The objective of LIFE ECOGRANULARWATER project is to demonstrate a new treatment system, low-cost and environmentally friendly, based on biological methods and powered by solar energy, for the purification of groundwater, polluted by nitrates, intended for human consumption. With this aim, the installation of a full-scale plant in Torre-Cardela (760 inhabitants; Granada, Spain) has been carried out, where high nitrates contents have been reported from the 1990s. It is expected that the new plant will achieve the same results (water suitable for human consumption) but with an improved cost-effectiveness ratio in the production process than the current treatment (reverse osmosis).
The study of groundwater characteristics is essential, in order to improve the efficiency of the new treatment proposed. For this reason, a comprehensive characterization of the aquifer (Calcarenitas de Torrecardela, ES050MSBT000054106) that supply the municipality has been carried out, through reliable groundwater sampling campaigns.
Main lithologies present on the studied groundwater body are calcarenites, bioclasts sandstones and marls, Eocene-Oligocene, affected by faulting and bending. The resulting aquifer is fissured-karstic, classified as moderate productivity and with a good global status (Hydrological Basin Plan of the Guadalquivir river basin).
Sampling campaigns were carried out from February to December (2018). Water samples were collected from springs, supply wells and boreholes, on which pesticides, predominant cations and anions, and nitrates have been analysed.
Interpretation of the hydrochemical data results indicated that the main hydrochemical facies was calcium-bicarbonate and nitrates concentration varied on those months between 0.4-105 mg/L, although on samples from the main supply well ranged between 23-84 mg/L. Regarding the content of pesticides, only two substances were detected above 0.100 μg/L (diphenylamine and fluazifop) at two different sampling points (springs). In general, the load of organic pollutants was low (from 0.072 to 0.474 μg/L).
Higher nitrates contents have been detected after rainfall events that took place after olive trees crops fertilization periods (main economic activity of area inhabitants). Therefore, fluctuations were consequence of the combination of crops fertilization cycles and rainfall events, that allowed the percolation of the nitrogen excess accumulated in the soil to the water table.
In conclusion, it is essential to anticipate these nitrates concentration variations in order to adapt the operational tasks of the full-scale plant to improve the bioreactor working and produce water suitable for human. For this reason, nitrate contents in raw water will be monitored in the facility itself, in order to adjust the cycles/turnover time of treatment depending on nitrates contents. These biological analyses are in progress. At the end of this part, the project purpose will be reached, a replicable and low-cost drinking water treatment, affordable for small communities, and with easy operating and maintenance tasks.