F: Grease separator, P: sampling system
DIN EN 1825-2
Firstly, it must be ascertained whether the discharge points for Grease wastewater are located below the backwater level. Even if this does not pose a risk, it must also be checked whether the calm water level in the grease separator is below the backwater level.
In principle, grease separator systems must not be operated in a back-up state, as this interrupts the necessary aeration and creates a risk of grease discharge. For this reason, DIN EN 1825-2 stipulates: Grease separator systems whose calm water level (SWL) lies below the backwater level (BFL) must be drained via a downstream backflow prevention system.
How can grease trap systems be protected?
The following can be used to prevent backflow in grease separator systems:
- Lifting stations in accordance with DIN EN 12050-1
- Lifting stations approved by the manufacturer in accordance with DIN EN 12050-2
- Backwater pumping stations approved by the manufacturer for this purpose
- hybrid lifting stations approved by the manufacturer for this purpose
As there is a risk of the grease separator flooding in the event of operational faults in wastewater lifting systems, these must be equipped with a mains-independent warning device. This is intended to signal the interruption of the wastewater flow to operating personnel both visually and acoustically.
The rules of DIN EN 12056-4 apply when sizing a lifting station. The partial flow supplied by the grease separator must be set to the value Qs (maximum wastewater inflow) in accordance with DIN EN 1825-2.
RWS: calm water level
F: grease separator
P: sampling system
Grease separator without a safety device
If the calm water level (NWL) is below the backwater level (BFL), backflow protection is essential. This applies to both underground grease separators and freestanding grease separators.
A backwater pumping station or hybrid lifting station protects the grease separator against backwater and drains it during normal operation without the need for pumping.
A backwater lifting station or hybrid lifting station protects the grease separator against backwater and provides drainage during normal operation without the need for a pump. In the event of backwater, drainage is provided via a pressure pipe through the backwater loop to the sewer.
Backwater protection inside buildings with a gradient towards the sewer
Wastewater disposal via a pressure pipe through the backwater loop, even in the event of backwater from the sewer.
Backwater protection inside buildings without a gradient towards the sewer
Furthermore, the discharge restrictions set out in DIN EN 858-2 must be observed. “Only wastewater containing fats and oils of plant and animal origin may be discharged into a grease trap. In particular, no
- wastewater with sewage (‘black water’)
- rainwater and
- wastewater containing light liquids, e.g. fats and oils of mineral origin
be discharged into a grease separator system.
A backwater pumping station protects the grease separator against backwater and drains it during normal operation without the need for the pump to run.
A backwater lifting station protects the grease separator against backwater and performs drainage during normal operation without the need for a pump. In the event of backwater, drainage takes place via the backwater loop to the sewer.
