Pilot Plant Study of Simultaneous Sewage Sludge Digestion and Metal Leaching |
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Authors: | Jean-Fran?ois Blais Nathalie Meunier Guy Mercier Patrick Drogui Rajeshwar Dayal Tyagi |
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Affiliation: | 1Institut National de la Recherche Scientifique (INRS-ETE), Université du Québec, 2800, Rue Einstein, C. P. 7500, Sainte-Foy PQ, Canada G1V?4C7 (corresponding author). 2Institut National de la Recherche Scientifique (INRS-ETE), Université du Québec, 2800, Rue Einstein, C. P. 7500, Sainte-Foy PQ, Canada G1V?4C7. 3Institut National de la Recherche Scientifique (INRS-ETE), Université du Québec, 2800, Rue Einstein, C. P. 7500, Sainte-Foy PQ, Canada G1V 4C7.
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Abstract: | This research is related to a preindustrial pilot scale study of the performance of the simultaneous sewage sludge digestion and metal leaching (SSDML) process for decontamination and stabilization of sewage sludge. Ten batch tests were carried out in two 4?m3 bioreactors under various conditions of operation. Results indicated that the addition of 1.0 to 1.5?g?S0/L, which is the equivalent of approximately 30 to 50?kg?S0 per tons dry sludge, is sufficient to obtain conditions of acidity (pH<2.5) and oxido-reduction potential greater than 500 mV necessary for an effective solubilization of toxic metals. The final average of metal solubilization in the output sludge during the SSDML process varied in the following ranges: 25–78% Cd, 9–32% Cr, 48–100% Cu, 77–99% Mn, 15–53% Ni, 12–47% Pb, and 66–100% Zn. The N, P, and K contents were also preserved in the decontaminated sludge. Moreover, the use of low concentrations of elemental sulfur makes it possible to obtain decontaminated sludge with a low total sulfur content (1.4–1.5% S) compatible with agricultural use. The suspended solids removal calculated for the SSDML process was slightly lower, (2.5±0.4)% volatile suspended solids per day, than those reached using standard aerobic digestion. Finally, the SSDML process was found to be effective in removing bad odors and in the destruction (99–100%) of indicator bacteria. |
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Keywords: | Sewage sludge Sludge digestion Leaching Waste treatment Stabilization |
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