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In many cases, there is no waste heat available. As such, an all-electric means of producing potable water is required. Reverse osmosis can be a cheap means of producing potable water if a relatively constant supply of clean feedwater is available.

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Absolutely. In fact, each application should be carefully reviewed to ensure that the pretreatment and components are specifically suited for it.

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The reliability of any RO installation is dependant upon a number of things. First, the quality of the feedwater supplied to the unit and the unit's ability to handle that supply. Clean seawater is best. However, as the water quality varies or diminishes with increases in turbidity, pollutants or other issues, operations may become more troublesome. The reliability is also dependant upon the design of the unit relative to the quality of the water supplied. Proper pretreatment of a given water source is imperative for proper membrane operation. Thorough operator training, routine monitoring and regular maintenance are also important to successful operation.

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RO units need a good bit of attention. The RO unit should be monitored on a daily basis and records should be kept on pressures, flowrates, and water quality. This helps determine when the RO unit is experiencing problems with scaling, biofouling, membrane degradation, etc. Since problems with RO units are usually not associated with catastrophic failures, having the ability to trend data makes diagnosing a problem much easier.

Membrane cleaning is a task that will have to be performed on a regular basis. Cleaning of the membranes is required for removal of scale and biofouling. Depending on the size of the RO unit, it should be noted that cleaning may be a very time consuming task and the RO unit must be shutdown.

Even with proper care, RO membranes will have to be replaced. The average life of one is about three years. Replacement will require a full shutdown of the RO unit. Depending on the number of membranes in the system, this can be an expensive maintenance cost that should not be overlooked.

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Component selection is a primary consideration. It's important the unit is equipped with a reliable high-pressure pump that operates under the design conditions and is constructed of a suitable material. The unit should be fully equipped with the necessary valves and instruments for proper operation, including the periodic cleaning of the membranes.

Membrane selection is another area of importance. Although there are numerous membrane configurations available, the equipment supplier should provide you with the one most suitable for your application. Any of the major membrane suppliers produce a high quality product.

Membrane flux is the amount of water that can be passed through a square foot of membrane. The unit of measure for flux is referred to as GFD (gallons per square foot per day). The higher the flux rate, the higher potential for scaling problems. It is best to consider a conservative flux rate when designing an RO system. Running the membranes close to their maximum flux will increase the potential for scaling and will shorten the life of the membranes.