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Otimização da codigestão anaeróbia de Lamas Mistas de ETAR com diferentes proporções de Águas Ruças
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A presente dissertação tem por base a ETAR da Fonte Quente (Abrantes), no que res-peita às suas condições de codigestão anaeróbia de Lamas Mistas (LM), provenientes do tra-tamento das águas residuais e Águas Ruças (AR), provenientes dos lagares de azeite da re-gião. As AR são rececionadas na ETAR e armazenadas num tanque a céu aberto. Vão sendo depois bombadas e misturadas com as LM, numa proporção de aproximadamente 4% (v/v) para a codigestão anaeróbia.
Foi estudada a influência de diferentes proporções de AR (2, 4 e 8% v/v) na codigestão com LM produzidas na ETAR no processo de codigestão e rendimento em biogás e metano (CH4).
Os ensaios decorreram num digestor com um volume útil de 2,70 L, operado em condi-ções mesófilas (35 ± 1°C) e com um Tempo de Retenção Hidráulico (TRH) de 25 dias. A ali-mentação foi efetuada por impulso (alimentações discretas), em 3 dias uteis por semana (com 257 ml/dia de alimentação).
Os resultados mostraram que o ensaio de codigestão de 98%LM + 2% (v/v) de AR con-tribuiu para um aumento do rendimento de biogás e CH4, destacando-se significativamente do ensaio de controlo (100% LM v/v), com um rendimento de 353 L/kg SVaplicados em biogás, 1,9 vezes superior ao ensaio de controlo e 268 L/kg SV aplicados em CH4, 1,8 vezes superior ao ensaio de controlo. A eficiência de remoção em CQOs, com valores entre 72,14 e 84,65%, bem como o um teor de CH4 entre 76,12 e 78,21% (v/v), não indicaram diferenças significativas entre os ensaios, mas demonstraram uma atividade eficaz por parte do consórcio anaeróbio, durante o processo de digestão e codigestão.
Não se verificaram diferenças significativas no Poder Calorífico Inferior (PCI), com va-lores entre 27,40 e 28,16 MJ/m3.
The present dissertation is based on the Fonte Quente, Wastewater Treatment Plant (WWTP), regarding the co-digestion conditions of mixed sludge produced from the wastewater treatment and Olive Mill Wastewater (OMW) from olive oil production plants located in the region. The WWTP receives the OMW which is then stored in a reservoir. For several month this wastewater is added to the mixed sludge in a proportion of 4% (v/v) to be co-digested. In order to optimize the effect of OMW in the co-digestion process, when it comes to the biogas and methane yields, three experiments were done with mixed sludge and different proportions of OMW (2, 4 and 6% v/v). For this study, a digester with a working volume of 2,70 L was used and was operated in mesophilic conditions (35 ± 1°C). The feeding was done by impulse (discreet feedings), only three days per week (257 ml/day) with a hydraulic retention time of 25 days for each experi-ment. The co-digestion experiments showed that the 98% mixed sludge + 2% (v/v) AR co-di-gestion assay was the best result, showing a significantly higher biogas and CH4 yields (352 L/kg SV added and 268 L/kg SV added, respectively), 1.9 e 1.8 times higher compared to the digestion control assay (100% mixed sludge). The Dissolved Chemical Oxygen demand (d-COD) removal efficiency, with values between 72.14 and 84.65% and the CH4 content between 76,12 and 77,21% (v/v), didn't Indicate significant differences between the assays, however the results showed an effective activity of the bacterial consortium in the digestion and codiges-tion process. Concerning the Lower Heating Value (LHV), the results showed no significant differ-ences between the assays with values between 27 and of 28.16 MJ/m3.
The present dissertation is based on the Fonte Quente, Wastewater Treatment Plant (WWTP), regarding the co-digestion conditions of mixed sludge produced from the wastewater treatment and Olive Mill Wastewater (OMW) from olive oil production plants located in the region. The WWTP receives the OMW which is then stored in a reservoir. For several month this wastewater is added to the mixed sludge in a proportion of 4% (v/v) to be co-digested. In order to optimize the effect of OMW in the co-digestion process, when it comes to the biogas and methane yields, three experiments were done with mixed sludge and different proportions of OMW (2, 4 and 6% v/v). For this study, a digester with a working volume of 2,70 L was used and was operated in mesophilic conditions (35 ± 1°C). The feeding was done by impulse (discreet feedings), only three days per week (257 ml/day) with a hydraulic retention time of 25 days for each experi-ment. The co-digestion experiments showed that the 98% mixed sludge + 2% (v/v) AR co-di-gestion assay was the best result, showing a significantly higher biogas and CH4 yields (352 L/kg SV added and 268 L/kg SV added, respectively), 1.9 e 1.8 times higher compared to the digestion control assay (100% mixed sludge). The Dissolved Chemical Oxygen demand (d-COD) removal efficiency, with values between 72.14 and 84.65% and the CH4 content between 76,12 and 77,21% (v/v), didn't Indicate significant differences between the assays, however the results showed an effective activity of the bacterial consortium in the digestion and codiges-tion process. Concerning the Lower Heating Value (LHV), the results showed no significant differ-ences between the assays with values between 27 and of 28.16 MJ/m3.
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Palavras-chave
Águas Ruças Biogás Codigestão Estação de Tratamento de Águas Re-siduais (ETAR) Lamas Mistas Metano