Question

1. because of safety issues associated with the reliance of chlorination and improvements in ______ technology, it has experienced increased acceptance in municipal water systems. two systems are certified and classified by the nsf under standard 55. the type of unit depends on the situation for use, source of water, and water quality. the dosage is affected by water clarity. when turbidity is 5 ntu or greater and/or total suspended solids are greater than 10 ppm, pre-filtration of the water is highly recommended. it is advisable to install a 5 to 20 micron filter prior to the disinfection system.

a. ozone
b. chloramination
c. ultraviolet light
d. chlorine dioxide

Explanation:

Ultraviolet (UV) light is a chemical-free water disinfection technology that has grown in acceptance as an alternative to chlorination (which has safety concerns from disinfection byproducts). NSF Standard 55 certifies UV systems for water treatment, and UV efficacy is highly dependent on water clarity—pre-filtration (for high turbidity/suspended solids) is explicitly recommended for UV systems, which matches the details provided. The other options are all chemical-based disinfection methods related to chlorination, not the alternative technology described.

Answer:

c. ultraviolet light