Manganese greensand filters can be regenerated by using what solution?

• A. Sodium hypochlorite solution
• B. Calcium hypochlorite solution
• C. Potassium permanganate solution
• D. Hydrochloric acid solution

Answer: (C)

Manganese greensand filters are used primarily to remove iron, manganese, and hydrogen sulfide from water. Regeneration of these filters is necessary when they become saturated with the contaminants they are designed to reduce. The appropriate method for regenerating manganese greensand involves the use of potassium permanganate solution.

When potassium permanganate is introduced to the greensand, it helps to replenish the manganese oxide coating on the sand particles. This coating is essential for the filter's ability to oxidize and subsequently remove iron and manganese effectively during the filtration process. Potassium permanganate reacts with the contaminants, facilitating their separation from the water and enhancing the overall performance of the filter.

The other solutions listed would not effectively regenerate manganese greensand. Sodium hypochlorite and calcium hypochlorite are both chlorine-based compounds but do not specifically serve to restore the manganese oxide layer on the greensand. Hydrochloric acid, on the other hand, is used primarily for cleaning purposes, such as removing scale or calcification, but it does not regenerate the filtering material needed for iron and manganese removal in the same manner as potassium permanganate. Thus, potassium permanganate is the optimal solution for the regeneration of manganese greensand filters.