One Industry's Waste is Another Industry's Carbon Source

Wastewater treatment and whiskey distilling, two seemingly unrelated industries that deal with waste on a daily basis, have the opportunity for an innovative, sustainable, and mutually beneficial partnership. At Laws Whiskey House (Laws), a craft whiskey distiller located in South Denver, two waste streams are generated with production: stillage, a byproduct of the stripping still, and heads, the undesirable alcohols extracted during the distillation process. These streams, high in alcohol and carbon content, present disposal challenges for distillers but are potentially valuable carbon sources for wastewater treatment processes.

Just down the street at South Platte Renew (SPR), the third largest water resource recovery facility (WRRF) in Colorado, carbon is delivered weekly in the form of Methanol to support the nitrogen removal process in the denitrification filters. SPR discharges directly into the South Platte River, an area largely known for recreation, thriving aquatic populations, and used as a water source downstream. As such, maintaining stream health through nutrient reduction is vital. With the desire of reducing chemical purchase costs, decreasing chemical footprints, and improving community and environmental stewardship SPR created an unlikely partnership with Laws.

This partnership led to the Laws Denitrification Pilot (Pilot), conducted through SPR's Pilot and Research Center (PARC), aiming to prove that whiskey distillation byproducts could support nitrogen reduction in wastewater treatment.

The Pilot, beginning in the fall of 2023, utilized a return sludge flow to dose the stillage and heads into the reaeration basin where the necessary retention time and anoxic environment could be met to promote denitrification. A staff member from Laws delivered the waste products to the plant site each week where it was held in a storage tank and then pumped into the return sludge stream, which flows at approximately 28 million gallons per day. To monitor progress and ensure no unwanted disruptions to downstream treatment processes, SPR staff monitored several key performance indicators in numerous locations:
- Reaeration (RA) Basin: Influent and effluent nitrate, air flow, carbonaceous oxygen demand (COD)
- Solids Contact Tanks (SCTs): Air Flow, influent and effluent phosphorus
- Stillage Holding Tank: Carbon, alcohol by volume, metals, phosphorus
- Denitrification (Denite): Methanol usage

In addition, factors such as alkalinity and mixed liquor were monitored to maintain the health of the overall SCTs and to observe plantwide impacts. The overall goal for the Reaeration Basins was to see a ten percent nitrate reduction which has the potential to save over 24,000 gallons of Methanol at Denite.

Initial dosing periods showed low COD content in the deliveries and minimal denitrification. These initial deliveries were mostly stillage, this waste product is more abundant but not as strong as the heads which are generated later in the distilling process. Therefore, after shifting to deliveries of heads alone in early 2024, denitrification was observed, with a 42% nitrate reduction and a COD of 310,000 mg/L.

The Laws Pilot, while deemed successful, was not free from obstacles. Inconsistent waste deliveries due to varying distillery operations caused challenges in creating a stable testing environment. The next phase of the Pilot is aimed at addressing this concern through community outreach and creating additional partnerships with other distilleries in the area to rerun the pilot as a long-term application.

The successful results of the Laws pilot at SPR shows great potential for a repeatable partnership at WRRFs across the US. Any wastewater treatment process requiring a carbon source has the opportunity to partner with a local whiskey distiller or community discharger. As long as the world keeps drinking whiskey, wastewater treatment could have a consistent and sustainable supply of carbon to use for treatment. These distillers and other community dischargers are often heavily regulated and can be fined for disposal of these waste sources. But just a small redirection of where those streams are entering the treatment process from the influent to secondary treatment can actually enhance processes, increase sustainability, and has the potential to save over $50,000 a year in operational expenses. This Pilot highlights the importance of external collaboration and seeking solutions outside of just the water and wastewater industry.

This presentation will showcase the innovative partnership between SPR and Laws, outline the pilot setup, methodology, and results, and introduce a sustainable treatment technology that any utility with nutrient limits can explore.