0709_A novel method for on-line evaluation of floc size in coagulation process



ESEL Paper Review_20110609
By Hong Guo

1,Title and Author

Title: A novel method for on-line evaluation of floc size in coagulation process


WenPo Cheng,Yu pin Kao, Ruey Fang Yu

Department of Safety,Health and Environmental Engineering, National United University, No.1 Lien Da, Kung Ching Li,Miaoli 360, Taiwan

2. Summary of Paper
  Chemical flocculation is an important water treatment process and its efficiency seriously affects the operation and efficiency of subsequent sedimentation and filtration. However, the flocculation process is not studied a lot and the relationship between flocculation condition and floc formation area.
This paper discusses about a nephelometric turbid meter method based on online monitoring was devised to determine the floc size variance during flocculation.
  The system consists of the jar test apparatus and the nephelometric turbid meter attachment. In this system they use the light-emitting diode illuminate the solution at 90 degree to the path of light entering the turbid meter. By measuring every second, the intensity of the light (860nm red light) can be converted to the turbidity value by computer analysis. The system can be measured in the range of 0~4000NTU. 
  The results are as follows:
1, During the flocculation the suspension s with larger but fewer flocs caused the illuminated flocs to become less uniform and the turbidity value to fluctuate with greater fluctuate, thus, the size of the flocs was proportional to the amplitude of turbidity fluctuations. 
2. After the comparison of linear regression, it was found that in a different particle size range the linear relationship between the square root of flocs size and the SD of measured turbidity fluctuation has the best R square value.
3. The perfect linear relationship between the SD of NTU data and the square root of flocs diameter was valid for both organic and inorganic particles as well as a large particle size range.
4. The turbidity SD increased initially and then became steady indicating that the flocs gradually grew in size during the flocculation and also we can know that the flocs formation or SD values appeared to be affected by the slow mixing time. The shorter slow mixing time did not favor the formation of flocs and it verified that SD values really were dependent on the flocs size.

3. Contribution:
  This paper talks about nephelometric turbidity meter which can obtain the raw water’s turbidity changing and be used in and on-line monitoring of the state of coagulation enabling automatic control of coagulation for optimum system design.
  And Now I ran the advanced water treatment plant which is designed for the removal of phosphors and CSOs (combined sewer overflows). For my study, the efficiency of the coagulation directly affects the system results. 
  This paper shows me the one of the method to track the flocs size and I hope it also can help the members of our lab.

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