Avaliação do ciclo de vida regionalizada dos sistemas de tratamento de esgoto sanitário
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Data
2022-03-04
Autores
Teixeira, Rossana Borges
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Universidade Estadual Paulista (Unesp)
Resumo
A falta de tipos de tratamentos biológicos não é o motivo para o baixo índice de tratamento de esgoto no Brasil. O clima quente torna esses tratamentos mais eficientes em remoção de matéria orgânica, requerendo menores volumes. 3 tipologias dominam no Brasil: Lagoas de Estabilização (LE), Reator Anaeróbio de Fluxo Ascendente e Manta de Lodo (Reator UASB) e Lodos Ativados (LA). A LA, apesar de apresentar melhor eficiência de remoção de poluentes, demanda eletricidade e gera mais lodo. As outras duas tipologias, de baixa complexidade, não demandam eletricidade e materiais para as remoções, porém a LE demanda grandes áreas para construção. O Reator UASB, que é compacto e produz biogás, demanda um tratamento complementar. Assim, a hipótese é que as tipologias LE e Reator UASB sejam mais sustentáveis para o Brasil e outras regiões de clima quente. Entretanto, a sustentabilidade destas não são tão avaliadas quanto a LA. Para comparar os impactos ambientais destas 3 tipologias, aplicou-se a Avaliação de Ciclo de Vida (ACV) englobando os estágios de construção, operação, destinação de lodo e lançamento do esgoto tratado. Para obter resultados mais acurados, a Regionalização da ACV foi aplicada com o uso de dados primários e secundários brasileiros para o inventário, parâmetros de clima quente para o dimensionamento dos tratamentos, matriz elétrica brasileira e a versão para a América Latina do método Impact World+. A tipologia LA foi avaliada separadamente e em complemento ao Reator UASB (UASB+LA). A tipologia UASB+LA apresentou menos danos ambientais para as 2 áreas de proteção (AP), Saúde humana (SH) e Qualidade dos ecossistemas (QE) e a LA mais danos, ainda que usando métodos não regionalizados. A maior contribuição é devido aos metais no esgoto tratado e no lodo gerado, respectivamente, nas categorias Ecotoxicidade de Água Doce e Toxicidade Humana Não Cancerígena, ambas de Longo Termo. A construção, mesmo da tipologia mais tecnológica, LA, tem impactos significativos. Utilizar o lodo como biofertilizante aumenta os danos à saúde humana ao alterar o uso do solo de geral para agrícola. As tipologias dependentes de eletricidade, LA e UASB+LA, são mais sensíveis as: 1- alterações na matriz elétrica, com elevação dos danos devido a maior participação de fontes não renováveis (comprovando a importância da Regionalização), e 2- as quantidades consumidas de eletricidade na fase de operação. Porém não o suficiente para alterar a ordem de danos: LA > LE > UASB+LA, assim como no uso dos métodos globais IW+ e ReCiPe 2016. Apesar dos danos ambientais, todas as tipologias reduzem em aproximadamente 100% estes em comparação ao lançamento do esgoto sem tratamento para a QE, porém aumentam os danos para a AP SH. O método ReCiPe 2016 indica que a tipologia UASB+LA reduz os danos em comparação ao lançamento de esgoto sem tratamento, exceto para a AP Escassez de recursos. A tipologia UASB+LA é a menos danosas de acordo com a ACV Regionalizada num cenário Brasileiro. Recomenda-se esta tipologia, de simples operação e baixos custo, para a ampliação do tratamento de esgoto em regiões de clima quente.
