Florida Drinking Water Operator "B" Practice Test

Which chemical can be used to mask red water problems by bonding with iron, but could increase corrosion by reducing effective calcium carbonate scale-forming ability?

1. Sodium hexametaphosphate

2. Calcium chloride

3. Magnesium sulfate

4. Potassium nitrate

The correct answer is: Sodium hexametaphosphate

The chemical that can be used to mask red water problems by bonding with iron is sodium hexametaphosphate. This compound is often employed in water treatment processes to address issues caused by high levels of iron, which can give water a reddish appearance. By forming a complex with iron, sodium hexametaphosphate effectively keeps the iron in solution and prevents it from precipitating out, which would otherwise contribute to color issues in the water. However, while sodium hexametaphosphate can help mitigate the appearance of red water, it has implications for water chemistry that merit attention. One significant concern is its effect on calcium carbonate, a critical component in the formation of scale in pipes and treatment systems. When the ability of calcium carbonate to form scales is reduced, it can lead to increased corrosion of pipe materials. This is especially important because the protective scale build-up that normally occurs can help inhibit corrosion in drinking water systems. By understanding the dual effects of sodium hexametaphosphate, operators can make informed decisions about its use in settings where red water problems are prevalent while also being cognizant of the potential for increased corrosion.