Food / beverage
Wastewater / effluent
Wehrle was commissioned by Chivas Brothers in 2008 to design and install a wastewater treatment plate at the Glenallachie Distillery near Aberlour in Scotland.
The effective treatment of distillery wastewater has always been important, particularly at locations which require the removal of copper, and the Chivas Brothers chose to implement Best Available Technology (BAT) to ensure they could consistently meet their discharge licence conditions for the local watercourse.
The new effluent treatment system has a small footprint coupled with reduced sludge yield compared to the old technology, as well as a low environmental impact. The main process plant is installed inside an existing building at the distillery with two modular bioreactors located outside this building.
All wastewater on the site is treated by a two-stage, aerobic cascading MBR system after it is collected in three separate holding tanks. Foul condensate is diluted with washing water from around the site before entering the mixing tank. Spent lees from the second distillation stage also enters the mixing tank and the combined wastewater is then pH corrected, using kalic (18% liquid lime) and/or caustic, before being treated by the MBR system.
By careful design, the process is able to tolerate the influent copper and biodegrade the mostly soluble organic loading, chemicals and fine solids in the wastewater to a level suitable for membrane separation through a cross-flow ultrafiltration (UF) system. The pH in each bioreactor is controlled to ensure the influent copper is kept in its relatively inert insoluble or ‘complexed’ form.
The UF process separates the mixed activated sludge into a concentrated stream that is returned to the first bioreactor for subsequent re-treatment, and a permeate stream of treated water with exceptionally low solute and solids content. The copper is effectively all retained in the biomass.
Treated water meets the final discharge water quality requirement as licensed by the Scottish Environmental Protection Agency (SEPA) and is discharged to the local watercourse.
The MBR plant is designed to treat a flow of 144 m3/day of combined wastewater. The biological stage is designed to process influent COD of 3,000 mg/l with two bioreactors.