Without water there would not be stainless

Water is used in various phases of the manufacturing process, like casting of steel slabs at melt shop, hot rolling and annealing and pickling at cold rolling. The wet polishing at cold rolling need water to cool down the heating of the strip generated while it is polished to create the desired surface finish. In 2014, the yearly consumption of water at Outokumpu was 40 million m³, of which more than 36 million m³ was surface and rainwaters. In all processes water is recycled if applicable, for instance through cooling towers. Without recycling the used amount water would be multiple.

Water is worth saving

Outokumpu has production sites all over the world. Most of them have an abundant of fresh water available, but for one there is scarcity of fresh water due to its location in an arid region. In both cases it is equally important to save water. The effect on the environment is vast but for very different reasons.

Mexinox reuses up to 99% of process waters

In Mexico, San Luis Potosí, Outokumpu’s cold rolling mill is located in a dry, arid area, where groundwater is a valuable asset for people. The less our production consumes it, the more can be used for drinking, farming and vegetation. In the past, the recycling of water at Mexinox mill begun in aim to prevent potential problems in water supply.

In 2001 the new imposed environmental conditions to discharge gave the opportunity to recycle water back to process in a larger scale. Today, the monthly consumption of water is 45,000 m³. 99 per cent of the process waste waters are treated and recycled. The savings in fresh water usage is equivalent to the quantity consumed by 1,100 households yearly. The plant has also achieved its own target in water use per rolled ton of steel.

“For us to continue recycling water is important because it allows us to contribute to environmental care as an organization. We fulfill the environmental regulations and give an example of social responsibility”, says Jorge Vieyra, head of production and environmental management at Mexinox.

Kemi mine withdrawal of fresh water is only 4%

When there is only 70 rainy days a year in Mexico, in Finland, the Outokumpu chrome mine area in Kemi has rain on average almost every other day throughout the year. There is plenty of water available. Still, Outokumpu chooses to recycle and reuse process waste waters. Thus, only 73 liters of fresh water was used to produce one ton of chrome concentrates in 2014.

Water is a vital part in the mix

Water is used in various processes in Kemi mine. In underground mine water is used for example for dust handling. Recycling of water in underground is cost effective, reducing the need to pump drainage waters to the surface. In concentrator plant finely crushed ore is mixed with water and heavier chromium rich particles are separated in spirals. In total, the concentrator plant uses annually approximately 2.5 million m³ of process water.

Nature takes care of the water recycling at Kemi mine

Only four percent of the total amount of water used in the mine area’s processes is water outside the mine area, and the rest, 96 percent, is recycled water. The treatment of the process waters is done in a most nature conserving way, taking advantage of tailings and sedimentation ponds inside the mining area.

“Sedimentation doesn’t need any external energy or chemicals; it’s based on long enough retention time of water. Nitrogen compounds are removed with passive nitrification-denitrification reaction occurring commonly in natural wetlands”, explains Samuli Nikula, responsible for the environmental affairs at the Kemi mine.

“Recycling makes water available to processes in great quantities and reduces the need for water withdrawal from outside the mining area”, concludes Nikula.