Consolidated Metal Products, Inc. faced a wide variety of problems in its Cincinnati automotive U-bolt manufacturing facility. These included zinc phosphating wastewater, low pH, high zinc and trace other metals, high oil and grease, chelated cleaners, citric acid, high temperature and phosphate, and cleaner concentrate dumps. The facility's mostly unskilled operators had to pretreat to POTW National Metal Finishing Limits, but found the process very difficult using the old system.
Management decided to install a new system in the basement, beneath the phosphating line, with only 10 ft. of headroom and access through a small freight elevator. The average flow at this facility was 30 gpm, two shifts per day, six days per week. The company turned to Enprotec of Hebron, Kentucky, to develop a solution. Enprotec designed and installed a turnkey system guaranteed to meet effluents limits.
Before the new system was installed, the phosphating/wastewater chemical supplier had considerable trouble meeting effluent limits and instructing the operators on the system's daily operation because of the varying waste stream. To resolve this situation, Enprotec switched the chemistry to a single, innovative, proprietary powder.
Another major drawback of the old system was the complexity of the waste materials. High-tech coatings and cleaners required to meet automotive corrosion resistance tests created highly complex wastes, making it very difficult to reduce the zinc to required levels. The new system presently exceeds current limits and is designed to meet future Metal Products & Machinery (MP&M).
The current process includes a custom built clarifier and tanks designed to fit in the low headspace. Three concentrates including citric acid, spent zinc phosphate, and spent alkaline cleaners are held in separate tanks and metered into the equalization tank. The pH is adjusted from 2-3 to over 7 to allow for discharge, and the innovative chemical is added volumetrically at about 4,000 ppm as a dry powder. Although the clarifier is substantially overloaded, the overflow remains clear due to the higher settling rate of the floc over conventional hydroxide precipitate flocs. A triple cell granular multimedia filter polishes the effluent before final monitoring and discharge to the POTW. Because only simple pH adjustment is done and only one other chemical is added, the system is easy for operators to understand, operate and keep in compliance.
Enprotec ¥ Hebron, KY
Phone 606-689-4300 ¥ FAX 606-689-4322 ¥ www.enprotec-usa.com