Simultaneous sewage sludge digestion and metal leaching—Effect of sludge solids concentration

• Published in: Water research (Oxford) Vol. 31; no. 1; pp. 105 - 118
• Main Authors: Tyagi, R.D., Blais, J.F., Meunier, N., Benmoussa, H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1997; Elsevier Science
• Subjects: Applied sciences; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biotechnology; elemental sulfur; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; metal leaching; Other industrial wastes. Sewage sludge; Pollution; sewage sludge; sludge digestion; sludge solids; stabilization; thiobacilli; Wastes; metal leaching; thiobacilli; sludge solids; stabilization; sludge digestion; sewage sludge; elemental sulfur; Aerobic digestion; Thiobacillus thioparus; Bioreactor; Thiobacillus thiooxidans; Heterotrophy; Bacteria; Lixiviation; Metal; Coliforms; Experimental study; Sewage sludge
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(96)00247-3

The effect of sludge solids concentration on the simultaneous sewage sludge (mixture of primary and secondary sludge) digestion and metal leaching (SSDML) process was studied in shake flasks (500 ml capacity) and in laboratory bioreactors of 20 liters working volume. The bioreactor studies demonstrated that an increase in sludge solids concentration increased the sulfuric acid production rates in the range of solids 8 to 30 g/l. The metal solubilization efficiency (Cu, Mn, Ni and Zn) during the SSDML process in the bioreactor was not affected by sludge solids concentration to a large extent, except Cd, Cr and Pb, which were less soluble at increased solids concentration. The sludge solids content, in the range of 16 to 30 g/l did not affect the sludge solids (total solids, volatile solids, total suspended solids and volatile suspended solids) reduction during the SSDML process operation at bioreactor scale. The fertilizer value of the processed sludge remained intact. Tests in shake flasks and bioreactors demonstrated that the SSDML process was more efficient than aerobic sludge digestion for the destruction of total coliforms in the range of solids concentration 10 to 50 g/l.