Water plays a central role in our pulp, paper and board production processes. The structure of paper is dependent on water, as hydrogen bonds are needed to keep the wood fibres together. Water is also used for cooling machinery at the mills, for cleaning, and as a carrier of energy in the form of steam. Water is additionally needed as a medium to carry fibres through production processes.
Almost all of the water we use directly comes from lakes and rivers, and around 95% of this total volume is recycled back to the environment. This recycling occurs either after appropriate treatment (for process water), or without treatment where this is not necessary (for cooling water). Stora Enso's approach to water and its use is also described in our Water Use Statement, available at www.storaenso.com/sustainabilitypolicies.
Water also plays a key role in creating the electricity we use and purchase, particularly in hydropower plants. Our mills producing solid wood products additionally need low volumes of water in their manufacturing processes.
Quality of treated process water
All our wastewater streams are carefully purified in our treatment plants before being released back into the natural environment. This is essential, since impurities in water discharges can harm ecosystems in lakes, rivers and other natural water bodies. Stora Enso uses top class wastewater treatment systems to ensure that the water we release is purified, ecologically safe, and meets all regulatory requirements. Our water treatment systems also recycle water within mills where feasible, reducing the need for water intake.
During 2013 our normalised discharges of chemical oxygen demand (COD), calculated per saleable tonne of pulp, paper and board, continued to decline. Since 2007 we have reduced our normalised COD discharges by 10%.
In 2013 our normalised discharges of nitrogen and phosphorus increased. Over the past five years our normalised discharges of phosphorus have increased by 2% and discharges of nitrogen have increased by 11%.
In 2013 we continued to reduce our normalised discharges of Adsorbable Organic Halogen Compounds (AOX). AOX is a collective term for the amounts of chlorine or other halogens bound
to organic matter in wastewater. In recent years our discharges of AOX have fluctuated within a range that represents good performance. This is because Stora Enso has not used elemental chlorine in its bleaching processes for over 20 years.