Canadian Consulting Engineer
Chloramines may release lead in pipesEngineering
A report in Scientific American's on-line magazine suggests that the effort to reduce the chlorine content of treat...
A report in Scientific American’s on-line magazine suggests that the effort to reduce the chlorine content of treated water may be causing more problems than it cures in some situations.
In Washington, D.C. at least 157 houses in the area have lead levels higher than 300 parts per billion, and thousands have exceeded the EPA limit of 15 parts per billion. The high levels of of the neurotoxic metal prompted a congressional investigation and resulted in the firing of a health official.
One possible theory for the high levels of lead is that the mineral is released due to a relatively new practice of using a mixture of chlorine and ammonia – chloramines – to disinfect the water. Chloramines are being used as a means of meeting rules that now restrict the addition of the traditional disinfectant, chlorine. Chlorine has become suspect because it reacts with natural organic and inorganic matter to form halogenated organic compounds. Tests have linked these compounds with animal cancers, so in recent years water treatment plants have been encouraged to limit chlorine’s use.
A researcher at the U.S. Environmental Protection Agency discovered that mineral scales that form on the lead service pipes in Washington — especially lead dioxide scales — may have broken down after the water chemistry changed. The researchers suspect that the treatment plant’s switch to chloramines for disinfectant may have lowered the oxidizing qualities of the district’s water, which then dissolved lead dioxide scales on the service pipes and liberated the lead.
Source: “Leading to Lead: Conflicting rules may put lead in tap water,” by Rebecca Renner, ScientificAmerican.com, June 21, 2004.