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Rehabilitation of Tailing Ponds

Date started: 1989

Progress. The word sums up the technique used today by the company, enabling the rehabilitation of the tailing ponds - reservoirs constructed on mined areas - through reforestation.

Understand the technique used in the rehabilitation of tailing ponds requires, first, the understanding of a process that has evolved considerably in recent decades.

Even 80 years after studies and analyzes of various alternatives for tailings from the ore deposits, we put in place a technology hitherto unheard of in bauxite mining, the use of mined-out areas for the disposal of clay from the beneficiation plant.

The change began when we transfer the ore washing plant from the port area for the mine and increase production capacity. The technique used was to give a new destination for water used in washing of bauxite. We then created a large artificial lake. In this reservoir, the solid particles settle and the supernatant water is collected and conducted back to the processing plant, adding to the fresh water which is added in the washing process of the ore. That is, part of the water began to be reused. A gain environmental and productive.

After the sedimentation tank to reach 35% to 40% solids, the reject is pumped dredged and other areas as mined. There, the tailings remain permanently, so that the wastewater is gradually eliminated, until conditions at the site allow for planting native species.

Today, the tanks are smaller than those used in the 80's, just to facilitate the rehabilitation process, which is done primarily with legumes, as a technique using hydroseeding. The purpose is to fix nitrogen in the soil. In a second stage, recovery is done with native trees, plants that are definitive of the future forest. The work is done in partnership with the Brazilian Agricultural Research Corporation (Embrapa) and the Federal University of Viçosa, responsible for annual monitoring of physical and biological parameters of the area.

From 2011, we took other significant steps in this process because we believe that evolution has to be constant. We created the Environmental Recovery Index (ARI), which is an indicator of sustainability (measured structure reforestation, return animals to s place of origin, among others), incorporate organic matter from the composting process of urban waste, the garden prunings and sewage treatment system (sludge) to the washing of bauxite tailings, and we select the nitrogen-fixing bacteria and fungi micorrízidos for native species of Porto Trombetas with potential for revegetation of mined areas.

History – In the first year of operation of the company, the tailings resulting from processing bauxite was arranged in Batata lake, which today is constantly monitored and reference studies of the scientific community of ecological principles to mitigate the impact.

Revegetation by hydrosemination
Revegetação por hidrossemeadura
Revegetação por hidrossemeadura

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