The citizens of Colorado selected neutralization followed by biotreatment as an alternative to incineration for the Colorado stockpile of mustard agent munitions stored at the U.S. Army Pueblo Chemical Depot.

“Getting the technology we wanted, a technology the citizens of Pueblo could support, was one of the most gratifying moments of the time I have served on the commission,” said Irene Kornelly, chair of the Colorado Chemical Demilitarization Citizens’ Advisory Committee.

Projectiles and mortar rounds containing mustard agent will be processed by the plant’s Munitions Washout System, which will drain and scour the munitions with hot water. The drained agent will be piped into a holding tank and will be combined with water, producing hydrochloric acid and thiodiglycol. Sodium hydroxide is then added, causing the neutralization process and producing hydrolysate, a combination of thiodiglycol, salt and water, said Greg Mohrman, site project manager, Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP).

“In simplest terms, this process will neutralize the mustard agent by causing a chemical transformation. The chemical properties of the mustard will be destroyed, leaving it innocuous,” Mohrman said.

Hydrolysate will be pumped into Immobilized Cell Bioreactors to be further broken down by biomass, or microbes. The biomass releases enzymes which will break down the hydrolysate into an organic waste known as biosludge. The biosludge is sent to the Brine Reduction System, where water will be removed and recycled back into the plant. The resulting salt cake will be disposed of at a permitted Treatment, Storage and Disposal Facility, said Dr. Jim Earley, chief scientist, PCAPP.

Before closing the plant, PCAPP will neutralize and biotreat mustard agent from approximately 780,000 munitions and mortar rounds.