Biotechnology and the paper industry aerated lagoon for wastewater treatment

Biotechnology generates tools: enzymes and microorganisms that permit one (i) to reduce pollution, chemical and energy requirements, and (ii) to obtain biodegradable and less toxic side products. This is mainly related to the high specificity of enzymes which hydrolyse lignocellulosic materials. Enzymes can be used to prevent or minimise pollution in the process, and microorganisms for the elimination of pollution. In the first part, we shall review the utilisation of enzymes in pulp and paper industry and we shall focus on the hydrolases both for improving drainage (cellulases) and boosting bleaching and bleachability (biobleaching by hemicellulases). Enzymes provide the possibility for targeted chemical changes in lignocellulosic materials. Processes are fast, controllable, environmentally friendly, and integrable in classical plants. In the second part, we shall review the biodegradation of xenobiotics from pulp and paper plants and we shall focus on aerated lagoons for final wastewater treatment. A new approach for hydrodynamics, aeration and mixing has been applied to the aerated lagoon of the Tartas mill from ''Cellulose du Pin'', France (volume 300,000 m(3)). The compartmentalization of the existing lagoon (according to the BOD removal kinetics), the addition of fluidic deviators on the feed input (generating unsteady flows) and hydroejectors for aeration (with a new design) allowed the BOD removal to be increased from 60% to 85%. This original approach is currently being used to modify existing aerated lagoons to successfully meet the new legislation on effluent quality in the food and chemical industries.