Low-effluent recycled paper mills

With increasing pressure on discharge quality and uncertainty of water supply in many parts of the world, the pressure to move towards effluent-free papermaking is increasing. The advantages of operating an effluent-free mill are that it requires no discharge licence, requires very little fresh water and can offer a product with good environmental credentials. Closure of a mill water system can result in a range of problems, the severity of which will depend on the nature of product being produced, the quality of the raw material and the degree of closure attempted. In most cases some additional treatment will be required before recycling the water. Commonly this will include at least one stage of biological treatment, but membrane processes, evaporation and other steps may also be required. Poorly applied, such processes can be very expensive and to be most cost effective the treatment process must be tailored to the needs of the mill and designed into the basic mill flow scheme. The types of problem that might be encountered are described and how these have been tackled in cases from mills employing very simple closure, through extensive biological treatment up to fully liquid effluent free mills.