摘要
This study traces both the long-term deterioration of the ground water supply in two neighboring villages that had relied upon cesspits/cesspools for waste disposal, as well as the subsequent progressive improvement to original water quality levels. The rapid improvement is attributed to the replacement of the cesspits by a central sewage disposal network. In each of the villages of Kefar Bara and Kefar Kassem, a single, relatively deep, community well supplies drinking water. These wells were drilled into the underlying carbonate Judea Group aquifer that initially provided very high quality potable water. Over time, large increases in the nitrate contamination, reaching to as high as 67 mg/L nitrate, paralleled the population growth. The higher dissolved nitrate concentrations were also marked by enrichments in the δ15 N (approximately 8 ‰(air)) values above those of the surrounding and regional uncontaminated background δ15 N values (in the range of 3 to 6 ‰ (air)). Within several years after the cesspit disposal was terminated the nitrate values declined to concentrations that were reported (approximately 25 mg/L-NO3) decades prior, when the water quality monitoring had just commenced. This study demonstrates not only how water quality can degrade but also how it can be restored once the problem is identified and countered. This simple method of ameliorating a water quality problem that was tending towards reaching serious proportions would seem to be quite efficacious for any area lacking economic alternative water resources.