CLEARING THE AIR


FDHS: HOW IT WORKS


The Field Deployable Hydrolysis System (FDHS) is an envi- ronmentally secure, high-throughput system used to destroy chemical warfare materiel. It neutralizes chemical agents and their precursors through a process known as hydrolysis, a reaction in which water, mixed with reagents and heated, irreversibly converts these chemicals into compounds not usable as weapons.


Two modular FDHS units aboard the MV Cape Ray hydro- lyzed HD, also known as sulfur mustard or mustard gas, and DF, a sarin precursor, from Syria under environmentally secure conditions that ensured the safety of FDHS opera- tors, the ship’s crew and the surrounding environment. An on-ship chemical analysis laboratory verified the required destruction levels of all chemicals.


Following are the key steps in the processes for HD and DF.


HYDROLYZING MUSTARD First, hot water is added to the FDHS large mixing tank; then HD is fed into the water and mixed vigorously. Hydrolysis of HD removes reactive chlorine atoms, resulting in a waste product called hydrolysate, which, in this case, includes thiodiglycol, a chemical used in ink, and hydro- chloric acid (HCl), a chemical often used to clean concrete or remove rust. The hydrolysis process is irreversible; HD cannot be recreated from hydrolysate.


The hydrolysate is then pH-adjusted with sodium hydrox- ide—a caustic, or base—which neutralizes the HCl. The end product is a solution of thiodiglycol, sodium chloride (NaCl, common salt), and water.


Finally, the hydrolysate, which is neither explosive nor flam- mable, is stored on the ship until it is moved to an approved disposal facility for additional treatment.


HYDROLYZING SARIN First, DF is mixed directly with room-temperature water in the FDHS static mixer. A two-step reaction occurs, which removes reactive fluorine atoms. The resulting hydrolysate is a solution of methylphosphonic acid and hydrofluoric acid. This is an irreversible process; DF cannot be recreated from the hydrolysate.


The hydrolysate is pH-adjusted with sodium hydroxide to form an aqueous solution of sodium fluoride and methyl- phosphonate, a salt.


Finally, the hydrolysate is stored on the ship until transfer to an approved disposal facility for additional treatment.


FDHS operators store all waste generated from this pro- cess in approved containers aboard the ship. There is no discharge of FDHS liquid waste into the water. When operations are complete, the containers are off-loaded for delivery to disposal facilities in Finland and Germany selected by the Organisation for the Prohibition of Chemical Weapons.


All of the air surrounding the FDHS process is directed through a filtration system before it is released back into the environment. Thus, the air that exits the ship is cleaner than the air that enters the ship.


—JPEO-CBD


RAPID FIELDING


One of two FDHS units is installed aboard the Cape Ray in Portsmouth, VA, Jan. 2, 2014. FDHS was created, fabricated and deployed within a year. (DOD photo by C. Todd Lopez)


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Army AL&T Magazine April–June 2015


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