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Wastewater Reuse in the Llobregat: The Experience at the Prat de Llobregat Treatment Plant

Abstract:

Water scarcity is a consequence of both natural and anthropogenic factors including highly variable temporal and spatially heterogenic distribution of precipitations, growing populations, increasing water demand particularly for agriculture, and the widespread contamination of water resources by a plethora of organic and inorganic contaminants. In the countries bordering the Mediterranean Sea, water is a renewable resource relatively scarce during certain periods. Therefore, sustainable management of water resources is of utmost importance in these countries. In Catalonia a Mediterranean region located in the northeast of Spain, the reuse of tertiary treated wastewater is evaluated as alternative resource for water supply. On this basis, several campaigns on water reuse were conducted by the Catalan Water Agency in order to artificially enhance the flow along the river. In fall of 2009, the impact of tertiary treated effluent discharge on the ecology (pathogens and indicators, macroinvertebrate community assemblages, and biomarkers) and water quality of the river (priority and emerging pollutants: polar pesticides, illicit drugs, estrogens and pharmaceuticals as well as on the pathogens and microbial indicators of faecal contamination) and consequently to the drinking water supplies was evaluated in the lower stretch of the Llobregat River located in the vicinity of the town of Barcelona (NE Spain). The key findings of this study are reported in this book chapter. Chemical parameters were not significantly affected by the reclaimed water discharge with the exception of a slight increase in the ammonium concentration, conductivity, and TOC. Concerning priority substances, three pesticides increased in concentration but only diazinon exceed the quality threshold for human supply. Regarding the ecotoxicological assessment of illicit drugs and pharmaceuticals using algae for the toxicity value, differences between river upstream and downstream to the discharge of the treated tertiary wastewater were detected. For the other organisms the differences were imperceptibles. No perceptible effects were detected either in the ecological status of the river or in the load of pathogens and fecal indicators of the river water. In conclusion, the use of tertiary treated effluent for water reuse did not produce important alterations on river water quality downstream of the reclaimed water discharge.