Suspended solids and turbidity can be removed by physical filtration. Dissolved contaminants such as chlorine, organic compounds, colour, taste, and odour are a different challenge. These are molecules in solution, and they pass through conventional media filters without being captured. Activated carbon filtration addresses this category of contamination through a process called adsorption, where dissolved molecules are attracted to and held within the porous structure of the carbon media.

The activated carbon used in these filters has an extremely high internal surface area created during the activation process. This surface area provides the sites where dissolved contaminants are captured and retained as water passes through the carbon bed. The capacity of the media depends on the specific contaminants being removed and their concentration, but a well-specified carbon bed provides effective removal over an extended service period before regeneration or replacement is needed.

Chlorine removal is one of the most common applications for activated carbon filters in water treatment. Chlorine and chloramines used for disinfection in municipal water supplies can affect the taste and odour of the water and can damage sensitive downstream equipment such as RO membranes. Activated carbon effectively removes these disinfection residuals, protecting both the water quality and any downstream treatment processes.

In wastewater reuse applications, activated carbon polishing is used to remove residual organic compounds and colour from secondary or tertiary effluent, improving the quality of reclaimed water to the standard required for its intended reuse application.

Service life depends on the volume and concentration of contaminants being removed. Periodic testing of the filter outlet allows the carbon media capacity to be monitored and replacement scheduled before breakthrough occurs.