ABSTRACT
R horizon — Bedrock, such as limestone, sandstone, or shale.
R&D — See research and development. R/O — Acronym for rule out or reverse osmosis. R/O unit — A reverse osmosis unit used for water puri-
fication.
R horizon — Bedrock, such as limestone, sandstone, or shale.
R&D — See research and development. R/O — Acronym for rule out or reverse osmosis. R/O unit — A reverse osmosis unit used for water puri-
fication.