The European Union (EU)-funded REWAGEN project, which is being headed by the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) alongside the Spain-based Leitat Technology Centre, aims to develop a "multistage" electrochemical system for the treatment of dairy wastewater.
Wastewater discharged during the production of dairy products such as cheese, quark, and yogurt, can contain lactose, proteins, and milk fats. It may also contain surfactants and disinfectants used during the cleaning of production lines. Cheese production also produces a watery whey by-product solution – commonly known as sweet whey – that contains milk proteins and lactose.
The system being developed under the REWAGEN project is based on a combination of three technologies - electrocoagulation, electrooxidation, and a technology to reutilise the treated water and generate hydrogen. This water can be used directly – to clean, for example – and the hydrogen generated as a by-product from the electrolysis of the water can be used to supply the treatment plant with electricity.
Provide a substance flow that can be fed back into the system
To achieve this, Fraunhofer and its project partners aim to combine four different electrochemical processes.
It is first necessary to eliminate fats and oils from the wastewater. These substances are separated using a pulsed electro coalescence process – where dispersed droplets of oil and fat move around the alternating electric field and merge to form larger drops that can be separated mechanically.
Particulate impurities – tiny pieces of solid of liquid matter – are then separated using electro flocculation.
In a third electrochemical cell, dissolved organic components – such as proteins, fats, and lactose - are then degraded suing electro oxidative processes.
In the fourth and final stage, dissolved salts are removed using capacitive deionisation.
Dairy wastewater treatment “very cost intensive”
According to Fraunhofer, the disposal of this wastewater has until now been “very cost-intensive.”
Many larger dairy processors treat their wastewater in large-scale biological wastewater plants. But for small and medium-sized dairies, this sort of investment is unrealistic, said Fraunhofer.
The modular design being developed under project REWAGEN will, however, make it possible to adapt the system to the varying amount of wastewater at smaller dairies, according to Fraunhofer.