REVISITING THE GEOCHEMISTRY OF RESIDENTIAL WATER WELLS, COLUMBIA COUNTY, PA

Many residents of Pennsylvania rely on residential water wells for their water supply, and the area around Bloomsburg, PA, is no exception. Water quality can be quite variable depending on factors such as land use, well construction, and the geologic formation from which the water is being produced. To explore the chemical makeup of groundwater in the Bloomsburg area, we sampled both untreated and (where applicable) treated well water at five single-family residences whose owners volunteered to participate in the study. Samples were tested in-situ for pH, conductivity, and dissolved oxygen. Lab analyses were conducted to determine acidity and alkalinity. Metal constituents were determined by ICP-OES, and anions were identified using ion chromatography. Comparing the lab data with historical well data from known aquifers in the Bloomsburg-Berwick-Danville area, shows that current groundwater chemistry is similar to that determined in previous studies, and comparing study results to the EPAs MCLs indicates that water quality after treatment generally meets applicable primary drinking water standards. Barium was elevated (100 ppm) in untreated water from one well, but was not detected after treatment. Nitrate was detected at about 1.5 times the MCL of 10 ppb in one well, an improvement on a previous study in which all but one well had elevated nitrate concentrations. Arsenic, another relatively common solute in PA groundwater that has been measured at elevated levels in Columbia County, was not detected in this study. This may, however, be an artifact of the high limit of detection rather than the absence of As. A constituent of emerging concern, manganese, was detected in one well at levels above the EPA’s lifetime health advisory value of 300 ppb, even after treatment. At two of the sampling sites, water treatment systems to include reverse osmosis, water softening, and water oxidizing systems. These treatments were found to be effective at decreasing the amount of metal constituents in the water like iron, aluminum, and barium. Further sampling and tests would need to be conducted to determine if contaminants such as arsenic are at levels known to be safe in drinking water.