The pulp and paper industry is a very large water user and there are many different types of flows that may need to be treated. Around the paper machine or the drying machine, there are long and short circulations, and then there is a fiber-carrying wastewater. The pulp and paper industry includes wastewater flows from, for example, debarking, as well as acidic and basic bleaching effluents, and potentially the treatment of dissolved and leached electrofilter ash from the soda boiler. The compounds that are typically targeted for removal in relation to paper production are mainly suspended substances and oxygen-consuming substances.
In relation to the pulp and paper industry, the focus is often on phosphorus, but also on suspended substances and oxygen-consuming substances. In relation to bark water, transition metal ions are often important, as well as suspended substances and oxygen-consuming substances. In relation to electrofilter ash, the focus is on transition metal ions.
Typical reductions of different categories of substances are presented below:
• Suspended solids: 90+%
• Oxygen-consuming substances (BOD/COD/TOC): 30%
• Nutrients – Phosphorus: 90+ %
• Nutrients – Nitrogen: 20%
• Transition metal ions: 90+ %