Confronting the Problem of Lead in Drinking Water: What Can and Should Be Done - Global Drinking Water Management and Conservation - page 236

Lead vs pH

0.35

0.3

0.25

0.2

y = 0.003x 2 - 0.0643x + 0.3622
R 2 = 0.9247

0.15

0.1

0.05

0

0 2 4 6 8 10 12 14

pH

Fig. 11.1 Lead versus pH with fitted functional form (according to the data from U-MATE
International)

Fig. 11.2 Schock s( 1989 ) analysis of lead versus alkalinity is similar to the functional form

observed in U-MATE data (the thermodynamic data used is from Schock and Wagner ( 1985 )

'

orders is not very meaningful; also we did not want to over t the dataset that was

quite small. Estimated fitted values (not shown) for lead for higher polynomial

orders were sometimes negative, and therefore the fitted higher order polynomial

functions were not practically useful.
We then took each of the pH values for Ottawa and obtained the '

or lead values according to the quadratic equation. We did the same for the average
pH of the rest of Ontario data. The associated lead value for each pH value of the
Ottawa data would then be increased by the percentage difference between y-values
for Ottawa and the y-value for Ontario. In this way, we could obtain Ottawa lead
values with a pH of 7.4. For instance, from Fig. 11.3 , if we take Ottawa pH of 9.57
and use the

tted ' y-values

fitted quadratic functional form, we can estimate the lead value if its pH
was 7.4 (the Ontario average).
Figures 11.4 , 11.5 , 11.6 and 11.7 show the results of the estimation process of
Sect. 11.3.2 . The Ottawa data are also grouped into Spring 2007, Summer pre
water-main rehab 2007, and Summer post water-main rehab 2007. This is for the

first liter only with a stagnation time of 6 h.