Which of the following is NOT typically removed by chemical coagulation processes?

Chemical coagulation processes are primarily used in wastewater treatment to remove suspended solids, colloidal particles, and sometimes microorganisms like bacteria and viruses. The coagulation process involves adding chemical coagulants (such as aluminum sulfate or ferric chloride) to the water, which helps to destabilize the particles and allows them to aggregate into larger flocs that can then be removed through sedimentation or filtration.

Suspended solids are the primary target of coagulation, as the addition of coagulants leads to the formation of larger aggregates that can settle out of the water more effectively. Bacteria and, to a lesser extent, viruses can also be removed via this process, as they can be encapsulated within the formed flocs, making them easier to remove from the water.

Heavy metals, on the other hand, while they can be precipitated and removed using other chemical treatments in some contexts, are generally not removed efficiently through standard coagulation processes. Coagulation primarily addresses particle size and charge, and heavy metals often exist in forms that do not readily combine with typical coagulants. Specialized methods, like precipitation or adsorption onto specific materials, are usually needed for the effective removal of heavy metals from wastewater. Therefore, heavy metals are the correct choice as they are