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Mining – New Caledonia

Cannon Artes supplied a complete waste water treatment plant that treats the effluent produced by Koniambo S.a.S; one of the biggest Nichel producer complexes in New Caledonia. The plant at full operation produces 60’000 tons of nichel.

Great attention was paid towards all water-related problems, to avoid overexploitation of the existing fresh water sources and any possible pollution of the nearby sea, where a rich bio-environment is present.

The Industrial Waste Water Treatment covers an area of 7500 m2 and treats different industrial waste streams produced at the “Vavouto” site. A flow rate of 150 m3/h of the treated effluent is available for Re-use for dust suppression and potentially for other applications such as make-up to the ferro-nickel shotting system and as service water inside the waste water treatment plant. Excess treated effluent is discharged to the marine environment.

The effluent produced from the complex is rich of solids and heavy metals such as Iron, Zinc, Aluminium, Nickel, Manganese and Chromium, moreover the last one is very hard to be removed.

Cannon Artes studied a dedicated process for the removal of solids and metals besides Chromium (VI) reduction. In order to reduce their presence waste water is collected from the equalization plant to coagulation and then to flocculation treatment with the dosing of Ferrous Chlorine, Caustic Soda and Flocculant (polymer). The Caustic Soda allows the precipitation of heavy metals as hydrates as well as to adjust the pH. Presence of Ferrous Chlorine, in the coagulation tanks enhances the aggregates (flocs) formation.

In the second step, flocculation, the flocs increase by adding polymer. Effluent, prior to discharge, passes through sand filtration. The plant design puts great attention to sludge treatment and dewatering because customer recovers metals from it using a proprietary technology.

Cannon Artes’ solution was highly appreciated by the Customer. Thanks to its consolidated approach as an Engineering Company, it proposed some changes to the basic tender specification to optimize the chemicals consumption, to choose the correct process for Chromium reduction and to guarantee very high performance.