What type of chemical is injected into the water after sedimentation and before filtration?

The injection of filter aid chemicals into the water after sedimentation and before filtration is crucial to enhance the filtration process. These chemicals, which may include substances such as diatomaceous earth or perlite, help create a precoat layer on the filter media. This layer improves the efficiency of the filtration by preventing fine particles and solids from escaping into the treated water. The use of filter aids can lead to longer filter runs, more effective solid capture, and reduced backwashing frequency, ultimately improving the overall quality of the treated water.

In contrast, disinfectants are typically used after the filtration process to kill any remaining pathogens in the water. Flocculants are added during the coagulation process to agglomerate smaller particles, facilitating their removal during sedimentation. Coagulants are also used to destabilize colloidal particles to aid their subsequent removal; however, their application occurs prior to the sedimentation phase. Understanding the role of each chemical in the treatment process helps to ensure effective water treatment and compliance with health standards.