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Determination of carbon dioxide evolution rate using on‐line gas analysis during dynamic biodegradation experiments
Author(s) -
Spérandio Mathieu,
Paul Etienne
Publication year - 1997
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19970205)53:3<243::aid-bit1>3.0.co;2-i
Subject(s) - carbon dioxide , respirometry , chemistry , mass transfer , oxygen , anoxic waters , carbon fibers , oxygen balance , thermodynamics , environmental chemistry , materials science , chromatography , organic chemistry , physics , composite number , composite material
Respirometry is a precious tool for determining the activity of microbial populations. The measurement of oxygen uptake rate is commonly used but cannot be applied in anoxic or anaerobic conditions or for insoluble substrate. Carbon dioxide production can be measured accurately by gas balance techniques, especially with an on‐line infrared analyzer. Unfortunately, in dynamic systems, and hence in the case of short‐term batch experiments, chemical and physical transfer limitations for carbon dioxide can be sufficient to make the observed carbon dioxide evolution rate (OCER) deduced from direct gas analysis very different from the biological carbon dioxide evolution rate (CER). To take these transfer phenomena into account and calculate the real CER, a mathematical model based on mass balance equations is proposed. In this work, the chemical equilibrium involving carbon dioxide and the measured pH evolution of the liquid medium are considered. The mass transfer from the liquid to the gas phase is described, and the response time of the analysis system is evaluated. Global mass transfer coefficients ( K L a ) for carbon dioxide and oxygen are determined and compared to one another, improving the choice of hydrodynamic hypotheses. The equations presented are found to give good predictions of the disturbance of gaseous responses during pH changes. Finally, the mathematical model developed associated with a laboratory‐scale reactor, is used successfully to determine the CER in nonstationary conditions, during batch experiments performed with microorganisms coming from an activated sludge system. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 243–252, 1997.