WO9219551-A  A.H. DIRKZWAGER, P. L'HERMITE 'Sewage Sludge Treatment and Use: New Developments and Environmental Effects' 1989 , ELSEVIER SCIENCE PUBLISHERS , LONDON, GB Page 145, W.H.Rulkens et al.: "Removal Of Heavy Metals From Sewage Sludge";  GWF WASSER ABWASSER. vol. 120, no. 7, July 1979, MUNCHEN DE pages 329 - 335; WOFGANG SCHOeNBORN ET AL.: 'Entfernung von Schwermetallen aus Klaerschlaemmen durch bakterielle Laugung'WO9219551-A1  A.H. DIRKZWAGER, P. L&apos;HERMITE &apos;Sewage Sludge Treatment and Use: New Developments and Environmental Effects&apos; 1989 , ELSEVIER SCIENCE PUBLISHERS , LONDON, GB Page 145, W.H.Rulkens et al.: &quot;Removal Of Heavy Metals From Sewage Sludge&quot;;  GWF WASSER ABWASSER. vol. 120, no. 7, July 1979, MUNCHEN DE pages 329 - 335; WOFGANG SCH\NBORN ET AL.: &apos;Entfernung von Schwermetallen aus Kl{rschl{mmen durch bakterielle Laugung&apos;US5454948-A  Anderson et al, Aerobic sludge digestion with pH control-preliminary investigation, Journal WPCF, Jul. 1984, 57(7):889-897;  Anderson et al., Improvement in aerobic sludge disgestion through pH control: initial assessment of pilot-scale studies1, Can. J. Civ. Eng. 1987, 14:477-484;  Couillard et al., Bacterial Leaching of Heavy Metals from Aerobic Sludge, Bioresource Technology, 1991, 36:293-302;  GWF Wasser Abwasser vol. 120, No. 7, Jul. 1979, pp. 329-335 Entfernung Von Schwermetallen Aus Kkarschlammen Durch Bakterielle Laugung, Schonborn et al.;  Hayes et al., "Heavy Metal Removal From Sludges Using Combined Biological/Chemical Treatment", 34th P.I.W.C. 1979 Ed. J. M. Bell, Pub, Ann Arbor Science, pp. 529-543;  Henry et al, Fate of indicator organisms in sludge during bacterial leaching of metals1, Can. J. Civ. Eng., 1991, 18:237-243;  Int'l Metallurgical Rev., Rev. 179, vol. 19, No. 3, Mar. 1974 pp. 25-31, Use of Micro-Organisms for the Recovery of Metals;  Jenkins et al., "Metals Removal and Recovery from Municipal Sludge", Journal WPCF, vol. 53, No. 1, Jan. 1981;  Martin, Jr. et al, Reductions of Enteric Microoganisms During Aerobic Sludge Digestion, Wat. Res., 1990, 24(11):1377-1385