Predicting the Floc Characteristics and Settling Velocity of Flocs under Variable Dosage of Polyacrylamide

  • Zhipeng Shi Northwest A&F University
  • Gen-guang Zhang Northwest A&F University
  • Guo-liang Pei Northwest A&F University
  • Guo-yun Zhang Northwest A&F University

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Abstract

In this study, floc characteristics such as fractal dimension and settling velocity were investigated through a flocculantion process with a polyacrylamide (PAM) flocculant over a range of suspended particle concentrations, suspension type and flocculant dosage. The floc’s structure and morphology were characterized by optical microscopy and scanning electron microscopy (SEM) methods. Floc settling velocity was measured in a settling column in a laboratory. The results showed that, the surface fractal dimension ranged from 1.044 to 1.415, which quantitatively confirmed the round and layered structure of flocs observed in SEM analyses. The PAM flocculant was proved to be more effective in flocculantion process, increasing the settling velocity. Therefore, an appropriate PAM dosage is an excellent candidate as efficient flocculant. A possible flocculantion mechanism for PAM was further analyzed. For alkaline or neutral environments, adsorption and bridging effects are dominant while charge neutralization is favored in acidic conditions.

Author Biographies
Zhipeng Shi

College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, 712100, P. R. China

Gen-guang Zhang

College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, 712100, P. R. China

Guo-liang Pei

State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, 712100, P. R. China

Guo-yun Zhang

State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, 712100, P. R. China

Keywords
Flocculation characteristic, polyacrylamide, fractal dimension, settling velocity, flocculation mechanism.

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