A review of process and wastewater reuse in the recycled paper industry

Abstract

Water plays several essential roles in paper manufacturing. It serves as a suspending medium and a swelling agent for the fibres, dispersing and forming them into a uniform sheet during the initial stage of the papermaking process. It also serves as the solvent for a variety of chemicals and additives to adjust product quality. Water reclamation has always been a momentous task in the pulp and paper (P&P) industry. The main driving forces for the adoption of process water and wastewater treatment technologies are environmental regulations, costs of wastewater discharge and the high cost of freshwater. Recent developments have made it possible to not only reduce water consumption and environmental impacts, but also to recover treated water and valuable compounds such as fibres, making water recycling technologies cost-efficient. Thus, the economic viability of these technologies has played an important role in their application. The technologies applied, the level of reduction in water consumption and the extent of water recycling are different for each mill, since the quality of whitewater and wastewater varies depending on the raw materials and products. The maintenance of the balance between partial equilibria of process variables such as water flowrates, pulp consistency, physiochemical, thermal and microbiological properties through water management is important for maintaining efficient water use and lowering the need for consumption of additional fresh water.