Our team of wastewater specialists have 150+ years of knowledge, so if you don’t see your heavy metal headache listed below rest assured someone is sure to have solved a problem like yours!
The Challenge
Limco Airepair specializes in the manufacture and re-manufacture of a variety of heat transfer components, used in aerospace applications. Chromium creates hard, long-lasting surfaces and coatings. It’s an excellent material for high-performance heat exchanger components. However, as part of the refinishing processes, chromium also ends up in wastewater, from where it must be removed.
| Product | Nickel | Copper | Zinc | Lead | Chrome | Cadmium |
|---|---|---|---|---|---|---|
| Aquapure I-300 | x | x | x | x | ||
| Aquapure AP 99 | x | x | x | x | ||
| Aquapure T-500 | x | x | x | |||
| Aquapure P-601 | x | x | x | x | x | x |
| Aquapure T-800 | x | x | x | x | x | x |
The problems presented in wastewater when hexavalent chrome is introduced requires special attention and experience in reducing to less hazardous trivalent chrome. Here are 2 recommended ways to reduce chrome after precipitation.
1). While holding the pH at 2.0- 2.5 with sulfuric acid, sodium meta bisulfite needs to see the ORP value at positive 250 Mv. When the change in ORP value is noted, this indicates the reaction is complete. This process takes 15 minutes so it is crucial that the pH and ORP of the water be held tightly as not to mistake a rise in pH for the completion of the reduction reaction. Once reduction has occurred the color will also change from orange to blue and the pH can then be adjusted up using caustic soda to 9.0-9.5 for the best removal of the trivalent chrome.
2). If you are at a pH > than 2.5 and don’t want to add acid, reduction of hexavalent chrome can be done by the addition of wastewater treatment chemicals. Typical additions are 1-3 mls/gallon of rinses contaminated with hexavalent chrome but may require more. Jar testing should be done to determine the best dosing.
In all cases, water needs to meet local, state and federal guidelines for chrome removal.
A well known military metal finishing operation in Pennsylvania was having trouble treating hexavalent chromate rinses that also had cadmium in them. Our team of experts set the system up to treat both the hex chrome and cadmium-bearing rinses in the same tank. The Aquapure® I-300 was used for chrome reduction and the Aquapure® P601 was used for treating cadmium to low levels and to ensure all chelated metals were reduced.
Reach out to our wastewater specialists to find out if AquaPure® HQ, AquaPure® I-300, AquaPure® 107 is right for your process.
