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Public water supply contamination

Published on 28/11/23 249 Views

Milwauke city water is sourced from Lake Michigan and supplied 2 water treatment plants (WTPs) on the North and South sides. The treatment process at both involved adding chlorine (disinfectant) and polyaluminium chloride (coagulant), rapid mixing, mechanical flocculation, sedimentation, and rapid sand filtration. The treated water was stored in a large clearwell before entering the distribution network. The filters were backflushed with treated water which was then recycled through the WTP. On 5th April 1993, widespread gastrointestinal illness and significant school and workplace absenteeism was reported amongst Milwaukee residents. A survey of diarrhoea cases in local nursing homes (geographically fixed populations) and testing of inspected resident’s stools for cryptosporidium revealed that the outbreak was concentrated on the south side.

Ask yourself and your crew:

  • How can something like this happen here (e.g. on our site)?
  • What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
  • How do we know the risk controls/barriers are working?
  • What improvements or changes should we make to the procedures, controls/barriers or the way we work?

Original content courtesy of IChemE Safety Centre