Evaluation of Methods for Nitrogen and Phosporus Control in Sewage Effluents

The design parameters for the City of Copenhagen sewage-treatment works were established on an experimental basis, and parallel studies of six pilot plants were made over a two-year period. The key parameters are (a) the rate of nitrification and denitrification, (b) temperature, and (c) BOD:N ratio in the influent. The data obtained from different methods had to be normalized with respect to the fraction of nitrifiers, temperature, and concentrations of substrates in order to achieve consistent results. The results indicated a substantial inhibition of the nitrifiers, i.e., a 20-30% reduction of the reaction rate. Significant savings were made possible by a comprehensive analysis of the temperature conditions.