Brewing Water
Water Treatment
A dependable supply of high-quality water is a vital component for brewing beer. Characteristics of water that define its quality vary with the source of the water. There are regional differences in water characteristics, based mainly on geology and climate. There may also be great differences in the quality of water available on a local level depending on whether the source is from above ground (rivers and ponds) or from groundwater aquifers with varying geology, and whether the water has been chemically treated as in the case of municipal water. The actual extent of water conditioning is governed by the concentrations of anions, the dissolved organic substances, and the presence of aggressive gases in the untreated water. Most brewers find it necessary to treat the water coming into the brewery. Treatment of brewing water depends on the specific needs of the brewer and on the particular beer required.
Removal of Suspended Solids
If the brewery uses municipal water, the water must meet certain mandated conditions; however, the water picks up contaminants in the pipes from the water treatment plant to the brewery. These contaminants usually consist of scale from the pipes, sediment, and rust particles. Breweries drawing on owned borehole or spring supplies may also have to treat the water for suspended solids. There is a wide variety of filter systems used to remove contaminants from either source.
Media Filters
Media filters (Figure 5.1) have been used extensively in filtering water in greenhouse operations. Media filters are often used to remove organic materials (e.g., bacterial slimes and algae), fine silt, or other fine organic or inorganic materials from ponds and surface water. These filters trap contaminants in irrigation water in a deep column of sand, recycled glass, packed mineral or glass fibers, and/or other dense substrates. The most notable of these is conventional sand of selected sizes placed in pressurized tanks that filter contaminants as the water flows through the filtering media.
Screen Filters
Screen filter products are popular because they are inexpensive, easy to install and take up less space than a sand media filter. They come in various shapes and sizes, although most are horizontal cylinder types. Screen filters are most frequently used for removing inorganic contaminants.
Disc Filters
Disc filters are a cross between a screen filter and a media filter, with many of the advantages of both. Disc filters are good at removing both particulates, like small amounts of sand, and organic matter. Disc filters are better than screen filters for retaining algae. The screening element of a disc filter consists of stacks of thin, doughnut-shaped, grooved discs, forming a three-dimension filter cartridge.
Dechlorination
Chlorine is typically found in municipal water supplies to assure the water’s disinfection from disease-causing organisms. To stabilize the chlorine molecule, water treatment facilities often add ammonia, which creates a chloramine, a process referred as chloramination. Chloramines can stay in a solution longer, providing greater control of bacterial growth both in the facility and the distribution system. Chlorine and chloramine removal from brewing water is critical for good brewing results. If chlorine and chloramine compounds are not removed from brewing water, they combine with the organic compounds naturally found in wort to form chlorophenols.
Aeration
Aeration is sometimes used for water dechlorination, although its efficiency decreases as the pH increases. This process is slow, especially when chlorine concentrations is low and is not effective against chloramines.
Boiling
Scheer reports that heating water in the holding tank at a temperature of 78 degrees C (172°F) overnight is sufficient to eliminate all chlorine, whether bound or free (Scheer, 1991).
Granular Activated Carbon Filtration
Activated carbon filtration is a common method used to remove chlorine and chloramines, but it also reduces the levels of other harmful contaminants like industrial chemicals, pesticides, trihalomethanes (THMs), as well as other halogenated organic compounds (Figure 5.2). It is also effective in removing bad odors and tastes. Activated carbon is made from raw organic materials, such as coconut shells or coal, which are high in carbon.
Empty Bed Contact Time. The chlorine and contaminant removal performance of activated carbon filtration is proportional to the amount of time the water is in contact with the activated carbon. The residence time for water passing through the carbon media must meet certain minimum durations. For hypochlorite removal, the residence time should be at least 2 to 3 minutes for chlorine.
Cartridge vs. Backwash Tank Systems. The brewer has two options when it comes to GAC filtration systems, the most popular for breweries being cartridge-based systems and back washing tank systems.
