EPA promulgated the Metal Molding and Casting (MMC) Effluent Guidelines and Standards (40 CFR Part 464) in 1985. MMC facilities discharge process wastewater directly to surface waters or indirectly to surface waters through publicly owned treatment works (POTW). The MMC regulation covers 28 process segments (processes such as casting quench, melting scrubber, mold cooling) in four subcategories: Aluminum Casting, Copper Casting, Ferrous Casting, and Zinc Casting. The Effluent Guidelines are incorporated into NPDES permits for direct dischargers and permits or other control mechanisms for indirect dischargers.
The NPDES permit program addresses water pollution by regulating point sources that discharge pollutants directly to waters of the United States (Link to NPDES Permit Program). Foundries that discharge process water and/or non-contact cooling water (other than stormwater) directly to waters of the United States are required to have an individual NPDES Permit (or state permit) which establishes effluent limits, monitoring and reporting requirements, etc. Currently, non-contact cooling water is likely the only “process water” that a foundry would get permitted to discharge directly to waters of the united states.
The national pretreatment program requires nondomestic dischargers to comply with pretreatment standards to ensure the goals of the Clean Water Act (CWA) are attained. These requirements are generally incorporated into an industrial waste water permit issued by the POTW.
The objectives of the national pretreatment program are to:
• Prevent the introduction of pollutants into a POTW that will interfere with its operation, including interference with its use or disposal of municipal sludge.
• Prevent the introduction of pollutants into a POTW that will pass through the treatment works or otherwise be incompatible with it.
• Improve opportunities to recycle and reclaim municipal and industrial wastewaters and sludges.
Most MMC facilities that discharge process wastewater do so indirectly through publicly owned treatment works (POTW) and will have an industrial waste water permit.