About two thirds of the total volume of brewery effluent derives from bottling hall waste waters. These are strongly alkaline due to the continuous discharge of caustic wash from the bottle washing and the periodic discharge of spent caustic solutions from CIP systems. On average, 1 lb of 50% sodium hydroxide is used per 15 gal of beer processed. The high pH and, frequently, high temperature requires that effective treatment be given before discharge. Neutralization is the only practical solution and the use of H2SO4 or is normal practice. Strong mineral acids are corrosive and dangerous and give rise to salts (sulphates or chlorides) in the treated effluent for which maximum permitted levels will be steadily lowered in the future. Neutralization with carbon dioxide is an attractive alternative in that the final product, NaHCO3, has a pH in solution of 7.5 to 8.0 and overdosing with carbon dioxide will not significantly increase acidity, in contrast to overdosing with strong mineral acids. Some form of controlled metering may be advisable to avoid corrosion problems from dissolved carbon dioxide in the treated effluent. Commercial carbon dioxide is approximately twice as expensive as H2SO4 but waste fermentation carbon dioxide is abundantly available in breweries and the same is true of boiler flue gas which contains 9 to 14% carbon dioxide by volume. Utilization of these sources is illustrated and the economics are discussed. They offer environmentally more acceptable alternatives at minimal cost than conventional acid treatments.
Keywords: alkali brewing bottling effluent treatment equipment