Characterization of Flocs and Floc Size Distributions Using Image Analysis

Area of Science:

• Water treatment
• Particle science
• Colloid chemistry

Background:

• Understanding particle aggregation is crucial for water treatment processes like coagulation and flocculation.
• Accurate measurement of particle size distribution is essential for characterizing these aggregation mechanisms.

Purpose of the Study:

• To develop and validate a nonintrusive digital imaging process for quantifying particle size distributions.
• To study particle aggregation and sedimentation behavior under varying operating conditions.
• To analyze the impact of coagulant dose on floc characteristics and sedimentation efficiency.

Main Methods:

• Developed a digital imaging technique calibrated with polystyrene standards.
• Automated identification and removal of out-of-focus flocs using LabVIEW.
• Measured kaolin clay particle size and aggregates formed by polyaluminum chloride.
• Quantified floc removal during sedimentation and correlated turbidity with particle concentration and coagulant dose.

Main Results:

• Established a linear relationship between turbidity and clay particle concentration determined by imaging.
• Demonstrated a linear correlation between the logarithm of aluminum dose and the negative logarithm of remaining turbidity after settling.
• Observed maximum floc size in settled water below 120 μm, consistent with theoretical predictions.

Conclusions:

• The developed digital imaging process is effective for studying particle size distributions in flocculation and sedimentation.
• The technique provides insights into aggregation mechanisms and the influence of coagulant dose.
• Results support the use of imaging for optimizing water treatment processes and predicting sedimentation performance.