Dear Muhammad,

Yes. Water desalination is possible with tubular membranes.  The following text contains an overview on Tubular membranes and two examples: one in which tubular membrane is used in the desalination process itself and the other in the pre-treatment stage.

Tubular

While virtually any membrane design can be applied to water‐like liquids with low concentrations of suspended solids, viscous streams and fluids with large amounts of solids are best handled with tubular membranes, which are specifically designed for this purpose.  Tubular membranes operate in tangential, or crossflow, design where process fluid is pumped along the membrane surface in a sweeping action. This design maintains stable filtration rates for process streams with high concentrations of particles or macromolecules such as cells, proteins and precipitates. Tubular membranes have a rugged construction made of sturdy polymeric materials, so they can easily process high suspended solids and concentrate product proficiently and repeatedly to high end‐point concentration levels without plugging.  

High Efficiency: Durable and long‐lasting, low‐energy tubular membrane configurations are easy to operate, run in continuous, reproducible processing cycles, and offer optimal productivity, high flux, and high recovery.  

Flexibility: Tubular membranes are available in UF and MF technologies and come in an array of diameters. 

1-New membrane distillation configurations and a new membrane module were investigated to improve water desalination. The performances

of three hydrophobic microporous membranes were evaluated under vacuum enhanced direct contact membrane distillation (DCMD) with

a turbulent flow regime and with a feed water temperature of only 40 ◦C. The new configurations provide reduced temperature polarization

effects due to better mixing and increased mass transport of water due to higher permeability through the membrane and due to a total pressure

gradient across the membrane. Comparison with previously reported results in the literature reveals that mass transport of water vapors is

substantially improved with the new approach. The performance of the new configuration was investigated with both NaCl and synthetic sea

salt feed solutions. Salt rejection was greater than 99.9% in almost all cases. Salt concentrations in the feed stream had only a minor effect on

water flux.

http://inside.mines.edu/~tcath/publications/CathPub/1_Enhanced_DCMD.pdf

Use of Tubular membranes in the pre-treatment stage of desalination process:

2-The pre-requisite for operation of a RO plant requires feed pre-treatment for removal of suspended solids, bacteria, colloidal particles, etc, which would otherwise lead to fouling of RO membrane. In recent years, the performance of polymeric membranes for seawater pre-treatment has improved significantly. This enables a more advanced SWRO system design by providing good quality feed for RO system, which results in increased reliability and lower water cost. However, use of disposable polymeric cartridge leads to higher running cost and increased plant downtime because of the need of frequent replacement. The present study describes the pilot scale performance obtained on Arabian coastal sea water using tubular ceramic membrane (average pore diameter 0.1 µm) of 19-channel configuration as a pre-treatment system for RO. The MF pilot unit operated at fixed

TMP of 1.2 bar with 40 hrs continuous run, using filtrate water of pressure sand filter (PSF) as feed. Flux obtained was around 350-370 LMH. Turbidity came down to 1.0 NTU and SDI value to less than 3. The filtrate obtained was virtually free from any

suspended solids, colloids and bacteria, etc.

http://www.ijsrp.org/research-paper-1013/ijsrp-p2220.pdf

Hoping this will be helpful,

Rafik

Looking at the question, it refers to out to in membrane configuration. This is only possible in very small tubes, given the required pressure. The in-to-out route is possible as described above by Rafik. We have been supplying tubular RO for decades.

In case the search is for these fibers: Toyobo is the company which I believe still produces this product. Dupont was known to produce these, but stopped this product.

With respect to the need for taking solids out of the water prior to RO: given the configuration of tubes (sized half to 1 inch) very limited pretreatment is required.

Note that the cost is substantial, using tubular RO and currently the normal approach is to pretreat fluids with UF first to take out solids leaving the dissolved solids for spiral wound RO membranes.

with regards,

Ronald