title: Assessing the usefulness of clostridia spores for evaluating sewage sludge hygienization.
abstract: The capability of clostridia spores to act as pathogen indicators in sewage sludge treatment was investigated. Sulfite-reducing clostridia and E. coli levels were monitored during waste activated sludge pre-treatments (alkali and ultrasound) and its subsequent mesophilic anaerobic digestion. E. coli was maintained or reduced depending on treatment type and intensity. However, alkali pre-treatment (35.3gNaOH/kgTS) by itself and alkali (157gNaOH/kgTS) and ultrasound (27,000kJ/kgTS) pre-treatments followed by anaerobic digestion provoked reproducible clostridia increases. Specifically, up to 2.7log10after 35.3gNaOH/kgTS pre-treatment and up to 1.9 and 1.1log10after digesting the 157gNaOH/kg TS and 27,000kJ/kgTS pre-treated sludge, respectively. Having rejected the hypotheses of sporulation and floc dissipation, the most plausible explanation for these clostridia increases is re-growth. These results question the suitability of clostridia spores as indicators of sludge treatment and other biological treatments where clostridia may have a role.
authors.affiliation: Department of Genetics, Microbiology and Statistics, University of Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain; The Water Research Institute, University of Barcelona, C/ Montalegre 6, 08001 Barcelona, Spain. Electronic address: juliamadi@hotmail.com.
authors.forename: Julia
authors.initials: J
authors.lastname: Martín-Díaz
authors.affiliation: Department of Chemical Engineering, University of Barcelona, C/ Martí i Franquès 1, 6th Floor, 08028 Barcelona, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Ruiz-Hernando
authors.affiliation: Department of Chemical Engineering, University of Barcelona, C/ Martí i Franquès 1, 6th Floor, 08028 Barcelona, Spain; Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Sergi
authors.initials: S
authors.lastname: Astals
authors.affiliation: Department of Genetics, Microbiology and Statistics, University of Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain; The Water Research Institute, University of Barcelona, C/ Montalegre 6, 08001 Barcelona, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Lucena
mesh_terms: D000468:Alkalies; D058491:Bacterial Load; D003013:Clostridium / Q000302:isolation & purification*; D004926:Escherichia coli / Q000302:isolation & purification*; D012722:Sewage / Q000382:microbiology*; D013171:Spores, Bacterial / Q000302:isolation & purification*; D014465:Ultrasonics
chemical_list: D000468:Alkalies; D012722:Sewage
keywords: Anaerobic digestion; Clostridium spores; Hygienization treatment; Indicator; Sewage sludge