What is typically the first step in water treatment before other chemicals are added?

The first step in water treatment before other chemicals are added is generally the process of coagulation, followed closely by flocculation, which involves aggregating smaller particles into larger flocs that can then be filtered out. While polyphosphate injection can be part of the treatment process—primarily for preventing scale and corrosion—it does not traditionally precede the coagulation and flocculation stages.

Chlorination, on the other hand, is typically employed later in the treatment process to disinfect the water, ensuring that pathogens are eliminated before it reaches consumers. Filtration occurs after coagulation and flocculation to remove suspended particles and flocs from the water.

Therefore, while polyphosphate injection is useful, it does not represent the standard first step in the overall water treatment process compared to other options that directly lead to the clarification of the water. The correct context of the treatment process indicates that initial physical and chemical changes aimed at particle removal occur before adding stabilizers or disinfectants.