WWT reaction tank design.
What is considered to be the upper concentration limit for chromium +6 in a given influent rate for proper chrome reduction using the standard low pH-bisulfite process? Once the metals have been pre-treated (Cr reduction, metallic cyanide oxidation), what is the upper concentration limit for metals in a given influent rate for proper hydroxide formation using the standard CaCl2, NaOH process?
Are there any good reference materials available on design of WWT process tanks, gravity settlers, etc?
I don't know that there is any such limit. I haven't personally treated chrome plating solutions with bisulphate, but I have treated chromating solutions (2 to 5 percent chromic acid-sodium dichromate) and the reaction is not a problem.
Similarly, I have batch treated fairly concentrated acid dumps and cleaner dumps, and the reaction is not a problem.
However, there can be a logistics problem with physical separation processes (clarifiers, sludge thickeners, filter presses) as huge loads of solids come into play. And chrome waste are difficult to filter.
I don't know of any current books on the subject, although you might try to find Clarence Roy's book "Operation and Maintenance of Surface Finishing Wastewater Treatment Systems" [link is to book info at Amazon] or you might contact AESF (www.nasf.org) regarding the manuals from their waste ewater treatment training course.
Ted Mooney, P.E.
Pine Beach, New Jersey
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