Dewatering of urban residual sludges: Filterability and hydro-textural characteristics of conditioned sludge

摘要

The hydro-textural properties of different urban residual sludges, characterized by their organic matter content, were estimated and correlated with their limit water content, corresponding to their minimum water content obtained after constant high-pressure filtration. A conventional compression-permeability (C-P) cell was used to determine the limit water content (w_(lim)) whereas standardized soil mechanics tests were run to determine the liquid limit (w_L) and plastic limit (W_p) content, characterizing the hydro-textural properties. The results demonstrated that W_(lim), wL and w_P parameters depend on sludge composition: high organic matter content ratio is unfavorable to a low w_(lim) but favorable to a high plastic range and so a high deformation of the sludge. It appeared that the w_(lim) value was close to the w_P value, but lower than that obtained after mechanical dewatering in the wastewater treatment plants (WWTPs). It appears thus that the totality of the mechanically extractable water is not extracted by the WWTPs mechanical dewatering devices.