Factors Effecting Nitrogen Fixation in Pulp and Paper Mill Aerated Stabilization Basins

The aerated stabilization basins (ASBs) utilized for treating pulp and paper wastewater are typically rich in carbohydrates and poor in available nitrogen. Historically, supplemental nitrogen has been added to improve the rate and degree of biological treatment. However, several ASBs have been operated with no exogenous nitrogen addition with little or no adverse effects. In this paper, the genera and numbers of heterotrophic nitrogen fixing bacteria in 17 pulp and paper mill ASBs were determined. Nitrogen-fixing bacteria were detected in all 32 samples from 18 different mills. The genera and numbers of nitrogen fixing bacteria were widely varied, but appeared to be well correlated with redox, nitrogen content, and organic loading of the sample site. The rate of nitrogen fixation was reasonably well correlated to nitrogen deficiency, HRT, and BOD loading, was poorly coordinated to redox.