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DatoValore
TitleRHEOLOGY OF SLUDGE IN A COMPLETE RETENTION MEMBRANE BIOREACTOR
AbstractA rheological characterization of the sludge sampled from a complete retention membrane bioreactor was performed in order to correlate the apparent viscosity with the concentration of solids. The three most commonly adopted models were tested to select the one better fitting the experimental data. Ostwald model was choosen, and the relationship between the apparent viscosity and the shear rate was determined for mixed liquor suspended solids (MLSS) concentrations ranging between 9 and 25 g l-1. Ostwald model parameters k and n were correlated with MLSS concentration, comparing linear, power, and exponential-power (only for k) laws in terms of R 2 and Mean Root Square Error (MRSE). Both power and exponential-power functions provided good and comparable correlations for parameter k, while the linear relationship was much less accurate, especially at the highest solid concentrations. The parameter n was better modelled by a power function than by a linear one. Therefore two simulation models were proposed, both based on Ostwald's equation, where the two parameters k and n were expressed as functions of MLSS. Evaluation of energy consumption for mixing showed that the increase of solid concentration from 3 to 30 g l-1 resulted in a limited increase in energy requirement (25-30 %). In real systems, where Reynolds numbers shift towards the turbulent regime, the increase of energy requirements for increasing solids concentration is even less pronounced. The thixotropy of membrane bioreactor sludge was also evaluated by measuring the rHa (reduced hysteresis area) and relating this parameter to the characteristics of the sludge growing within the reactor.
SourceEnvironmental technology 27 (7), pp. 723–732
KeywordsHysteresis; Membrane bioreactors; Rheology; Sludge; Viscosity
JournalEnvironmental technology
EditorTaylor & Francis, Abingdon, Regno Unito
Year2006
TypeArticolo in rivista
DOI10.1080/09593332708618690
AuthorsPOLLICE A., GIORDANO C., LAERA G., SATURNO D., MININNI G.
Text42102 2006 10.1080/09593332708618690 ISI Web of Science WOS 000241459800003 Hysteresis; Membrane bioreactors; Rheology; Sludge; Viscosity RHEOLOGY OF SLUDGE IN A COMPLETE RETENTION MEMBRANE BIOREACTOR POLLICE A., GIORDANO C., LAERA G., SATURNO D., MININNI G. CNR Istituto di Ricerca Sulle Acque, Viale F. De Blasio 5, 70132 Bari, Italy CNR Istituto di Ricerca Sulle Acque, Via Reno 1, 00198 Roma, Italy A rheological characterization of the sludge sampled from a complete retention membrane bioreactor was performed in order to correlate the apparent viscosity with the concentration of solids. The three most commonly adopted models were tested to select the one better fitting the experimental data. Ostwald model was choosen, and the relationship between the apparent viscosity and the shear rate was determined for mixed liquor suspended solids MLSS concentrations ranging between 9 and 25 g l 1. Ostwald model parameters k and n were correlated with MLSS concentration, comparing linear, power, and exponential power only for k laws in terms of R 2 and Mean Root Square Error MRSE . Both power and exponential power functions provided good and comparable correlations for parameter k, while the linear relationship was much less accurate, especially at the highest solid concentrations. The parameter n was better modelled by a power function than by a linear one. Therefore two simulation models were proposed, both based on Ostwald s equation, where the two parameters k and n were expressed as functions of MLSS. Evaluation of energy consumption for mixing showed that the increase of solid concentration from 3 to 30 g l 1 resulted in a limited increase in energy requirement 25 30 % . In real systems, where Reynolds numbers shift towards the turbulent regime, the increase of energy requirements for increasing solids concentration is even less pronounced. The thixotropy of membrane bioreactor sludge was also evaluated by measuring the rHa reduced hysteresis area and relating this parameter to the characteristics of the sludge growing within the reactor. 27 http //www.tandfonline.com/doi/abs/10.1080/09593332708618690 Articolo pubblicato 2006_EnvironTechnol_27_7_723_732.pdf Articolo in rivista Taylor Francis 0959 3330 Environmental technology Environmental technology Environ. technol. Environmental technology. alfieri.pollice POLLICE ALFIERI giuseppe.laera LAERA GIUSEPPE giuseppe.mininni MININNI GIUSEPPE TA.P07.002.002 Sviluppo di nuovi processi di controllo dell inquinamento idrico. TA.P07.001.003 Processi innovativi per il trattamento e lo smaltimento dei fanghi di depurazione TA.P07.002.004 Processi biotecnologici e processi a membrana