Nitrogen Fixation in the Treatment of Pulp and Paper Wastewaters

Pulp and paper wastewaters are generally low in the key nutrient, nitrogen. Nitrogen supplementation is often practised to ensure effective BOD removal. Maintaining consistently low effluent discharge concentrations of nitrogen from nitrogen supplemented biological treatment systems is very difficult. Matching nitrogen addition rates to load variations is effective, but requires accurate flow and organic load measurements. By manipulating treatment conditions to select for the growth of nitrogen fixing microorganisms, it is possible to achieve good BOD removals without the addition of nitrogen. As the organisms only fix the nitrogen required for growth, very low soluble nitrogen discharge concentrations are possible. This concept has been explored in the development of a new technology for the treatment of nitrogen deficient wastewaters.