Why might iron salt be preferred over aluminum salt as a coagulant?

The selection of iron salt over aluminum salt as a coagulant can often be attributed to its cost-effectiveness. Iron salts, such as ferric chloride or ferrous sulfate, tend to be cheaper than aluminum salts. This financial benefit is particularly significant in large-scale wastewater treatment facilities where the volume of coagulant used can be substantial. Lower costs help to reduce the overall operational expenses of water treatment processes, making iron salts an attractive option for many municipalities and treatment plant operators.

While other factors like effectiveness, pathogen removal, and odor can be considerations in coagulant selection, cost is a crucial aspect that can heavily influence the final decision. Thus, in contexts where budget constraints are a primary concern, opting for iron salts is often favored.