Tennessee Wastewater Operator Practice Exam

What substance is typically used to acid wash a sand filter?

1. Hydrochloric acid

2. Sulfuric acid

3. Citric acid

4. Acetic acid

The correct answer is: Hydrochloric acid

The typical substance used to acid wash a sand filter is hydrochloric acid. This choice is correct because hydrochloric acid effectively dissolves minerals and contaminants that may accumulate on the sand filter over time. When sand filters are exposed to harmful substances such as calcium carbonate or other mineral deposits, they can experience reduced efficiency in filtering water. Hydrochloric acid provides a strong acid solution that can penetrate and dissolve these deposits, restoring the filter's functional capacity. Other acids, while they have their specific applications, are not as commonly used for sand filter acid washes. Sulfuric acid is more often associated with lead removal or battery cleaning due to its reactivity with certain metals, while citric acid and acetic acid are milder and may not effectively remove tougher mineral deposits that can hinder the performance of sand filters. Therefore, the use of hydrochloric acid remains a standard practice in effectively maintaining and cleaning sand filters.