Abstract
The main aim of studying the relation of carbon dioxide evolution rate CER to oxygen uptake rate (OUR) is the possible application of CER in mathematical modelling of aerobic biodegradation processes instead of OUR. Biodegradation tests using glucose and sewage sludge as feed were performed to compare the OUR and CER. The respiratory quotient (RQ) was 0.9 mol CO2 × mol O2-1 in endogenous stage while its value was increased to 1.2 mol CO2 × mol O2-1 during glucose degradation. At higher F/M ratios and high respiration rates RQ values up to 2.95 were observed which may indicate the appearance of anaerobic degradation pathways. These results prove that there is no direct, simple relation between OUR and CER in case of sewage sludge degradation so direct substitution of OUR with CER in modelling studies is not feasible.
Highlights
The progress of the biological sewage sludge and other highstrength wastewater handling processes appears on one hand in the permanent improvement of anaerobic sludge digestion
The increase of the carbon dioxide evolution rate (CER) and respiratory quotient (RQ) curves at the second feed is faster than in the first case which can be attributed to microbial adaptation to the glucose
5 Conclusions Thermophilic aerobic sludge digestion respiration tests were performed in order to investigate the relation between the carbon dioxide evolution and oxygen uptake rates
Summary
The progress of the biological sewage sludge and other highstrength wastewater handling processes appears on one hand in the permanent improvement of anaerobic sludge digestion. One of the most suitable methods for monitoring aerobic metabolic processes is respirometry. It has a wide application area e. Gas-phase CO2 measurement is especially popular in the monitoring of composting processes [6, 7] where the measurement in the solid phase is practically impossible. These measurements usually over-simplify the actual situation as they do not consider the effect of pH and CO2 transfer limitations. Spérandio and Paul [17] presented the applicability of Connection between oxygen uptake rate and carbon dioxide evolution rate
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