Abstract
In this work the aerobic degradation of phenol by acclimated activated sludge was studied. Results demonstrate that while the phenol removal rate by acclimated activated sludge follows the Monod model, the oxygen uptake rate obeys a Haldane-type equation. The phenol oxidation coefficient obtained at different intial phenol concentrations ranged from 1.9 to 2.6 mol O2 · mol-1 phenol. A mathematical model based on a simplified version of the catalytic mechanism of the enzyme phenol 2-monooxygenase was developed to predict transient phenol concentrations and oxygen requirements by phenol-acclimated activated sludge in batch reactors under different initial phenol concentrations. The proposed model not only adequately represents the experimental results of the present paper, but also those reported by other authors. Particular cases of the proposed model are discussed.Keywords: oxygen uptake rate; phenol; biodegradation; biokinetic model; respirometry
Highlights
Phenolic compounds are considered to be a major group of hazardous environmental pollutants
Contreras et al (2008) reported a value for KS = 11 μM, while Lepik and Tenno (2011) informed KS = 4 μM. These results demonstrate that the proposed model adequately represents the experimental results of the present paper, and several findings reported by other authors
This work demonstrates that while the phenol removal rate by acclimated activated sludge follows a Monod type kinetics, the oxygen uptake rate obeys a Haldane-type dependence with respect to the phenol concentration; the phenol oxidation coefficient cannot be considered as a constant
Summary
Phenolic compounds are considered to be a major group of hazardous environmental pollutants. In a typical activated sludge wastewater treatment plant, aeration costs represent approximately 45% of the total operative cost (e.g. energy for aeration, pumping, and sludge treatment) (Vanrolleghem and Gillot, 2002), accurate kinetic models help engineers to optimise operational conditions in order to meet discharge requirements, minimising operational costs For these reasons, in this work a mathematical model based on a simplified version of the catalytic mechanism of PH2MO was developed to predict transient phenol concentrations and oxygen requirements by phenol-acclimated activated sludge in batch reactors under different initial phenol concentrations. PH was adjusted to 7.0 ± 0.05 by adding a few drops of concentrated solutions of NaOH or HCl. After 70 days of operation, the model wastewater was replaced by a culture medium with phenol as the sole carbon-limiting source (Nuhoglu and Yalcin, 2005): (NH4)2SO4 226 mg∙l-1, K2HPO4 500 mg∙l-1, KH2PO4 250 mg∙l-1, MgSO4∙7H2O 25.2 mg∙l-1, MnSO4∙H2O 2.52 mg∙l-1, CaCl2 2 mg∙l-1, FeCl3 1.2 mg∙l-1, phenol 300 mg∙l-1. In these experiments the biomass concentration was 0.7 g∙l-1 TSS and tested initial phenol concentration (SO) ranged from 0.53 to 5.3 mM
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