Which of the following factors is crucial for effective coagulation?

For effective coagulation in water treatment processes, pH is a crucial factor because it directly influences the charge and solubility of the coagulants used, such as aluminum sulfate or ferric chloride. Coagulation involves the neutralization of the charges of suspended particles, allowing them to agglomerate and form larger flocs that can then be removed from the water.

At different pH levels, the effectiveness of coagulants can vary significantly. For instance, if the pH is too low or too high, the coagulant may not work effectively, leading to poor floc formation and inadequate removal of turbidity and contaminants. Therefore, maintaining the optimal pH range is essential to ensure that the coagulation process is efficient and effective.

Other factors, while they can influence coagulation to some extent, are not as critical as pH. For example, temperature can affect the kinetics of the coagulation process and the solubility of coagulants, but it does not determine the overall effectiveness to the same degree as pH. Similarly, pressure and salinity are generally less impactful in the coagulation process compared to pH, which is fundamental to optimizing the conditions for successful coagulation.