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Otimização do funcionamento de um reator biológico aeróbio do tipo SBR
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Advisor(s)
Abstract(s)
A dissertação realizou-se na Estação de Tratamento de Água Residual (ETAR) de Paço de
Sousa, detida pela SIMDOURO, tendo como objetivo principal a otimização da eficiência do
tratamento secundário da água residual, realizado em reatores do tipo RDS, relativamente aos
parâmetros carência química de oxigénio (CQO), carência bioquímica de oxigénio (CBO5), e
azoto total (Ntotal).
De forma a alcançar o objetivo proposto inicialmente realizou-se um diagnóstico do
funcionamento do tratamento secundário da ETAR através da recolha e análise dos dados
históricos analisando os caudais, concentrações e cargas de vários parâmetros característicos
deste processo de tratamento. A partir desses dados verificou-se que os parâmetros operatórios
carga orgânica mássica (F/M), carga orgânica volúmica (Cv), idade das lamas (ϴx) e índice
volumétrico de lamas (IVL) não se encontravam com valores próximos ao expectável e
projetado. Verificaram-se também elevadas eficiências de remoção de CBO5, CQO e sólidos
suspensos totais (SST) com valores de 85±15, 76±17 e 89±9%, respetivamente. Contrariamente
as eficiências de remoção de Ntotal, NH4
+
e fósforo total (Ptotal), com valores de 14±54, 6±62 e
36±53%, respetivamente, apresentam valores reduzidos face ao esperado. Os efluentes
descarregados durante esse período cumpriram os valores limite de emissão (VLE)
estabelecidos pelo Decreto-Lei nº 152/97 relativamente aos parâmetros CQO, CBO5 e SST,
sendo cumprida a atual licença de descarga. O mesmo não se observou quanto aos parâmetros
Ntotal, NH4
+
e Ptotal. Com base nestes resultados considera-se que a ETAR terá de fazer alguns
ajustes operacionais de forma cumprir os VLE de uma futura legislação aplicável com a
possível atualização da classificação do Rio Sousa como uma zona sensível. Concluiu-se
também que o arejamento nos Cyclor é insuficiente, comprometendo a remoção de alguns
poluentes, e que o tratamento terciário por desinfeção UV é ainda inviável dado que o efluente
do tratamento secundário se caracteriza por valores de transmitância superiores a 40%.
Foram realizadas 4 campanhas de amostragem no Cyclor A com o objetivo de fazer uma
avaliação inicial do seu funcionamento e posteriormente o otimizar. Assim, através da alteração
do set-point da sonda de medição de oxigénio dissolvido (OD) de 1,2 para 1,5 mg O2/L
conseguiu-se uma melhoria significativa das eficiências de remoção de CBO5, Ntotal, NH4
+
, Ptotal
nos ciclos analisados, atingindo-se valores médios de 98, 89, 97 e 75%, respetivamente.
The dissertation was carried out at the Paço de Sousa Wastewater Treatment Plant (WWTP), owned by SIMDOURO, with the main objective of optimizing the efficiency of secondary wastewater treatment, carried out in SBR-type reactors, regarding to the parameters chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and total nitrogen (Ntotal). To achieve the proposed objective, a diagnosis of the operation of the WWTP's secondary treatment was initially carried out through the collection and analysis of historical data, analyzing the flow rates, concentrations and loads of various parameters characteristic of this treatment process. Based on this data, it was found that the operating parameters mass organic load (F/M), volume organic load (Cv), sludge age (ϴx) and sludge volumetric index (IVL) were not close to the expected and projected values. There were also high removal efficiencies for BOD5, COD and total suspended solids (TSS) with values of 85±15, 76±17 and 89±9%, respectively. On the other hand, the removal efficiencies for Ntotal, NH4 + and total phosphorus (Ptotal), with values of 14±54, 6±62 and 36±53%, respectively, were lower than expected. The discharged effluent during this period complied with the emission limit values (ELVs) established by Decree-Law nº. 152/97 for the COD, BOD5 and TSS parameters, whereas the current discharge permit was accomplished. The same was not observed for the Ntotal, NH4 + and Ptotal parameters. Based on these results, it is proved that the WWTP will have to make some operational adjustments to comply with the ELVs of future applicable legislation with the possible updating of the classification of the river Sousa as a sensitive area. It was also concluded that aeration in the Cyclor is insufficient, compromising the removal of some pollutants, and that tertiary treatment by UV disinfection is still unfeasible given that the effluent from secondary treatment is characterized by transmittance values of over 40%. Four sampling campaigns were carried out in Cyclor A with the aim of making an initial assessment of its operation and subsequently proceeding its optimization. By changing the set point of the dissolved oxygen (DO) measuring probe from 1,2 to 1,5 mg O2/L, a significant improvement was achieved in the removal efficiencies of BOD5, Ntotal, NH4 + and Ptotal in the cycles analyzed, reaching average values of 98, 89, 97 and 75%, respectively.
The dissertation was carried out at the Paço de Sousa Wastewater Treatment Plant (WWTP), owned by SIMDOURO, with the main objective of optimizing the efficiency of secondary wastewater treatment, carried out in SBR-type reactors, regarding to the parameters chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and total nitrogen (Ntotal). To achieve the proposed objective, a diagnosis of the operation of the WWTP's secondary treatment was initially carried out through the collection and analysis of historical data, analyzing the flow rates, concentrations and loads of various parameters characteristic of this treatment process. Based on this data, it was found that the operating parameters mass organic load (F/M), volume organic load (Cv), sludge age (ϴx) and sludge volumetric index (IVL) were not close to the expected and projected values. There were also high removal efficiencies for BOD5, COD and total suspended solids (TSS) with values of 85±15, 76±17 and 89±9%, respectively. On the other hand, the removal efficiencies for Ntotal, NH4 + and total phosphorus (Ptotal), with values of 14±54, 6±62 and 36±53%, respectively, were lower than expected. The discharged effluent during this period complied with the emission limit values (ELVs) established by Decree-Law nº. 152/97 for the COD, BOD5 and TSS parameters, whereas the current discharge permit was accomplished. The same was not observed for the Ntotal, NH4 + and Ptotal parameters. Based on these results, it is proved that the WWTP will have to make some operational adjustments to comply with the ELVs of future applicable legislation with the possible updating of the classification of the river Sousa as a sensitive area. It was also concluded that aeration in the Cyclor is insufficient, compromising the removal of some pollutants, and that tertiary treatment by UV disinfection is still unfeasible given that the effluent from secondary treatment is characterized by transmittance values of over 40%. Four sampling campaigns were carried out in Cyclor A with the aim of making an initial assessment of its operation and subsequently proceeding its optimization. By changing the set point of the dissolved oxygen (DO) measuring probe from 1,2 to 1,5 mg O2/L, a significant improvement was achieved in the removal efficiencies of BOD5, Ntotal, NH4 + and Ptotal in the cycles analyzed, reaching average values of 98, 89, 97 and 75%, respectively.
Description
Keywords
WWTP activated sludge DO nitrogen removal nutrient removal