What dosage of coagulant is required for very fine suspended solids?

The requirement for an increased dosage of coagulant for very fine suspended solids is based on the nature of these particles. Very fine suspended solids, often referred to as colloidal particles, have a high surface area relative to their mass and are typically charged. This charge can prevent these fine particles from aggregating into larger particles that can be more easily removed from water through sedimentation or filtration.

When coagulants are introduced into water, they work by neutralizing the charge on these particles, allowing them to come together and form larger agglomerates or flocs. For very fine suspended solids, a greater quantity of coagulant is necessary to effectively neutralize the charges and facilitate the aggregation process. Thus, an increased dosage of coagulant is required to overcome the challenges presented by these very fine solid particles and to improve the efficiency of the coagulation and flocculation process.

In contrast, a decreased dosage, no dosage effect, or a regular dosage would not adequately address the need for additional coagulant to handle the specific properties of fine suspended solids, leading to inefficiency in the treatment process. Therefore, understanding the behavior of very fine suspended solids is crucial in determining the appropriate coagulant dosage needed for effective water treatment.