Biological Treatment of Chemical Agent Hydrolysate by Immobilized Cell Bioreactor Technology

The Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP) is for demilitarization of chemical weapons stored at the Pueblo Chemical Depot (PCD), Pueblo, Colorado. The PCD stockpile consists of projectiles and mortars containing blister agents (93.4% of total stockpile), explosives (4.2%), and propellants (2.4%). Agents are approximately 98% HD (distilled mustard, β, β'-dichloroethylsulfide), and 2% HT, a mixture of HD and T (bis-2-2-chlorethylthioethyl ether). Agent demilitarization involves: collection from munitions; hot water and caustic hydrolysis to produce agent-free hydrolysate; biological treatment of hydrolysate to reduce organic content; and effluent treatment to recover water for reuse. The selected biotreatment process for the hydrolysate is Immobilized Cell Bioreactor (ICB) technology. This paper describes the design of ICBs for PCAPP. The design is based on laboratory and pilot testing results, which defined organic loading rates, hydraulic retention times (HRT), aeration and nutrient requirements, and operational parameter ranges and controls (temperature, dissolved oxygen, and pH).