Brewery Wastewater Management
The most cost-effective method for significantly reducing effluent load of brewery wastewater is to separate the solid wastes from the wastewater itself. The equipment necessary includes holding vessels, tanker trucks that can haul away the material, pumps, and dedicated piping or hoses for transfer. Typical solid wastes include spent grains, trub, spent yeast, diatomaceous earth slurry from filtration, and packing materials.
Beer production results in a variety of residues, such as spent grains, which have a commercial value and can be sold as byproducts for livestock feed. The nutritional value of spent grain is much less than that of the same amount of dried barley, but the moisture makes it easily digestible by livestock. Farmers often mix it with silage to help prolong its storage time. Mushroom growers also use spent grain mixed with wood or grasses as an excellent growing medium.
Trub is slurry consisting of wort, hop particles, and unstable colloidal proteins coagulated during the wort boiling. The trub suspension can be treated in different ways, added to the spent grains or sent directly to the sewer system. To minimize the BOD/COD load and the extract loss, discharge of trub to the sewer system should be avoided.
In brewing, surplus yeast is recovered by natural sedimentation at the end of the fermentation and conditioning. Only part of the yeast can be reused as new production yeast. Spent yeast is very high in protein and B vitamins, and may be given to livestock as a feeding supplement. However, live yeast may harm livestock and should be killed before release by the brewery.
Diatomaceous Earth (DE) Slurry
Diatomaceous earth slurry from the filtration of beer also constitutes a very large category high in SS and BOD/COD. Different methods for regeneration are under development, but presently they are not capable of totally replacing new diatomaceous earth. Therefore, the disposal of diatomaceous earth is limited to landfills or used as a soil amendment.
Other solid wastes include label pulp from the washing of returnable bottles, broken glass, cardboard, bottle caps, and wood that is usually disposed of at sanitary landfills.
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