Which type of flocculation is most affected by low alum dosage?

Effective flocculation refers to the ideal scenario where flocculants, such as alum, promote the aggregation of suspended particles in water treatment processes. When the dosage of alum is low, there is insufficient coagulant present to neutralize the charges on particles, leading to a decrease in the ability of these particles to come together and form larger aggregates, or flocs. This deficiency results in ineffective sedimentation and overall poorer water quality as smaller particles remain suspended in the water.

In contrast, cohesive flocculation involves particles that are already capable of clumping together without significant assistance from coagulants, while surfactant flocculation relies more on surface-active agents rather than traditional coagulants like alum. Bacterial flocculation often pertains to the aggregation driven by bacteria in wastewater treatment, which functions independently of the alum dosage.

Thus, low alum dosage primarily impacts effective flocculation because it directly limits the coagulant's ability to attract and bind particles, ultimately hindering the treatment process’s effectiveness.