Effluents of pulp mills using chlorine for pulp bleaching do contain several, under aerobic conditions only weakly degradable (35-45%) toxic chloroorganic pollutants.
2. The solution
Preliminary biotretment tests under anaerobic conditions, using specially adapted microorganisms, immobilised on adsorbing, porous LEVAPOR carrier showed a remarkably increased degradation. Results obtained in continuous tests in pilot scale have confirmed the previous results and served as basis for conception and design of a full scale plant, comprising of microaerobic pre-treatment, anaerobic step and aerobic post-treatment.