Suchergebnisse

In situ pulse respirometry was applied in an activated sludge bubble column treating synthetic wastewater for the estimation of the (i) maximum specific oxygen consumption rate, (ii) substrate affinity constant, (iii) biomass growth yield, (iv) maintenance coefficient, and (v) specific endogenous respiration rate. Parameters obtained through respirometry were compared to those obtained by the chemostat method, based on substrate and biomass measurements, under several dilution rates. The low sensitivity of substrate measurement methods and the difficulties of sampling heterogeneous biomass suspension are critical issues limiting the applicability of the chemostat method. Additionally, the extensive time consuming nature of this method allows concluding that chemostat method presents several disadvantages in comparison with in situ pulse respirometric techniques. Parameters were obtained from respirograms by fitting ASM1 and ASM3 models, and from experiments performed by injecting pulses of increasing substrate concentration. The injection of pulses of increasing concentration was the most adequate method, with several advantages such as a simpler experimental data interpretation and results with better confidence. Considering the assessment and comparison of the experimental and calculation methods presented, it is recommended that kinetic and stoichiometric parameters estimation in mixed aerobic cultures should preferentially be performed by using in situ respirometric techniques. ; This project was financed by the European Union in the Framework of the Marie Curie Actions (IRG4 6647). C.S. Oliveira and F. Thalasso received a grant from Fundacao para a Ciencia e a Tecnologia (SFRH/BD/32289/2006 and SFRH/BI/15847, respectively). A. Ordaz received a grant from Conacyt ...

This article proposes a simple "in-situ" pulse respirometric method for the estimation of four important kinetic and stoichiometric parameters. The method is validated in a suspended biomass nitrifying reactor for the determination of (i) maximum oxygen uptake rate (OURexmax), (ii) oxidation yield (fE), (iii) biomass growth yield (fS), and (iv) affinity constant (KS). OURexmax and fE were directly obtained from respirograms. In the presented case study, a minimum substrate pulse of 10 mgNH4+-NL-1 was necessary to determine OURexmax which was 61.15 ± 4.09 mgO2 L-1 h-1 (5 repetitions). A linear correlation (r2 = 0.93) obtained between OURexmax and the biomass concentration in the reactor suggests that biomass concentration can be estimated from respirometric experiments. The substrate oxidation yield, fE, was determined along 60 days of continuous operation with an average error of 5.6%. The biomass growth yield was indirectly estimated from the substrate oxidation yield fE. The average obtained value (0.10 ± 0.04 mgCOD mg-1COD) was in accordance with the fS estimation by the traditional COD mass balance method under steady-state conditions (0.09 ± 0.01). The affinity constant KS was indirectly estimated after fitting the ascending part of the respirogram to a theoretical model. An average value of 0.48 ± 0.08 mgNH4+-NL-1 was obtained, which is in the range of affinity constants reported in the literature for the nitrification process (0.16-2 mgNH4+-NL-1). ; European Union in the Framework of the Marie Curie Actions ; Fundação para a Ciência e a Tecnologia (FCT) ; Consejo Nacional de Ciencia y ...