Permit-Free Chromium Plating

Article From: Products Finishing, , from Products Finishing

Posted on: 11/1/2002

Columbia Manufacturing needed to replace its chromium plating line, but not with a new finishing process. It kept the hexavalent chromium plating technology and installed a zero-discharge wastewater treatment system...

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Flash distillation process

Fig. 1 Flash distillation process

On this line all plating chemicals are recovered

On this line all plating chemicals are recovered along with DI water, which is sent back to the rinse tanks on the nickel and chromium plating line. Cleaners are also treated using vacuum distillation, and the DI water reused on the cleaning line.

You could learn a few things about efficiency, plating and wastewater treatment from Columbia Manufacturing. In 2001, the Westfield, MA, company removed its old plating line and retired its waste treatment operations. In turn, it installed a new, automated return-type system for nickel/chrome plating its line of school furniture. Of course, when installing a new plating line, it had to consider waste treatment/resource recovery strategies. Columbia chose to install a state-of-the-art resource recovery system to handle the nickel, hexavalent chrome, acids and cleaners instead of a traditional waste treatment system. Now the facility doesn't even need a discharge permit!

Columbia actually started as a bicycle manufacturing company in 1877. It still manufactures bicycles 125 years later; however, school furniture is its biggest seller now. It has been manufacturing school furniture for 50 years. The company continues to grow. "We continually improve our processes and product quality with a focus on technically innovative solutions," noted Gary Newmaster, engineering manager for Columbia. "We constantly invest in new resources to meet and exceed our customers' expectations for innovation, quality and on-time delivery."

This philosophy and the need to expand its manufacturing to meet the growing demand for their product inspired Columbia to improve its operations, including the installation of a new plating line with an integrated resource recovery system. It knew the old plating line was out-dated and undersized. Columbia also realized that the existing precipitation-based waste treatment system would not meet its future needs. The company was using 150,000+ gallons of water per day. It could have sent the furniture out for plating, however, the cost to wrap and ship all the furniture and then unwrap it and inspect it upon return was too expensive. Also, if the furniture was shipped out to three different platers, there was a chance the furniture would come back in three different colors. Not every shop plates hexavalent chromium to the exact shade and specifications Columbia wanted. The company kept the plating in-house for both cost purposes and quality control.

"We started with a clean floor," remarked Mr. Newmaster. "We removed everything and started new. The new Napco automated plating line went in first and the CASTion resource recovery system was installed last, due to the building setup." The new plating line, resource recovery system and Columbia's special rack design tripled the company's plating capacity while minimizing waste management.

School furniture is basically tubular steel that is bent and welded into various curves and shapes. All of the welding and brazing takes place prior to plating. The product is exceedingly difficult to plate due to its size, multiple configurations and tubular nature. The parts drag out large quantities of plating solution, and the line runs continuously at a very high rate of production. This made Columbia's line especially challenging to close loop.

The resource recovery system was designed to close-loop the entire plating operation, including the cleaners. All water is returned to the rinse tanks and plating solutions are recovered and returned directly to the plating tanks. "We recover and reuse 600 pounds of chromium trioxide per week," noted Mr. Newmaster. Columbia has also cut back on its city water use and wastewater discharge by 130,000 gallons per day. "The city forced us to install a smaller water meter, because the one we had was too large to read the new flow," said Mr. Newmaster. Plus, Columbia is saving on sewer fees because nothing is going to drain.

How can Columbia close loop a nickel chrome plating line with acidic and basic cleaning chemicals? Each plating chemistry and the cleaning lines have their own CAST-ion recovery system. (See Fig. 1)

Typical to most plating lines the front end consists of alkaline soak cleaners, cathodic acid, electro-clean and an acid activator. The alkaline soak cleaners, cathodic acid and electroclean remove oil, dirt, rust, scale and smut from the carbon steel tube stock. Each of these process tanks is followed by multiple rinse tanks. Concentrated rinse waters from these operations are combined and processed by a large vacuum distillation system. The dilute rinse waters are commingled and ultra-filtered. The distillate, ultra-filter permeate and acid rinse are combined and sent to the counter current ion exchange system for reuse on the plating line as DI water. The ion exchange system consists of oil adsorbent prefiltration, granular activated carbon, duplex separated bed counter current ion exchange, final filtration and ultraviolet sterilization. The DI water produced is stored in a 5,000 gallon tank and is returned to the plating line at the required flow rate and pressure in a continuous fashion.

The pre-filtration media and the granular activated carbon filtration remove suspended solids, insoluble iron and organic contaminants. The ion exchange columns remove soluble iron, sulfates, sodium hydroxide and other dissolved inorganic contaminants contributed by the cleaners and acids. The final filtration and ultraviolet sterilizer assure particle and bacteria free DI water for reuse on the plating line.

The ion exchange columns are regenerated with 40 gallons of HCl and 70 gallons of NaOH and DI water. Regeneration produces 3,000 gallons of 30,000 ppm effluent. The regeneration effluent is commingled with the concentrated rinse waters from the front end of the plating line and processed by the large vacuum distillation system. This system recovers 4,800 gallons per day of clean distilled water that is brought back to the front of the ion exchange system to be polished and reused on the plating line. The concentrated waste from the system is fed to a filter press and the waste cake is manifested for off-site disposal.

Valuable nickel plating chemistry is recovered from a multiple counter flow rinse tank arrangement by a second vacuum distillation system. This system recovers 2,000 gallons per day of clean distilled water that is brought back to the front of the ion exchange system to be polished and reused on the plating line. Two hundred gallons of dilute nickel plating chemistry is fed through carbon filtration to remove organics and returned to the nickel plating bath.

The hexavalent chromium recovery process is similar to the nickel, except that the chromium plating chemistry is purified using a porous pot system prior to reuse.

Columbia's investment in this turnkey wastewater treatment system and plating line has resulted in several factors:

  • All wastewater is recovered as DI water and recycled to the rinse baths;
  • 98% of all nickel plating chemistry is recovered and used;
  • 98 % of all chromic acid plating chemistry is recovered and used;
  • There is zero discharge to the air or sewer;
  • Massachusetts DEP has exempted Columbia from air and water discharge permits;
  • Columbia is exempted from RCRA hazardous waste TSDS permits;
  • The metal content of the manifested filter cake has been significantly reduced; and
  • Columbia estimates its payback is about two years.

"We have school districts that are concerned about what we are doing environmentally," stated Mr. Newmaster. "They care about how their furniture is manufactured, not because the finished product could be harmful in any way, but because they want to buy from a company that is practicing ‘green' manufacturing."

Ninety-five percent of the furniture produced at Columbia is chromium plated. Initially, Columbia Manufacturing wanted to wean its customers from chrome plating and provide them with painted school furniture. The market preferred the chrome-plated furniture. This forced Columbia to expand and improve its chrome plating capabilities to meet both current and future requirements. The success the new plating line and the CASTion resource recovery system won Columbia the Governor of Massachusetts "Green Seal" award for environmental stewardship.

Columbia's investment has benefited the company, Massachusetts the school furniture market and the environment.

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