Ask the Expert Question-and-Answer Archive (Wastewater Treatment)

by Mike McGinness, EcoShield Environmental Systems, Inc.
February, 2002

Ultrafiltration (UF) vs. Microfiltration (MF) for an Iron Phosphating Solution

Q. We have an one step paint pre-wash system. The cleaner is called iron phosphate cleaner/coater from Coral Chemical Company. pH is about 2.4 and temperature is about 170F. If we want to recycle this water or cleaner, do you prefer using UF or do you think MF is enough? Eco-cleaning is good at neutral or basic pH condition. What do you recommend for acidic aqueous cleaning recycling. How do you solve the problem of salt and organic accumulation when doing recycling?

A. Thanks for the question. I am not sure either one is really a good idea. I suspect you will have major problems with either one due to the fouling potential of the iron phosphate rinse water (and calcium & magnesium if soft water is not being used). I have a client in Houston who is using a biological waste water treatment process (customized unit that I designed) to convert the oil & grease and surfactants into filterable non-hazardous bio-mass. The bugs (natural nonpathogenic waste water treatment bacteria) also use up the phosphate, sulfur and nitrogen in the waste water. The system has a Clean Water Act direct discharge permit. They treat the rinse water and the bath dumps with this method. However, they had to use an iron phosphate that was Truly biodegradable. Formulas with NBS (Nitro-Benzene-Sulfonate) in the formula will not work, they are too toxic and do not biodegrade easily.

For your second question, I have looked at the chemistry of the acid iron phosphate cleaners very thoroughly and I am now 100% convinced that the EcoShield ACRS systems can and will work on this particular chemistry as well. We are looking for a willing beta test site to demonstrate this right now! Would you be interested in this? If so give me a call and we discuss it further.