Estudo de Bacias de Retenção / Tratamento em Auto-Estradas - Caso da A24
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2010
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Ao longo dos tempos, a degradação das águas superficiais e subterrâneas tem vindo a
aumentar devido a várias fontes de poluição. Entre estas, pode-se destacar a água proveniente
de infra-estruturas rodoviárias, dado que nestas escorrências se encontram diluídos e em
suspensão poluentes. Estes poluentes estão associados, fundamentalmente, ao tráfego e
desgaste automóvel, tal como ao tipo de via e infra-estruturas nela instaladas, sendo mais
gravoso quando a descarga destas escorrências é efectuada em zonas sensíveis.
Para mitigar este tipo de impactes no meio hídrico e solos, procede-se à implementação de
sistemas de tratamento dessas águas de escorrência. Os sistemas de tratamento habitualmente
implementados são os sistemas secos ou os sistemas húmidos. Os sistemas secos podem ser
com coberto vegetal, por infiltração/filtração em bacias de infiltração, pavimentos porosos e
pavimentos reservatório. Os sistemas húmidos são por retenção e detenção em lagoas ou
bacias, ou por aplicação em zonas húmidas. No caso das bacias de retenção/ tratamento, estas
são dimensionadas de forma a receberem as águas de escorrência dessas infra-estruturas,
armazenando-as durante um determinado período de tempo, para que ocorra uma redução da
concentração dos poluentes afluentes à bacia, antes da água ser encaminhada para o seu
destino final, geralmente uma linha de água.
Tendo em conta esta problemática, os objectivos desta dissertação consistem no estudo dos
aspectos relacionados com o dimensionamento das bacias de retenção/tratamento e no
levantamento de casos de estudo no mesmo âmbito, para desta forma se avaliarem os
parâmetros escolhidos na monitorização de cinco bacias de retenção/tratamento instaladas no
sublanço E1 da auto-estrada A24. Também será efectuada uma análise das concentrações de
poluentes à saída dessas bacias, comparando-as com valores de outros casos de estudo e com
a legislação em vigor, bem como a avaliação da concentração de poluentes a estas associada.
Proceder-se-á ainda à determinação das suas eficiências, tendo em conta as concentrações de
poluentes presentes nas águas de escorrência à entrada e à saída.
Dado que a presença destes poluentes está relacionada, fundamentalmente, com a intensidade
de precipitação e com o volume de tráfego da infra-estrutura viária, para atingir os objectivos
supracitados foi efectuado um levantamento da precipitação e tráfego médio diário (TMD)precedente a cada campanha de monitorização, para desta forma se poder relacionar e avaliar
a relação das concentrações de poluentes com o TMD e com a precipitação.
As concentrações dos poluentes à saída das bacias, foram comparadas com os valores limite
de emissão (VLE) para descarga de águas residuais, com os valores máximos admissíveis
(VMA) e com os valores máximos recomendados (VMR) para águas destinadas à rega, do
Decreto-Lei 236/98, tendo-se concluído que as concentrações à saída cumprem estes limites,
não havendo necessidade de se recorrer a formas de mitigar o seu impacte no meio hídrico,
nomeadamente a zona de Protecção dos Aquíferos.
Over time, the degradation of surface and groundwater has been increasing due to various pollution sources. Among these, one can highlight the water from the road infrastructures, since in these are diluted runoff and particulate pollutants. These pollutants are associated, primarily, to automotive traffic and wear, as to the type of road and infrastructure installed in it, being more drastic when the discharge of such runoff is carried out in sensitive areas. To mitigate such impacts on the aquatic environment and soils, it proceeds to the implementation of systems for treatment of groundwater runoff. The usually implemented treatment systems are dry systems or wet systems. The dry systems can be with vegetation covering, percolation/filtration in infiltration basins, porous pavements and reservoir pavements. Wet systems are for retention and detention ponds or basins, or for use in wetlands. In the case of the detention/treatment basins, they are scaled so that they receive the water runoff of these infrastructures, storing them for a certain period of time to be decreased the concentration of pollutants flowing into the basin before the water is routed to its final destination, usually a water line. Given this problem, the objectives of this thesis are to study aspects related to the design of detention /treatment basins and to collect case studies in the same scope to be this way assessing the parameters chosen for the monitoring of five detention/treatment basins installed in subsection E1 of the A24 highway. It will also be made an examination of the pollutant concentrations at the exit of these basins, comparing them with values of other case studies and legislation, as well as evaluating the concentration of pollutants associated with these. It will also be determined its efficiency, taking into account the concentrations of pollutants in water runoff at the entry and exit. Since the presence of these pollutants is related mainly with the rainfall and the volume of traffic on road infrastructure, to achieve the above objectives was carried out a survey of precipitation and average daily traffic (ADT) each year preceding the monitoring, thus being able to relate and evaluate the relationship of pollutant concentrations with the ADT and the precipitation.The concentrations of pollutants to the watershed outlet, were compared with the emission limit values (ELVs) for discharging wastewater, with the maximum allowable values (MAV) and with the maximum recommended values (MRV) for water intended for irrigation of the Decree-Law 236/98, concluding that concentrations outside meet these limits, and that there is no need to resort to ways of mitigating their impact on the aquatic environment, namely the zone of protection of the aquifers.
Over time, the degradation of surface and groundwater has been increasing due to various pollution sources. Among these, one can highlight the water from the road infrastructures, since in these are diluted runoff and particulate pollutants. These pollutants are associated, primarily, to automotive traffic and wear, as to the type of road and infrastructure installed in it, being more drastic when the discharge of such runoff is carried out in sensitive areas. To mitigate such impacts on the aquatic environment and soils, it proceeds to the implementation of systems for treatment of groundwater runoff. The usually implemented treatment systems are dry systems or wet systems. The dry systems can be with vegetation covering, percolation/filtration in infiltration basins, porous pavements and reservoir pavements. Wet systems are for retention and detention ponds or basins, or for use in wetlands. In the case of the detention/treatment basins, they are scaled so that they receive the water runoff of these infrastructures, storing them for a certain period of time to be decreased the concentration of pollutants flowing into the basin before the water is routed to its final destination, usually a water line. Given this problem, the objectives of this thesis are to study aspects related to the design of detention /treatment basins and to collect case studies in the same scope to be this way assessing the parameters chosen for the monitoring of five detention/treatment basins installed in subsection E1 of the A24 highway. It will also be made an examination of the pollutant concentrations at the exit of these basins, comparing them with values of other case studies and legislation, as well as evaluating the concentration of pollutants associated with these. It will also be determined its efficiency, taking into account the concentrations of pollutants in water runoff at the entry and exit. Since the presence of these pollutants is related mainly with the rainfall and the volume of traffic on road infrastructure, to achieve the above objectives was carried out a survey of precipitation and average daily traffic (ADT) each year preceding the monitoring, thus being able to relate and evaluate the relationship of pollutant concentrations with the ADT and the precipitation.The concentrations of pollutants to the watershed outlet, were compared with the emission limit values (ELVs) for discharging wastewater, with the maximum allowable values (MAV) and with the maximum recommended values (MRV) for water intended for irrigation of the Decree-Law 236/98, concluding that concentrations outside meet these limits, and that there is no need to resort to ways of mitigating their impact on the aquatic environment, namely the zone of protection of the aquifers.
Descrição
Dissertação de Mestrado em Engenharia Civil