Working towards reductions in water discharges

From an environmental perspective, the most significant components in water discharges from stainless steel production processes are metal compounds and nitrates resulting from the neutralisation of acidic waste generated in cold rolling units. Effluent discharges at all of Outokumpu's production units are controlled in order to minimise their impact on the environment. At Tornio Works, for example, levels of metals in the main discharges from the plant are much lower according to external studies, than the natural loading of metals in local rivers that flow into the Gulf of Bothnia.

Action to reduce nitrate loads

Nitrate loadings originate in the pickling acids used in descaling stainless steels. A number of different techniques are employed by the Group to reduce the nitrate load in effluent discharges from these operations, including pickling acid recycling technologies. Outokumpu is working on the development of discharge handling techniques to further reduce effluent loadings.

At the Group's Kemi Mine, the main source of nitrates is explosives. A small proportion of the explosive charges used remains and washes out into the water circulation system. Passage through three large ponds (a total of almost 200 hectares) located upstream of the point at which discharges into the recipient water system take place results in the water's nitrate content being reduced by some 60%. These water ponds are natural removal units and there are no negative impacts on the recipient water system, the Iso-Ruonaoja.

R&D to reduce water discharges

Several research projects aimed at reducing nitrate discharges have been carried out at a number of Outokumpu's production sites in Sweden. At Avesta, this has resulted in the investment of EUR 28 million in a new acid recycling system. Installation will take place during 2010 and process start-up is scheduled for early 2011. Discharges of nitrates will be reduced drastically through the recycling of acids. As the process also produces a metal oxide that can be used as a raw material in the steel melting process, the new system will also reduce the amount of sludge sent to landfill.

The oil separation station at the Avesta site used for purifying cooling water and rainwater converted into a modern lamella filter unit. The process control ensures that oil is separated from the water stream. At Tornio, plans have been made to use the large dredging pond near the harbour as a post treatment area for process waste waters with the aim of further reducing concentrations of nitrogen and suspended solids.