Characteristics of leachate from pyrolysis residue of sewage sludge

Abstract

The pyrolysis residue (SP) of sewage sludge (SS) produced at 500 °C was subjected to batch and column leaching tests to investigate the release of its organic and inorganic constituents and metals. For comparison, incineration ash (SI) obtained from a SS incinerator was also tested. Pyrolysis and incineration reduced organic matter of SS from 0.78 kg kg -1 -dry SS to 0.16 and 0.01 kg kg -1 -dry SS, respectively. Heavy metals remained in SP without being volatilized, although Cd and Pb were transferred into the off-gas during incineration.In the batch leaching test with the leaching liquid-to-solid mass ratio (L/S) = 10, the pH of the SS, SP, and SI filtrates was 6.3, 7.9, and 11.0, respectively. The total organic carbon concentrations were in the order SS (877l mg l -1 ) >> SP (99 mg l -1 ) > SI (26 mg l -1 ). The SP and SI filtrates met the landfill standard for the Cd and Pb concentrations (< 0.3 mg l -1 ). In the column tests, although the SP contained more organic matter than that of SI, its carbon discharge into the leachate under aerobic conditions was similar to that of SI under anaerobic conditions. The leaching of heavy metals, such as Cd, Cr, Pb, and Zn, was also suppressed in SP during the active decomposition of organic matter.We demonstrated that pyrolysis reduces the potential release of pollutants from sewage sludge in landfill, making it a promising method of treating sewage sludge before landfilling.

Characterization of chars produced in the co-pyrolysis of different wastes: Decontamination study

“…However, it was previously demonstrated that Zn mobility/leachability (Bernardo et al, 2010) is suppressed in the extracted pyrolysis chars. Also, previous studies (Hwang et al, 2007;Kistler et al, 1987) have shown that pyrolysis may have a positive effect on the immobilization of heavy metals in solid chars. Table 3.…”

Comparative Study on the Migration of Heavy Metals in the Sewage Sludge Treated by Supercritical/Subcritical Water Oxidation Process

“…4, that, comparing with raw sewage sludge and the sewage sludge residue after subcritical treatment, the content of element C in sewage sludge residue after supercritical treatment decreases obviously, showing that the decomposition of organic matters in sewage sludge residue is more thorough. Meanwhile, Fe, Al and Ca in sewage sludge residue after supercritical treatment can generate phosphate, aluminum phosphate and calcium phosphate with phosphorus, thus realizing the role of stabilizing the heavy metal ions [8,9] .…”

Distribution and Contamination Hazards of Heavy Metals in Solid Residues from the Pyrolysis and Gasification of Wastewater Sewage Sludge

“…He et al [24] determined the chemical composition and thermal stability of solid residues, as well as migration and transformation of HMs during SS pyrolysis. Hwang et al [25][26] found that most HMs was completely retained by solid residue after SS pyrolysis treatment and the composition of raw SS had a significant influence on the quality of the resulting residue and thus, the mobility of HMs. Lu et al [27] also studied the influence of pyrolysis temperature on physical and chemical properties of pyrolysis residue.…”