The pollutant burden of effluent is commonly measured in terms of chemical oxygen demand (COD), defined as the quantity of oxygen which would be required for the complete oxidation of all organic effluent constituents (i.e. the conversion of all carbon to carbon dioxide and of all hydrogen to water). In breweries, most of the organic content of effluent is derived from the wort extraction process, in such forms as lauter tun last runnings, wort residues in by-products such as trub, and wort and beer losses during subsequent processing. An investigation is described in which it was shown that there is a close correlation between the original gravity of a wort and the COD of the effluent from its production and processing operations. The application of this relationship is also described using two case studies, one concerning the determination of the irreducible minimum effluent output from a brewery in order to ascertain what scope there was for reducing the existing COD level, the other concerning the identification of the most important organic pollution sources within a brewery with a view to reducing COD levels where possible.
Keywords : brewery COD effluent original gravity wort