“Our niche is packaged systems, while
other companies might specialize in systems built onsite.”
RO membranes can be made in different materials and designs. But the
basic principle, states the National
Academy of Sciences, is the same: The
“membrane allows water molecules to
pass through it, but catches and retains
other dissolved or suspended substances.” The process is called reverse
osmosis because “the system pressurizes
the solution to such an extent that water
flows from a more concentrated solution, through the membrane, and into
the more dilute solution—the opposite
of natural flow by osmosis.”
Requirements for flow control and
valving begin with the initial intake of
seawater or brackish groundwater. Typically this water is pretreated to remove
particulates that could clog the membranes and reduce their efficiency and
longevity. According to a CM2H Hill
“Though desalination can’t be competitive
with nearby surface water, there
are areas that are running out of
water options. Unless we see a spike in
electricity costs, desalination is
competitive.”
white paper, “The capital and operating
cost of a membrane pretreatment system can be 50% of the overall cost of a
membrane desalination or reuse plant.”
For that reason, new plants are now
built with low-pressure microfiltration
and ultrafiltration membranes at the
pretreatment stage.
Next the water is forced under pressure through the membranes. Since the
amount of pressure needed depends on
the amount of total dissolved solids in
the water, seawater desalination
requires more pressure—and consumes
more electricity—than the desalting of
brackish groundwater. According to
Morgan, seawater reverse osmosis
(SWRO) may require pressures of
between 700 and 900 pounds per
square inch (psi), while brackish water
reverse osmosis (BWRO) may require
100 to 400 psi.
“If you can reduce the pressure
needed, then you reduce the energy
consumption and thus the total cost,”
Morgan points out. Advances have
helped make RO the leading desal
technology, he says, “along with the
fact that RO plants have a smaller
footprint than other technologies,
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