Residue characteristics of sludge from a chemical industrial plant by microwave heating pyrolysis

Abstract

Sludge from biological wastewater treatment procedures was treated using microwave heating pyrolysis to reduce the environmental impact of a chemical plant. In this study, major elements, trace elements, PAHs and nitro-PAHs in raw sludge, and pyrolysis residues were investigated. The contents of major element from raw sludge were carbon 46.7 ± 5.9%, hydrogen 5.80 ± 0.58%, nitrogen 6.81 ± 0.59%, and sulfur 1.34 ± 0.27%. Trace elemental concentrations including Zn, Mn, Cr, Cd, As, and Sn were 0.410 ± 0.050, 0.338 ± 0.008, 0.063 ± 0.006, 0.019 ± 0.001, 0.004 ± 0.001, and 0.003 ± 0.002 mg/g, respectively. For various pyrolysis temperatures, Ca, Fe, Sr, Cr, and Sn contents remained at almost the same level as those in raw sludge. Results indicated that these elements did not easily volatilize. The content of 16 PAH species was about 4.78 μg/g in the raw sludge and 23-65 μg/g for pyrolysis residues associated with various temperatures. The content of ten nitro-PAHs was about 58 ng/g for the raw sludge and 141-744 ng/g for pyrolysis residues. The total nitro-PAH content was highest at 600 °C and then decreased when the temperature was over 600 °C. Total nitro-PAH content was about 247 ng/g at 800 °C.

Environmental risk assessment in livestock manure derived biochars

“…Previous studies have reported that Cd evaporates with increasing pyrolysis temperature. 47 Cadmium chloride, produced by the combination of Cd and chloride, is the major Cd species in the vapor phase during pyrolysis. 48,49 In this study, the bioavailability and ecotoxicity of Pb in livestock-manure-derived biochars was reduced aer pyrolysis.…”

Transformation of Heavy Metals during Pyrolysis of Predried Dyeing Sludge

“…The results show that the content of heavy metals in the pyrolysis residue is about 2.5–3.5 times that of the sludge. Lin et al found that the contents of Ca, Fe, Sr, Cr, and Sn in sludge pyrolysis residues of chemical plants were almost the same as those of original sludge at 400–800 °C pyrolysis temperature. Because of the low boiling point of Cd, the content of Cd in residues decreased with the increase in the pyrolysis temperature.…”