Sand Filter for Seawater Desalination

Taxonomy

• Sand Filter
• Water Treatment & Control
• Filters
• Water Treatment Solutions
• Sea Water Filtration
• Filtration
• Sea Water Desalinisation
• Sustainable Desalination
• Desalination

15 Answers

1. There are many types of media bed materials available.  Making any recommendation will depend on the process for the desalination and the contaminants and concentrations.

   For example if your process requires chemical oxidation prior to media bed filtration then the catalytic type media will be favourable.  If the project is economically savvy then the modern technology textile media bed filters present the best CAPEX and OPEX cost to performance ratio.  Textile media is also better performing in high turbidity so will provide a better performance when the sea water is turbid, such as during a climate event.

   If the project already has sand filters and are wishing to replace the media then a review of the particle shape parameters is required.  Along with pressure differential limitations and pressure at discharge requirements.  The maximum sand media grain size will have a limitation relating to the back washing process, liekwise the minimum sand grain size will have limitation relating to the tank screens design

   at a very basic level the physics of sand are independent of water chemistry, but over long operational life the mineralogy of the sand can show huge performance differences.  

2. Once you get your pre filtration system chosen for desalinization, please consider: Laminar Flow in Magnetic Labyrinth for desalinization; which is the latest technology, with many advantages over last century R.O.   . Visit www.BlueFinWater.com

    

3. I suggest that you may instead use Active Filtration Media from Dryden Aqua. www.drydenaqua.com

4. the best sand filters are compact sand filters that work submerged, also known as ceramic flat sheet membranes - contact Cerafiltec, they are the best in class, their CEO is based in Dubai: kay@cerafiltec.com

5. There are no differences in media selection for sand filters between clean water and seawater. Typically multi media filters are used. Media option could be garnet or anthracite depending on influent suspended solids and turbidity levels.

   Reputed membrane manufactures  recommend influent water with SDI

6. The best  practical answer for your question can be derived from watts .com web site http://www.watts.com

   Multimedia sand filtration:  This system is similar to the rapid sand filtration method.

   Figure 14: MULTI-MEDIA SAND FILTRATION

   

   2 Comments

   1. One of the beds can also be zeolite depending on content of Se or others similar if "tile" water.

   2. Sir,this a much better i am now working with Multi media sand filter.very good result.

7. The principles of using denser media to enable finer grades and better filtration are precisely what we have used to develop our brand of media, called FilterClear. Sand and anthracite are useful to filter out large solids then we use layers of alumina and magnetite of much finer grades to polish the water. Experience shows we can reach an SDI less than 3 without chemicals. Plus, with a media filter you get some removal of soluble carbon too.

8. I once trail sand for a slow sand filter ,using layer of brick at bottom of the tank to channel your water to the outlet and your sand on the top and have water coming in and the result was not satisfying but it make our decision to choose other option

9. I once trail sand for a slow sand filter ,using layer of brick at bottom of the tank to channel your water to the outlet and your sand on the top and have water coming in and the result was not satisfying but it make our decision to choose other option

10. I once trail sand for a slow sand filter ,using layer of brick at bottom of the tank to channel your water to the outlet and your sand on the top and have water coming in and the result was not satisfying but it make our decision to choose other option

11. Full agreement with Ken about using sand, no difference.

    I slightly differ on Garnet reasons for performance, but would be a long detour of theoretical reasoning.

12. Tirellil,

    There is no difference in how to choose a granular filter media for seawater versus fresh water.  It is based on Stokes Law to determine the terminal velocity of the media particle when backwashing.  In brief, it depends on the intended backwash flux, backwash water temperature and the media's specific gravity.  I previously worked for a seawater filter manufacture (equipment vendor).  For most of their seawater filters, they used fine garnet, not sand.  Garnet has a higher specific gravity than silica sand, thus, they can use smaller grain size which provides finer filtration.  

    Ken Martins

    CH2M, Global Practice Director, Industriial Water

     

13. Better to use a membrane filter e.g.MF or UF rather than a granular filter medium. If you can afford RO you can afford a pre membrane.

14. If you are using RO and lowering the SDI is important to the design (to increase flux) there are granular alternatives to sand that will provide higher filtration rates and better quality. 

15. Dear Tirellil.

    What type of Desalination technology is planned:

    If Thermal, no particular issues are there for filtration. Even the fine filtration by deep sand bed is not necessary and eventually one self-washing filters (about 1 - 1,5 mm mesh) is quite enough-

    If RO, the sand filtration is actually crucial in the pre-treatment sequence, with two main issues to be considered:

    a) Degree of fine filtration: I suggest a typical sand particle size meshed in the range of 0,7 to 1 mm

    b) Sand not releasing silica into the filtered water, because silica is very difficult to be reduced by RO. Quartzite sand is therefore to be preferred because of the lowest degree of impurities (impurities cause the release of silica)