Bacteriological quality of groundwater used for household supply

Science Center Objects

In fractured bedrock aquifers used for domestic supply conditions can exist where contaminants such as bacteria are not filtered out by the soil. Once in the fracture system, little additional filtration takes place.

The results of a synotic sampling of domestic wells in the Lower Susquehanna River basin, Pennsylvania and Maryland, showed that bacteria concentrations were higher in areas with high levels of agricultural activity, likely due to the application of manure on farm fields.

Highlights

  • 146 domestic supply wells sampled for bacteria
  • Bacteria were found in 80% of the wells sampled
  • 70% of the samples were positive for total coliform
  • 25% of the samples were positive for fecal coliform
  • 65% of the samples were positive for fecal streptococcus
  • E. coli were found in water from 30% of the 88 wells
  • Bacteria were more likely in water from wells in agricultural areas
  • Bacteria were more likely in water from wells in the Ridge and Valley Province
  • E. coli concentrations were higher in areas underlain by carbonate bedrock
  • Correlations between bacteria concentrations and well characteristics and water-quality constituents are small

 

Photo of a truck spraying an agricultural field with manure

Manure-based fertilizers can be an agricultural source of pathogens. (Public domain.)