The Sierra Nevada Brewing Company opened a 500,000-barrel-per-year facility, which includes an on-site industrial wastewater pretreatment plant. The pretreatment technology comprises an anaerobic sequencing batch reactor (ASBR) to remove solids and organics prior to discharge to the local sewer. Since the predominant livestock in the region is swine, it is not cost-effective to sell the waste yeast to farmers as feed for dairy cattle. Instead, the ASBR was designed to process this spent yeast. The resultant biogas is fed to microturbines to generate green electricity.

The brewing company faced multiple challenges, including obsolete microturbines and a reduced treatment capacity because of the low biomass inventory in the ASBR. Not to mention, the significant cost to build a new wastewater pretreatment plant to accommodate the brewery’s expansion to produce 750,000 barrels per year.

RETTEW identified several solutions to improve the operation of the ASBR and avoid the large capital expense of building a new replacement wastewater pretreatment plant. The selected solutions to be implemented include new online sensors, new ASBR mixing, continuous influent feed, and a new sludge thickening tank.