Treating Wastewater from Pre-Paint and Pre-Treatment Process Lines
December 19, 2014
Wastewater pre-treatment lines and pre-paint lines of traditional zinc, manganese phosphate, and/or iron phosphate will typically have two primary discharge concerns: zinc metal and phosphorus.
Green pre-treatment process lines will use siloxane, silane, zirconium, or possibly several other more exotic elements.
These process lines will contain a variety of alkaline or acidic cleaners in the substrate preparation phase, as well as activators and stabilizers in the actual process coating step.
Surfactants, wetting agents, chelants, organic phosphates, and silane/siloxane/zirconium complexes all make the precipitation of zinc or phosphate down to discharge limits a difficult task.
SO WHAT CAN BE DONE TO MEET COMPLIANCE?
- Act as absorbents for solids of phosphate and other anions - surfactants/wetters.
- Act as solids' conditioners, neutralizing net anionic charges, forming a distinct “microfloc” in system neutralization tanks.
- Act as metal capture agents. Upon pH adjustment, OMEGA BP-4123 or OMEGA C-3112 can co-precipitate both zinc and iron residuals from the process stream.
Look for a dose based upon solids concentration and the phosphorus level of the influent.
A typical dose of OMEGA BP-4123 is 10X times the phosphate level in the wastewater.
- 100 ppm phosphate untreated: dose OMEGA BP-4123 or OMEGA C-3112 at 1,000 ppm
- 20 ppm phosphate untreated: dose OMEGA BP-4123 or OMEGA C-3112 at 200 ppm
A pH level of 9.5 is desirable. Caustic is recommended. Lime can be used, but creates more sludge and is not required for this process.
- OMEGA AP-2140 for a smaller wastewater volume of 100 to 10,000 gallons per day
(dose OMEGA AP-2140 at 50 to 100 ppm).
- OMEGA AP-2040 for a larger wastewater volume of 10,000 and more
(dose OMEGA AP-2040 at 2 ppm to 15 ppm).
How do you determine which Coagulant to use? Simply submit a water sample and a Survey Form explaining your process to COVENTYA for a laboratory analysis.