel, which makes it possible to take a representative sample from the "flowing wastewater stream" with a standardized sampling bottle.
Purpose and locations
Oil separators are required on all surfaces where substances hazardous to water occur in the form of light liquids in order to separate these pollutants from the wastewater and retain them in the system so that they can be discharged to disposal facilities such as public sewers or possibly even into a body of water . In their waste water statutes, some waste disposal authorities therefore prescribe the operation of a light liquid separator or such limit values for substances that are introduced so that they can only be achieved through such waste water pretreatment. Affected are, for example, petrol stations , vehicle workshops, washing areas for cars or agricultural machinery or other factories. When draining such systems into a body of water via oil separators, they have to meet additional requirements in Germany, such as a sewage-free workshop operation, circulation of water, extensive separation of rainwater and a restriction on the use of cleaning agents that are easy to separate ; After pretreatment, the liter of wastewater may contain a maximum of 20 mg hydrocarbons (i.e. oils), whereby this limit value is considered to be complied with when operating a state-of-the-art separation system.
Maintenance, control and relevant standards
Before there is more light liquid in the separator than it can hold without impairing its function, it must be disposed of from the system. These oily solid, sludge or liquid substances are all hazardous waste (waste codes 130501 * to 130508 * according to the European waste catalog ). Technical standards stipulate controls and maintenance of the system so that this disposal point or a fault can be detected reliably and in good time. A distinction is made between the
- Self-control after successful specialist training by an instructed person and the
- Six-monthly maintenance, which should be carried out by a specialist in separator technology.
Both are to be documented in the operating log.
Germany
Monthly check
In Germany, maintenance is based on DIN 1999-100 / 200. The monthly inspection by an expert (DIN 1999-100 point 14.3) is mandatory
- Measurement of layer thickness or volume of the separated light liquid
- Measurement of the sludge level or volume
- Check the functionality of the automatic shut-off of the separator (which blocks the separator when the collection volume is exhausted) or, if available, the alarm device that indicates the exhaustion of the collection capacity. The latter is only necessary again 6 months after a general inspection.
- Visual inspection of the water level in front of and behind the coalescing insert during flow to detect any blockage of the insert.
- Control of any special constructions
Semi-annual maintenance
According to item 14.4 of the standard, maintenance by a specialist every six months is also mandatory
- Control of the coalescing insert with cleaning or replacement according to the manufacturer's instructions
- if necessary cleaning and emptying
- If available, cleaning of the drainage channel in the sampling shaft
The maintenance period can be extended to a maximum of 12 months if the system is only used to protect areas and systems or to treat rainwater.
Knowledgeable
The necessary expertise can be acquired through a briefing to be documented by the manufacturer, expert organizations in the field of separators, chambers of crafts or professional associations (point 14.7 of the standard).
General inspection
Before commissioning and every 5 years, every operator of a separator system is obliged to undergo a comprehensive general inspection by a specialist. This test also includes the tightness and all technical parts from the condition of the inner wall to the taring of the independent locking system. The operating log and the provision of the technical documents and permits and the evidence of the disposal of the separated contents of the system are also checked. The actual waste water accumulation must also be assessed according to origin, quantity, substances, detergents and cleaning agents, operating and auxiliary materials, compliance with boundary conditions and, in relation to this determined waste water accumulation, the suitability, performance and dimensioning of the separation system. Defects must be recorded in the comprehensive test report and, if necessary, rectified in consultation with the responsible authority (point 14.6 of the standard).
During the leak test, the separator system is usually filled to the lower edge of the lid. A common reason for the leakage of separation systems is often the poor execution of the grouting in the area of the shaft structure.
Even in the case of fault-free systems, the test reports and the operating log must be kept and presented to the responsible supervisory authorities or the operators of the respective municipal sewage systems on request (point 14.7 of the standard).
In addition to DIN 1999-100, the European standard EN 858-2 must also be observed for the warning device.
Automatic warning device
According to DIN EN 858-1 6.5.4, separator systems must be equipped with an automatic warning device. According to DIN 1999-100 5.7, a warning device can be dispensed with if it is impossible for light liquid to escape from the system and the shaft structures. Warning devices monitor the oil layer with the help of a sensor and give an alarm before the automatic lock closes. The alarm is transmitted from the separator to the display device via cable. With the radio warning system, the data transmission of the measured values from the sensor (in the separator) to the evaluation unit (in the building) takes place via a 2.4 gigahertz radio link. The warning system is subject to a regular test. For petrol stations every five years. All others are to be checked every 3 years.
Cant
If it is not possible to maintain an excess, a warning device for light liquids must be installed in old systems (see 5.3 EN 858 T2); For new systems, the standard EN 858-1 in the 2004 version applies.
history
The first oil separators were small casting pots that were integrated into the drainage system. Some can still be found today, e.g. B. at old closed petrol stations or in garage yards .
Later a mud trap was built as a concrete shaft in front of it. The reinforced concrete design in a shaft structure with a coating and internal components developed from this. This design has proven itself to this day.
In the past, systems were also built using in- situ concrete , today only systems can be used that have building authority approval and are therefore manufactured in a factory.
particularities
The so-called oil skimmers are a special type of oil separator . These remove floating oils and grease from the surface of the liquid by means of a carrier. This collects the oil or fat from the surface and is cleaned by scrapers in the device. The removed oil / fat is then collected in a separate container.
The separator system is not suitable for treating an emulsion . Then an emulsion splitting system must be installed downstream.
Special, mostly mobile oil separators are used in the rehabilitation of, for example, mineral oil accidents (hydraulic rehabilitation).
Norms
The technical standards for oil separators are EN 858-1 and EN 858-2 as well as the German (residual) standards DIN 1999-100 and DIN 1999-101:
- DIN EN 858-1 Separator systems for light liquids (e.g. oil and petrol) - Part 1: Construction, functional and test principles, labeling and quality control; German version EN 858-1: 2002 + A1: 2004
- DIN EN 858-2 Separator systems for light liquids (e.g. oil and petrol) - Part 2: Choice of nominal size, installation, operation and maintenance; German version EN 858-2: 2003
- DIN 1999-100 Separator systems for light liquids - Part 100: Requirements for the use of separator systems according to DIN EN 858-1 and DIN EN 858-2
Technical limits
An oil separator mechanically separates two immiscible liquids from each other. It should be noted that the separation of the phases up to a state of equilibrium and the formation of stable phases with a clearly defined boundary line takes some time and thus some time is required for the liquids that are still mixed in the inflow. Otherwise unstable emulsions will form without a clear boundary line, which makes it difficult to separate the two liquid phases by suction or immersion walls.
In addition, an oil separator cannot under any circumstances separate the oil dissolved in the water . The solubility of smaller molecules such as butane or pentane is considerable (around 40 mg / l for pentane and 60 mg / l for butane), but higher alkanes and fats are much less soluble.
See also
Web links
Individual evidence
- ↑ for example Stadtentwässerungsbetrieb der Stadt Düsseldorf in its leaflet light liquid separator
- ↑ B. and E. in Appendix 49 to the AbwasserV
- ↑ Information portal for waste assessment (IPA) from LANUV u. a. Waste authorities: Waste profile 1305 Contents of oil / water separators, origin and characteristic composition