Reclaiming Dairy Wastewater with Hydrothermal Liquefaction
Faculty Mentor Information
Dr. Owen McDougal, Boise State University
Presentation Date
7-15-2026
Abstract
Suspended Air Flotation (SAF) is a water treatment process used by the dairy industry to remove solids from wastewater, which yields a high water containing sludge that is transported to lagoons for disposal. Hydrothermal liquefaction (HTL) is a biomass conversion process that uses high pressure and temperature to turn waste sludge into biocrude oil, water, and biochar solids. Dairy wastewater flocculant from a SAF system can contain more than 90% water, and HTL offers a possible technology solution for reclaiming water for industrial usage while minimizing disposal costs. The goal of this project was to compare the quality of SAF water before and after HTL against wastewater regulations (i.e., pH, total solids, nitrogen, and phosphorus content). Post HTL, the water pH increased by 1.48 and LECO nitrogen analysis showed a nitrogen increase by more than 3,000 ppm. ICP-MS indicated an 86 ppm decrease in phosphorus, and Sartorius moisture analyzer showed a 0.12% decrease in total solids. Future work will measure the biological and chemical oxygen demand and total suspended solids, as well as run the post-HTL water through reverse osmosis and test the same parameters to determine the optimal conditions for water reclamation.
Reclaiming Dairy Wastewater with Hydrothermal Liquefaction
Suspended Air Flotation (SAF) is a water treatment process used by the dairy industry to remove solids from wastewater, which yields a high water containing sludge that is transported to lagoons for disposal. Hydrothermal liquefaction (HTL) is a biomass conversion process that uses high pressure and temperature to turn waste sludge into biocrude oil, water, and biochar solids. Dairy wastewater flocculant from a SAF system can contain more than 90% water, and HTL offers a possible technology solution for reclaiming water for industrial usage while minimizing disposal costs. The goal of this project was to compare the quality of SAF water before and after HTL against wastewater regulations (i.e., pH, total solids, nitrogen, and phosphorus content). Post HTL, the water pH increased by 1.48 and LECO nitrogen analysis showed a nitrogen increase by more than 3,000 ppm. ICP-MS indicated an 86 ppm decrease in phosphorus, and Sartorius moisture analyzer showed a 0.12% decrease in total solids. Future work will measure the biological and chemical oxygen demand and total suspended solids, as well as run the post-HTL water through reverse osmosis and test the same parameters to determine the optimal conditions for water reclamation.