Brewery wastewater has a characteristic of its own. It exhibits substantial peaks both in the quantity delivered and the concentration of waste carried. This unbalanced waste consists mainly of carbohydrates. Further characteristics are the changing pH and the influence of the cleaning process and disinfectants. In a well run plant with careful process control, small material waste and reuse of by-products the following are typical values:
Specific water use: 0.4 - 0.8 m³/hl sellable beer
(1/2 -. 1 ft³/US gallon)
Specific wastewater effluent: 0.25 - 0.6 m³/hl sellable beer
(1/2 -. 2/3 ft³/US gallon)
Specific BOD5 freight: about 0.5 Kg BOD5/hl sellable
Beer or about 8 population equivalent in 60 days/hl*
The quantity of wastewater depends on the production process. It contains various substances from the brewing process. In the brew-house, where the wort is cooked, a starch and protein rich flocculent mass known as the "kettle” break (some 120 g BOD5/kg) remains. Addition of yeast ferments the wort into beer in tanks in the fermentation cellars. A yeast residue (150 g BOD5/kg) and a beer-water mixture remains after pumping and emptying the tanks. The same is true in the storage cellars where a yeast residue of some 130 g BOD5/kg enter the drains. Pumping, filtration and bottling or casking all cause beer loss (80 g BOD5/kg).
A brewery, like all food processing industries must be kept very clean. Automatic processes clean all tanks and pipes with caustic soda and nitric acid and sometimes disinfect them. This wastewater is then strongly alkaline with a pH > 10.
Breweries release their wastewater only indirectly into the public drains. They have to keep it within the prescribes temperature and pH limits (temp 35°C, pH between 6.5 and 10) and should pretreat it. The simplest way to do this is use closed buffer tanks holding three hours' waste-water production. If necessary, a neutralizing stage using sulfuric acid, carbonic acid from fermentation or flue gases is added.
The wastewater can be graded and partially treated biologically in aerated mixing and compensating tanks provided excess sludge can be obtained from the communal treatment plant.
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