Dissolved air flotation for a fish factory


ClearFox® dissolved air flotation for a fish factory as a containerised wastewater treatment plant in Hungary


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Fish processing wastewater treatment

Technical Information


Dissolved air flotation for a fish factory






70 m³/day


  • Reliable degradation of COD and BOD5
  • Reliable purification for direct discharge


Food and beverage


A fish factory in Hungary processes around 500 kg of trout every day. This produces about 70 cubic metres of wastewater per day, which comes from three sources: Firstly, the fish itself brings liquid with it, which dissolves during transport, and secondly, the fish is regularly washed during the entire processing process. The third source of wastewater is the employees’ sanitary facilities.

The fish factory receives the goods from the catching stations and processes them into fish fillets. In the process, fish scales mix into the wastewater, as do fats, oils, and blood. This increases the COD to up to 7000 mg/l, the BOD5 to around 3000 mg/l and the FOG content to around 1000 mg/l.

ClearFox wastewater treatment


ClearFox DAF for a fish factory

The challenge in this project was an existing wastewater treatment plant that was completely overwhelmed with the wastewater load. During a site visit, ClearFox® engineers discovered that the existing plant was clogged with sludge. Thus, they had to find a solution that could meet the specified requirements. After treatment, the wastewater quality should be so good that the fish factory can discharge it into a public watercourse.


The solution for this project was a ClearFox® dissolved air flotation system. As the fish factory already had a collection tank for the wastewater, which they wanted to continue using, they wanted the complete wastewater treatment plant in a sea container. This was to be located outside the production halls on the company’s premises. A screw screen separates all coarse solids from the wastewater before it flows into the DAF.

The ClearFox® dissolved air flotation system is an ideal solution for wastewater from the food and beverage industry. It reliably removes emulsified, dissolved, and suspended substances from the wastewater. The efficiency is between 95 and 99 per cent. In this project, it reduces the COD to 700 mg/l, the BOD5 to 250 mg/l and the FOG content to 100 mg/l.

ClearFox screw screen
ClearFox flotation system for fish factory

At the beginning, the fish factory took wastewater samples, which the ClearFox® team analysed in the in-house laboratory. The laboratory staff then determined the perfect ratio of precipitants and flocculants. These bind all substances so that the ClearFox® DAF can discharge the resulting flocs as sludge. A neutralisation unit adjusts the pH value of the resulting clear water. This makes it ideal for direct discharge.

For this project, the ClearFox® team took over the complete planning of the project, the analysis of the wastewater, the development of the dissolved air flotation, the dismantling of the existing treatment system, the shipping, the installation on site and the training of the employees.

Read More about ClearFox® Projects with DAF technology

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