Water recovery and reuse at the Pueblo chemical agent-destruction plant (PCAPP)

One design constraint for any project in southern Colorado is the shortage of water. The State of Colorado encourages recycling water and minimizing water usage to the extent practicable. The permitted capacity of the wells supplying the PCAPP water system is 218,800 gallons per day (gpd). Well water is mainly used by cooling towers, sanitary facilities, laundry facilities, utilities, decontamination facilities, and process water makeup. Water usage above this level must be provided by additional sources. One of the features of the PCAPP design is using a zero-liquid-discharge (ZLD) system to recover and reuse the water from the biologically treated hydrolysate stream. A Brine Reduction System (BRS) will be used to recover water from the biotreated effluent. The BRS will include an evaporator and crystallizer system to remove dissolved solids, organic compounds, dissolved gasses and residual suspended solids from the biotreated effluent and from other process waste streams such as cooling tower blowdown, reverse osmosis (RO) reject, and boiler blowdown. The 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. Process water recovered at the BRS is mainly used by the biotreatment system, cooling towers, RO system, offgas treatment system scrubber, agent hydrolysers, autoclaves, and pumps. At the design flow rate, the BRS can recover approximately 165,000 to 175,000 gpd of the water used at PCAPP. These recovery levels correspond to water recovery percentages of 94 to 100%. This paper will describe challenges of water management at the PCAPP, water usages by different process units, variations in water usage in summer versus winter, and processes used to reclaim and reuse wastewater at the site.