Wastewater reuse in las tablas de daimiel national park by improving its quality through constructed wetlands

Abstract

The Tablas de Daimiel National Park (TDNP) is a floodplain wetland which covers 1928 ha, located in the Upper Guadiana Basin (14000 km2) over the West Mancha aquifer (5500 km2) in Central Spain. This aquifer has been subject to intensive pumpage since the late 1970s, resulting in the decrease of the phreatic level. Therefore, wetlands have been disconnected from the regional aquifer, producing serious environmental damage on TDNP. In this work, the efficiency of the reuse of treated sewage effluents (TSE) from 8 Wastewater Treatment Plants in the surroundings of the wetland is analysed. The quality of the TSE would be increased through the formation of several Constructed Wetlands, which would act as transition between the sewage plants and the natural wetland. Management of a freshwater National Park like this, threatened by drought, may be controversial. Although research about environmental management has been wide, there is a lack in terms of knowledge transfer concerning this management practices. A mass balance model for predicting efficiency of water recharge in the TDNP has been developed, considering several scenarios of meteorology, inputs and outputs. The modelling of the water conditions into the Created Wetlands has been also realized, in order to evaluate the viability of this system. The TSE available for the recharge of the TDNP has an approximate volume of 10 Mm3. Regarding the biochemical characteristics of these effluents, it is necessary around 150 ha of Constructed Wetlands to guarantee an acceptable water quality for this purpose. The modelling results demonstrated that in this site, with the present volume of reclaimed water, it is difficult to obtain a great inundated surface a cause of the increase of infiltration and evaporation with the inundated area, but this solution allows maintaining a considerable inundated surface throughout the year, with a seasonal comportment.