By way of introduction can I please point out from the off-set that I am fairly new to the distilling industry and my only real interest prior to 2009, was in collecting single malts, a hobby that I still invest in, much to the despair of my partner who cannot understand why I want to just collect bottles of malt whisky and not drink them!
I should also point out that this paper concentrates solely on our work undertaken on Scottish Malt Whisky Distilleries, although I would like to point out that the team at Penderyn Distillery in Wales have also helped in preparing this paper, however all their effluent is tankered away from site at present. Similarly at St Georges in England their effluent is tested and sent for land-spreading. However I would like to apologise to our Celtic Cousins from Ireland who might be here, having felt the wrath of your own Environment Agency (EA) in other industries, I am sure that this paper will have some relevance to you as well as our friends in Scotland, should your own Environment Agency start to move the goal posts on effluent discharges.
Copper within whisky is traditional associated with coming from the distillation processCopper pot stills are used even on the newest malt whisky distilleries for their efficient heat transferring process, the Copper playing a very important role in the spirit quality, as the spirit vapour comes into contact with the Copper still, it generally reduces the less desirable sulphur compounds, such as Dimethyl Trisulphide (DMTS). The greater reactions being between the Copper and the spirit vapour than the copper and spirit still in its liquid form. Although our forefathers could not have known the full benefits of using Copper in the manufacturing of pot stills, there is little doubt that overall the use of copper in the distilling process has a positive benefit to the process
It is also picked up when various parts of the system are cleaned. Normal cleaning programmes introduce high alkaline detergents (caustic), which pick up the Copper as a Hydroxide and carry it through into the discharge water.Typically levels of above 10ppm (mg/l) are found in the effluent at this stageThe traditional way of extracting the Copper would have been by allowing balancing of the effluent discharge. This means typically having a large enough tank system to be able to hold at least a full day’s worth of effluent from the distillery. This then balances out (hopefully) the extremes of pH variation throughout a days’ discharge. A lot of sites then have biological processes, to hopefully take out the high levels of copper. This would be okay if the biological plant was good enough to cope with the normal standard discharges. However discharges with high pH from the cleaning process, followed by low balancing capacity, usually resulted in traditional effluent treatment systems not always taking out copper. Say a balance tank that can only hold 50cum3 and the site is discharging 200cum3/per day, then the holding capacity could be as low as 6 hours. If this ties in with a major cleaning programme then the effluent plant would not be capable of balancing out the effluent, including dealing with the Copper.