CMS SOM App. H, Tag V199

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5.2.7 Reverse osmosis (configuration)

6.2.7 Reverse osmosis (monitoring)

Refer to RD62:2001, 4.3.7 Reverse osmosis: When used to prepare water for hemodialysis

applications, either alone or as the last stage in a purification cascade, reverse osmosis

systems shall be shown to be capable, at installation, of meeting the requirements of Table

1, when tested with the typical feed water of the user, in accordance with the methods of

[AAMI] 5.2.2.

5.2.7 Reverse osmosis

Users should carefully follow the manufacturer’s instructions for feed water treatment and

monitoring to ensure that the RO is operated within its design parameters.

6.2.7 Reverse osmosis

All results of measurements of RO performance should be recorded daily in an operating

log that permits trending and historical review.

Interpretive Guidance § 494.40(a)

ANSI/AAMI RD52:2004

5.2.7 Reverse osmosis

Reverse osmosis (RO) systems have become widely used in hemodialysis water purification

systems, largely because these devices remove dissolved inorganic solutes as well as bacteria

and bacterial endotoxins.

The RO membrane separation process components are a semipermeable membrane, typically in

a spiral-wound configuration, a pump, and various flow and pressure controls to direct the flow

of water through the system. In operation, feed water is pressurized by the RO pump and is then

directed along the surface of the semi-permeable membrane. A portion of the water is forced

through the membrane, a process that removes inorganic salts, bacteria, and bacterial

endotoxins. The remainder of the water continues along the membrane surface and is directed to

drain. Water passing through the membrane is referred to as “product water” or “permeate.”

The water that flows along the membrane surface and to the drain is known as “reject water” or

“concentrate.” This flow configuration, known as “cross-flow filtration,” prevents a progressive

build-up of materials on the membrane surface that would eventually lead to fouling and

membrane failure. In some reverse osmosis systems, a portion of the reject water stream is

recycled to the feed water stream. This recycling enables higher velocities across the membrane

surface, which may help reduce membrane fouling, while also allowing for a higher overall use

of water. RO systems usually operate in a single-stage configuration.

However, if a higher level of purification is required, a two-stage RO can be used. In a two-stage

RO, the product water from the first stage acts as the feed water for the second stage.

Depending on membrane configuration and materials of construction, RO systems are sensitive

to various feed water conditions that may lead to diminished performance or premature failure.

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Additional Guidance:

The facility should have documentation of the RO manufacturer’s DFU of feed water and

monitoring, and facility procedures must reflect them. The RO parameters must be recorded and

monitored each day the facility is operating. The medical director, nurse manager and chief

technician should be able to describe how trends in the RO function are monitored to detect

problems.