The lack of biological wastewater treatment types is not the reason for the low index of safely treated sewage in Brazil. The warm climate turns those treatments more efficient in organic matter remotion, demanding smaller volumes. Three typologies corner this market: Stabilization Ponds (SP), Upflow Anaerobic Sludge Blanket (UASB), and Activated Sludge (AS). AS, although presents better pollutants remotion, requires electricity, and generates more sludge. The other two, low complexity ones, do not require electricity and materials to remotion, however, SP requires a large land surface. UASB, which is compact and produces biogas, demands a complementary treatment. Thus, the hypothesis is that the typologies SP and UASB are more sustainable for Brazil and other warm climate regions. Although, their sustainability is not frequently assessed as AS. To compare the environmental impacts of these three typologies, Life Cycle Assessment (LCA) was applied to construction, operation, sludge destination, and effluent discharge stages. To get more accurate results, LCA Regionalization was applied, Brazilian foreground and background data to inventory, warm climates parameters to construction sizing, Brazilian electricity matrix, and Latin American version of Impact World+ were used. AS typology was assessed lonely and as a supplement to UASB (UASB+AS). UASB+AS presented less environmental damage for the two Areas of protection (AOP), Human Health (HH) and Ecosystem Quality (EQ), and LA presented more damage, although using no regionalized methods. The great contribution is due to metals on effluent and sludge generated, respectively, in the categories Freshwater Ecotoxicity and Non-Cancer Human Toxicity, both in long term. Construction, though the more technological, AS, has significant impacts. Reusing sludge as a biofertilizer increases damage to human health because it changes soil uses from general to farm soil. The more power-dependent typologies, AS and UASB+AS, are more sensitive to 1- electrical matrix changes, damages variability related to matrix fossil fuel participation (as proof of Regionalization importance), and 2- power consumption during the operation stage. Although keeping the same damage order among systems: AS > SP > UASB+AS, in the same way when using non-regionalized methods Default IW+ and ReCiPe 2016. Despite the damage to the environment from domestic sewage treatments, all WWTPs assessed reduced by approximately 100% the damage caused by the release of untreated domestic sewage into water bodies for the AOP EQ, while these treatments increased damages to AOP HH. ReCiPe 2016 shows that UASB+AS reduces damages in comparison to the release of untreated sewage, except for AOP Resource Scarcity. UASB+LA is the less damage typology in accordance with this Regionalized LCA in a Brazilian scenario. This typology, of simple operation and small costs, is recommended to increase sewage treatment in warm climate regions.
The lack of biological wastewater treatment types is not the reason for the low index of safely treated sewage in Brazil. The warm climate turns those treatments more efficient in organic matter remotion, demanding smaller volumes. Three typologies corner this market: Stabilization Ponds (SP), Upflow Anaerobic Sludge Blanket (UASB), and Activated Sludge (AS). AS, although presents better pollutants remotion, requires electricity, and generates more sludge. The other two, low complexity ones, do not require electricity and materials to remotion, however, SP requires a large land surface. UASB, which is compact and produces biogas, demands a complementary treatment. Thus, the hypothesis is that the typologies SP and UASB are more sustainable for Brazil and other warm climate regions. Although, their sustainability is not frequently assessed as AS. To compare the environmental impacts of these three typologies, Life Cycle Assessment (LCA) was applied to construction, operation, sludge destination, and effluent discharge stages. To get more accurate results, LCA Regionalization was applied, Brazilian foreground and background data to inventory, warm climates parameters to construction sizing, Brazilian electricity matrix, and Latin American version of Impact World+ were used. AS typology was assessed lonely and as a supplement to UASB (UASB+AS). UASB+AS presented less environmental damage for the two Areas of protection (AOP), Human Health (HH) and Ecosystem Quality (EQ), and LA presented more damage, although using no regionalized methods. The great contribution is due to metals on effluent and sludge generated, respectively, in the categories Freshwater Ecotoxicity and Non-Cancer Human Toxicity, both in long term. Construction, though the more technological, AS, has significant impacts. Reusing sludge as a biofertilizer increases damage to human health because it changes soil uses from general to farm soil. The more power-dependent typologies, AS and UASB+AS, are more sensitive to 1- electrical matrix changes, damages variability related to matrix fossil fuel participation (as proof of Regionalization importance), and 2- power consumption during the operation stage. Although keeping the same damage order among systems: AS > SP > UASB+AS, in the same way when using non-regionalized methods Default IW+ and ReCiPe 2016. Despite the damage to the environment from domestic sewage treatments, all WWTPs assessed reduced by approximately 100% the damage caused by the release of untreated domestic sewage into water bodies for the AOP EQ, while these treatments increased damages to AOP HH. ReCiPe 2016 shows that UASB+AS reduces damages in comparison to the release of untreated sewage, except for AOP Resource Scarcity. UASB+LA is the less damage typology in accordance with this Regionalized LCA in a Brazilian scenario. This typology, of simple operation and small costs, is recommended to increase sewage treatment in warm climate regions.
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Palavras-chave
Regionalização, Tratamento de menor complexidade, Impacto ambiental, Inventário do Ciclo de Vida, ETE, Regionalization, Environmental impact, Life Cycle Inventory, Low complexity treatment, STP