Metal finishing - Chemetal Corporation - case study


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Chemetal Corporation of Easthampton, Massachusetts chemically treats the surface of 4 x 8 foot copper and brass sheets to create interesting patterns and color schemes. The decorative sheets are then sold as laminates for counter tops, furniture making, wall treatments and architectural accents. Each sheet pattern and color scheme requires a different proprietary chemical formulation. Copious amounts of fresh water are used to rinse the sheets between chemical treatment steps.

Wastewater Description
The wastewater contains highly variable chemical treatment formulations, including proprietary salts, organic acids, concentrated bases, synthetic dyes and colorants, chlorine bleach, potash, water and substituted ammonium compounds.

Waste Disposal Goals
The goal is to recover the associated rinse waters from the manufacturing process, minimize the volume of waste resulting from the process and maximize the dissolved solids content. Ideally, the client wanted to decrease sludge volume and produce a high quality distillate that could be reintroduced into the rinsing process, limiting the use of potable water. Wastewater Treatment Challenge

Former Process
The client was using a standard physical chemical process to precipitate metals and dissolved solids. The system utilized coagulation, flocculation, pH con-trol and post filtration.

Permitting Considerations
The client was dependent on the local POTW for discharge of their clarified final effluent. The existing POTW permit had strict discharge limits for copper, zinc and molybdenum. Molybdenum was the primary regulatory driver with an allowable dis-charge limit of 0.06 PPM. The former treatment system had difficulties achieving the permitted molybdenum limit. Regulatory oversight and frequent chemical monitoring by the municipality became a weekly requirement.

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