DISTILLING | WATER AND WASTEWATER
The first written record of Irish whiskey dates back to 1405, making it one of Europe’s earliest distilled beverages. In 1608 the first licence to produce whiskey granted at the site that is now the Bushmills Old Distillery in County Antrim and this is where whiskey production became an industry. Since then the popularity of Irish Whiskey has grown around the world.
In 2010, four distilleries were producing around 6 million cases (72 million bottles), compared to 2019, with 31 distilleries operating on the Island of Ireland producing 10.7 million cases (130 million bottles) per annum. This phenomenal growth is expected to continue, investors and developers have pumped resources and finance into the industry in recent years. With this surge in distilleries, investment, and brands exporting their products internationally, the origin and story of the Whiskey is almost as important as the product itself.
This has resulted in old distilleries reopening their doors and new distilleries being built in old buildings such as churches, mill houses, and stable yards for example. Many conversion projects and new builds have opted to include visitor centres to showcase their product and the beautiful settings in which they are located, which often means remote locations without access to main gas, mains water or a sewer network.
A distillery producing 1.5 million litres of pure alcohol (lpa) per annum will have a large water demand. A good option for the cooling water is to use a nearby river or lake for extraction and discharge. For example, a license may be granted to allow the discharge of 1000m3/day with a maximum temperature of 30°C separate to process effluent. During the summer when the water bodies are warmer, cooling becomes more of an issue and some borehole water may have to be used to increase cooling capacity, other options may include cooling towers or chillers. Without a connection to mains water, process water and potable water will usually be sourced from a borehole, the treatment and final quality depends on the application within the process. For example, spirit reduction and boiler feed water need to be treated using a reverse osmosis unit.
All the above unit operations require a large amount of electrical energy. However, the heating energy required on a distillery is greater again, and without a gas mains connection, most distilleries turn to LPG stored onsite and delivered at approximately 40c/l. Therefore, even at 100% efficiency, it would cost around €54,000 to triple distil 1.5million LPA. Good designs and specialist process selections by the Master Distiller may reduce unit energy demand (MJ/l) for the distillation process by up to 33%. Implementing energy-saving measures in a distillery offers an attractive return on investment.
At WEW Engineering we do not believe in “one size fits all” design solutions and we tailor our designs to individual client needs and site constraints. For example, when considering using a local body of water subsidized with borehole water for cooling stills the following parameters, some of which are dynamic, need to be considered to achieve maximum energy efficiency:
• Temperature of the water body
• Max allowable discharge temperature
• Temperature of borehole water
• Hydraulic head from waterbody to the stills
• Hydraulic head from borehole to the stills
• Borehole yield
For Reverse Osmosis water borehole may not always be the best source if there is a lot of hardness or minerals in the water, this could cause excessive fouling of the RO membranes. One solution is to use rainwater harvesting, as rainwater will not have the same mineral loading. A cost-benefit analysis can be easily carried out to calculate the payback period of the extra Capex versus the savings on membrane fouling. However, solutions like this not only have a financial saving for the distillery, but they also improve the green credentials of the brand, which is very important nowadays. Reducing the litres of water used per LPA or to say the spirit is diluted with 100% Irish rain before bottling, an authentic marketing story which appeals to the target consumer. Sustainability, CO2 reduction, circular economy, water/energy/nutrient reuse, are popular marketing tools in today’s global marketplace.
Distilleries have huge opportunities to reduce their water and carbon footprints, a significant proportion of these be derived from postproduction activities. After each distillation, several by-products remain, spent grain, pot ale, spent lees and wash water. Using the example of the 1.5 million LPA per annum these products have a polluting potential equivalent to 40,000 people. The pot ale alone can have a Biological Oxygen Demand (BOD) of up to 50,000mg/l, therefore these products need to be managed correctly. Spent grain and pot ale are frequently sent for animal feed as they have a high calorific value and are high in protein. In this instance the spent lees and wash water will be considered a waste product, it may be possible to send them to sewer if one is available, but the spent lees still have a BOD of up to 2,000mg/l which is higher than most Discharge To Sewer (DTS) licences will allow. An onsite wastewater treatment plant (WWTP) will be required.
Another option which we have designed and implemented in recent years is to retain the pot ale on-site and treat it along with the spent lees and wash water in an anaerobic digester (AD). A digester treating 1,000kg of BOD per day could produce biogas with an equivalent energy value of around 1.2GWh, or €60,000 per year when compared to LPG. If a project were accepted in the Support Scheme for Renewable Heat (SSRH) the distillery would receive an extra €30,000 in grant aid per year for 15 years.
Other benefits of a well-designed AD and WWTP integration is the vast reduction in Excess Sludge (ES) production, up to 75%. Disposal of which can be one of the biggest operational costs associated with an activated sludge plant. WEW Engineering has designed systems which treat distillery effluent (pot ale, spent lees and wash water) in an AD. Downstream of this nitrogen and phosphorus are removed via Enhanced Biological Phosphorus Removal (EBPR) and concurrent Nitrification/Denitrification in an A2O process to discharge to a water body with BOD, Suspended Solids, Ammonia and Total Phosphorus licence limits of 15mg/l, 15mg/l, 3mg/l and 2mg/l respectively. This design produces a sludge high in nitrogen and phosphorus which will be spread to land to grow barley which will be used to produce more whiskey.
We produce designs and reports to assist our clients to obtain planning permission, grant aid, and investor support incorporating innovations to maximise energy efficiency, nutrient and energy reuse, which guarantee environmental protection through high-quality effluents. We assess options as client representatives, our experience and non-biased approach allows us to carry out due diligence assessment of equipment, manufacture’s sales claims, and we assist our clients in making the best decisions for their project and sites.