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Santa María de la Isla, Spain

Aragon C.,Center for New Water Technologies Foundation | Coello M.-D.,University of Cadiz | Quiroga J.M.,University of Cadiz
Chemical Engineering Research and Design | Year: 2010

The aim of this study was to determine the effect of manganese(II) on the respiratory activity and cellular metabolism of activated sludge from two different wastewater treatment plants (WWTP). The tested manganese concentrations were: 0.5, 1, 1.5, 2, 4 and 6mg/L. The effect of this heavy metal on endogenous metabolism was studied by determining the specific endogenous respiration rate (SOURendo), chemical oxygen demand (COD) and measures of enzymatic activity (dehydrogenase activity), while the effect on the biodegradation capacity was determined through the terminal velocity of oxygen consumption (OURexo). Measurements were taken at 30min, 3h and 24h of exposure of the sludge to the heavy metal. The results showed that concentrations below 1ppm produce an increase in the respiratory activity of both sludges. Increasing the concentration of manganese (≥2mg/L) resulted in substantial reductions in respiratory activity, being more significant for long exposure times. Finally, it was observed that activation of the endogenous respiration rate at low concentrations of manganese during the first hours of the test produces greater stabilization of the sludge, as identified by a lower terminal velocity of synthetic wastewater degradation and lower values of COD measured in the supernatant. © 2009 The Institution of Chemical Engineers.

Bouza-Deano R.,Center for New Water Technologies Foundation | Salas-Rodriguez J.J.,Center for New Water Technologies Foundation
Ecological Engineering | Year: 2013

This paper describes the sludge accumulation and its characteristics after several years of operation (15-20 years) of an urban wastewater treatment system using stabilization ponds (anaerobic, facultative, and maturation ponds) in southern Spain. The rate of sludge accumulation (0.011m3/person year for anaerobic pond) was lower than previously reported by other authors (0.04m3/person year) due to the effects of degradation and consolidation after this long period of time, and the vertical distributions of humidity and volatile solids indicate a consolidation and mineralization of sludge with depth. Confirmation of this fact by new experimental data might require a reconsideration of desludging times in such systems.Principal component analysis revealed some specific features of the data structure, and three principal components were identified which collectively accounted for 91.1% of the total variance. Principal components analysis results were confirmed by cluster analysis. Three clusters of variables were detected, corresponding to the three previously identified components. These results confirm that there are clear differences in the physico-chemical properties of sludges deposited in each pond. Vertical distributions of parameters indicate a consolidation and mineralization of sludge with depth. This supports the hypothesis of consolidation, mineralization, and volume reduction of sludge after long periods of time. © 2012 Elsevier B.V.

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