Car wash Glossary


Device that uses gravity to prevent harmful substances from entering the drainage system by separating them from the wastewater, e.g. grease separator, separator for light liquids (petrol separator, heating oil separator), heavy liquid separator, starch separator

Absorption of one substance into the interior of another without the chemical contamination of both substances as opposed to adsorption = surface accumulation (e.g. oil binder)

Waste water
Run-off water altered by use and any water entering the sewage system

Used oil
Spent mineral oil products or residues belong to hazardous waste. The Waste Oil Act of 23/12/1968 regulates the collection, transport and treatment of waste oil in order to protect groundwater. Note: One litre of oil can make a million litres of water undrinkable!

Adsorbable Organic Halogens

Aromatic hydrocarbons
Collective term for ring-shaped compounds based on benzene (e.g. aniline, phenol, toluene).

Swellable clay-based adsorbent

Biochemical oxygen demand

Benzene, toluene, xylene

Chlorinated hydrocarbons which are mainly used as solvents and are generally assigned to Water Ordinance Class 3

Chemical oxygen demand

Washing-active substances with surface-active properties. Detergents are used as washing, rinsing and cleaning agents as well as flotation and fire extinguishing agents. The Detergents Act regulates the requirements for detergents and cleaning agents with regard to their ingredients that are hazardous to water.

Ratio of mass to volume

Additives/chemicals by which a separation or splitting of emulsions is possible

Finest distribution of a substance in another without a solution being formed

Dissolved, organically bound carbon

German Standard Procedure
DEV for water, waste water and sludge analysis: (DEV) generally binding analytical regulations, which have since been incorporated into the DIN set of standards

Sensor, which is usually based on amperometric or potentiometric principles and is used to measure the concentration of various substances.

Flotation process in which the gas bubbles (hydrogen and oxygen) are generated by electrolysis. Used primarily in the treatment of oil-emulsified wastewater.

Chemicals to reduce surface tension – used to stabilise emulsions

Mixture of two liquids that are not soluble in each other, in which one is dispersed in the other in the form of fine droplets (e.g. milk)

Emulsion splitting plant
Plant for splitting an emulsion for the purpose of separating the individual components

Extraction / leaching / washing out of a substance from a mixture with an extraction agent – e.g. in the residual oil determination of mineral oil separators

Explosion protection
Measures and equipment for protection against explosions, in particular caused by ignition sparks of electrical systems. The relevant accident prevention regulations, as well as special ordinances and regulations, in particular on electrical installations in potentially explosive atmospheres, the general regulations on the Ex ordinance and the VDE regulations VDE 0165 and VDE 0171

Precipitation process
Conversion of soluble compounds into undissolved ones after chemical reaction with a precipitating agent. The resulting precipitation product can be separated by suitable physical processes (physio-chemical purification process)

Lyophilic light substance with a lower density than water, which is only slightly soluble in water, as well as saponifiable and polar, e.g. food fats and oils of animal and vegetable origin

Collective term for processes used to artificially produce flocks, to absorb and trap the suspended and colloidally dissolved component of water

Agglomeration of particles under cross-linking

Chemicals that enable or accelerate flocculation but do not themselves form flocks

Sensor usually based on amperometric or potentiometric principles used to measure concentrations for various substances.

Process in which substance particles are floated out of the substance mixture by fine gas bubbles, e.g. air flotation, dissolved air flotation. This process produces flotation (floated sludge)

Hazardous substance
Toxic, corrosive, oxidising or carcinogenic substances – in accordance with the Hazardous Substances Ordinance –

Affinity to water


Cold cleaningr organic liquid, used at room temperature for cleaning and degreasing

Discharge of the electrical potential of colloids by oppositely charged ions

Process of enlarging colloids to form loose structures, also droplet union

Cohesive force within a body, based on intermolecular forces inside

Chemical compound of carbon with hydrogen, some of which include fuels. Hydrocarbons are in part difficult or impossible to degrade and are harmful to health

Hydrocarbon content
Content of mineral oils and their products in a wastewater sample determined by extraction (e.g., in accordance with DIN 38409, Part 18 – Trichloroethane) in mg/l or ppm. In connection with separators, in accordance with DIN 1999, the hydrocarbon is usually determined according to the non-dispersive infrared analysis method in order to assess the effectiveness, in particular of separation stage 2.


Light liquid directly separable
Mass fraction of the light liquid present in the waste water which has separated from the water by physical means after 15 min. due to the difference in density (DIN 38409 Part 19)

Light liquid not directly separable
Mass fraction of the light liquid present in the waste water which is emulsified or colloidally (apparent solution) or genuinely molecularly dissolved in water (DIN 38409 Part 19)

Light liquid separator
Drainage structure for retaining mineral oils in accordance with DIN 1999

Liquids in which other substances, liquids or gases can be dissolved without reacting with them. Organic solvents, e.g. chlorinated hydrocarbons, sometimes have a toxic or degrading effect on bacteria.

Nominal size
Dimensionless characteristic value for the hydraulic dimensioning of separators (usually maximum flow rate l/s)

Surface tension
Property of liquids which, as a result of intra-molecular electrical forces, form an interface which makes wetting more difficult

Common term for water-insoluble, liquid, organic compounds of vegetable, animal or mineral origin

Oil separator
see Light liquid separator

Oil binder
Oleophilic agent which is spread on oil – e.g. on soil/water and absorbs it. Oils which have been impacted must be disposed of.

Affinity to oil


pH value
Measure for determining the acidic or basic character of solutions (pH 7 = neutral)

With local charge distribution

Sludge trap
Device to be installed upstream of a separator for trapping the contaminants (settleable substances) of the waste water which pollute the separator

Heavy liquid
Liquid with a greater density than water, which is only slightly soluble in water, is unsaponifiable and non-polar (e.g. trichloroethylene, chlorofluorocarbons, chlorinated hydrocarbons, etc.).(e.g. trichloroethylene, chloroform)

Settling of solid particles suspended in a liquid under the influence of gravity

Hazardous waste
Collective term for waste which, due to its nature or quantity, may not be collected and disposed of with household or commercial waste (Sect. 2.2 Waste Disposal Act)

Washing-active substances (synthetic soaps) which reduce the surface tension of water and promote the dissolution of dirt. Surfactants are contained in detergents and cleaning agents

Total Organically Bound Carbon

Process for removing minute particles from gases or liquids by means of membrane filtration

Viscidity of liquids due to internal friction

Substances hazardous to water
May not be discharged into the sewage system or into a body of water. These include, for example, sulphuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, caustic soda, caustic potash solution, caustic chlorine solution, methanol, phenols, tars, mineral oils, petrol, benzene and others.

Water recovery
Purification and/or treatment of wastewater for reuse

Benefit/expense ratio