Effectiveness of water treatment methods for removal of haloforms and their precursors
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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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