Water – a natural resource for cooling
Steel manufacturing requires high temperatures. Whenever large amounts of heat are generated or used, cooling is required to protect people and equipment. As in most industrial processes, water is the natural resource used for cooling. Outokumpu's main production operations also use large volumes of water for rinsing and cleaning tasks. To minimise the risk of pollution that could affect local resources, water used in the Group's production processes is recirculated.
All Outokumpu's melt shops are situated in areas where the intake or use of cooling water does not place an unreasonable burden on the water resource environment.
At Avesta, for example, the Group's water intake is less than 0.05% of the total volume of the Dalälven river which runs past the site. Environmental impacts in this location are further reduced by the fact that most of the water used is only employed in cooling processes and then returned to the river (source: Dalälvens Vattenvårdsförening).
| 2009 | 2008 | 2007 | |
| Water withdrawal by source | |||
| Surface water, million m³ | 17.2 | 19.3 | 20.3 |
| Municipal water, million m³ | 0.9 | 1.1 | 1.1 |
| Water discharges by type and destination | |||
| Cooling water out, million m³ | 8.1 | 11.5 | 10.6 |
| Waste water out, million m³ | 7.3 | 7.8 | 8.6 |
| Metal discharges to water, tonnes | 9.9 | 15.5 | 17.2 |
| Nitrogen in nitrates, tonnes | 437 | 578 | 574 |
High levels of water recycling
Cooling water is used either directly in contact with steel or indirectly via a heat exchanger in which fresh cold water is used to reduce the temperature of a continuously circulating stream of cooling water. In the latter case, the only contamination associated with the outgoing water is that it has a higher temperature than incoming water when it is pumped back into the water system from which it was extracted. The percentage of water recycled at each Outokumpu site varies, but the average is above 90%.
High levels of recycling of cooling and process waters are achieved at many of the Group's sites by employing recirculating cooling systems and water treatment programmes. The actual recycling rate varies from season to season. In Tornio in winter, for example, cooling water is only partially recycled – after it has been used for cooling, some water is pumped into the Tornio harbour basin to help reduce the amount of ice. In a cold climate, preventing ice formation in the harbour is more energy efficient than operating ice breakers. Even though cooling water is used in this way, considerable reductions in overall water use have been achieved as can be seen in the above mentioned table.
Responsible treatment of rainwater
Significant volumes of rainwater fall on Outokumpu sites. At Avesta, for example, where the works cover a total area of 2.4 square kilometres, at least a million cubic metres of water falls as rain or snow each year. While some of this water evaporates, a large proportion is collected and combined with used cooling water. All of this water is channelled through oil separation facilities before being discharged into watercourses.
At Tornio, rainwater that has filtered through the landfill is collected. These filtrates are alkaline and also contain small amounts of hexavalent chromium, a harmful form of chromium that can not be released without further treatment. An automated reducing and neutralisation station has therefore been constructed. In the neutralisation process, ferrosulphate is used to reduce the hexavalent chromium to a harmless oxidised state and also neutralise the water before it is discharged.