Environmental Considerations on underground water Wells in La rioja, Argentina

CALBO, V.; FURLONG, O.; TORRES DE LUIGI, M.; MARCHEVSKY, E.;

BUENOS AIRES

Simposio; 5 ISEBE; 2016

CONICET, INTA, IMBE, CIC, UNIVER. NAC. SAN MARTIN

Recently, underground water studies were carried out in La Rioja within the framework of agreements with the World Bank. In these studies, two environmental issues to be considered were identified: the water quality against the rapid corrosion of pumping facilities in the capital city of La Rioja, and the disposal of waste from the inverse osmosis plants that are used to treat underground brackish water in some of the province departments. Regarding the first issue, an already concluded study detected that the premature deterioration of the pumping facilities is due to the MIC phenomenon (Microbiologically Induced Corrosion). Some signs of the MIC phenomenon in a well during its operation are the decrease of flow without a decrease in the phreatic level, and the alteration of the organoleptic quality of the water. Another sign appears during maintenance, in which the obstruction and embedding of filters and pressure pipes can be observed. These aforementioned signs are present in La Rioja.In order to confirm the MIC phenomenon and propose the necessary corrective measures, microbiological and optical microscopy tests were performed. Complementarily, scanning electron microscopy tests were performed as well.The microbiological cultures grown in liquid and solid media showed the presence of aerobic ferrobacteria (iron bacteria) and anaerobic sulfate-reducing bacteria, which is consistent with the MIC phenomenon.During this phenomenon, bacteria accelerate the metal corrosion of the facilities. The rusted and dissolved metal precipitates as bacterial metabolites in the form of biominerals. These biominerals have the same chemical composition as the iron minerals, but a peculiar structure is peculiar. The scanning electron microscopy performed on the embedded samples detected the organic morphology of the mineral, and the energy dispersive spectrometer detected the spectrum of the iron oxides.The MIC phenomenon is confirmed, so that corrective and preventive measures are required, since it is possible that the bacteria are nonnative and reach the aquifers by contamination. These bacteria produce endospores when their environment is adversely altered, and reactivate when the conditions become adequate once again. The spores can contaminate the drilling equipment, which in turn, can inoculate them in another aquifer.In regard to the second issue, it is still under study. A priori, two alternatives are being considered for the disposal of the brackish water: natural evaporation in the case of facilities with low capacity, and the disposal in deep perforations or very salty waters in the case of facilities with higher capacity. Keywords: Environment, Underground, Water, La Rioja