Caustic bottle washing liquors from breweries are too alkaline to be passed directly as municipal effluent and must be neutralised before being released to the sewer. A system has been developed at the Carling Brewery, Vancouver to lead flue gas from the boiler which is slightly acidic due to the presence of carbon dioxide through the effluent to neutralise it. The effluent includes minor caustic loss at the washer, discharge of the water tank and all other run-off from bottling equipment. This mixture feeds by gravity through a trap to remove glass, through hydrasieves to remove other solids and then to a mixing and surge tank. After, solids still present are allowed to settle, the supernatant is pumped to the top of the packed process vessel through which the flue gas flows in counter current. The pH of the neutralised effluent from the process vessel is measured by a pH meter placed in the outlet line. Various safety measures have been installed including a carbon dioxide line from the brewery to neutralise the effluent if there is any failure to provide flue gas. Although the boiler runs on natural gas as fuel there appears no reason why flue gas from oil or coal fired boilers could not be used.
Keywords : acidic alkaline brewery carbon dioxide caustic effluent treatment