| The sewage sludge commonly contained a lot of water. The volume of the sludge must be reduced before disposing for low costs of transportation, handling and disposal. However, chemical conditioning prior to mechanical had difficulties improving the sludge cake solids content because sewage sludge dewatering was often hindered by blinding of the filtration media and the filter cake itself. This experiment studied the effect of the addition of alum sludge for the sewage sludge dewaterability.Polyaluminium chloride(PACl) as flocculant in the water treatment plant produced a lot of alum sludge, alum sludge contained residual polyaluminum chloride(PACl) and large amount inorganic matters. Alum sludge acted as chemical conditioner and physical conditioner improved the sewage sludge dewatering. The SRF of blended sludge decreased from 4.0×1013m/kg to 1.6×1013m/kg, the moisture content of blended sludge with plate-and-frame filter press decreased from 85% to 64%, when the blend ratios is 1kg/kg.According to the analysis of particle, XRF and energy dispersive spectrum of sludge, it indicated that the particle of alum sludge is at 3.5-63.1μm, and the alum sludge could act as skeleton builder for sewage sludge and the addition of alum sludge resulted in the increase of Al and Si element in blended sludge. The 3D-Excitation-emission matrix(3D-EEM) was used to analyze the sludge dewatering process. A mechanism hypothesis of adding alum sludge in sewage sludge for improving the sludge dewatering was proposed. Alum sludge implements the charge neutralization and adsorption bridging effect, provides friction and squeeze for crushing sludge particles even cell, and acts as skeleton builders in the sludge to improve the sludge dewatering. |
