A recently commissioned, 150,000-ton/yr facility in Sumner, Wash. is the first wastewater-treatment plant to deploy a new liquid-waste treatment technology. Owned by Generate Upcycle (San Francisco, Calif.; www.generatecapital.com), and operated in partnership with Sedron Technologies, LLC (Sedro-Woolley, Wash.; www.sedron.com), the facility treats septage- and biosolids-laden slurry using Sedron’s Varcor technology to split the waste into clean water, a dry solid and a solution of low-boiling-point constituents, such as ammonia, explains Stanley Janicki, chief revenue officer at Sedron Technologies. “A Varcor system is unique, in that it replaces four traditional systems in a wastewater-treatment plant — dewatering, drying and sidestream nutrient removal for nitrogen and phosphorus — while ensuring that the energy source is electricity, making the process easily decarbonized,” adds Janicki.
The process combines mechanical vapor recompression and distillation with thin-film and scraped-surface drying on a series of hollow rotating disks (diagram). Slurry is poured over the outside of the disks, and solids collect on the disk while the vaporized portion is sent for compression. The higher-temperature compressed vapor is passed back through the inside of the disks and condensed, providing the heat needed to continue to vaporize the slurry product. Because of this configuration, the system requires little heat input and no treatment chemicals. Notably, the water produced from the Varcor system is clean enough to be blended with the plant’s effluent water, which significantly reduces the overall load on the plant.
Furthermore, the process yields both solid and aqueous nitrogen fertilizers, which can be upcycled as key agricultural inputs, explains Bill Caesar, president of Generate Upcycle. “The ability to extract nitrogen allows the Sumner facility to reduce nutrient pollution by diverting hundreds of thousands of pounds of nitrogen from existing wastewater plants and producing a fertilizer that displaces the production of fossil fuel-derived fertilizers,” he adds.