Two-phase (acidogenic–methanogenic) anaerobic thermophilic/mesophilic digestion system for producing Class A biosolids from municipal sludge

• Published in: Bioresource technology Vol. 101; no. 2; pp. 576 - 585
• Main Authors: Rubio-Loza, L.A., Noyola, A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2010; [New York, NY]: Elsevier Ltd; Elsevier
• Subjects: Acids - metabolism; Anaerobiosis; Animals; Applied sciences; Biological and medical sciences; Class A biosolids; Enterobacteriaceae - isolation & purification; Exact sciences and technology; Feces - microbiology; Fundamental and applied biological sciences. Psychology; Helminth eggs; Helminths - isolation & purification; Mesophilic; Methane - biosynthesis; Pollution; Salmonella - isolation & purification; Sewage - microbiology; Thermophilic; Two-phase sludge digestion; Volatilization; Wastes; Wastewaters; Water treatment and pollution; Class A biosolids; Mesophilic; Thermophilic; Two-phase sludge digestion; Helminth eggs; Egg; Waste treatment; Urban waste; Thermophily; Digestion; Sewage sludge; Acidogenesis; Anaerobe; Mesophily; Methanogenesis; Urban waste water
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2009.08.066

Two different arrangements of two-phase anaerobic sludge systems were operated treating a mixture of primary and secondary sludge. Two steady state periods were evaluated: the first acidogenic thermophilic phase was operated at hydraulic retention times of 3 and 2
days and the second methanogenic (mesophilic and thermophilic) phases at 13 and 10
days. The two-phase systems had an efficient removal of pathogens and parasites, achieving values lower than those specified for Class A biosolids, according to the Mexican Standard NOM-004-SEMARNAT-2002. The first thermophilic phase achieved almost complete destruction of pathogens and parasites by itself. During the second steady state period, volatile fatty acids accumulated in the second methanogenic phases (HRT of 10
days and an organic load of 3
kgVS/m
3d) indicating that the systems were overloaded, mainly the mesophilic digester. In this case, the accumulation of propionic acid may be related to a deficiency of micronutrients. The results show that the two-phase thermophilic/mesophilic anaerobic sludge digestion may be considered as an adequate option for the production of Class A biosolids.