Quality of Water Wells in an Agricultural Area in the City of La Plata,Argentina

The quality of the water from 62 home wells in a section (with no sewerage system) of the agricultural-industrial area of La Plata, was analyzed. The measurement of the studied parameters concentrations were compared with those obtained in seventeen water wells located in another area of town, with commercial characteristics. The pH, total dissolved salts (TDS), nitrates, chlorides, total hardness (TH) and coliform bacteria, these being differentiated between colifaecals and IAC group bacteria, were studied. The average concentration of TDS was 619 and 497 mg L^-1 respectively. 34% of the samples exceeded the limit of 45 mg L^-1 established by the World Health Organization (WHO). The nitrate levels varied widely from 6 to 216 mg L^-1, with an average value of 56 mg L^-1 in the agricultural area, and between 5 and 61 mg L^-1 in the commercial area, with an average of 19 mg L-1. The average concentrations of chlorides and TH were 89 mg L^-1 and 177 mg L^-1, respectively in the agricultural area; while in the other area, the average levels were 38 mg L^-1 chloride and 107 mg L^-1 TH. Significant differences were observed between the chemical parameters evaluated in the two areas analyzed. E. Coli bacterium was detected in 49% of the well water samples analyzed. IAC group bacteria were confirmed in 28% of the samples. The average depth of the water wells within 10 m from the cesspits was 28.2 m, and those situated farther than 10 m. had an average of 39.9 m depth. Results indicated a remarkable quality degradation of the well waters as regards their contents of E. Coli bacteria and nitrate. This could be due to the deficient construction of the absorption wells, to their closeness with cesspits and the inexistence of septic chambers within every dwelling.