Contribuição para o aprimoramento de projeto, construção e operação de reatores UASB aplicados ao tratamento de esgoto sanitário-Parte 5: Biogás e emissões fugitivas de metano Contribution for improving the design, construction and operation of UASB reactors treating sewage-Part 5: Biogas and fugitive methane emissions
This study aimed to undertake an environmental life cycle assessment (LCA) of a sewage treatment plant (STP) equipped with low-rate trickling filters (TFs) as post-treatment of upflow anaerobic sludge blanket (UASB). The STP is located in South Brazil and uses landfill and agriculture as sludge-disposal alternatives. The evaluation was performed using the LCA technique and SimaPro® 9 software. The results revealed that the gases methane (CH4) and sulfur dioxide (SO2), emitted into the atmosphere after the partial burning of the biogas in flares, are mainly responsible for impacts in the categories of global warming (GW) and terrestrial acidification (TA), respectively. Due to the low rate of hydraulic sewage application in TFs, nitrous oxide (N2O) emissions stood out due to their high impact in the category of stratospheric ozone depletion (SOD). The use of sludge in agriculture obtained a greater potential for environmental impact compared to landfills in five of the eight categories evaluated. The main impacts of agricultural use were in the category of human toxicity (HT), due to the high concentration of zinc present in the sludge, and in the category TA, due to the emission of ammonia (NH3) during hygienization of the sludge. In turn, the main positive aspects were avoided products, such as urea, phosphate fertilizer and limestone. The results contribute to a greater discussion of sewage-treatment processes, as well as sludge-management alternatives used in developing countries.
Alkaline stabilization (AS) is one of the most widespread processes in the world for the sanitization of sludge produced in sewage treatment, although in Brazil it is used by only a few sanitation companies. The fact that an environmentally sustainable destination for sewage sludge is not mandatory, as well as a series of economic, technical and operational factors, end up limiting the AS process application. The increase of AS practices are expected due to the the Brazilian CONAMA Resolution nº 498/2020, which aims to increase the use of biosolids in agriculture and to further deepen technical and operational knowledge related to this practice. This technical note (TN) presents the main forms of the storage and application of lime, as well as the minimum parameters required for designing maturation and curing yards. In this TN, the intrinsic AS costs and best engineering practices used are discussed, in view of reducing possible problems and maximizing its usage throughout the national territory.
RESUMO O gerenciamento do lodo de esgoto é um dos principais responsáveis pelos elevados custos de operação de estações de tratamento de esgoto no Brasil. Isso se deve, principalmente, pela necessidade de etapas de desaguamento e higienização desse material, sendo essa última realizada quando o uso agrícola do lodo é escolhido como forma de destinação. Para tentar reduzir os custos e melhorar o gerenciamento do lodo em uma estação de tratamento de esgoto, uma opção que vem sendo amplamente discutida é o aproveitamento do biogás, produzido em reatores anaeróbios de fluxo ascendente de manta de lodo, para a secagem térmica do lodo. Nesse contexto, o presente trabalho vem relatar um estudo sobre a secagem térmica, de diferentes tipos de lodos, em um sistema piloto envolvendo o aproveitamento energético do biogás produzido em reatores anaeróbios de fluxo ascendente de manta de lodo, de uma estação de tratamento de esgoto de médio porte. O secador reduziu em aproximadamente 80% a massa dos diferentes tipos de lodos submetidos ao processo de secagem térmica, aumentando a concentração de sólidos totais nesses materiais de 20 para 80%. Os valores da demanda energética do secador para remoção de 1 kg de água presente nos diferentes tipos de lodos variaram de 1.195 a 1.323 kcal. Adicionalmente, as características microbiológicas dos diferentes tipos de lodos, após o processo de secagem, evidenciaram a possibilidade da utilização agrícola desses materiais. Esses resultados apontam a secagem térmica do lodo, utilizando biogás produzido em sistemas anaeróbios de tratamento, como uma promissora ferramenta para a sustentabilidade no setor de esgotamento sanitário brasileiro.
Contribución para el perfeccionamiento del diseño, la construcción y la operación de reactores UASB aplicados al tratamiento de aguas residuales urbanas-Parte 5: Biogás y emisiones fugitivas de metano Contribution for improving the design, construction and operation of UASB reactors treating sewage-Part 5: Biogas and fugitive methane emissions
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