|dc.description.abstract||Coagulation is an important process for the removal of suspended particles and dissolved substance from water. The dosage of coagulant is usually determined by jar test or the experience of operators, which usually leads to overdose of coagulant. Overdose of coagulant causes high cost for chemicals and sludge treatment. A novel monitoring technique, floc image colorimetric analysis (FICA), have been developed in our research groups to monitor performance of coagulation. The evolution of the red, green, and blue (RGB) values, obtained by analyzing the image of the suspension, can be used to determine performance of the coagulation. In this research, river water was used to examine whether this technique can be applied when there are colored particles and dissolved substances. Also, more image analyses were conducted to see if FICA can provide more information to determine the performance of coagulation of source water. The flocs size and structure were also analyzed to understand correlations between the flocs growth and the RGB values.
The results showed that when the coagulation was effective, the RGB values decreased significantly and the standard deviation of the RGB values increased within rapid-mixing. Then, as the flocs became bigger during the slow-mixing, the flocs passed through the observation window and scattered great amount of light. As the consequence, the RGB values jumped up and the standard deviation of the RGB values increased. Because of the color of clay, the color of the raw water is light brown, in which the changes in the R-value are more obvious than G- and B-values. It is also found that the optimal dosage of coagulant occurred when the slopes of B－R or G－R are the same for the neighboring dosages, which indicate the structure of flocs are similar. The evolution of the standard deviations of RGB values agreed with evolution of floc size obtained from image analysis. In conclusion, by conducting coagulation of river water, it is sure that FICA, which can determine the optimal dosage during rapid- or slow-mixing, can be a useful tool for the monitoring of coagulation processes. Also flocs can be observed and further analyzed to examine the floc size and shapes.