Costs

As CMF-S is a submerged process, pressure vessels are not required to house the modules. This greatly simplifies the system design and reduces the capital cost. In addition the design of CMF-S lends itself to scale-up more readily as large membrane area can be installed in each cell.

The disadvantage of a submerged process is that it is TMP limited. It is not possible to run the system to TMP's greater than the pump design will allow, without adding liquid height above the membranes. The practical outcome is that the operating TMP range of CMF-S is less than in a pressurised process.

This means that a lower flux (or greater membrane area) is needed if the CIP interval is to be the same for both processes. A design flux for CMF-S between 75% and 95% of CMF is typical, depending on the feed water. However, any increase in membrane area is more than offset by a lower power cost (due to lower TMP) for the CMF-S process.

The power consumption for the CMF-S process is up to 50% of that for conventional CMF.

Chemical consumption is approximately the same, and maintenance costs are expected to be lower due to fewer valves and a less demanding operating cycle.

The net result is that the operating cost of the CMF-S process is usually less than for conventional CMF (typically about 5% lower).

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