Design of a Zero-Liquid Discharge (ZLD) System to Recover and Reuse the Biotreated Hydrolysate at the Pueblo Chemical Agent-Destruction Plant (PCAPP)

The U.S. Department of Defense (DOD) has engaged in destroying the U.S. stockpile of chemical weapons under the convention that was signed on January 13, 1993 on the prohibition of development, production, stockpiling and use of chemical weapons, and on their destruction of chemical weapons. The Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP) is designed and constructed to destroy chemical agents by hydrolysis at a chemical munitions disposal facility of the DOD in Pueblo, Colorado. The State of Colorado encourages recycling water and minimizing water usage to the extent practicable because of the water shortage in southern Colorado. The permitted capacity of the wells supplying the PCAPP water system is 218,800 gallons per day (gpd). Water usage above this level must be provided by additional sources. PCAPP water usage in summer is estimated to be approximately 60,000 gpd. PCAPP design uses Veolia Water evaporation and crystallization technologies to recover water from the biotreated effluent. More than 80% of the recovered water is used to dilute the hydrolysate for biotreatment. Approximately 103 gpm (148,000 gpd) biotreated effluent is evaporated to recover water for reuse at the site. PCAPP permit requires that the recovered water quality from the BRS is acceptable for use as an effective substitute for well water at the site. Therefore, the recovered water is processed through granular activated carbon (GAC) adsorption units to comply with the Maximum Concentration Levels (MCLs) listed in the National Primary Drinking Water Standards. This paper presents results from evaporation/crystallization, dewatering, and carbon adsorption tests to confirm performance to meet the design parameters. Material selection for high chloride content (4,000-5,000 mg/L), foaming resulting from biosolids, and organics removal from offgas were some of the design challenges.