Oil separators (EN 858-1)

Separator systems for light liquids (e.g. oil and petrol) according to EN 858-1, also called oil separators, are waste water treatment plants in which light liquids are retained and separated. The functional principle is based on the difference in density between water and, for example, oil. The lighter phase (petrol, oil) floats up and can then be sucked off the water surface. The coalescence separator offers a further and effective method. Fine oil droplets are deposited on the surface of a special filter insert and finally join together to form an oil film. After a certain layer thickness is reached, the oil film breaks off and forms a larger oil drop which rises in the water and is separated.

On request, PIA GmbH will test your separator according to EN 858-1, whereby a practical test on your separator determines, among other things, the class and the nominal size.

Separator classes and requirements:

ClassMaximum permissible content of residual oil in mg/lSeparation technology
I 5,0 coalescence
II 100,0 gravity


Grease separator (EN 1825-1)

PIA GmbH tests separator systems according to EN 1825. These systems are used to separate animal and vegetable greases and oils from wastewater by gravity without needing an external energy source.

The nominal size of the separator plants for grease is determined either by the rated value found in the standard (EN 1825 Table 2 - Main dimensions for grease separators) or by a test according to EN 1825-1 8.5.1. In the practical test, the content of hydrocarbons in the effluent of the specimen must not exceed 25 mg/l.

Rainwater treatment

At the federal level, the Water Resources Act requires that precipitation water be handled as locally as possible. This can be promoted through the use of decentralised rainwater treatment plants. At the national level, a distinction must be made between the discharge of precipitation water into surface waters and the discharge into the soil or groundwater system. There are no federal legal requirements for discharge into surface waters, but country-specific requirements must be met. Requirements for discharge into soil or groundwater are regulated on the part of the Federal Government by the approval principles of the Deutsches Institut für Bautechnik (DIBt). Since 2005, DIBt has been developing approval principles at federal level for the discharge of traffic area runoff into soil and groundwater. In the approval process, a distinction is made between surface pavements and decentralised systems for connecting larger areas. New approval principles were formulated in 2011 for decentralised plants for the treatment of traffic area runoff with subsequent discharge into soil and groundwater. The specified test procedure is based on the guideline values of the Federal Soil Protection Ordinance (BBodSchV) and provides limit values for the parameters filterable substances, copper, zinc and mineral oil hydrocarbons.

The effectiveness of the treatment plants is tested under laboratory conditions. The tests of the AFS and MKW retention capacity are carried out on the original plant, the tests of the heavy metal retention on a reduced filter segment or a filter column. The aim of the approval principles is to create a framework for the granting of approvals by the building authorities. In North Rhine-Westphalia, the separation decree also allows the operation of decentralised precipitation water treatment plants with subsequent discharge into a surface water body. By proving the comparability of decentralised plants with at least one central rainwater clarification tank with regard to material retention and continuous operation, approval can be granted at state level.

Tests under laboratory conditions are performed at PIA GmbH. In addition, as shown in the photos, we offer charging solutions individually adapted to the test piece or manufacturer's requirements.



Wastewater lifting plants

Test according to EN 12050

EN 12050-1:2001

  • Wastewater lifting plants for buildings and sites
  • Principles of construction and testing
  • 1: Lifting plants for wastewater containing faecal matter

EN 12050-2:2000

  • Wastewater lifting plants for buildings and sites
  • Principles of construction and testing
  • 2: Lifting plants for faecal-free wastewater

EN 12050-3:2000

  • Wastewater lifting plants for buildings and sites
  • Principles of construction and testing
  • 3: Lifting plants for wastewater containing faecal matter for limited applications

EN 12050-4:2000

  • Wastewater lifting plants for buildings and sites
  • Principles of construction and testing
  • 4: Non-return valves for faecal-free wastewater and wastewater containing faecal matter
Testing of hydraulic performance

Recent News



Designation as DIBt test center

Since March 2021, PIA GmbH has been a designated testing body by Deutsches Institut für Bautechnik (DIBt) for the testing of systems in accordance with the approval principles for storm water treatment systems Part 1: Systems for the decentralized treatment of wastewater from motor vehicle traffic areas for subsequent infiltration into soil and groundwater.

The testing of the plants includes the retention of fine particles with Millisil W4, the retention of mineral oil hydrocarbons and the retention of the heavy metals zinc and copper. The latter test is carried out on a scaled-down filter element. In order to obtain building authority approval for the system, a particle retention of at least 92 % and a hydrocarbon retention of at least 80 % must be demonstrated. Within the scope of the heavy metal test, the effluent values of ≤ 1,875 µg/l for zinc and ≤ 144 µg/l for copper must be complied with. In addition, heavy metals may only be redissolved by de-icing salt within specified limits.

To date, ten storm water treatment plants of various designs have been tested in the test hall built by PIA GmbH for this purpose. The existing infrastructure allows the testing of plants with a connection size of up to 8,000 m². Underground storage tanks guarantee a receiving water volume of 80 m³. The discharge water is cleaned on site via buffer tanks and a light liquid separator before it is discharged into the sewer.

At the international level, test requirements vary with regard to the rainfall donors used, the pollutant load and the composition of the test media. The use of alternative test media helps to understand the effectiveness of the system under real-world conditions. For example, rubber dust can be used to represent tire abrasion and microplastics. In addition, different requirements for feeding the plant require individual solutions, which are implemented in a practical manner at the test institute.

Lecture new storm water treatment

Lecture on the current topic:

Decentralized storm water treatment in times of climate change and microplastics

Urban flash floods, the progressive sealing of soils and anthropogenic pollution such as microplastics urgently require alternative solutions in the field of precipitation water treatment. Local treatment and infiltration help to relieve hydraulically loaded combined sewer systems and to take targeted action at the point of pollution. Decentralised rainwater treatment plants can offer an alternative. In Germany, but also in other countries, requirements are therefore already being placed on these systems and tested under laboratory conditions. The lecture shows the current problems, gives an overview of the different treatment systems and their possible applications, and presents the test requirements and the tests.

Speaker: Daniel Verschitz, Time: 24.02.2021 at 10:00 a.m., Language: English

Duration: Max. approx. 30 minutes each + 10 minutes questions / discussion / feedback

If you are interested, you can register here: