Water is used in two distinct ways: as an ingredient in malt whisky, and in a more practical manner to heat the stills and cool the condensers.
As an ingredient water is used for mashing (when hot water is added to the barley, converting the starches it contains into sugars). Subsequently, water is added to new make spirit to reduce the alcoholic strength prior to filling into casks for aging. Water is also added to mature malt whisky (as required) so that it can be bottled at a specific alcoholic strength.
Meanwhile, steam is the standard method of heating the stills. A boiler heats water with the resulting steam conducted through pipes in the boil pot (base) of the still. This in turn heats the charge (alcoholic liquid being distilled), causing alcoholic vapours to rise to the top of the stills, from where they are conducted to the condensers, in order to condense back into liquid alcohol.
Water used to steam heat the stills is effectively in continuous circulation within the heating system. However, water used to cool the condensers is abstracted from a local source, such as a river, and subsequently returned to it (subject to certain conditions).
Many distilleries use a 'shell and tube' condenser, which contains long copper pipes running the length of a large vertical chamber. Cold water is continuously pumped through the pipes, and when alcoholic vapours come into contact with the pipes they condense into liquid alcohol (then roll down the surface of the pipes and drain from the base of the chamber, into a separate vessel).
The ambient temperature of the water is typically around 15 degrees centigrade when entering pipes at the base of the chamber. However, as the water rises through the pipes the heat of the vapours also increases the temperature of the water. By the time the water is discharged from the top of the chamber it could reach a temperature of around 50 degrees centigrade.
Regulations stipulate that any warmer water being returned to the source must not raise the ambient temperature of that source by more than either two or three degrees centigrade (depending on the classification of the river by SEPA), in order to protect aquatic life.
Calculating the maximum temperature at which water can be returned to the source depends on the degree of dilution the water source provides. For example, a narrow, shallow river would experience greater 'temperature uplift' (the technical term used) compared to a deeper, wider river which provides a greater degree of dilution for warmer water. Similarly, the 'flow rate,' i.e. rate at which warmer water is returned to the source, is also determined by the degree of dilution.
Consequently, the flow rate and maximum temperature permitted are specific to each distillery's water source, and stipulated in the license granted by SEPA. If necessary, the water temperature can be reduced before returning it to the source.
"Many distilleries have cooling towers. Hot water from the condensers enters at the top of the tower, and air is blown into the water to help cool it down. This continuous, rapid process takes less than a minute from water entering the tower to leaving. Another option is to have a pond or mixing tank to give the water time to reduce in temperature. Each distillery monitors and records the temperature and flow rate of water being returned to the source, while also recording the overall quantities of water abstracted. These statistics are submitted in an annual return to SEPA," says Ronald Daalmans, Environmental Sustainability Manager, Chivas Brothers.
Water for mashing, and reducing the strength of new make spirit and mature malt whisky, as well as water used to heat the stills, is effectively abstracted on a permanent basis. However, these account for a fraction of the total water used. Meanwhile, water to cool the condensers totals around 90 per cent of water usage, though this is returned to the source.
Applying for a water licence from SEPA
"We try to deal with an application for a license within four months, but the best advice for any prospective new distiller is to speak to us early on. Licenses are open-ended, although we do have the powers to revoke a license if there is good reason for this. If a distillery wants to increase production capacity, and so would need to abstract greater quantities of water, the distillery needs to apply for a variation of the existing license. If the water course can cope with the additional quantities required, that's fine. If not, the options include establishing additional storage capacity (via tanks or lagoons) to store additional quantities of water. SEPA works closely with the whisky industry, which is exemplary in setting its own significant environmental targets. These are detailed in the Scotch Whisky Association Environmental Strategy which SEPA strongly supports as a great example of good environmental stewardship promoted on an industry-wide basis," says Andy Rosie, SEPA's Head of Operations - North.