On-line nitrification monitoring in activated sludge with a titrimetric sensor

Nitrification is an important part of activated sludge wastewater treatment processes in view of the severe effluent discharge standards for nitrogen (N) that are nowadays imposed by legislation. Several on-line analyzers have been developed to achieve better monitoring and control of biological N removal processes. In this paper, the results of on-line experiments on a pilot-scale activated sludge plant with a recently developed titrimetric sensor are described. Based on a titration of an activated sludge sample, it was possible to estimate the ammonium N (NH4+-N) concentration in the activated sludge, without the need for any sample pretreatment. The NH4+-N concentrations obtained with the titration method were consistent with the NH4+-N concentrations measured with an on-line analyzer, which was operated on the effluent of the pilot plant. Contrary to chemical on-line NH4+-N analyzers, the titration method provides data about the nitrification rate of the activated sludge.