The Drinking Water Inspectorate brought charges against the utility firm for two failures at the Coppermills site in Walthamstow, which takes water from a series of reservoirs fed by the river Lee. The regulator told Stratford Magistrates’ Court that treatment of the raw water includes filtration through sand beds and dosing with sodium hypochlorite disinfectant.
In February 2017, electrical maintenance activities led to the control of the disinfection system being lost. The second incident, which occurred the following July, was linked to disturbed water flow through the sand filter. This increased the water’s turbidity, which in turn affected the adequacy of disinfection.