Which of the following is a disadvantage of using chlorination?

Chlorination is a widely used method for disinfection in water treatment due to its effectiveness in killing harmful microorganisms. However, one of the notable disadvantages of this process is the potential for the formation of harmful by-products during water treatment. When chlorine reacts with organic matter present in the water, it can form compounds known as disinfection by-products (DBPs). Examples of these DBPs include trihalomethanes (THMs) and haloacetic acids (HAAs), which have been associated with adverse health effects. This concern highlights the importance of balancing effective disinfection with the minimization of chemical by-products during water treatment processes.

The other aspects mentioned in the question do not align with disadvantages of chlorination. It is considered inexpensive compared to many other treatment options, while the required contact time can vary but is generally manageable within treatment protocols. Additionally, chlorination is quite effective against bacteria, making it a preferred method in many water treatment facilities.