The influence of well construction on bacterial contamination of private water wells in Pennsylvania.* Pennsylvania has a large population that relies on private water wells. * No statewide regulations govern the location or construction of the wells. * Bacterial contamination occurs in nearly half of these wells, representing a health risk to rural residents. * The role of large-scale aquifer aquifer (ăk`wĭfər): see artesian well. aquifer In hydrology, a rock layer or sequence that contains water and releases it in appreciable amounts. contamination versus wellhead well·head n. 1. The source of a well or stream. 2. A principal source; a fountainhead. 3. The structure built over a well. wellhead Noun 1. contamination from poor construction is poorly understood. * The authors disinfected Disinfected Decreased the number of microorganisms on or in an object. Mentioned in: Isolation and installed sanitary well caps on 16 wells that contained coliform bacteria coliform bacteria Rod-shaped bacteria usually found in the intestinal tracts of animals, including humans. Coliform bacteria do not require but can use oxygen, and they do not form spores. They produce acid and gas from the fermentation of lactose sugar. and retested them after 30-60 days and one year. * Coliform bacteria were present in seven of the 16 wells within 30-60 days and all but two wells within one year. * The occurrence and prevalence of bacteria in wells appeared to be influenced by weather conditions during the study. * The few wells where disinfection disinfection, n the process of destroying pathogenic organisms or rendering them inert. disinfection, full oral cavity, n a procedure used to reduce active periodontal disease, usually completed within a certain short time frame. and installation of a sanitary well cap were successful had low initial coliform bacteria and no E. coli E. coli: see Escherichia coli. E. coli in full Escherichia coli Species of bacterium that inhabits the stomach and intestines. E. coli can be transmitted by water, milk, food, or flies and other insects. . * Samples were also collected from 24 new wells that were constructed with a grout Grout A binding or structural agent used in construction and engineering applications. Grout is typically a mixture of hydraulic cement and water, with or without fine aggregate; however, chemical grouts are also produced. seal and sanitary well cap. * Twenty-nine percent contained coliform bacteria, and 17 percent contained E. coli. * The small sample size justifies caution in interpreting the results. * Climate-related differences in bacterial contamination indicated that sanitary surveys of wells might best be conducted subsequent to active periods of groundwater recharge. * Wells in carbonate bedrock areas were more likely to contain coliform bacteria and E. coli bacteria than were wells in noncarbonate bedrock regardless of well construction. * This result suggests that aquifer contamination was more prevalent in carbonate aquifers. * New and existing wells constructed in noncarbonate bedrock had lower bacterial contamination rates. * Overall, aquifer contamination from areas other than the well-head appeared to be an important source of bacterial contamination in the study wells. * Contamination in wells influenced by aquifer contamination cannot be fully addressed with improved well construction practices alone. * Greater attention to curtailment of polluting activities appears warranted. |
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