Ultraviolet Light
Another way to remove chlorine or chloramine is ultraviolet light (UV) with the added benefit of killing 99.99 percent of bacteria and viruses. This is a high intensity method of chlorine removal that uses broad spectrum ultraviolet irradiation to dissociate free chlorine and chloramines, turning them into easily removed byproducts. Water is treated in UV systems by passing it through a steel treatment chamber containing a UV lamp enclosed in a quartz sleeve (Figure 5.3).
Chemical Dechlorination
Reduction reactions occurring from metabisulfites (e.g., potassium metabisulfite or sodium metabisulfite) are effective in removing hypochlorite and chloramine. When sodium content in the brewing water is a concern, potassium metabisulfite may be preferred.
Reduction in Alkalinity
The necessity to control the inorganic content of brewing water is clearly a well-established principle, and, following the pretreatments described earlier, most brewers will employ some form of treatment to reduce the content of certain ions (e.g., bicarbonate) and enhance the levels of other ions (such as calcium, chloride, and sulfate). There are several procedures available for reducing alkalinity (i.e., decarbonation).
Food Grade Acids
Alkalinity can be reduced by additions of food grade acids (sulfuric, hydrochloric, phosphoric), but sometimes citric and lactic acids can be used too. Food grade implies the acid does not contain hazardous or toxic impurities and is generally recognized as safe and/or suitable for human consumption in accordance with the U.S. Food and Drug Administration. Off-the-shelf acids from the hardware or auto-parts store, for example, may contain hazardous amounts of heavy metals or other impurities.
pH Reaction Time. A common problem when adjusting pH is the process reaction time. Typically, it can take several minutes or even hours after the addition of a pH amending substance for the pH to fully stabilize.
Tips on Mixing Acid. It is best to inject acid directly from a concentrate tank into the supply line so there is no handling. This is the safest option.
Carbon Dioxide
In Germany and in other countries where mineral acids (i.e., food grade acids) are prohibited, pH reduction can be achieved by using carbon dioxide. Carbon dioxide is introduced into the high pH water by means of a diffuser, which is typically installed in an existing pressurized pipe or at the bottom of a tank.
Deionization
Deionization can be used to alter the ionic composition of water and is often used for removal of bicarbonate ions in water, called dealkalization. Deionization entails removal of electrically charged (ionized) dissolved substances by binding them to positively or negatively charged sites on a resin as the water passes through a column packed with this resin.
Reduction of Total Dissolved Solids
Total dissolved solids (TDS) are a measurement of a variety of compounds like minerals, salts and organic compounds that are dissolved into water through contact with rock and other surfaces. The principal constituents are usually the cations calcium, magnesium, sodium, and potassium and the anions carbonate, bicarbonate, chloride, sulphate and, particularly in groundwater, nitrate (from agricultural use). Total dissolved solids can be removed by several water purification systems—nanofiltration, reverse osmosis, and deionization
Nanofiltration
Nanofiltration (NF) is one of the four membrane technologies, which utilize pressure to effect separation of contaminants from water streams. The other three are microfiltration, ultrafiltration and reverse osmosis (RO). All of these technologies utilize semi-permeable membranes that have the ability to hold back (reject) dissolved and/or suspended solids from a water stream containing these contaminants.
Reverse Osmosis
Reverse osmosis (RO), or commonly referred to as membrane filtration, removes contaminants such as iron, manganese, calcium, magnesium, chlorine, microorganisms, and many high molecular weight organics and can render almost any water source usable for brewery production. System capacity depends on the water temperature, total dissolved solids in feed water, operating pressure and the overall recovery of the system (Figure 5.4).
Deionization
In the context of water purification, ion-exchange is a process in which the dissolved ions present in the water are replaced by ions released by an ion-exchange resin. The most common ionized minerals found in source water include calcium (Ca2+), magnesium (Mg2+), sodium (Na⁺), potassium (K⁺), iron (Fe2+), chloride Cl¯), bicarbonates (HC03¯), carbonates (CO2¯), nitrate (NO3¯), and sulfate (SO4¯). An ion is an atom or group of atoms with an electric charge. Positively-charged ions are called cations and are usually metals; negatively-charged ions are called anions and are usually non-metals.
