The invention discloses a combined chemical conditioning method for deep
drying of dehydrated
sludge. The method comprises steps as follows: to-be-treated dehydrated
sludge is diluted with water, so that the
moisture content of the dehydrated
sludge is 90%-93%, strong acid is added to adjust the pH value to range from 4 to 5 after
dilution, then
potassium ferrate with the adding amount accounting for 0.1%-0.5% of that of absolutely dried sludge amount is added in the form of a solution with the
mass percent concentration of 0.5%-2% and the pH value of 9-11, and oxidation treatment is finished after stirring for full reaction; then poly-aluminum
chloride salt with the adding amount accounting for 4%-10% of that of absolutely dried sludge amount is added for coagulation treatment; then
calcium hydroxide with the adding amount accounting for 0.3%-1% of that of absolutely dried sludge amount is added to adjust the pH value to range from 6 to 7, finally, poly-
quaternary ammonium salt with the adding amount accounting for 0.1%-0.3% of that of absolutely dried sludge amount is added for
filtration aiding, and chemical conditioning is finished. Through optimized combination of
dilution, acidification, oxidation, coagulation,
flocculation,
filtration aiding and the like, the effect of
bound water on sludge can be reduced, indexes including
specific resistance of sludge,
compressibility, hydraulic characteristic and the like can be improved, the proportion of releasable
free water can be effectively increased, and the sludge dehydrating effect can be improved.