Substrate inhibition of nitrification

Abstract

Operating data from a full‐scale nitrifying activated sludge plant have been collected and analyzed. The rate of nitrification, expressed as the specific oxidation rate, follows the van't Hoff‐Arrhenius relationship which indicates that the activation energy is approximately 12350 cal per mole, and that the Arrhenius frequency factor is 2.18 × 10⁹ day^‐1. The data indicate that substrate inhibition due to ammonium ion concentration occurs in this system. This relationship has been expressed as a Haldane inhibition model in which the maximum specific oxidation rate is 3.5 g N oxidized per g biomass‐day, K_S is 4 mg per liter, and K_I is 36 mg per liter.