Grease separators – when to use them?
21/04/2022
Grease separators are required in the sewer system by the Environmental Protection Act. Water contaminated with oils or fats must not be discharged into the public sewage system. Wastewater containing oils and fats easily clogs pipes if the fat hardens upon cooling. Corrosive vapours and fatty acids also attack cast iron pipes and quickly lead to damage.
Where does this need occur and how does it work?
The mandatory installation of fat separators applies to catering facilities, kitchens in mass catering facilities, butchers, meat and sausage factories, oil presses, canneries, abattoirs, fish processing plants, dairies and catering companies. Grease separators are essential because introducing fat into sewer systems causes many operational problems and has a negative impact on the operation of sewage treatment plants.
These problems are due to the fact that fat is not soluble in water, but rather is present in form of hardly decomposable, sticky lumps. Fat separators are therefore used to separate fats from waste water.
This is achieved by flotation, i.e. according to the gravity principle. Lighter, lipophilic substances move upwards inside the separator as a result of density differences. Lipophilic substances are those that tend to dissolve in fats and oils. The sludge is collected in the lower part or in a separate chamber upstream of the separator and the grease-treated effluent is discharged further.
How often should the grease trap be cleaned?
The frequency of cleaning depends on the amount of inflowing wastewater and its characteristics (concentration of grease and suspended solids). The recommended frequency of inspection and removal of pollutants is once every two weeks. According to EN 1825-2, fat separators should be drained and washed at least once a month, but it is safer to do it every 14 days.
When deciding on the type of separator, the most important factor to bear in mind is that emptying the separator should be as safe as possible for the environment. Below-ground separators are the most popular due to their price and practicality during emptying. After opening the covers of the device, the tank truck pumps out the contents of the separator. If there is not enough space outside to place the separator or if it is necessary to run a long waste water pipe, the separator should be placed inside the building. Otherwise a pipe that is too long will become overgrown.
It is best to consider installing two devices at the same time: a settling tank and a separator, or to choose a device integrated in one chamber. The advantage of the latter solution is, besides saving space necessary for installation, a faster and simpler assembly. Ecol Unicon grease separator EST-H has these exact advantages and is designed to treat wastewater with a hydraulic flow from 1 m³/s to 25 m³/s.
Scope of inspection
When emptying the unit each time, pay attention to:
- visual assessment of technical condition of components,
- checking the amount of accumulated fat and sludge layer (also in devices without a sludge section).
Current operations do not require going inside the manholes and can be carried out from the ground level. Removal of accumulated pollutants should be performed by a licensed company with appropriate equipment for collection, transport and disposal of pollutants and holding relevant permits. In order to ensure full comfort of users, together with the grease trap we also recommend using of sub-manhole odour neutralisers.