46007

Iron Phosphatizing Safety and Waste Water Issues [Missouri] 

August 2, 2007

Can anyone help me find out about the safety issues with Iron Phosphatizing and any wastewater issues. Are there any articles out there that discusses these issues. I need as much info as I can get.

Rosy DeSimone
Employee - Kansas City, MO, USA

Ed. note: Rosy asks our supporting advertisers to call her on this.

Iron phosphating is a Federal categorical process, with defined pretreatment discharge limits. The most likely contaminant in spent rinse water is zinc, if you are applying this coating on galvanized steel. An adjustment of the pH to 9 - 9.5, followed by the addition of flocculant, and settling, should leave the residual Zn in the decant below this limit. (monthly average = 1.48 mg/l; daily max = 2.61 mg/l)

Your local POTW may have restrictions on the discharge of iron and/or phosphorus. Get with them and see what their policy is.

Both the settled sludge from this operation, and the tank bottoms, are categorical hazardous wastes. They need to be dewatered, and hauled to a haz waste landfill.

Dave Wichern - Bronx, NY, USA

Phosphatizing is a listed process in Section 433 of EPA regulations for the Metal Finishing Category. However, if you are doing iron phosphatizing and not zinc phosphatizing, you may not have any worries, since iron discharges are not regulated in these regulations. However, as the previous responder noted, zinc and nickel (a common ingredient in zinc phosphate coating solutions) are regulated.

Most iron phosphate operations that I know of have no waste treatment other than possibly neutralization. These operations often haul any concentrared dumps off-site for treatment and disposal.

Even if there are no Federal Regulations that apply to your situation, you would still need to meet the requirements of your local sewer use code. Many local codes allow up to 50 mg/L or more of iron, and allow a fairly high concentrate of phosphates before any surcharge would be levied. So, if you are just doing iron phosphate coating, I suggest that you contact your local sewer authority for advice.

Lyle Kirman
water treatment systems - Cleveland, Ohio