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Membrane Processes 565

bore feed, and any other information that may be of GLOSSARY
interest.
Acronyms for membrane materials and membranes:
17.4 Effect of Temperature on Flux Density
Acronyms are used commonly to designate different
Given
membrane materials. Some include polysulfone
An MF membrane element has a given flux density, for (PS), polyvinylidenefluoride (PVDF), polyacryloni-
2
3
example, j w m water=m membrane=s for temperature
trile (PAN), and polyamines (PA). For membranes,
208C.
microfiltration is MF, ultrafiltration is UF, nanofiltra-
Required tion is NF, and reverse osmosis is RO (RO has also
Calculate the relative flux density, j w , for 98C. been called ‘‘hyperfiltration’’).
17.5 Osmotic Pressure ACS: Acronym for American Chemical Society.
Anisotropic: Contrast with: isotropic–exhibiting properties (as
Given
velocity of light transmission, conductivity of heat or
A brackish water has a TDS ¼ 3500 mg=L.
electricity, and compressibility) with the same values
Required
when measured along axes in different directions
Calculate the osmotic pressure.
(http:==www.merriam-webster.com, 2003).
17.6 Calculation of Flux Density and Permeability for RO
Anti-scalant: Usually an acid rinse used in the cleaning cycle
Membranes
to remove mineral scale that has deposited on the
Given membrane surface as a foulant.
The problem is referenced to the RO membrane system Array: See membrane technologies.
at Brighton (see Section 17.7.1). The membranes are ASTM: American Society for Testing Materials.
2
8 in. diameter, 40 in. long with a reported area 33.9 m . Asymmetric: (1) Not symmetrical (http:==www.merriam-
The Brighton plant with three trains has 324 elements webster.com, 2003). (2) As used with respect to mem-
per train. A fourth train was being installed as we visited branes, a dense layer is on the separating surface,
the plant on April 6, 2000. The influent pressure at start- underlain by a support layer (Cheryan, 1986, p. 365).
up in 1994 was 154 psi; in December, 1996 when Tory (3) Heating, that is, ‘‘annealing’’ certain membranes
Champlin and I visited the plant, the pressure was causes shrinkage of the pores on one side, but not on
164 psi. Let T ¼ 208C. the other; discovered by Sidney Loeb and
S. Sourirajan, c. 1960. The discovery was a ‘‘break-
Required
through’’ that paved the way toward development of
(a) Calculate the design water flux density for the mem-
commercial membranes since a homogeneous mem-
branes at Brighton. (b) Estimate the intrinsic permeabil- 2
brane had a flux density of only about 0.05 L=m =h,
ity coefficient, k, for the membranes.
while with the asymmetric membrane, the flux density
2
was about 14.5–0.05 L=m =h. This was due to the thin
ACKNOWLEDGMENTS
‘‘skin’’ on one surface, about 0.1–0.2 mmthick,while
Ed Burke, director of utilities at Brighton, Colorado, and the main body of the membrane was ‘‘sponge-like’’
Rodney Evans, plant supervisor, provided ready access to with voids of high porosity. Previously, the homoge-
their plant and provided whatever data were needed neous membranes had a thickness of about 100–200
and gave permission to photograph the installation. Burke mm (from Cheryan, 1986, pp. 10–13).
was helpful over a period of years in helping the author Clean-in-place: A more thorough cleaning of a membrane
become acquainted with the membrane technology, begin- that occurs at an interval of perhaps every 30 days,
ning with the pilot plant phase and extending through depending on conditions and manufacturer’s recom-
operation. Photographs of the Brighton membrane facility mendations.
were used with permission of the city of Brighton through Cleaning: An action that removes a portion of the foulants
Burke and Jodie Carroll. from the membrane surface, that is, the ‘‘reversibly’’
This chapter has utilized sections from handouts and pre- fouling, such that the water flux density is restored as
sentations by Dr. Tory L. Champlin, senior project engineer, it was at the beginning of the cycle minus the ‘‘irre-
Parsons, Tampa, Florida, while at Colorado State University versible’’ fouling.
during the period 1992–1998, including photomicrographs and Composite membrane: A two-layer membrane consisting of
findings from his doctoral thesis; all material was used with his a dense-film layer laminated to a microporous sup-
permission. The chapter also utilized report material from port, for example, a PS surface layer on top of a
sponsored research by the Environmental Protection Agency, polyester support layer.
Cincinnati, in which Dr. Champlin served as research assistant. Concentrate: The portion of the feed flow that does not pass
In addition, Dr. Champlin has provided suggestions on parts of through the membrane but leaves the membrane
the manuscript concerning current practice, drawing on his element. The concentrate flow is sometimes called
experience in design and in pilot plant studies. the ‘‘reject’’ flow.