Environmental protection has been in focus for many years and especially clean water is scarce in many places. Water treatment issues are becoming increasingly important for the pulp and paper Industry as extensive amounts of water are used in the production processes.

 

Biological treatment has for some time been state of the art for effluent treatment but as energy costs are soaring new ways of minimizing treatment costs are sought. Increased water reuse by closing up water circuits without ruining the quality of final products is an important aspect. Pretreatment of selected process streams prior to external treatment will in many cases be beneficial from both cost and environmental points of view.

 

The focus on the environmental impacts of pulp and paper mill effluent have in recent years shifted from broad terms such as color, suspended solids and organic matter to more specific terms like sterols and “endocrine disruptors”. The interest for specialized effluent treatment methods is growing as mills will have to monitor their emissions in much more detail in the future.

 

Several methods of removing different types of organic matter are described. The removal efficiency differs considerably between various treatment procedures. Low molecular mass material is easily degraded by biological means whereas more complex, often colored, compounds like lignin and lignans call for more advanced treatment methods.