What is typically the main disadvantage of using chlorine gas in water treatment?

Using chlorine gas in water treatment primarily presents the disadvantage of producing harmful byproducts. When chlorine reacts with organic materials in water, it can form a number of potentially harmful compounds, including trihalomethanes (THMs) and haloacetic acids (HAAs). These byproducts can pose health risks to humans and are regulated due to their link to various health issues, including cancer.

The generation of these harmful byproducts is a critical consideration in water treatment, as operators must ensure that they are maintaining water quality while minimizing the formation of such compounds. This concern guides many treatment protocols and drives the exploration of alternative disinfection methods or the use of additional treatment steps to remove or mitigate these byproducts.

While other options presented may have relevant points, they do not center on the central concern associated with chlorine gas usage as effectively as the production of harmful byproducts does.