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Coagulation of humic-kaolin-PACI aggregates
1Chemical Engineering Department, National Taiwan University, Taipei 106, Taiwan.
Summary
Humic acid has a mild effect on water treatment flocs formed with polyaluminium chloride (PACI). While floc strength decreases, leading to higher organic matter in treated water, the overall structure remains largely unaffected.
Area of Science:
- Environmental Science
- Water Treatment Technologies
- Colloid and Surface Chemistry
Background:
- Water treatment residual flocs are complex fractal aggregates.
- Understanding coagulation dynamics is crucial for effective water purification.
- Polyaluminium chloride (PACI) is a common coagulant in water treatment.
Purpose of the Study:
- To investigate the coagulation dynamics of humic-mineral-PACI aggregates.
- To assess the impact of humic acid on floc formation and characteristics.
- To analyze the influence of humic acid on supernatant quality after settling.
Main Methods:
- Small-angle light scattering techniques to study aggregate structure.
- Free-settling tests to evaluate floc settling behavior.
- Analysis of supernatant turbidity and organic content.
Main Results:
- Humic acid presence did not result in looser flocs, contrary to some literature.
- Coagulation dynamics and final floc characteristics were only mildly affected by humic acid.
- Floc strength decreased with increasing humic acid concentration.
- Supernatant turbidity and organic levels increased with humic acid presence.
Conclusions:
- Humic acid has a limited impact on the fractal structure of humic-mineral-PACI flocs.
- Reduced floc strength due to humic acid can compromise treated water quality.
- Further research may be needed to optimize PACI coagulation in the presence of humic substances.
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