Reverse Osmosis - Principles & Operations

Advantages and Disadvantages of RO Systems

Advantages:

bulletRO performs a separation without a phase change. Thus, the energy requirements are low.
bulletRO systems are compact, and space requirements are less than with other desalting systems, e.g. distillation.
bulletRO equipment is standardized - pumps, motors, valves, flowmeters, pressure gages, etc. Thus, the learning curve for unskilled labour is short.
bulletMany RO systems are fully automated and designed to start-up and shutdown automatically through interlocks. Thus, RO plants usually require little labour.
bulletDue to their modular design, maintenance is easy. Scheduled maintenance can be performed without shutting down the entire plant.
bulletThe modular design also makes expansion an easy option.

Disadvantages:

bulletThe applied pressure must exceed the osmotic pressure to obtain product flow and to separate the solute from the solvent. The maximum feed pressure for seawater devices varies from 800 - 1000 psig, while the limit for brackish water varies from 400 - 600 psig. Due to the high pressure requirement (about 200 psig or more above the osmotic pressure) RO is usually not applicable for concentrated solutions.
bulletBecause all RO membranes and devices are susceptible to fouling, the RO process usually cannot be applied without pretreatment.
bulletRO feed streams must be compatible with the membrane and other materials of construction used in the devices. If the feed stream contains incompatible compounds, these must be removed in pretreatment, or another compatible device and/or membrane must be considered.


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