Application of low-mixing energy input for the coagulation process

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Coagulation Chemistry

Background:

• Rapid mixing is crucial in water treatment, but its impact on coagulation effectiveness remains unclear.
• Optimizing mixing energy is key for efficient removal of natural dissolved organic matter (DOM).
• High organic content water (SUVA ≥ 2-2.5 m⁻¹/(mg/L)) presents challenges for conventional treatment.

Purpose of the Study:

• To optimize direct energy use in coagulation for natural DOM removal.
• To investigate the role of mixing intensity (G-value) on TOC and turbidity removal.
• To determine energy-saving opportunities in enhanced coagulation processes.

Main Methods:

• Standard jar tests were performed using ferric sulfate coagulant.
• Coagulant dose and pH were optimized for organic and particle removal.
• Mixing intensity (G-value) was varied from 0 to 1500 s⁻¹ under optimized conditions.

Main Results:

• Optimal coagulation at pH 4.5 ± 0.3 and iron dose <0.3 mM achieved >75% TOC removal.
• Effective TOC and turbidity removal occurred at a low mixing intensity range (110 s⁻¹ < G < 450 s⁻¹).
• Mixing intensities above 450 s⁻¹ offered negligible improvement in TOC removal.

Conclusions:

• Energy consumption in enhanced coagulation can be minimized by operating within the 110–450 s⁻¹ mixing intensity range.
• Effective DOM and turbidity removal can be maintained at lower mixing energies.
• Findings offer significant energy-saving potential for the water industry without compromising treatment quality.