Can we solve the water problem in chromite mine area?

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Sukinda Valley contains 97% of India's chromite ore deposits and is one of the largest open cast chromite ore mines in the world. 

Approximately 70% of the surface water and 60% of the drinking water contains hexavalent chromium. The levels of contamination are more than double national and international standards. Levels of over 20 times the standard have been recorded. 

How should the contaminated water be treated? Is there a simple method of treating extremely contaminated water and how can the groundwater contamination from these mines be prevented?

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13 Answers

  1. 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

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

      1 Comment reply

      1. 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
         

         

         

  3. Metal pollution in water environment and the associated human health risk from drinking water: A case study of Sukinda chromite mine, India,http://www.tandfonline.com/doi/abs/10.1080/10807039.2016.1185355

    1 Comment

    1. Researcher developing cost-effective water treatment technologies to meet industrial, agricultural and domestic needs.The new technology is robust and versatile, capable of removing a broad spectrum of toxic materials from some of the most challenging and complex wastewaters. The materials removed include metals such as selenium, mercury, arsenic, chromium, cadmium, vanadium and lead.

      Read more at: http://phys.org/news/2016-09-cost-effective-treatment-technologies-industrial-agricultural.html#jCp

       

  4. Hi Sukla, preventing or remediating groundwater impacted with chromium can be done in several ways. One option is to use the mine dewatering as a tool, another could be to install barrier wells combined with in in-situ or ex-situ treatment. Is it an open pit of underground mine facility?

    1 Comment

  5. Dear Shukla jee,

    Chromite mining can create hostile conditions for organisms in the surrounding environment. 

    Hexavalent chromium  is a form of the metallic lement  chromium . Chromium  naturally occurs in rocks, animals, plants, soil, and in volcanic dust and gases. ...  Hexavalent chromium , or  Chromium  (VI), is generally used or produced in industrial processes,

    Chemistry of the Treatment Processes

     Chromium Removal Chemical Reaction The chemical reaction for reduction of hexavalent chromium to trivalent state with sodium Meta bisulphite at a PH range of 2.0 to 3.0 takes place stoichiometric ally and is an instantaneous reaction according to the following equations.

    4 H2CrO4 + 3 Ca(OH)2 + 3 H2SO4 = 2 Cr2(SO4)3 + 3 Na2SO4 + 7 H2O

    The Trivalent Chromium is removed as chromium hydroxide by precipitation it with lime at PH 8.5 to 9.0 as follows.

    Cr2(SO4)3 + 3 Ca(OH)2 = 2 Cr(OH)3 +3 CaSO4

  8. I suggest our technology of reduction with Hidrogen. It Works very well with Cr+6, and the product of the reaction is H20.

  9. In the north of Orrisa State, you have a couple of sponge iron plants that may provide reduced iron (waste) materials for the reduction of mobile toxic chromate to immobile and relatively harmless chromite. In the south of the State, you have bauxite refineries that produce iron-oxide rich red mud waste, which, after acidification, provides a good adsorbent for chromate.  

    1 Comment

    1. Is it economical to acidify the red mud supposed to employ as adsorbent? How  about the leaching of different heavy metals in red mud when it is applied for adsorption of Cr in acidic range?

      1 Comment reply

      1. As concerns economics, it depends on too many (local) factors to give a proper answer. The Red Mud has considerable acid neutralizing capacity of up to 4 moles per kg at the pH 5.5 of maximum chromate adsorption capacity. Leached concentrations of metal(oid)s at that pH remain well below European limit concentrations for inert (waste) solids. You may find some publications on: https://www.researchgate.net/profile/JJP_Hans_Zijlstra2/timeline/publications

  11. There are two scenarios, one try Phytoremediation, this as Sudhakar has suggested can be complex and time consuming. The contaminants can be extracted out of the soil using leafy plants like cabbages and the biomass can be used for generating biogas, however, the sludge shall have to be incinerated before disposal.

    While the contamination of existing groundwater is difficult to address, the fresh rainwater collections can be directed into sterile artificial aquifers made with geocellular blocks, humongous capacities can be created without sacrificing the land use in builtup campuses. The sand bed filters made with sterile rock dust powder ensures that there is no possibility of the water getting in contact with chromite ore or any other pollutants. The rootzone over the sandbed provides the first barrier against contamination.

    Water can stay put in these HDPE lined tanks for a long time if proper precautions are taken to prevent biofilms and dust laden pollen from getting in contact with water. Raw water can be released for drinking water purposes after suitable tertiary treatments and testing. 

  12. Hexavalent chromium is treated by redox reactions that convert to trivalent chromium in insoluble form. Zerovalent metals are used in the redox reactions. We have developed technology for hexavalent chromium removal from drinking water. The technology is at pilot stage  and we  could share it.

    Off the shelf technology  for domestic use would be use of RO technology; but do verify the desired drinking water limits are reached after RO treatment.

    Remediation of groundwater is more complex and would involve use of PRB's or pump and treat methods.

    Prof Sudhakar Rao

    IISC Bangalore

  13. Hexavalent chromium is treated by redox reactions that convert to trivalent chromium in insoluble form. Zerovalent metals are used in the redox reactions. We have developed technology for hexavalent chromium removal from drinking water. The technology is at pilot stage  and we  could share it.

    Off the shelf technology  for domestic use would be use of RO technology; but do verify the desired drinking water limits are reached after RO treatment.

    Remediation of groundwater is more complex and would involve use of PRB's or pump and treat methods.

    Prof Sudhakar Rao

    IISC Bangalore

    1 Comment

    1. We propose some biological in situ treatment using indigenous strain with high Chromium resistant. The strain have capability to donate electrons on the cell surface to reduce highly soluble hexavalent to insoluble trivalent Chromium in a direct redox process.

      2 Comment replies

      2. Dear Mr. Lala Behari Aukla,

        Please view these two websites:

        www.neatenvironment.com 

        www.powellwater.com

        We can provide a full and complete treatment of the Chrome and all other contaminations with a one pass treatment through our Electrocoagulation equipment.  Very easy to operate and very easy to dewater the sludge, which should be no-leatchable for disposal or refining.

        Please contact Mr. Scott Powell for futher information.

        Thank You for your time and consideration of this information.

        Ken Gardner,

        President

        N.E.A.T. Environment, Inc.