Pulp and paper manufacturing is a water-intensive process. All of our mills are located in watersheds with sufficient supplies, but responsible water management and water conservation will always be a significant part of our sustainability efforts at Domtar.
In 2017, our mills used enough water to fill 164,000 Olympic-sized swimming pools. Although our mills have access to sufficient water from local rivers and lakes, that water is not immediately suitable for pulp and paper making and requires both mechanical and chemical treatment.
How we treat water differs at each location and depends on factors such as:
•Natural water chemistry
•Effluent from upstream users
•Surrounding land use
•Season of the year
•Weather events, including droughts and floods
•Which products the mill makes
But there are some steps in our water management process that are consistent from location to location. Here’s a look at water usage and water conservation at a typical mill, from intake to discharge.
Water’s Journey From River to Mill
Water’s journey through the pulp- and paper-making process begins most often at a nearby river or lake. The water, which is often cloudy when withdrawn from the river, requires significant filtering and clarifying so that it is suitable for making high-quality pulp and paper. We need to remove debris, particles and chemicals that will damage manufacturing equipment. Our water filter plants are the first step to cleaning the water.
Water is drawn through a bar screen to remove large debris, such as branches, sticks and, sometimes, trash. The water continues to flow through finer screens, removing leaves and other small debris.
Next, the water is pumped to a raw-water clarifier where chemicals, such as alum, are added to remove suspended solids from the water. Other chemicals are added to adjust pH levels, prevent corrosion and scale, and control microbiology that might create slime.
Finally, water travels through a sand filter bed (a much-larger version of a typical backyard-pool sand filter) for a final cleaning before collecting in a clear well or storage reservoir. It stays in the well until it is needed by various water users in the mill.
more detail at: https://newsroom.domtar.com/water-conservation/