Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal

Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal 2017-04-04T06:57:46+00:00
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Treatment of TDS acid water (4 replies)

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

Which is the Best way to determine the Residence time to reach a neutral pH, and guarantee the formation of all metal hydroxides, such as Fe(OH)3, Al(OH)3, in an active TDS acid water with Ca(OH)2?

Oberfuhrer
2 years ago
Oberfuhrer 2 years ago

We use aeration/oxidation combined with either lime or carbonates to achieve the desired pH for downstream water treatment from the raw AMD water (as we use biological treatment a consistent pH is important to us). We have found calculating it is not reliable so we conduct lab testing on the water. Our experience has been that the iron precipitates out as a ferrous iron quickly (rate depending on the volume of added chemical). It generally takes a further period (up to 16 minutes) for the ferrous iron in the treated water to convert to ferric iron. This is witnessed by the bluey green color of the ferrous iron, then the reddish brown ferric iron color. Also, the dissolved oxygen of the water will reduce until all the iron is converted, after which the dissolved oxygen will increase and the pH will drop, (usually by about 1 unit).

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

Thanks a lot for your answer, Assuming that the Iron is all in form of ferric ion in the Raw AMD, what kind of lab tests, Can I do to determine the real residence time to ensure the Iron precipitation as Fe(OH)3?

David Kano
2 years ago
David Kano 2 years ago

You may also want to consider a hydrotalcite-based method I have developed. This uses one or more of Mg or Al salts and NaOH. You get rapid and broad spectrum contaminant removal and the potential for form an "ore" given the high concentration factor. The technology has been trialed or used on many types of acidic wastewater with considerable success. It represents having to break with the tradition of lime use (which is hard for some), but in many circumstances there are advantages. I can forward three separate studies published in the peer-reviewed literature.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

Could you send me more details of the method? The way to eliminate sulfates and Heavy metals?

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