A novel method for on-line evaluation of floc size in coagulation process.
Chemical coagulation is a simple and widely used water treatment process. A jar test based on the residual turbidity in the treated water was used to evaluate the optimal conditions for floc formation. However, the final residual turbidity does not show up variation of turbidity and floc formation during the flocculation process. Hence, a nephelometric turbidimeter method based on on-line monitoring was devised to determine the floc size variance during flocculation. A nephelometric turbidimeter coupled with a data acquisition unit was used to measure turbidity every second at 3 cm below the water surface during the coagulation process. Laboratory results indicated that this new instrument was capable of recording floc agglomeration during slow mixing very accurately. The standard deviation (SD) of the measured turbidity was proportional to the square root of the floc size; a greater SD indicated larger floc sizes. Hence, in addition to monitoring turbidity, the nephelometric turbidity meter is also a valuable tool to study the floc agglomeration process and variations in the resulting floc size. This method is simple and effective; it contributes significantly to the selection of coagulant and optimal flocculation conditions to improve water treatment.
Cheng
Wen Po
WP
Department of Safety, Health and Environmental Engineering, National United University, No. 1, Lien Da, Kung Ching Li, Miaoli 360, Taiwan. cwp@nuu.edu.tw
Kao
Yu Pin
YP
Yu
Ruey Fang
RF
D017607:Aluminum Compounds / Q000737:chemistry; D005427:Flocculation; D009391:Nephelometry and Turbidimetry; D009862:Online Systems; D010316:Particle Size; D013997:Time Factors; D018508:Water Purification / Q000379:methods*
D017607:Aluminum Compounds