Lesson 8 - Water Final SAQ

***Your brewery brews a range of ales. Your water source is perfect for these beer styles, with medium to high levels of calcium carbonate/bicarbonate, calcium sulphate and sodium chloride salts. You have decided to launch a pale lager to meet consumer demand, although the percentage of sales is forecast to only be about 15% of your brewery output. How would you approach water treatment to meet the need for both ales and lagers at the brewery?

Response:

In order to brew both types of beer styles at the brewery, you will need to introduce some form of water treatment, as the current water will be too hard for a lager. Lager water should have low levels of the salts mentioned. There are a number of water treatment options available.

Reverse osmosis would be an extreme option, as the current water already meets all of the ale’s requirements. A reverse osmosis plant is expensive to run, with very high pressures and a concentrated brine waste stream that is not always easy to dispose of. The membrane replacement is expensive and can be damaged by carbonate scale and other elements fouling the membranes. This means that you would need some form of water treatment prior to the RO anyway, such as ion exchange. Since the lager volume is only going to be a maximum of 15% of the total sales, it seems excessive to have a RO and an ion exchange plant in place, as 85% of the water will not need to be treated at all.

Since the mineral content making up the water hardness is not just temporary hardness, it would not be an effective solution to soften the water via boiling, lime addition, acid addition or in fact by using a Weak Acid Cation exchanger (as this does not remove permanent hardness).

The best option may be to introduce an ion exchange water softening system. Since there is both temporary and permanent hardness in the water, you will require a cation and anion exchange unit. Having two separate units in series could be beneficial if you need to make small adjustments to the water for the ale on occasion. However, as the water source has always been used for the ale without any known issues, it may be more beneficial to use a mixed bed reactor, where there is only one unit (and not two to purchase and maintain).

The mixed bed reactor should ideally have both a Strong Acid Cation (H⁺-type) and a Strong Base Anion (OH^-) exchanger. The SAC exchanger will exchange the calcium and sodium ions for hydrogen ions. The SBA will then remove the carbonates, chlorides and sulphates and exchange them for a hydroxyl ion.

The hydrogen and hydroxyl ions will then combine to form water.

The disadvantage of these units is that they require strong acids and caustics to regenerate the system, but since the volume of lager produced is so small, the system will only occasionally need to be regenerated.

The water that is to be used for lager can be redirected through the ion exchange system, whilst the water used for the ales can bypass this system and go directly into the brewery as before.