Question

Ozone is a possible replacement for chlorine in municipal water purification. Unlike chlorine, virtually no ozone remains after treatment. This has good and bad consequences. Explain.

Short answer

Water that has been treated with ozone does not contain any ozone, but it will become polluted again over time. Chloride ions stay in the water after chlorine treatment, preventing contamination.

Step-by-step solution

Concept Introduction

Three oxygen atoms make up ozone (${\mathit{O}}_{\mathbf{3}}$), a highly reactive gas. In the Earth's high atmosphere, it is both a natural and a man-made substance. The upper atmosphere (the stratosphere) and the lower atmosphere (the troposphere).

Pros and Cons of Ozone in water purification

Ozone has been widely known as a good replacement for chlorine in sterilizing and disinfecting waters, in short, it iseffective in eliminating bacteria.

Advantages of ozone –

Unlike chlorine which cannot kill all the bacteria, ozone is proven stronger than chlorine that it can kill more bacteria whenapplied to the water. Since ozone does not leave any residues in water unlike chlorine, it will be safer for it to be used toreduce the exposure to some toxics that may cause diseases.

Disadvantages of ozone –

Since when ozone is applied to water it leaves no traces, the water cannot be secured that it will be safe from therecontamination of bacteria. Also, in comparison to chlorine, ozone has a lesser solubility which results in requiring moremixing methods for it to be completely dissolved in water.

Therefore, water after ozone treatment does not contain any ozone, but this means that it will become contaminated again over time.While after chlorine treatment, chloride ions remain in the water and prevents contamination.