Brewing Business: Water treatment and solutions for distilleries
Many different forms of wastewater can be generated during the production of whisky. Here, David Gaskill, Proposal Manager at Siltbuster Process Solutions (SPS), a leading UK water treatment specialist, discusses the latest thinking when it comes to getting treatment right.
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The Threat of Wastewater
Given how damaging untreated water can be if discharged to local watercourses, especially to the flora and fauna of an area, it is no surprise that discharge consents can be demanding. With this in mind, it’s essential that best practice is adhered to when it comes to wastewater treatment.
Historical Treatment
Distillery wastewater often has a high organic load and is often highly biodegradable. It also contains suspended solids, copper – from the stills – and it will vary in its pH. These characteristics all present threats to the environment.
With this in mind, it is good practice for distilleries to install a Balance Tank with pre-screening. This helps to collect wastewater and minimises the size of downstream wastewater treatment plant processes, as the flow and characteristics of the wastewater are buffered within the tank.
Once the wastewater has been balanced, a wastewater treatment plant can set to work often reducing the suspended solids first. From there the wastewater is often biologically treated followed by further suspended solids removal so it can be discharged offsite within consent criteria. Aerobic processes are particularly dominant at smaller distilleries, while larger distilleries tend to involve an anaerobic stage – producing valuable biogas – before initiating an aerobic stage and then additional downstream treatment.
Historically, smaller distilleries use traditional Trickling Filters for the aerobic stage. This involves circulating water over a fixed media bed – rocks or plastic media on which bacteria grows – and allowing natural ventilation to provide the oxygen for the aerobic process.
Although effective, lots of these plants are beyond their design life and the structure of many Trickling Filters can be unstable, presenting a hazard. An additional problem is that during their lifetime, the media often gets blocked by excess biomass.
New Ways of Thinking
At SPS, we can replace Trickling Filters with a more compact aerobic process facilitated by Moving Bed Biofilm Reactors (MBBR). By using blowers to provide oxygen and mixing, the media houses the bacteria within the MBBR. This enables a large volume of wastewater to be treated in a much smaller footprint than is achievable with other aerobic processes. The air helps to scour the excess biomass from the media, enabling fresh biomass to process the wastewater and reduce the Biological Oxygen Demand (BOD) and the associated Chemical Oxygen Demand (COD). Also, since the bacteria are grown on and within the media, MBBR units are more resilient to any shock loadings when compared to any other aerobic processes.
Fresh Thinking In Practice
In one distillery, SPS enhanced the existing treatment plant by adding a Dissolved Air Flotation (DAF) unit after the Balance Tank. This worked to reduce the suspended solids which would otherwise be determinantal to downstream processes. This was installed with gravity flow to and from the DAF, within the existing plant which was installed last century.
Five years later on the same site, SPS also installed a packaged MBBR prior to the existing Trickling Filter. This was done on a hire basis to allow an opportunity for the distillery to assess its impact on processing the site’s wastewater. The performance was such that the distillery purchased the unit.
SPS worked with the distillery in order to identify the tie-in points and ensure that the pre-tested equipment was delivered, installed, commissioned and processing wastewater at full flow within a couple of days. This minimised disruption to production at the distillery.
In Conclusion
By working collaboratively with wastewater treatment providers, distilleries can incorporate plants designed to maintain or even grow production while safeguarding the environmental protection of their surroundings, avoiding potentially costly fines in the process.
