By Karl Kin (Brewing Techniques)
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The chemical calculations for water treatment can be intimidating to those who are not professional chemists. A spreadsheet and a simple approach demystify the process.
We often take water for granted, but its composition — a critical concern when you’re treating water for brewing — is far from simple. Full coverage of water treatment is beyond the scope of this article. I present here a simplified way to calculate adjustments based on addition of salts, acids, and dilution water.
Extract manufacturers treat their water, and you get whatever salts are left in the extract after mashing and concentration. A sound general practice is to use soft or distilled water for dilution. Water treatment is most important when mashing, whether all-grain or mash-extract.
If you’re trying to match a classic style, the water you use must closely match the water composition used by the local brewers of that style. Ironically, the water used in many of the classic styles is hardly ideal for brewing; recipes often are adapted to the shortcomings of the brewing water. For example, in locations where the water contains a high concentration of carbonates, dark malts are often used because their natural acidity neutralizes the excess alkalinity of the carbonates.
You may not want to match a classic style, and instead want to adjust your water for a beer of your own design. Whatever your aim, the first step is to consider whether the water you want to use is appropriate for brewing.
The first and simplest test is, does it taste good? What is the water’s chemical composition? How much chlorine does it contain? Treating water that is loaded with metals and chlorine is an uphill battle. Does the water contain biological contamination, pesticide residues, or radioactivity? To find the answers to these questions, obtain an analysis from the source or have your water analyzed professionally.
A key measurement of a water’s suitability for brewing is the parts per million (ppm) it contains of certain electrolytes: calcium, magnesium, sodium, sulfate, chloride, and chlorine. You also need to know the pH, the hardness in parts per million, and the alkalinity in parts per million of calcium carbonate. It is useful to measure the parts per million of iron, manganese, copper, zinc, and potassium. Water is suspect for brewing if one or more of the concentrations shown in Table I are significantly exceeded. (Beer — maybe even great beer — can be made with these ions at higher concentrations, but if I found a flavor defect I would have to wonder whether it had been caused by too much of one of these ions. Therefore, I recommend fairly low levels.)
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table i
|
Recommended maximum concentrations of metals in water. |
|
|
Metal |
Concentration (ppm) |
|
Iron |
0.05 |
|
Manganese |
0.1 |
|
Copper |
0.1 |
|
Zinc |
0.5 |
|
Potassium |
10.0 |
|
Chlorine |
0.1 |
Trace metals can be reduced by deionization, reverse osmosis, distillation, or dilution with purer water. Chlorine can be removed by boiling, activated carbon filters, reduction with vitamin C, or exposure to direct sunlight for 10 min.
Many sources discuss how to reduce hardness and alkalinity by boiling the water to precipitate calcium carbonate and decanting the water from the precipitate. This process works, but preboiling all the mashing and sparge water is expensive. Distilled water is commonly sold at large supermarkets. Purchase in quantity for better prices. One might have to talk to the store manager to get the larger quantities. Deionized water can usually be purchased from a laboratory at nominal cost. Some water bottling companies sell distilled or deionized water in 5-gal carboys. For those in remote places, the cost of transportation could be high enough to make preboiling less expensive.
The approach I use here is to acidify the water (if it is too alkaline) or to dilute with distilled or deionized water; in some cases, both approaches can be used.
Salt is added as necessary. Although numerous salts can be used, I chose only those that are readily available and easily handled. The acids used are also readily available. Concentrated acids are hazardous to work with and difficult to measure without proper equipment; you can save considerable trouble by purchasing acids in 1 M or 0.1 M dilutions. If you perform dilutions yourself, always wear safety glasses, and always add the acid to the dilution water. Do not add the dilution water to the acid.
Anything added to your water should be suitable for consumption — that is, it should be food grade, USP, or analytical-reagent grade. Don’t even think about using something from the hardware store. The salts used are shown in Table II. It is unlikely that a given treatment will use all of these. If your source water is low in chloride, hydrochloric acid is the easiest modifier to find and use. Phosphoric acid, a yeast nutrient, is neutral in flavor, but large amounts may reduce calcium. Lactic acid is also neutral in flavor but can be considered a foreign substance — natural waters do not contain lactate. Do not use anhydrous calcium chloride; it absorbs water and is difficult to weigh accurately. Because calcium carbonate does not dissolve in water, add it directly to the mash.
Table II
|
Salts used in water treatment. |
|
|
Chemical Name |
Common Name |
|
CaSO4*2H2O |
|
|
CaCl2*2H2O |
|
|
CaCO3 |
|
|
MgSO4*7H2O |
|
|
NaCl |
Sodium chloride (not table salt) |
|
HCl |
Hydrochloric acid (0.1 M) |
|
H3PO4 |
Phosphoric acid (0.1 M) |
|
HLactate |
Lactic acid (0.1 M) |
It is tempting to relate weights of salts to volume so that you can measure by volume. Do so only if you have derived the relationship for the particular product you’ve purchased. Otherwise, measure salts by weight.
After you have determined the key ionic concentrations for your water and have set some target concentrations based on a style or a desired result, you are ready to begin the water treatment process. The process involves dilution with pure water, addition of salts, or addition of acid to arrive at the target concentrations.
It is possible to calculate nearly all additions to get the desired result. When an exact solution to the problem is unavailable, a least-squares analysis may get close enough. My spreadsheet is not set up for that kind of analysis; it uses trial-and-error methods that are well suited for general analysis. Although it’s not elegant, the method is educational because it shows the results of various choices. The spreadsheet uses practical measures and quantities, so you end up with a bill of materials.
Enter the total volume of water you need and the details of your source water and the desired water. If present concentrations of calcium, magnesium, sulfate, or chloride are considerably higher than the desired concentrations, you must dilute with pure water (deionized or distilled). You enter a dilution factor (0 = no dilution, 0.5 = 50:50 dilution); the spreadsheet calculates the concentrations in the diluted water, the required volume of source water, and the required volume of dilution water.
After dilution, ions that are at insufficient levels are brought up to desired levels by adding salts. The added amounts are entered, and the result is displayed next to the column of desired results. If carbonate levels are too high, reduce them by adding acid. If carbonate levels are too low, increase them by adding calcium carbonate. Don’t be too concerned about getting a perfect match for sodium and magnesium. The calcium and carbonate levels are the ones that really matter.
You may find that you can’t reach your target even after many attempts. Perhaps the salts used in the spreadsheet are not the best choices for the case at hand, or the source water may not be well suited for achieving the target water profile. If your source is Burton water, for example, trying to treat it to make it suitable for Pilsner is a waste of time.
If your water analysis does not provide all the required information, the following formulas may be useful:
Ca+ 1.65*Mg = 0.4*H
Where Ca = calcium (ppm), Mg = magnesium (ppm), and H = hardness (ppm calcium carbonate), and
C = 0.6*ALK
Where C = carbonate (ppm), and ALK = alkalinity (ppm calcium carbonate).
Salt additions are straightforward, but acid additions are trickier because it is easy to overshoot the target. Add acid in 10% increments, and monitor the pH of the water using either a pH meter or pH paper. Measure a small sample of the water and discard it after the measurement. Be sure to stir the water well so that the liberated carbon dioxide can leave the water. You won’t have the final pH until the water has outgassed.
It is helpful to plot pH versus amount of acid needed. As you reach neutrality, the pH may change a large amount with only a small addition of acid. This titration may be time-consuming, but it will save a great deal of time on subsequent batches. Correcting water that has been overacidified can be difficult. The final pH should usually be between 7.0 and 7.2. Unless you’re using a lot of dark malt, pH values greater than 7.5 are not desirable.
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