Thermal hygienization of excess anaerobic sludge: a possible self-sustained application of biogas produced in UASB reactors

Abstract

The main current trends in final disposal of sludge from Wastewater Treatment Plants (WTP) include: safe use of nutrients and organic matter in agriculture, sludge disinfection and restricted use in landfill. As to sludge hygienization, helminth eggs have been used as a major parameter to determine the effectiveness of such process, and its inactivation can be reached by means of thermal treatment, under varying temperature and other conditions. In such context, the objective of this research was to determine how effectively biogas produced in UASB reactors could be used as a source of calorific energy for the thermal hygienization of excess anaerobic sludge, with Ascaris lumbricoides eggs being used as indicator microorganisms, and whether the system can operate on a self-sustained basis. The experiments were conducted in a pilot-scale plant comprising one UASB reactor, two biogas holders and one thermal reactor. The investigation proved to be of extreme importance to developing countries, since it leads to a simplified and fully self-sustainable solution for sludge hygienization, while making it possible to reuse such material for agricultural purposes. It should be also noted that using biogas from UASB reactors is more than sufficient to accomplish the thermal hygienization of all excess sludge produced by this system, when used for treating domestic sewage.

Leveraging Rural Energy Investment for Parasitic Disease Control: Schistosome Ova Inactivation and Energy Co-Benefits of Anaerobic Digesters in Rural China

“…Ova of Ascaris spp. have previously been used as models for helminthes in sewage sludge [40] , [41] . To assess the suitability of A. lumbricoides ova sedimentation as a proxy for S. japonicum sedimentation, the theoretical settling velocities of ova were calculated using known values for ova dimensions and densities, and a modified Stoke's equation following Shuval et al [42] : where is the terminal velocity(cm sec −1 ); is gravitational acceleration; is the ovum density (g cm −3 ); is the liquid density (g cm −3 ); is the drag coefficient (24/Re); is the ovum projected area (cm 2 ); and is the ovum volume (cm 3 ).…”

Tratamiento de aguas residuales municipales

“…El material flotante, típicamente compuesto de aceites y grasas y otros detritos no removidos durante la etapa de tratamiento preliminar (nata), es removido en la superficie de los decantadores primarios. En esta unidad se espera una eficiencia de remoción de sólidos en suspensión entre 60 y 70% y de DBO entre 25 y 40%, asociada a la fracción de DBO particulada removida por sedimentación (von Sperling y Chernicharo, 2005).…”

“…En el caso del tratamiento secundario, se espera una eficiencia de remoción de sólidos en suspensión entre 65 y 95% y de DBO entre 60 y 99% (von Sperling y Chernicharo, 2005). Tales rangos de valores serán explorados en mayor detalle para cada una de las tecnologías consideradas en el resto de Notas Técnicas de esta colección.…”

“…Específicamente con relación al secado térmico, diversas configuraciones tecnológicas son posibles para todas las escalas de las PTARs. Para sistemas de pequeña y media escala, las siguientes opciones con bajos costos de implantación y operación son posibles: (i) lechos de secado modificados para promover el secado e higienización simultáneos del lodo (Andreoli et al, 2001;Ferreira y Nishiyama, 2003); (ii) los tanques de higienización seguidos de lechos de secado convencionales (Borges et al, 2005); y (iii) los lechos de secado convencionales seguidos por lechos de secado con calentamiento para la higienización del lodo Wagner et al, 2015). Para PTARs de gran escala (> 100.000 hab.…”

Aproveitamento do biogás produzido em reatores anaeróbios de fluxo ascendente de manta de lodo para a secagem térmica de lodos de estações de tratamento de esgoto

“…Resultados similares aos obtidos no presente trabalho foram reportados por Borges et al (2005) e Lobato et al (2012), tendo esses autores conduzidos experimentos de tratamento térmico de lodo, utilizando biogás de reatores UASB como fonte de energia, em escala de protótipos. Estudos conduzidos por Batistella et al (2015) em um secador granulador rotativo, semelhante ao empregado no presente estudo, também evidenciaram redução significativa nos indicadores biológicos para uso agrícola do lodo.…”