NITRIFICATION MONITORING IN ACTIVATED-SLUDGE BY OXYGEN-UPTAKE RATE (OUR) MEASUREMENTS

A simple measuring system was developed that yields information about the presence of NH4+ and NO2- nitrogen in mixed liquor samples. In add ition, it allows monitoring of the rate of both NH4+ and NO2- oxidatio n simultaneously with the carbon substrate oxidation using OUR measure ments. The method is based on the subsequent addition of NaClO3 and al lylthiourea, selective inhibitors of Nitrobacter and Nitrosomonas resp ectively, to the mixed liquor sample in a closed batch respirometer. T he presented method is valuable for detailed monitoring of the nitrifi cation process in a reactor: it is simple, inexpensive, robust and gen erally applicable for nitrifying reactor systems. The measurement of N H4+ and NO2- oxidation rates enables the operator to detect the presen ce of NH4+ and NO2- species. This allows action to be taken to improve the performance of the system. The method is validated on a SBR. It i s indicated that optimal SBR phase scheduling can be based on such OUR measurements. Copyright (C) 1996 Published by Elsevier Science Ltd.