Use of carbon dioxide evolution rate for determining heterotrophic yield and characterising denitrifying biomass

The aim of this work was to show the potentiality of carbon dioxide evoluti on rate measurement (CER) in characterisation of heterotrophic biomass, esp ecially in anoxic conditions, in view of modelling and design denitrifying processes. The carbon dioxide evolution rate (CER) was determined in a resp irometer by infrared analysis associated to a modelling technique. During a noxic and aerobic batch experiments CER was qualitatively correlated with o ther respirometric methods (OUR and NUR) and with organic carbon consumptio n. Yield coefficients were determined under aerobic (Y-H) and anoxic (Y-HD) conditions by means of carbon balances using CER and organic carbon measur ements. Compared to the COD balances, accuracy of the yield estimation was improved and results obtained were not significantly different. Measured an oxic yields were systematically lower than aerobic ones, and the observed r atios between them were in the range from 0.66 to 0.85. By comparing aerobi c and anoxic CER two methods were proposed to determine the correction fact or for anoxic growth tie The first results obtained were consistent with th ose given by the classical method (NUR/OUR). (C) 1999 IAWQ Published by Els evier Science Ltd. All rights reserved.