Mineral Salt Adjustment
Historically, breweries were located on sites with established, consistent water supplies having characteristic mineral compositions. This led to the emergence of regional beer characteristics in locations such as Burton-on-Trent, Dortmund, Pilsen, and Vienna. Mineral salt adjustment was held to a minimum and, often, recipes were adapted to the shortcomings of the brewing water. For example, dark malts often were used because their natural acidity neutralized the excess alkalinity of high carbonate waters.
Calcium Carbonate
Calcium carbonate (CaCO3) is used in brewing to raise pH levels and is generally used in making dark beers. The presence of carbonates can offset the acidity of dark malts. Munich, Dublin, and London are examples of classic water sources that exhibit high calcium carbonate levels.
Calcium Sulfate
Calcium sulfate (CaSO4) can be used to lower the pH and accentuates the hop bitterness and enhances the flavor and fullness of the beer. It is often used as a source of calcium ions and is generally used in brewing British pale ales and bitters.
Magnesium Sulfate
Magnesium sulfate (MgSO4) is similar to calcium sulfate but is not as effective as calcium in reducing the pH of the mash as demonstrated by the calculation for residual alkalinity.
Calcium and Sodium Chlorides
Unlike many other ions found in brewing water, neither the sodium nor the chloride ions contribute significantly to the activity of mash enzymes, kettle boil coagulation, or yeast metabolism. Both these ions do, however, contribute immensely to flavor and taste perception in final beer.
Sulfate-to-Chloride Ratio
Sulfate accentuates the hop character, and chloride accentuates the malt character. Calcium sulfate (gypsum) is commonly used to accentuate the hop character of an India pale ale, making the bitterness more assertive and the beer drier.
Water Sterilization
All waters contacting the product stream should be free of water-borne organisms such as bacteria. In general, most of the water used for brewing will be heated prior to mashing and boiled in the kettle, thereby ensuring it is free from microorganisms. However, water used for diluting worts, beer, or rinsing equipment may not be microbiologically sterile. Water can be treated by physical methods such as ultraviolet light and sterile filtration or by using chemical treatments such as chlorine dioxide and ozone.
Ultraviolet Light
Ultraviolet (UV) light is a highly effective option to control pathogens in brewing water. Viruses and bacteria generally are more easily killed than some yeasts, fungi, and spores. The treatment works because UV light penetrates an organism’s cell walls and disrupts the cell’s genetic material, making reproduction impossible. It is effective against algae, fungi, bacteria, and viruses, but these pathogens vary in their susceptibility to UV.
Sterile Filtration
Another option in sterilizing water free of pathogens is sterile filtration using absolute (i.e., membrane) filters. Membrane filters, also referred to as cartridge filters, are the perpendicular flow membranes used for the sterile filtration of beers just prior to bottling. They are called membrane filters since they collect particles at the surface. Membrane filtration is different from depth filters.
Chlorine Dioxide
Brewing water may require chemical treatment to reduce or eliminate microorganisms. Chlorine dioxide is a soluble gas dissolved in water and used as an aqueous solution. Chlorine dioxide is a strong oxidizing agent. It is effective against a variety of beer spoilage organisms, including bacteria, yeast, and mold.
Ozone
As a water treatment, use of ozone has proved successful in brewery applications in removing most water-born organisms. Ozone is a powerful oxidizer which destroys fungi, pathogenic bacteria, and viruses which cause waterborne diseases. Once dissolved in water, ozone destroys pathogens and then safely reverts into oxygen. Ozonation deploys the unstable gas ozone (O3), which is produced on site by an ozone generator (Figure 5.6) and is bubbled through the water where it rapidly reacts with microorganisms and organic matter.
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