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Abstract(s)
As preocupações com questões relativas à preservação ambiental tornaram-se mais pertinentes com a crescente industrialização e consequente urbanização. Os resíduos e as águas residuais originados nestas actividades têm que ser geridos de forma adequada, como é o caso das ETAR, caso contrário contribuem para diversos problemas ambientais como o aquecimento global. Actualmente, as lamas produzidas nas ETAR podem ser transformadas em biogás através da digestão anaeróbia. A optimização deste processo é desejável, no entanto a quantidade de lamas produzida já não apresenta na actualidade um grande potencial de crescimento em volume (ou massa), uma vez que a infra-estruturação do país está consolidada. Há, no entanto, uma oportunidade de identificar potenciais de optimização e valorização das etapas de digestão anaeróbia nas ETAR quer seja por optimizações de operações e/ou processos, quer seja pela realização da co-digestão anaeróbia das lamas com outros substratos.
No presente trabalho pretendeu-se realizar um levantamento das principais ETAR de Portugal com tratamento das lamas por digestão anaeróbia. Face ao elevado número de instalações foram seleccionadas seis ETAR da Região Centro e Sul. Analisando os resultados verificou-se que apenas uma das ETAR apresenta capacidade para co-digestão anaeróbia. Assim, optou-se por estudar a hipótese de melhorar o pré-tratamento das lamas, nomeadamente com incrementos no teor de sólidos totais (ST), de mais 1 e 2 % ST e de duas vezes o teor de ST das lamas (Cenário I). Posteriormente avaliou-se a introdução de substratos, seleccionados entre os disponíveis em Portugal, fracção orgânica dos resíduos sólidos urbanos (FORSU), chorume de suinicultura e resíduos alimentares (frutas e legumes) (Cenário II). Verificou-se que com a co-digestão desses substratos com as lamas é possível uma produção média de biogás de 1 400 – 36 200 m3/d, ou seja, até três vezes superior à quantidade obtida só com lamas. Assim, foi possível uma produção de energia nas ETAR de 1 130 – 70 870 kWh/d.
A eficiência de cogeração de energia de biogás é de 30%, pelo que a substituição dos equipamentos de co-geração existentes nas ETAR deve ser equacionada, por forma a possibilitar ganhos significativos de energia. É ainda de referir a significativa perda de energia na forma de calor. No total da energia consumida pelas ETAR, a energia do biogás representa cerca de 10 a 30%, podendo chegar a cerca do dobro com a co-digestão e reduzir significativamente a contribuição para os gases com efeito estufa.
Concerns with environmental preservation issues have become more relevant with increasing industrialization and urbanization. And the waste and wastewater from these activities have to be managed properly, as in the case of WWTP otherwise they contribute to various environmental problems such as global warming. Nowadays, the sludge produced at WWTP can be transformed into biogas through anaerobic digestion. The optimization of this process is desirable, however, the quantity of sludge produced no longer presents a great growth potential in volume (or mass), once the country's infrastructure is consolidated. However, there is an opportunity to identify potentials for optimization and valorization of the anaerobic digestion stages in the WWTP, either by optimization of operations and/or processes, such as thickening pre-treatment and operating conditions, such as temperature and pH, or by performing the sludge anaerobic co-digestion with other substrates. In the present work it was intended to carry out a survey of the main WWTP of Portugal with sludge treatment by anaerobic digestion. Because of the high number of facilities, six WWTP were selected in the Central and South Regions. By analyzing the results, it was possible to verify that only one of the WWTP has the capacity for anaerobic co-digestion. Therefore, it was decided to study the possibility of improving sludge pretreatment, in particular with increases in total solids (TS) content of 1 and 2 % TS and twice the TS sludge content of (Scenario I). Afterwards, the introduction of specific substrates was selected, among those available in Portugal, organic fraction of the municipal solid waste (OFMSW), pig slurry and food wastes (fruits and vegetables) (Scenario II). It has been found that with the anaerobic co-digestion of these substrates and sludge allows an average biogas production of 1 400 – 36 200 m3/d, representing three times more than the amount obtained with sludge alone. Thus, an energy generation of 1 130 - 70 870 kWh/d was possible in the WWTP. The biogas energy cogeneration efficiency represents around 30%. Therefore, the replacement of existing cogeneration equipment in the WWTP must be considered in order to allow significant energy gains. It is also worth mentioning the significant energy loss in the form of heat. In the total energy consumed by the WWTP, the biogas energy represents about 10 to 30 %, being able to reach about double with the co-digestion and significantly reduce the contribution to greenhouse gases.
Concerns with environmental preservation issues have become more relevant with increasing industrialization and urbanization. And the waste and wastewater from these activities have to be managed properly, as in the case of WWTP otherwise they contribute to various environmental problems such as global warming. Nowadays, the sludge produced at WWTP can be transformed into biogas through anaerobic digestion. The optimization of this process is desirable, however, the quantity of sludge produced no longer presents a great growth potential in volume (or mass), once the country's infrastructure is consolidated. However, there is an opportunity to identify potentials for optimization and valorization of the anaerobic digestion stages in the WWTP, either by optimization of operations and/or processes, such as thickening pre-treatment and operating conditions, such as temperature and pH, or by performing the sludge anaerobic co-digestion with other substrates. In the present work it was intended to carry out a survey of the main WWTP of Portugal with sludge treatment by anaerobic digestion. Because of the high number of facilities, six WWTP were selected in the Central and South Regions. By analyzing the results, it was possible to verify that only one of the WWTP has the capacity for anaerobic co-digestion. Therefore, it was decided to study the possibility of improving sludge pretreatment, in particular with increases in total solids (TS) content of 1 and 2 % TS and twice the TS sludge content of (Scenario I). Afterwards, the introduction of specific substrates was selected, among those available in Portugal, organic fraction of the municipal solid waste (OFMSW), pig slurry and food wastes (fruits and vegetables) (Scenario II). It has been found that with the anaerobic co-digestion of these substrates and sludge allows an average biogas production of 1 400 – 36 200 m3/d, representing three times more than the amount obtained with sludge alone. Thus, an energy generation of 1 130 - 70 870 kWh/d was possible in the WWTP. The biogas energy cogeneration efficiency represents around 30%. Therefore, the replacement of existing cogeneration equipment in the WWTP must be considered in order to allow significant energy gains. It is also worth mentioning the significant energy loss in the form of heat. In the total energy consumed by the WWTP, the biogas energy represents about 10 to 30 %, being able to reach about double with the co-digestion and significantly reduce the contribution to greenhouse gases.
Description
Trabalho final de mestrado para a obtenção do grau de Mestre em Engenharia Civil, perfil de Hidráulica
Keywords
Lamas WWTP sludge Digestão anaeróbia Anaerobic digestion Biogás Biogas Valorização energética Energetic valorization Co-geração Co-generation
Citation
ALVES, Fernando Ferreira Pinto - Avaliação do potencial de optimização energética da digestão anaeróbia de lamas de ETAR. Lisboa: Instituto Superior de Engenharia de Lisboa, 2018. Dissertação de mestrado.
Publisher
Instituto Superior de Engenharia de Lisboa