Water is the major component of all fermentation media, and is needed in many of the ancillary services such as heating, cooling, cleaning and rinsing. Clean water of consistent composition is therefore required in large quantities from reliable permanent sources. When assessing the suitability of a water supply it is important to consider pH, dissolved salts and effluent contamination.
The mineral content of the water is very important in brewing, and most critical in the mashing process, and historically influenced the siting of breweries and the types of beer produced. Hard waters containing high CaS04 concentrations are better for the English Burton bitter beers and Pilsen type lagers, while waters with a high carbonate content are better for the darker beers such as stouts. Nowadays, the water may be treated by deionization or other techniques and salts added, or the pH adjusted, to favour different beers so that breweries are not so dependent on the local water source. Detailed information is given by Hough et al. (1971) and Sentfen (1989).
The reuse or efficient use of water is normally of high priority. When ICI pic and John Brown Engineer ing developed a continuous-culture single cell protein (SCP) process at a production scale of 60,000 tonnes per year it was realized that very high costs would be incurred if fresh purified water was used on a once-through basis, since operating at a cell concentration of 30 g biomass (dw) dm~3 would require 2700 X 106 dm3 of water per annum (Ashley and Rodgers, 1986; Sharp, 1989). Laboratory tests to simulate the process showed that the Methylophilus methylotrophus could be grown successfully with 86% continuous recycling of supernatant with additions to make up depleted nutrients. This approach was therefore adopted in the full scale process to reduce capital and operating costs and it was estimated that water used on a once through basis without any recycling would have increased water costs by 50% and effluent treatment costs 10-fold.
Water re-usage has also been discussed by Topiwala and Khosrovi (1978), Hamer (1979) and Levi et al. (1979).
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