Force Plant #44 Hughes Missile Systems Company - Tucson, AZ
As the result of the mandated
closing of all surface impoundments at Air Force Plant #44 (AFP44) associated
with process waste and waste water treatment, the need to minimize plating and
surface finishing wastes and to conserve process rinse waters in general
became critically important. A number of water recycling and waste
minimization strategies have been implemented to date.
Process rinse waters have been recycled at AFP44 for many years through the use of clarification, ultrafiltration and reverse osmosis technologies. Recent equipment upgrades and use of statistical process control has resulted in a consistently improved reclaimed water quality being sent back to the plantsite. One immediate benefit has been a decreased demand for the more costly deionized water in the process shops. In addition, the reclaim water now feeds the ion exchange units in the deionization area as it contains approximately 80% less total dissolved solids (TDS) than contained in city water. This has resulted in a less frequent requirement to regenerate the ion exchange resins with hydrochloric acid and sodium hydroxide which, in turn, has reduced even more chemical waste.
Additional water recycling has occurred in the General Plating Shop through the installation of ion exchange systems for all chrome and nickel plating rinse waters. Twenty gallons per minute of chromium and nickel ion loaded rinse waters are passed through separate cation and anion resin columns for complete removal of metal as well as deionization. The result has been less water entering the plantsite waste water stream and, more importantly, minimal chrome and nickel to treat by more costly methods downstream. The success of this effort has resulted in a second project to similarly remove copper, tin and lead ions from printed wiring board process rinse waters at their source. Approximately thirty gallons per minute of re deionized water will be recycled back to the original processes.
In the area of chemical waste minimization, electrolysis copper plating which contains a very difficult to waste treat chelating agent EDTA has been eliminated. A new process utilizing a suspended graphite colloid to accomplish the metalization step has resulted in ease of chemical waste treatment and dramatically reduced rinse water requirements.
Acid recycling units are also being installed. Using a resin based technology, metals ions (copper, nickel, tin, lead, iron) will be removed from what are otherwise active acids resulting in near indefinite use of these process solutions.
Reduction of chemical wastes being generated; reduction
in overall water usage; lower operating costs; continued and, in some cases,
improved product quality.