A YEAR OF MONTHLY MONITORING WATER FOR HUMAN CONSUMPTION IN A REGION WITH HIGH AGRICULTURAL AND FARMING IMPACT IN SALTA, ARGENTINA.

MERCEDES CECILIA CRUZ, DOLORES GUTIÉRREZ CACCIABUE, OSCAR GAMBONI, LUIS CÉSAR ROMERO, MARÍA SOLEDAD VICENTE, ELIO EMILIO GONZO, AND VERÓNICA BEATRIZ RAJAL

NAXOS ISLAND, GRECIA

Simposio; 15TH INTERNATIONAL SYMPOSIUM ON HEALTH RELATED WATER MICROBIOLOGY; 2009

This study was performed in a semirural area to the west of the Salta city in the northwest of Argentina, which is crossed by the Arenales River. The river is used as a water source for a drinking water plant, for agricultural irrigation, and for livestock maintenance. The poor water quality of the river and an associated irrigation channel were reported previously together with high incidence rates of diarrhea in the area (Rajal et al, 2009). The region is agriculture intensive, and there are many farms (mainly poultry) on the margins of the river and the channel that were identified as sources of pollution (Gil et al, 2009). The drinking water plant provides water for the local municipalities. As tap water provision is intermittent during the day (just for a few hours), people usually also use groundwater supplied from wells that are not deep enough --less than 10 m-- to ensure the absence of microbial contamination. Our hypothesis was that due to the soil characteristics the impact of land use would strongly affect the water table aquifer with high nitrate and ammonia concentrations from agriculture and farms, as well as high coliform counts due to the proximity of septic tanks.  The aim of this study was to determine the quality of groundwater intended for human consumption in the region to test the hypothesis. Two wells were selected for this study: one from a private home (called well P), located immediately in front of a poultry farm, and the other from the school of the area (called well E), where children spend the day and eat there. For comparison, two additional samples were analyzed: One from the Arenales River as it enters the area of study (just before water is diverted to the irrigation channel, so before it receives the impact of all the agricultural activities) and the other from the irrigation channel (after the water has passed through two poultry farms and through illegal solid waste dumps), which provides water to the drinking water plant.Water samples from the two wells, the river and the channel (during the times of the year that it had water flowing) were analyzed monthly for an entire year. Temperature, pH, conductivity, salinity, turbidity, and dissolved oxygen were measured in situ. Suspended, dissolved, and total solids, nitrates, ammonia, carbonates, bicarbonates, hardness (as calcium carbonate), magnesium and calcium were determined in the laboratory to complete the physicochemical characterization. The microbiological quality of the water was assessed by determination of total and fecal coliforms bacteria. Our results are shown in Table 1.Table 1. Characterization of the Arenales River and the Irrigation Channel as surface water, and of two wells (P and E) as groundwater, in two seasons: dry (from April to October) in square brackets and wet (from November to March), expressed as ranges (minimum-maximum).Both wells showed consistent results and were clearly different from the river for pH, conductivity, dissolved oxygen, calcium, magnesium, and bicarbonates. Ammonia and nitrates showed much higher values for groundwater due to the impact of land activities. Microbiological quality of the river was generally better than the wells. This is especially apparent when the concentration of fecal coliforms is analyzed: ten of twelve measurements were lower for the river than for groundwater. Well P was highly impacted by proximity to the poultry farm, especially when the rainy season started. Of great concern is that none of the samples intended for human consumption achieved the quality required by the Argentinean Alimentary Code for drinking water. Well E served a school that hundreds of children attended; thus the children were exposed to drinking water with high coliforms counts and potentially affected by any waterborne disease present. As a result of these studies the school now uses water from a different source for cooking and for direct consumption. A suitable system for disinfection by ultrafiltration of water is currently under study to be installed there.