Lesson 7 - Brewing Product Water Final Treatment SAQ

**Your marketing department has identified a need for a pilsner in the brewery’s brand portfolio. However, your primary water source has high levels of temporary hardness. How would you overcome this problem? What are the advantages and disadvantages of your solution?

Response:

Pilsner style beers are traditionally brewed with soft water. As we have hard water, this poses a problem. Temporary hardness relates to high levels of carbonate or bicarbonate in the water. There are several options available to reduce the hardness and make the water suitable for brewing a pilsner. These include the following:

The water can be heated to above 70-80˚C, which will cause the bicarbonate to be converted to calcium carbonate (CaCO₃) and precipitate out of solution.

Although simple in application, the cost of heating all the water is energy intensive. It also releases carbon dioxide (CO₂), which as a health and safety risk, needs to be vented out.

Decarbonation can be achieved by adding calcium hydroxide (lime), which reacts with bicarbonate to form calcium carbonate.

This system is relatively cheap, easy to use and effective. However, it requires downstream filtration to remove the suspended solids in solution.

Inorganic or organic acid can be added to the water, which reacts with the bicarbonate to release CO₂ and form calcium.

This method releases CO₂ which will need to be vented, and the water will need to be degassed to remove any CO₂ that has dissolved (this requires additional plant). Handling acids can be dangerous and caution is required.

The use of a cation exchanger can be used to remove bicarbonates from the water. A WAC (weak acid cation) exchanger will exchange a hydrogen ion for the calcium in calcium bicarbonate, converting the calcium bicarbonate into water and CO₂.

This system requires additional plant that can be expensive. The ion exchange resin is regenerated using acids, such as sulphuric acid (although this can lead to the formation of calcium sulphate which can foul up the exchanger) or hydrochloric acid. These acids can be dangerous to handle. However, the exchanger can remove all calcium and magnesium ions associated with temporary hardness and the system has a high throughput and is easily regenerated.

Another cation exchanger is the SAC (strong acid cation) exchanger. This system removes all types of hardness – including temporary and permanent hardness. The ions exchanged are either sodium or hydrogen ions for cations.

Or

The production of HCl will cause the water pH to drop very low, thus the pH will need to be corrected. If sodium chloride is produced, then the sodium chloride levels in the water will be high, which could negatively impact health (and make the beer taste salty).

Although a SAC can be used to remove temporary hardness, it is probably unnecessary if the only problem is temporary hardness.

A final option would be to use a SBA (Strong base anion) exchanger, which can remove carbonates, by exchanging it with hydroxide or chloride.