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On site disposal of pickling rinsewater

We need to do some on site pickling of 304 and 316 stainless steel using the standard Nitric/HF solution. The plant does not have a treatment facility. All water and sludge must be disposed of off-site. Pickling solution manufacturers suggest neutralizing the rinse water to precipitate the metals. Has anyone ever tested the water to see if it is then deemed non-hazardous? Do all the metals drop out in the neutralized sludge?

Todd Turner
industrial cleaning - Monroe, Louisiana
2007

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Hazardous waste? Almost certainly not. However, it won't be good to go down the drain because of high nickel, and possibly chromium.

You could neutralize with sodium hydroxide, then evaporate.

Dave Wichern
Consultant - The Bronx, New York
2007

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2007

The spent pickling solution will be hazardous waste due to acidity, metals and fluoride. Rinsewaters are likely hazardous unless using enormous flows. Commonly, a drag-out rinse (non-flowing) is followed by a flowing rinse. The drag-out rinse is treated often enough that carryover doesn't cause the flowing rinse to be considered hazardous.

Permits are required to generate, store, treat & transport hazardous waste. The City of Monroe enforces the national pretreatment standards for industrial discharges to POTWs (sewage plants) per 40 CFR. Pickling regulations are perhaps in Subpart F -- Chemical Etching and Milling Subcategory (§ 413.60).

Consult with the City; they may be lenient regarding treatment of relatively low concentrations of hazardous waste. Ask about 'Permit-by-Rule.' They will definitely want to analyze any treated wastewater before allowing its discharge to the sewer. If fluoride is a concern, precipitate as CaF2 using quicklime. Final pH adjust is easier using sodium hydroxide solution. A pH of 9.5 may work; it is a compromise between the optimal pH values for Cr & Ni precipitation. See the graph of pH vs. Metal Concentration in wastewater www.finishing.com/library/metalpH.html

Evaporating water from the residual sludge (about the only procedure not requiring a permit) will reduce its quantity to allow longer on-site storage and lessen disposal costs. Perhaps even reach a de minimis quantity to lessen regulatory oversight. An EPA Hazardous Waste Generator ID no. is required to get the sludge transported via EPA-licensed hauler to an EPA-licensed TSDF. Use a TSDF that recovers metals (rather than uses landfills) to minimize your long-term liability.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

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Thank you for the good replies. This project is not a vat type pickling operation. It is treating large pieces of fabricated equipment, up to 50,000 square feet in all.

As I understand it, you can do elementary neutralization on site without having to get a hazardous waste treatment permit. I was in hopes that basic neutralization would precipitate the chromium and nickel to a sludge for disposal as a hazardous waste and that the clear rinse water on top could be disposed of as non-hazardous industrial waste.

I know the pH will be acceptable but still am concerned about some traces of chromium remaining in the clear rinse water.

I'm surprised that on-site evaporation does not require a permit.

By the way, this work is proposed for the Houston area, not in my town.

Thanks again. Any other suggestions or ideas?

Todd Turner
- Monroe, Louisiana
2007

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You are more likely to have difficulty removing the nickel to low levels. This is especially true if, as is often the case, you have some ammonium ion in there.

But if you are going to haul the water and the sludge away, you do not need to be concerned about Ni or Cr, at the levels they will be at after neutralization.

Dave Wichern
Consultant - The Bronx, New York
2007

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Treating an acidic, metals-containing hazardous waste from metal finishing processes without a permit is categorically illegal under 40 CFR §413. US laws apply even in Louisiana, New York and Texas. Contact the City of Houston Pretreatment/Industrial Wastewater Service if within their service district.

The comment about ammonium is valid; it's a chelating agent for nickel. So, use HF rather than ammonium bifluoride. Also, neutralizing large quantities of nitric acid is considered the generation of nitrates by the EPA, subject to TRI reporting. Perhaps find an acids recycler.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007

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I believe that Ken is right about this. Except that the waste is hazardous not because of its metal content or fluoride content, it's hazardous by law. When we say that the industry is "categorically regulated", what we mean is that all waste products from the entire category are automatically hazardous^^regulated waste by law no matter if harmless in actuality.

You probably have to work with the local wastewater regulators even though you don't intend to leave a drop of water on-site.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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We should be careful about giving proper advice and using the correct terminology here. The best advice is to contact your local pretreatment coordinator if the disposal is to a POTW. If disposal will be offsite, contact your state regulatory agency for assistance, they will all help you to insure you do not violate the law.

The term "categorical" is typically used in the clean water act to regulate wastewater discharge requirements. This wastewater is not typically considered as a hazardous waste. Your business will determine your category and your category will determine the limits on your discharge permit. You will have to have a permit to discharge anything.

Hazardous wastes are of 2 kinds, listed and characteristic.
All metal finishers are familiar with F006 a listed waste which is defined as a wastewater treatment sludge from a metal finishing operation. If you do metal finishing and generate sludge in your wastewater treatment operation it is a hazardous waste. Notice that there is no mention of what is in the sludge. You will have to be permitted to generate the sludge, as well as dispose of it.

You will likely require regulatory permitting on numerous levels to avoid an illegal activity. Remember that "ignorance of the law is not a defense."

Kurt Sammons
- Inman, South Carolina
2007

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It is not really obvious to me or certain that this is a 413.60 operation. In truth it will be whatever category the particular regulator you contact claims that it is.

Kurt is correct that "you will likely require regulatory permitting on numerous levels". But as a taxpayer, you should recognize that each such contact you make will result in that department using your contact as evidence that they must increase their staff, which will result in the need for twice as many permits next time, which will result . . .

While you perhaps should contact the local POTW and/or the state regulatory agency, I think your best first contact will be the state's small business ombudsman so that some small part of your taxes go toward helping you rather than harassing you :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007