Pyrolysis of Municipal Sewage Sludge to Investigate Char and Phosphorous Yield together with Heavy-Metal Removal—Experimental and by Thermodynamic Calculations (original) (raw)

Sewage sludge is regarded as a potential source for soil fertilizer However, the direct utilization of sewage sludge in agricultural land is restricted since it also contains heavy metals, pathogens, and toxic compounds. Pyrolysis of the sewage sludge destroys the organic pollutants and partly volatilizes the heavy metals. In this study, pyrolysis of sewage sludge was carried out in order to determine the optimum residence time and temperature to recover the phosphorous and remove heavy metals from the resultant sewage sludge char (SSC). Pyrolysis was conducted on dried sewage sludge (DSS) by means of thermogravimetric analysis (TGA) and high-temperature oven with an N2-atmosphere. Microwave Plasma-Atomic Emission Spectroscopy (MP-AES) was used to determine the concentration of P and trace elements in the resulting solid char fraction. A combination of chemical fractionation (step-by-step leaching) of the DSS and thermodynamic equilibrium calculations were utilized to estimate the a...