What are the respective clear spacings for bar racks and bar screens?

The correct choice specifies the clear spacings for bar racks and bar screens as being between 2.0 to 4.0 inches for bar racks and 0.25 to 2.0 inches for bar screens. This spacing is essential in wastewater treatment processes to effectively capture and remove larger solid debris from the water, allowing for better purification and reducing potential damage to downstream equipment.

Bar racks generally have a wider spacing to allow larger solids to be captured without clogging, while bar screens have tighter spacing to catch smaller debris, such as plastic, rags, and other contaminants. This distinction in spacing is crucial as it aligns with the specific functions of each device, ensuring optimal flow and preventing blockages.

The other options suggest either too wide or too narrow spacings, which could either fail to capture necessary debris effectively or result in excess clogging that obstructs flow and necessitates more frequent maintenance.