EnviroChemie GmbH

Energy from wastewater How breweries can tap undiscovered energy resources

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Courtesy of EnviroChemie GmbH

The fact that beer is a nourishing energy supplier was known to beer-brewing monks as early as the Middle Ages. After all, it also had to act as food during the hard times of Lent. However, the fact that this beverage, which is popular throughout the world, could become an energy supplier for the brewery and the environment in the course of the manufacturing process – to be exact, during the treatment of the brewery's wastewater – is something new, in view of the centuries-old history of brewing.

As prices rise, large quantities of excess sludge from the treatment of wastewater have to be disposed of, which puts an enormous damper on profit margins. Another factor is the increasingly strict requirements concerning wastewater discharge parameters. This is a situation which does not necessarily give rise to much joy in many breweries here and around the globe. In the search for modern and cost-effective wastewater management, some breweries have already installed their own biological wastewater pretreatment facilities. In the long term this is a lucrative solution, because on the one hand anaerobic wastewater pretreatment, i.e. without oxygen, creates significantly less excess sludge, for example, and on the other hand the extensive independence from the future development of wastewater fees is a decisive criterion today. The convincing ecological aspect: biogas as a 'free by-product' of wastewater treatment can be fed back into the energy cycle of the brewery.

Composition and quality of brewery wastewater
During the production process, wastewater accumulates from the various component processes (wort production, fermentation, storage, filtration, bottling). In mixed wastewater, the COD concentrations are between 1400 - 6000 mg/l (COD is the parameter for wastewater contamination and indicates the chemical oxygen demand). The nitrogen content (N) of 50 - 100 mg/l results mainly from organic nitrogen (protein, yeast) and only partly from ammonium and nitrate. For biological wastewater treatment, the nitrogen and phosphorus concentrations are sufficient, without additional metering of chemicals. When the efficiency of a biological installation is being determined, it must be remembered that wastewater is not created continuously during brewing operations: there are significant fluctuations in quantities and concentrations. The pH-value also varies very substantially, but it is usually in the alkaline range. Peak loads may occur, e.g. when cleaning and disinfectant agents are being used (soda lye), which cause wastewater with pH-values of over 11.

The various processes for treating brewery wastewater
Whatever process or process combination is suitable for wastewater purification depends largely on whether the wastewater is to be discharged directly into a drainage system or indirectly into a public sewage treatment plant.

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