AWWA WQTC58822

Floc structural characteristics are fundamental to the efficient removal of organic material at water treatment works. Assessment of floc structure can therefore be an important tool in determining operational performance at the waterworks. Floc size, strength and settlement characteristics were assessed for three coagulant doses using an iron based coagulant. Size and strength was determined using conventional light microscopy and an on-line laser diffraction technique. Settlement characteristics were measured using a settling column with a CCD video camera and image analysis software. Significant differences in floc size, strength and settlement were observed using the above techniques. The coagulant dose as used by the waterworks at the time of abstraction gave the best floc structure. Complex interactions occur between organic material and coagulant during the coagulation process and floc structure is likely to be determined by the ratio of organic matter and coagulant within the floc structural mass. Includes 17 references, tables, figures.