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RESUMO Este artigo discute a dispersão no ambiente da matéria orgânica presente no esgoto doméstico a partir de modelos oxigênio dissolvido-demanda bioquímica de oxigênio (OD-DBO). O modelo relaciona a poluição de corpos d'água por matéria orgânica e a queda dos níveis de OD. Dá-se destaque à modelagem de diferentes tipos de lançamentos da carga poluidora, com a apresentação de quatro tipos, e os efeitos sobre a capacidade de autodepuração do corpo d'água, a partir de dois padrões de transporte apresentados pelo corpo receptor; primeiramente para uma vazão menor e posteriormente havendo um incremento de vazão. Discute-se, ainda, como modelos podem intervir com eficiência no lançamento de esgoto após tratamento e como podem contribuir com a saúde pública, o saneamento e na melhoria de conservação dos recursos hídricos.
ABSTRACT The focus of this article is to analyze the presence of organic matter in sewage from BOD-DO models. The model relates to the pollution of a water body by organic matter and the decrease in dissolved oxygen levels caused by the respiration of microorganisms involved in sewage purification. It is highlighted the modeling of different types of pollutant loading release, presenting four types of them, and the effects on the natural water bodies' self-purification, from two patterns of transport provided by the receiving body; first for a smaller flow and then there is a flow increase. This work also discusses how mathematical models can intervene effectively in the discharge of sewage after treatment and if these can contribute to public health, sanitation and improved conservation of water resources.
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Fish survival in lakes is strongly influenced by water temperature and dissolved oxygen (DO) concentration. A one-dimensional (vertical) lake water quality model MINLAKE 2012 was calibrated in 23 Minnesota lakes and used to simulate daily water temperature and DO concentrations in 36 representative lake types under past (1992–2008) climate conditions and a future climate scenario (MIROC 3.2). The 36 representative Minnesota lake types were developed based on three maximum depths (Hmax = 4, 13, and 24 m), three surface areas (As = 0.2, 1.7, 10 km2), and four Secchi depths (SD = 1.2, 2.5, 4.5, and 7 m, from eutrophic to oligotrophic lake). A fish habitat model using the lethal-niche- boundary curve of adult cisco (Coregnous artedi, a cold-water fish species) was then developed to evaluate cisco oxythermal habitat and survival in Minnesota lakes.The fish habitat model was validated in the 23 Minnesota lakes of which 18 had cisco mortality while 5 had no cisco mortality in the unusually warm summer of 2006. Cisco lethal and habitable conditions in the 23 lakes simulated by the model had anoverall good agreement with observations in 2006. After model validation, cisco lethal days in the 36 lake types were modeled using simulated daily temperature and DO profiles from MINLAKE2012. Polymictic shallow lakes with lake geometry ratio As 0.25/Hmax> 5.2 m-0.5 were simulated to typically not support cisco oxythermal habitat under past climate conditions and the future climate scenario. Medium-depth lakes are projected to be most vulnerable to climate warming with most increase in the number of years with cisco kill (average increase 13 years out of 17 simulation years). Strongly stratified mesotrophic and oligotrophic deep lakes are possible to support cisco habitat under both past and future climate conditions, and these deep lakes are good candidates for cisco refuge lakes that should be protected against water quality deteriorations.