Determination of nitrification kinetics by the ANITA-DOstat biosensor

The ANITA biosensor, which measures ammonium oxidation rate by alkaline tit ration at constant pH, has been recently coupled to open respirometry makin g it possible to evaluate NH4+ oxidation kinetics by two different and comp letely independent techniques. This paper describes the use of a new instru ment, also derived from the titration biosensor ANITA and named ANITA-DOsta t, which incorporates dissolved oxygen (DO) control by H2O2 addition. The p eroxide is very rapidly decomposed to H2O2 and O-2 by bacterial catalase an d supplies oxygen to the mixed liquor. The novelty lies not in the use of H 2O2 addition as a source of oxygen for bacterial respiration, but in the me asurement of kinetics by DOstat titrimetric respirometry which allows for e valuation of bacterial bio-oxidation parameters directly from the H2O2 flow rate at constant DO concentration. Preliminary results are presented on ni trification kinetics determination, for both ammonium oxidisers (AO) and ni trite oxidisers (NO), carried out by alkaline titration and by the new H2O2 DOstat titrimetric respirometry method.