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

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

Wastewater From a Lead-Acid Battery Washing Operation

Q. A facility in Colorado needs a system to wash damaged lead-acid batteries and treat the effluent for reuse or discharge to the sanitary sewer.So they will need to address Pb and H2SO4 to meet typical metro discharge standards. Any recommendations?

A. Yes, I have several recommendations.

First is wash in two or even three independent steps. The first would be a sodium carbonate solution wash down step (about 8 oz. per gallon). This would form (acid base neutralization reaction) low solubility lead carbonate, plus sodium sulfate and water. A second cleaner solution of sodium carbonate to remove and dilute the remaining lead on the batteries (same strength), followed by a third rinse of either a recycled DI water (using and Ion exchange resin column) rinse or a final dilute sodium carbonate solution rinse. I would try and avoid a discharge even to a potw and recycle the water on site. Precipitated lead carbonate solids could potentially be sold for metal recovery. They need to be sure and avoid chemical cleaning compounds and soaps since they generally contain chelating agents that will keep the lead dissolved in the water. I recommend just water and sodium carbonate with a pH meter or pH controller to maintain the pH at about 9.0.

Eventually the second rinse could be used as make up for the first rinse as water is lost to evaporation and water of hydration is lost to solids removal. If an Ion exchange resin column (sodium ion water softener style would work) is used for the final rinse they will need to deal with regeneration issues, on site or offsite! The first flush of regenerate would be lead chloride, highly soluble and definitely TCLP Hazardous waste unless their is a recycling exemption available.

I am sure their are other ways to do this but this seems to me to be the safest and simplest.

Please let me know if I can be of any further assistance. Also, we can offer a custom designed, simple, low cost system from EcoShield if they are interested, with or with out pH control, and filtration on the first rinse. If they wish to request a quote or discuss it they can email me at cpssco@earthlink.