Efficacy of Annual Bacteria Monitoring and Shock Chlorination in Wells Finished in a Floodplain Aquifer |
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| Authors: | JA Oliphant MC Ryan A Chu TW Lambert |
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| Institution: | Jennifer Oliphant;is an M.S. candidate in the Department of Civil Engineering at the University of Calgary. After graduating with a B.S. in environmental science at UC, she worked on ground water bacteria as a research assistant for a year before beginning her master's degree. She can be reached at the Department of Civil Engineering, University of Calgary, 2500 University Dr. N.W., Calgary AB, Canada: T2N1N4;(403) 220–8035;fax (403) 282–7026;. Cathy Ryan;, P.Eng, P.Geol., is an assistant professor in the Department of Geology and Geophysics at the University of Calgary (;403–220–2793). She is also the associate director of the Central American Water Resource Network (). She has an M.S. and Ph.D. in hydrogeology at the Department of Earth Sciences at the University of Waterloo. Her field-based research program is primarily focused on ground water impacts by agricultural activities. Angus Chu;is an associate professor in the Department of Civil Engineering at the University of Calgary (; 220–8987) and a wastewater microbiologist by training. He received a master's and a Ph.D. in civil engineering at the University of British Columbia. His research program includes biological phosphorus removal in municipal waste water treatment, and soil and ground water remediation. Timothy W. Lambert;, Ph.D., is a risk assessment specialist with Environmental Health at the Calgary Health Region (P.O. Box 4016, Station C, 320–17th Ave. SW, Calgary AB, Canada, T2T 5T1; 228–7499;and adjunct faculty member with Community Health Sciences in the Faculty of Medicine at the University of Calgary. He received an M.S. in environmental engineering on removal of cyanobacteria toxins from surface. His Ph.D. research in public health sciences was on ethics in public health practice. |
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| Abstract: | Public health authorities generally recommend annual water-quality monitoring of rural water wells and shock chlorination if coliforms are detected. It is implicitly assumed that shock chlorination is effective in ridding most wells of bacteriological pathogens for months to years. Neither annual monitoring nor shock chlorination was effective in addressing coliform contamination of selected water wells in a small town developed on an alluvial aquifer where septic system effluents are impacting well water quality. Considerable temporal variation in total and fecal coliforms was observed in water wells monitored for a six-month period. Individual wells intermittently met and exceeded the drinking water criteria, indicating annual sampling was insufficient. Shock chlorination of three contaminated wells and their associated distribution systems proved ineffective because colonies apparently originated from outside the wells and reappeared over relatively short time periods (ranging from less than one week up to 21 weeks). The relatively fast and similar rate of recovery of total heterotrophic bacteria suggested they are related to biofilm formation in the wells and not to ground water contamination. |
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