Dear Mr. LALA BEHARI SUKLA, ...

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Dear Mr. LALA BEHARI SUKLA,

Japan had the similar problems at domestic mining areas about 50-70 years ago.

To solve the problem, one of the best methods in both factors of the economy and the treatment efficiency was as follows;

1st step: Pretreatment.

Fine particles should be removed from the polluted water by conventional methods such as a grit chamber system using precipitation.

2nd step:  Chemical treatment.

After the 1st step, various chromite-complex ions which remained behind in the polluted water are changed the chemical forms into chromite-colloids by adding appropriate amounts of an inexpensive alkaline reagent. 

3rd step: Physical separation.

Chromite-colloids can be removed from the water by using a flotation method, enabling a high treatment speed and a low solid residues.

P.S: Flotation method is a popular technology to separate colloids from water in the mining technologies. But, the detail condition to operate the flotation method depends on the properties of treatment water. You are able to find a candidate of the best flotation method for fitting to your case on the web.

Best regards,

H. Koyanaka

1 Comment

Thanks for the post. This process looks attractive. I want to know about the Chemical treatment reaction and by-products.

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Hi Lala,

A reducing agent such as ferrous sulphate or calcium polysulphide will be able to convert the Cr6+ ion into Cr3+. This reaction takes time so a buffer tank of more than 30 minutes is required. After this, the water needs to be aerated to oxidise the ferrous to ferric which co-precipitates and flocculates the Cr 3+ ion to form a solid particle that can be easily removed either through a clarifier or filtration method.

The solid particle will need to be dried and disposed of. 

My company has experience with this sort of treatment process. If you are interested in working together, please email me at andrew@waterandoilsolutions.com.au
 

 

 

Published by Andrew Tran, Engineer

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