Chapter 9 : When the Well Runs Dry

Abstract:

John Snow, a physician and surgeon, studied the history of cholera's journey from Asia to England and the disease’s pattern of spread during an outbreak, and concluded that the disease was spread through contaminated food or water. There was a time when water from wells, lakes, and rivers was relatively free from fecal contamination and the pathogens associated with it. However, population pressure from humans and domesticated animals has changed the safety profile of surface and ground waters. Since the late 1980s, outbreaks of gastrointestinal disease due to Salmonella, Shigella, Plesiomonas, Escherichia coli (O157:H7 and O121:H19), Giardia, Cryptosporidium, and norovirus have been traced to drinking untreated well water and to recreational water activities such as lake swimming, water parks, swimming pools, and interactive water fountains. The northern and southern water treatment plants for the greater Milwaukee area obtained their raw water from different locations, but both followed the same procedure to purify water for the city’s residents. First, chlorine and polyaluminum chloride (a coagulant) were mixed into the water--the chlorine for disinfection and the polyaluminum chloride to encourage particles to stick together. Next, a sedimentation step allowed most of the floc to settle out. Finally, the water was filtered through sand to remove the remaining floc. The Centers for Disease Control and Prevention (CDC)-organized workshop in 1994 produced several recommendations, and the CDC impaneled the Working Group on Waterborne Cryptosporidiosis, made up of representatives from various agencies and organizations, to pursue the concerns highlighted by the workshop report.