PSS Natural Organic Matter Theory
A literature search on the effects of NOM on flocculation and effluent turbidity was done prior to the experiments to determine the expected results.
General Overview of Articles
Comparison of coagulation behavior and floc structure characteristic of different polyferric-cationic polymer dual-coagulants in humic acid solution
Authors: Jincheng Wei, Baoyu Gao, Qinyan Yue, Yan Wang, Weiwei Li, Xiaobiao Zhu
Summary of Experiment: Experiments were done on 3 different coagulants to determine the percentage humic acid removal under varying pH and dose conditions.
Conclusions: Generally, when pH is held constant (approximately 7.5) Humic Acid removal increases with increasing coagulant dosage. The correlation is not linear, however, and there is a point where additional coagulant will not result in significant humic acid removal. The maximum humic acid removal ranged from 80-90% in these experiments. When coagulant dosage was held constant and pH is increased from 3 to 10, humic acid removal decreases. The change in humic acid removal observed was approximately 10%.
Floc Strength Evaluation at Alternative Shearing with Presence of Natural Organic Matters
Authors: Shung-Shuan Sung, Sheau-Pyng Ju, Chien Hsu, Arun S. Mujumdar, and Duu-Jong Lee
Summary of Experiment: The effects of natural organic matters (NOM) on Al-floc stability were investigated by on-line probing of changes in floc diameters and interior fractal dimensions at alternative shearing using the small angle light-scattering technique. Humic acid is often used to simulate NOM in water.
Conditions used for experiment: Water with turbidity of 100 NTU, pH=7. Humic acid (pH=7) was added to the water and well mixed.
General Conclusions:Humic acid in the water will cause the flock size to decrease dramatically. In this particular experiment, the diameters of the flocs decrease from 32 nm to 25 nm. The more humic acid, the smaller the flocs. At low levels of humic acid, increased shear rate can allow the particles to regain their size. However, at higher levels of humic acid, decrease in floc size is completely irreversible. Note that when no humic acid is present and shear rate increases, floc size also increases. In addition to causing floc size to decrease, the humic acid also results in "loose" floc formulation.
Impact of Natural Organic Matter on Floc Size and Structure Effects in Membrane Filtration
Authors: Sangyuna Lee, Anthony G. Fane, and T. David White
Summary of Experiment: Examine the effect of a well-defined humic acid on the aggregation behavior of hematite colloids and, subsequently, assess the impact on the specific resistance and compressibility of microfiltration cakes formed from these aggregates.
General Conclusions:Floc size increases as a function of time when no humic acid is present. However, when humic acid is added, floc size decreases as a function of time. In general, more humic acid makes the decrease in floc size more pronounced.