Microbiological stability of wastewater sludges from activated sludge systems

• Published in: Bioresource technology Vol. 49; no. 3; pp. 203 - 207
• Main Authors: Surampalli, R.Y., Banerji, S.K., Chen, J.C.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1994; Elsevier Science
• Subjects: Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biotechnology; coliforms; Environment and pollution; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; pathogen reduction; regulation; Salmonella; Sludge; streptococcus; United States; North America; America; Salmonella; streptococcus; regulation; Sludge; coliforms; pathogen reduction; Volatile compound; Activated sludge; Stability; Dry matter content; Coliforms; Sewage sludge; Aeration; Streptococcaceae; Streptococcus; Pathogenic; pH; Micrococcales; Bacteria; Urban waste water; Oxidation; Regulation; Biological treatment; Waste water purification; Dissolved oxygen; Enterobacteriaceae; Environmental protection
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/0960-8524(94)90040-X

Proposed United States Environmental Protection Agency (EPA) regulations require that processed sludge, prior to disposal, must meet certain pathogen-reduction requirements. The present study was conducted to evaluate reductions in pathogen-indicator bacteria in the sludges of six wastewater plants. Five of the plants use extended aeration and oxidation ditches; the other is a trickling filter plant. Fecal coliform, fecal streptococcus, and Salmonella were measured on all sludge samples. Temperature, pH, dissolved oxygen, volatile suspended solids (VSS), and total suspended solid were also measured. The fecal coliform log reductions/g VSS for all the extended aeration and oxidation ditch plants were greater than 1·76. They varied from a log reduction of 1·76 to 4·21. The fecal streptococci reductions for the same sludge were generally lower than the fecal coliform reductions. The variations in the fecal streptococci log reductions in different plant sludges were from 0·87 to 2·73. The Salmonella log reductions varied from 1·39 to 4·7 and paralleled the fecal coliform reductions. The bacterial reductions were related to the plant design parameters. A longer storage of sludge usually produced a larger log reduction of the indicator bacteria. Generally, the extended aeration and oxidation ditch plants were meeting the proposed EPA class B Pathogen reduction criteria, a two-order reduction.