Which of the following statements is true regarding coagulants?

The statement that aluminum sulfate is a common coagulant is accurate because aluminum sulfate, often referred to as alum, is widely used in water treatment processes. It works by enhancing the aggregation of suspended particles, allowing them to clump together and settle out of the water, thus improving water clarity and quality. This process is known as coagulation, and it is a crucial step in water treatment to remove turbidity and other particulates.

Coagulants play an important role in the treatment of drinking water and wastewater, and aluminum sulfate is favored for its effectiveness, availability, and cost-efficiency. It is essential for operators to understand the nature and function of coagulants to effectively manage their use in water treatment systems.

The other statements do not accurately reflect the role or impact of coagulants, as they may mislead one regarding the functions and characteristics of these substances. For instance, while coagulants can influence the pH, they do not inherently improve pH levels; rather, they often require careful monitoring and adjustment. Not all coagulants are harmful, as many are safe and beneficial in controlled applications, and coagulants can be both organic and inorganic, not limited to just organic materials.