RESUMO
Air inside poultry houses must be removed on a regular basis to prevent excess of heat, particles and noxious gases that can imperil animals. To cope with this issue, natural ventilation could be an effective method when assisted by accurate predictions. This study investigates air discharges caused by natural ventilation of a poultry house by means of a three-dimensional computational fluid dynamics (CFD) model. It solves the governing equations of momentum, heat and mass transport, radiative transfers and animal-generated heat. Wind directions of 0°, 36° and 56° (0° corresponds to a wind blowing perpendicular to the ridgeline) were investigated; the CFD model predictions achieved a RMSE of 1.2 °C and 0.6 g[H2O] kg-1 [dry air] for internal temperature and absolute humidity, respectively, when air blew with an angle of 36°. Air renewal rates (ARR) were 39.5 (± 1.9), 34.9 (± 2.2) and 33.6 (± 1.7) volumes of the building per hour, when air blew at 0°, 36° and 56°, respectively. Such ARR predictions served to know how the gases contained in air would likely spread downstream from the building in order to define regions of potentially high gas concentration that could endanger neighbouring habitable facilities.
Assuntos
Monitoramento Ambiental/métodos , Hidrodinâmica , Vento , Animais , Gases/análise , Aves Domésticas , Temperatura , VentilaçãoRESUMO
As biosolids application to croplands becomes a common practice, potential harm from pathogenic microbes needs to be mitigated for its safe reuse. The objective of this study was to investigate the impacts of tilling treatment on biosolids drying and microbial inactivation during the solar drying process in a semi-arid and temperate region. Solar drying experiments were conducted in sand and gravel dying beds open-to-the-air and under covering structures with biosolids to 20 cm depth from 2004 to 2006. Anaerobically- and Aerobically-digested biosolids received different tilling treatments throughout the drying process, while a series of biosolids samples were collected to determine the impact on total solids and microbial concentrations (Salmonella spp and heminth ova). Tilling treatments appeared to enhance the biosolids drying and microbial inactivation. Tilling was more effective during the cold season compared with the summer season and tilling treatments were also helpful in elevating biosolids temperature by expediting biosolids drying. The combined effect of temperature increase and moisture decrease by tilling may have resulted in faster microbial inactivation, particularly for persistent helminth ova. It was concluded that incorporation of tilling into biosolids solar drying can expedite biosolids drying as well as microbial inactivation, and thus can be an effective measure for shortening the biosolids conversion to Class A biosolids in which pathogens are reduced to below detectable levels.