Abstract
The output of municipal sludge in large and medium-sized cities in China has increased year by year, which results in the dilemma of having no remaining land for sludge to filling. Therefore, it is urgent to reduce the amount of sludge storage in stock. “Chemical conditioning combined with vacuum preloading” is an effective in-situ treatment method for sludge reduction, but the properties of sludge from different sources and different sewage processes vary greatly. Besides, the existing research lacks systematic analysis of the consolidation and permeability properties of different types of municipal raw sludge and conditioned sludge. In this paper, different inorganic salts (Fe3+, Ca2+, Mg2+, Al3+) were selected to carry out chemical conditioning from different sources, and the influence of chemical conditioning on the consolidation characteristics of municipal sludge from different sources was studied. The test results show that the sludge with different pre-treatment process has a great influence on the consolidation and drainage characteristics of sludge. Shanghai municipal sludge using first-level enhanced coagulation process has the worst performance in consolidation and permeability characteristics. On contrary, sludges with A2/O process have the best performance of them. Fe3+ salt and Al3+ salt could improve the dewatering characteristics of different types of sludge, while Mg2+ salt and Ca2+ salt had weak effects. In addition, the specific resistance of Shanghai sludge after 10% FeCl3 conditioned decreased from 1.24×1011m/kg to 2.13×109m/kg, and the consolidation coefficient increased by 13.5–101 times.
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