Environmental Engineering Reference
In-Depth Information
Chapter 11
Confronting the Problem of Lead
in Drinking Water: What Can and Should
Be Done
11.1 Introduction
In the previous chapter, we reviewed the harmful effects of lead in drinking water
and highlighted the need to measure lead in drinking water using strict principles of
chemistry, and adopt a scienti
c protocol that is used consistently. The Appendix to
this chapter demonstrates statistically that the two sampling protocols under con-
sideration are indeed different, and therefore which sampling method is used does
matter in measuring lead accurately.
Adopting a scienti
cally sound sampling protocol that correctly measures lead in
drinking water is the only way of minimizing risk, even low-level current risks that
pose long-term health concerns. In this chapter, we attempt to answer two ques-
tions: (1) what can be done to reduce health risks from lead, and (2) what should be
done if the 30-min stagnation protocol cannot be changed. To answer the
rst
question, in Sect. 11.1 we turn to a case study of Denmark and outline how it has
met the lead challenge. Then in Sect. 11.2 onwards we carry out a statistical
simulation and show that if the sampling protocol is the 30-min stagnation used in
Ontario, then the obvious thing to do is to lower the regulatory maximum con-
tamination level (MCL) of lead, down from 10
g/L to something less than that. We
obtain that lower MCL for Ontario, using Ontario data, in Sect. 11.3.4 .
μ
11.2 Lead in Denmark
Danish Drinking water is obtained almost exclusively from groundwater. This
source accounts for 99 percent of the total water supply. In the majority of water
utilities, only aeration and
filtration is done before the water is pumped through the
delivery system. For the most part, no conditioning is done except for pH adjustment
and hardening in some soft water areas. Only a few waterworks use disinfection of
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