Which of the following methods can aid in backwashing a rapid sand filter?

Backwashing a rapid sand filter is an essential process to remove accumulated solids and restore the filter's efficiency. Mechanical surface wash and air wash are effective methods for this purpose.

The mechanical surface wash involves the use of mechanical devices that scour or agitate the filter media, helping dislodge trapped particles. This method ensures that the filter media remains in good condition while enhancing the removal of contaminants.

Air wash, on the other hand, introduces air bubbles through the filter bed, which helps lift the particles embedded within the sand. The air bubbles create turbulence, allowing trapped solids to be released and flushed away during the backwashing process.

Together, these methods effectively rejuvenate the filter, maintaining high performance in the filtration system. Other options, such as chemical wash, manual rinse, reverse osmosis, and steam cleaning, may not be standard practices for backwashing a rapid sand filter and might not effectively achieve the same level of cleaning or could be unsuitable for the specific context of sand filtration.