A food manufacturer in Austria prepares meals daily in its commercial kitchen for catering and institutional food service. Production runs for around 16 hours a day, generating 2 to 3 m³ of wastewater per hour. The wastewater is extremely contaminated: with around 5,000 mg/l COD and 3,000 mg/l of lipophilic substances, its load is many times that of typical domestic wastewater.
Until now, the wastewater passed through a grease separator and static screening before flowing directly into the public sewer. As an indirect discharger, however, the company must comply with the sewer operator’s discharge conditions at all times – even when production is running at full capacity.
A grease separator only retains free-floating fat. Emulsified fats, starch, proteins and colloidal substances largely pass straight through it. On top of this come sharp fluctuations: cleaning cycles with alkaline or acidic detergents cause the pH to swing between 5 and 9, while production peaks change flow and load within a matter of minutes.
For the operator, this creates a twofold risk. Even a single batch of non-compliant wastewater triggers regulatory conditions, surcharges or problems with the authorities. At the same time, a commercial kitchen does not simply halt production because its wastewater treatment briefly falls out of step. What was needed, therefore, was a plant that not only treats wastewater effectively, but never allows poor-quality water to reach the sewer in the first place – without disrupting kitchen operations.
On top of this came the constraints on site: limited space, a short construction period, no odour nuisance and an operation without its own wastewater specialists.
PPU Umwelttechnik supplied a fully automatic ClearFox® DAF F 3.0 in an insulated 20 ft high-cube container. On site, only a concrete foundation had to be prepared. The plant’s control system also manages the customer’s buffer and sludge tanks as well as the biofilter, so the entire wastewater treatment process runs from a single central PLC.
A pumping station transfers the wastewater from the grease separator into a 6 m³ feed tank and mixes the grease separator at regular intervals to prevent fat layers from building up. An agitator in the feed tank equalises the inflow. A variable-speed pump then feeds two redundant in-line screens. If one screen becomes blocked, the control system automatically switches to the second based on differential pressure and signals that cleaning is required.
In a pipe flocculator, the plant doses aluminium sulphate in proportion to the flow rate. Caustic soda keeps the pH controlled between 6.8 and 7.2. Polymer from a fully automatic make-up unit agglomerates the microflocs. The dosing panel is housed inside the building, protected from the weather, and connected to the container via heated, insulated conduit pipes. Leak sensors and level monitoring safeguard all chemicals.
A multiphase pump produces the recycle water saturated with compressed air directly in the saturation line, without a separate saturation vessel. As the pressure is released, microbubbles form and carry fats and flocs to the surface. A pneumatic sludge lift removes the float, and a progressive cavity pump transfers it to the sludge tank.
The clarified water flows by gravity into a pump sump. There, sensors continuously measure turbidity and pH. The sensors are mounted in retractable assemblies and can be cleaned and calibrated during operation. Only when both values are within the target range does the control system open the route to the sewer.
If the values deviate, the plant automatically closes the sewer outlet and returns the water to the feed tank, where it passes through the entire treatment process a second time. A time delay ensures that brief measurement spikes do not trigger unnecessary switching. During start-up, too, the clarified water always circulates in the loop until stable values have been reached. If a measurement fails or delivers implausible values, the plant likewise switches to recirculation: the safe state is always the loop, never the sewer.
For the operator, this means the kitchen keeps producing while the plant absorbs fluctuations on its own. The feed tank acts as a buffer until the water quality is back on target.
A refrigerated sampler in the container takes flow-proportional samples in 24 bottles and provides a complete record of effluent quality. The PLC can be accessed remotely and sends alarms straight to staff smartphones. This allows PPU to provide support directly from Bayreuth when required, without travelling to site.
An extraction fan draws air from the feed tank, the sludge tank and the container and passes it through a humidified biofilter. As a result, there is no odour nuisance on the premises either.
With the ClearFox® DAF, the food manufacturer gains a compact, fully automatic pre-treatment system that drastically reduces fat and COD. Above all, it gives the company the certainty that only verified water reaches the sewer.
The plant continuously measures turbidity and pH in the effluent. If the values fall outside the limits, it closes the sewer outlet and automatically pumps the water back into the feed tank, where it passes through treatment again. Non-compliant water never reaches the sewer.
The control system treats implausible readings as a fault and switches to the safe state, i.e. recirculation. The retractable assemblies allow sensors to be cleaned or replaced during operation.
No. The feed tank buffers the inflow while the plant recirculates the water until the quality is right again. Remote access and smartphone alarms notify staff immediately.
A refrigerated sampler takes flow-proportional samples, which are available for self-monitoring and official inspections.
As soon as emulsified fats, starch or proteins occur in larger quantities, as they do in commercial kitchens and food production. Only physico-chemical treatment with flotation removes these substances reliably.
Yes. PPU designs every ClearFox® DAF individually according to wastewater volume, composition and discharge conditions. Quality-controlled recirculation with online monitoring can be integrated into any DAF system.
