Use of Alcaligenes faecalis to Reduce Coliforms and Enhance the Stabilization of Faecal Sludge

Abstract

The disposal of human faecal sludge (FS) is one of the biggest environmental problems. It can be solved by using FS as an agricultural fertilizer. However, this is hampered by the presence of pathogenic microflora and high organic matter content in FS. This paper proposes a novel treatment approach for FS to address these issues. It consists of the preliminary aerobic incubation of FS with the bioaugmentation of bacterial culture Alcaligenes faecalis DOS7. A. faecalis has been shown to inhibit the growth of various microorganisms, including coliforms (Escherichia coli). For the treatment of FS, three tanks with a volume of 1 m3 each, equipped with a mixing and aeration system, were used. A. faecalis culture was introduced into two experimental tanks at a concentration of 106 and 6.5 × 106 cells/mL. The 11-day incubation in the experimental tanks resulted in the decomposition of organic matter in the FS that was several times faster than in the control (p < 0.05). Total suspended solids decreased 2.5–5-fold, chemical oxygen demand decreased 1.8-fold, 5-day biochemical oxygen demand decreased 1.5–2-fold. At the same time, after 4 days of incubation, no coliforms were detected in the experimental tanks, and in the control, coliforms accounted for 13.9% of the total number of cells after 11 days of incubation. The proposed method of FS pretreatment is a real alternative to the existing ones and can be used both individually and in combination with other methods, for example, composting.