Buyer/supplier teamwork helps minimize environmental impact
By Staff -- Purchasing, 11/18/1999
It can be very challenging for a manufacturing company to stay competitive while simultaneously minimizing the environmental impact from its manufacturing operations. Caterpillar Precision Pin Products and BetzDearborn teamed up recently to solve an environmental problem that not only solved the problem but also saved money.The problem: Caterpillar's Sumter, S.C., plant makes pins to high-quality standards for use in Caterpillar equipment. Plant management was concerned about the environmental impact of the spent chrome that is produced by the plant's metal-finishing and plating operations. Trucking this hazardous waste off-site for disposal was expensive and also threatened Caterpillar's "no landfill" status in the surrounding community.
The chrome recovery operations begin at an off-line holding tank for chrome-bearing wastewater. The water is pumped to a vacuum evaporator, where the chrome is concentrated and then returned to the plating tank. The process recycles 14,400 lb of waste chrome annually. Because not all chrome can be recovered, some rinse water enters the waste stream.
Tests by BetzDearborn proved that the spent chrome could be recovered using a proprietary chemical treatment program. Remaining wastewater could then go through a selective ion exchange process to produce a relatively pure form of sodium dichromate that Caterpillar hopes to sell. However, Caterpillar discovered that it would have to pay about $134,000 to ship and process 24 tanker loads each year. It also would have to pay another $30,000 per year to have spent sulfuric acid hauled away. The two companies looked for another solution.
When a Caterpillar employee suggested reducing the volume of spent chrome waste, BetzDearborn helped develop a dewatering process that produced a solid product--a concentrated sludge. Much less expensive to ship and process, the sludge also could be recycled instead of being sent to a hazardous-waste landfill. A process was developed to reuse spent sulfuric acid from plating lines, which saved more money. Each month, 1,000 gallons of acid are processed on-site.
The new treatment program was implemented at a one-time cost of $1,200. It reduces 4,000 gallons of liquid waste to one cubic yard of solid material that is disposed of for only $425.
To minimize the plant's environmental impact still further, Caterpillar and BetzDearborn purified the treated chrome rinse water to produce demineralized water that could be returned to the plating line. As a result, up to 80% of all wastewater now is reused. Chrome tank solutions from the demineralized water can be recycled indefinitely.
The results of the Caterpillar/Betz-Dearborn teamwork include: recycling 100% of hazardous electroplating waste on-site; avoiding $164,000 per year in disposal costs; elimination of scrap from the chrome plater since start-up; and the use of millions of gallons of recycled water, which results in additional cost savings.
"Caterpillar employees are proud of their success in developing an essentially closed system that recovers valuable resources and protects the environment and community," says Bob Jeanmenne, chemical operations manager at Caterpillar. "Our working together with BetzDearborn helped make it possible."
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