Which of the following is also used for pool disinfection alongside chlorine, chloro-iso-cyanurates, and bromine?

Iodine is used alongside chlorine, chloro-iso-cyanurates, and bromine for pool disinfection due to its effectiveness as an antimicrobial agent. Iodine has strong biocidal properties, which makes it suitable for various disinfection applications, including swimming pools. It works by disrupting the cellular function of microorganisms, thereby eliminating bacteria, viruses, and other pathogens in water.

In pool disinfection, iodine can be particularly beneficial because it can remain active for a longer period compared to some other disinfectants, offering prolonged residual disinfection in the water. Additionally, iodine's use is often associated with alternative methods for individuals or scenarios where traditional chlorine or bromine might be less desirable due to personal sensitivities or environmental concerns.

The other options listed do not serve the same purpose in pool disinfection. Alcohol is primarily a surface disinfectant and not typically used for water treatment. Formaldehyde, while a disinfectant, is more commonly used in laboratory settings and is not a standard choice for swimming pools due to its toxicity. Phenol is also more suited for disinfection of surfaces rather than water, and its use in pool disinfection is not standard practice. This makes iodine a more suitable option for enhancing pool sanitation alongside other traditional methods