| In this paper, to investigate the coagulation process of inorganic suspended particles (ISP), online monitoring of the coagulation process was conducted by using PDA2000. The process of floe formation and the morphological characteristics of floes were investigated in detail through TV-microscope. The mechanism of partical collision and coagulation kinetics were preliminary discussed.The result shows that the optimum coagulation pH of ISP is about 7-8. For aluminium sulfate(Al2 (804) 3), the optimum dose is 1.875mgAl/L, while for poly aluminium chloride (PAC) , theoptimum dose is 1.5mgAl/L. Both coagulants can achieve 90% turbidity removal. Absorption andcharge neutralization is the dominant mechanism when the dose is lower, and sweep flocculation is thedominant mechanism when the dose is higher.The output signal of PDA is affected by the suspended particle concentration, particle size, and the type and dosage of coagulant as well. By analysing the FI curve, it is found that the characteristic parameters of FI curve closely relate to aggregates size and turbidity removal The aggregates size and turbidity removal achieve the maximum when the amplitude of fluctuation is the maximum.The mean diameter and fractal dimension increase with agitation time, and finally reach a steady-state. The mean diameter increases with the increase of alum dose, but the fractal dimension does not vary. However, extremely high dose of sluminum results in an increase of floc diameter but a decrease of the fractal dimension. The main reason is the sweep floes is too loose in their structure, and can't resist the shear force. For poly aluminium chloride, the maximum mean diameter is 0.45mm, and the fractal dimension is about 1.65. For aluminium sulfate, the maximum mean diameter is 0.30mm, and the fractal dimension is about 1.78. |
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