Nitrification in a column reactor: Limitations, transient behaviour and effect of growth on a solid substrate

Abstract

Metabolic inhibition, insufficient O 2, CO 2 and trace metals, pH and bacterial wash-out were investigated as potential causes of incomplete nitrification of ammonium supplied to column reactors containing Nitrosomonas europaea and Nitrobacter agilis. Of these only the last two factors offered a partial explanation of the phenomenon. The transient behaviour of the columns after flow rate and nutrient perturbations could be classified as either short term (< 10 h) or long term (>20h). The major properties conferred by adhesion of the nitrifiers to a solid substrate in a nitrification column were the ability to respond rapidly to environmental changes, asymmetric transient responses and increased likelihood of multiple steady states.