In order to achieve the lowest total cost of ownership and the greatest process efficiency, recycling process water used in mass finishing processes is key. Reusing water not only reduces costs in the form of less consumables used, but also enables companies to reduce their discharge and disposal fees by replacing process water less often and complying with water and waste regulations.
Waste water from mass finishing applications is often referred to as effluent and must be cleaned for recycling or discharge.
Pollutant Impact on Surface Finishing Effluent
Common methods used to measure pollutants in finishing effluent, include increased pH and chemical on demand values, suspended solids, copper, zinc, aluminum, iron, and mineral oil. Based on the work-pieces being finished and the process required, pollutants can vary greatly.
- The pH value is determined by the compound used in a finishing process. Highly acidic or alkaline compounds can cause pH values between 2 and 12. The pH value will not change during settlement unless adjusted.
- Chemical on demand, also known as COD, is a measurement for the overall cleanliness of waste water.
- Total suspended solids, often referred to as TSS, measure how much solid material is contained in the waste water. These can be settled out if the particles are large enough.
- Values for metals in the effluent – most often copper, zinc, aluminum, iron, and mineral oil – can vary significantly depending on the process parameters. For example, the material of the workpieces being processed, compound used, media used, etc. will change the makeup of the effluent.
- Mineral oils are often introduced to the mass finishing system with the part. It is often from stamping and forming oils, die lubes, coolants, corrosion inhibitors, and numerous other process liquids.
Water treatment for discharge must ensure that the discharged water complies with federal, state, and local regulations. For discharge limits for your location and process, please consult your local authorities (city sewer department, local authorities, DEQ, EPA, etc.)