Process

Pathway

CC (coagulant injection)

Colloids’ occurrence:

1. Charge neutralization (CN) of the negatively charged colloids via adsorption of positively charged coagulant species.

2. Enmeshment of colloids in precipitated Me(OH)_3(s) flocs (e.g., Al(OH)_3(s), Fe(OH)_3(s)).

NOM’s occurrence:

1. Complexation of NOM with dissolved metal coagulant species (Al³⁺ or Fe³⁺), conducting to direct precipitation of a Me-NOM_(s).

2. Complexation of NOM with dissolved coagulant species, conducting to adsorption of such complexed material onto precipitated Me(OH)_3(s).

3. Direct NOM adsorption onto precipitated Me(OH)_3(s).

Colloids & NOM occurrence:

1. Dissolved coagulant species existing upon coagulant addition.

2. Existence of precipitated metal hydroxide solids.

3. Concentration of particles and NOM.

4. Chemical features of such pollutants and their responsiveness with dissolved coagulant species.

5. Coagulation’s pH is influenced by the coagulant’s chemistry and the water’s alkalinity.

Optimized coagulation (augmented coagulant injection)

Colloids’ occurrence:

1. More CN of the negatively charged colloids via adsorption of positively charged coagulant species.

2. More enmeshment of colloids in precipitated Me(OH)_3(s).

NOM’s occurrence:

1. More complexation of NOM with dissolved metal coagulant species, conducting to direct precipitation of a Me-NOM_(s).

2. More complexation of NOM with dissolved coagulant species, conducting to adsorption of such complexed mater onto Me(OH)_3(s).

3. More direct NOM adsorption onto the precipitated Me(OH)_3(s).

Colloids & NOM occurrence:

1. More dissolved coagulant species exist upon coagulant introduction.

2. More occurrence of Me(OH)_3(s).

3. Concentration of colloids and NOM.

4. Chemical features of such pollutants and their responsiveness with dissolved coagulant species.

5. Coagulation’s pH is influenced by the coagulant’s chemistry and the water’s alkalinity.

EnC (augmented coagulant injection & acidified pH)

Colloids’ occurrence:

1. Most CN of the negatively charged colloids by adsorption of positively charged coagulant species.

2. Less enmeshment of colloids in precipitated Me(OH)_3(s).

NOM’s occurrence:

1. Most complexation of NOM with dissolved metal coagulant species, conducting to direct precipitation of a Me-NOM(s).

2. Most complexation of NOM with dissolved coagulant species, conducting to adsorption of this complexed mater onto precipitated Me(OH)_3(s).

3. Less direct NOM adsorption onto the precipitated Me(OH)_3(s).

Colloids & NOM occurrence:

1. More dissolved coagulant species exist upon coagulant addition.

2. Less existence of precipitated metal hydroxide solids.

3. Concentration of colloids and NOM.

4. Chemical features of such pollutants and their responsiveness with dissolved coagulant species.

5. The coagulant’s chemistry and the water’s alkalinity affect the acidified pH of coagulation.

EC (coagulant injection & electric field (EF))

1. Migration to an oppositely charged electrode (electrophoresis) and aggregation due to CN.

2. Cations OH⁻ form precipitates with pollutants.

3. Metallic cation interacts with OH⁻ to form a hydroxide, which has high adsorption properties, thus bonding to the pollutant (bridge flocculation).

4. Hydroxides form larger lattice-like structures and sweep through the water (sweep flocculation) [55] .

5. Oxidation of pollutants to fewer toxic species.

6. Removal by sedimentation or electroflotation and adhesion to gas bubbles.