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Precision Tube Finishing Inc.

Year Submitted: 2003

Process: Parts Cleaning

Industry: Metal Fabrication

Wastes Reduced: Electrolyte Waste

Substance: Phosporic/Sulfuric

Equipment: Clarifier and Filter Press

Location: Houston TX

No. of employees: 16

Contact: Jim Toney

Phone: (281) 856-7400


Using a specialized electropolishing process, Precision Clean Piping, Inc. electrochemically cleans stainless steel piping components for high-purity applications in the microelectronics, biotechnology, pharmaceutical and health care industries. Tubing diameters typically range from 1/8-inch to 1-inch. The process drives large electric currents through the components by means of a strong, circulating electrolyte (a blend of concentrated phosphoric and sulfuric acids). Ultra high purity deionized water is used in a clean room to rinse aggregate residue from piping components after they have been processed.The resulting rinse water is hazardous by virtue of its low pH (pH 0.9 to 1.8, typical) and heavy metals content. Prior to this project the wastewater was concentrated via evaporation prior to deep-well injection.

P2 Application:

Precision Clean Piping, Inc., developed a four stage continuous neutralization and precipitation treatment system that eliminated the disposal of nearly all hazardous waste. The first stage adds ferrous sulfate and sodium hydroxide to reduce any water soluble hexavalent chromium to insoluble trivalent chromium and to form sodium phosphate that is soluble at low pH.The next stage raises the pH from 4 to 6 using calcium hydroxide, forming calcium sulfate that is soluble at that pH. The third stage adds an inorganic flocculent resin powder (Chemsorb-500®) which raises the pH to 8.8 and precipitates the phosphates and sulfates, as well as precipitating and stabilizing the metals. The suspended solids are then agglomerated by adding trace amounts of an anionic polymer and separated using an inclined plane rake clarifier and filter press. The effluent water not only meets all discharge limits, but could be used as input water for the Softener/RO/DI system feeding the Class 100 Clean Room after pretreatment by filtration to reduce TDS beneath the typical values for Municipal Utility District (MUD) water. The filter cake passes RCRA TCLP leaching tests and is a Class 2 waste that can be disposed in a land fill.

Environmental Benefits:

Precision Clean Piping, Inc., has been able to eliminate the disposal of 130-140 tons of hazardous waste per year and return 1.6 million gallons of water to the MUD for reuse. Solid waste contribution to Class 2 landfills is less than 30 cubic yards per year.

Details of Reductions

Additional Information :

Hardware costs for this system are approximately $40,000, and daily operating costs now about $30 per day, are expected to decline to $18 per day. The partially depreciated evaporator, which cost $60 a day to use and maintain, was sold to recover a large portion of its original costs. Precision Clean Piping, Inc., was able to go from being a Large Quantity Generator of hazardous wastes to Conditionally Exempt Small Quantity Generator (CESQG). Being CESQG has reduced regulatory activities by over 70%, or about $10,000 per year. The annualized savings for rinse water disposal costs alone are greater that $70,000 per year.

Source: TCEQ

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