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 remova l. Maintaining consistently low effluent discharge concentrations of nitrog en from nitrogen supplemented biological treatment systems is very difficul t. Matching nitrogen addition rates to load variations is effective,but req uires accurate flow and organic load measurements. By manipulating treatmen t 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 solub le nitrogen discharge concentrations are possible. This concept has been ex plored in the development of a new technology for the treatment of nitrogen deficient wastewaters. (C) 1999 Published by Elsevier Science Ltd on behal f of the IAWQ. All rights reserved.