Using a simulated lake water containing humic acid, various
combinations of water treatment processes were utilized to determine
their effect on precursor removal and haloform removal subsequent
to their formation.
Laboratory tests t including temperature, pH, alkalinity,
absorbance, and chlorine residual, were performed throughout the
treatment process. Samples were collected and shipped to California
Analytical Laboratory for volatile organic analysis.
The results of this study supported those from past studies
in that it showed humic .acid to be a precursor to volatile organics.
The data indicated that effective precursor removal could be
achieved by coagulation, flocculation, and sedimentation, especially
when followed by doses of activated carbon in the range of
30-50 mg/l.
It was also observed that the chlorine concentration had more
effect on the production of volatile organics than the humic acid
concentration. The reaction between humic acid and chlorine was
not instantaneous as haloform concentrations continued to increase
for up to eight or more hours after chlorination.
The data appear to show that the most effective treatment to
insure minimum concentrations of haloforms in finished waters is
precursor removal prior to chlorination. If the raw water is a
surface water, then coagulation, flocculation, and sedimentation,
and possible powdered activated carbon treatment, should proceed
chlorination. However, if prechlorination is necessary, chlorination
should be rapidly succeeded by the routine water treatment
processes which would insure reasonably low haloform levels in
finished water.
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