Removal of selenium

Taxonomy

• Heavy Metal Removal
• Water Wells
• Heavy metals
• Bore Well Recharge

10 Answers

1. Selenium is an important element that is required for humans, animals, plants and other life forms. Selenium is naturally present in the Earth’s crust and its worldwide distribution has led to complex interactions between selenium and the natural environment (water, soil, sediments and air).

   Two Process can be removed Selenium

   1. R.O. and

   2. Granular activated carbon (GAC) 

   The typical pressure-driven membrane separation technologies consist of microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Among these, only nano filtration and reverse osmosis are capable of separating selenium compounds from a contaminated wastewater stream. the use of nanofiltration was capable of selectively removing 95% of selenium from highly contaminated water. Solar powered ultrafiltration nanofiltration/reverse osmosis systems is capable of removing 74–94% of the initially present selenium concentrations. Further evidence of selenium removal by nanofiltration or reverse osmosis is, to say the least, very scarce in the reverse osmosis is listed as one of the best available technologies but that further industrial implementation of this technology is probably hindered by the fact that the solutions to be treated contain very dilute concentrations of solids, which is most often not the case for industrial wastewaters like acid mining wastewaters. Therefore, pre-treatment is required and reverse osmosis for selenium removal from polluted waste streams can only be used as a final polishing step, often described in the literature as a post-treatment step.as shown in the figure.

   Granular activated carbon (GAC) is moderately effective in selenite  removal  from wastewater. Activated alumina is effective for selenite  removal . Slow sand filtration and the algal-bacterial process have recently been shown to be effective for the  removal  of  selenium  from agricultural drainage  water .

2. What is level of Se present? To what level do you wish to remove Se. In which form is Se present (selenite or selenate)? 

   1 Comment

   1. Naveed Fakhar it would be helpful if you could supply this additional information to help to better answer the question.

3. A full water analysis with Se speciation is always useful to have. Some physico-chemical pretreatment may be required, but SUEZ's ABMET biological treatment system can remove most forms of Se. Your proviso of not changing chemical composition might be difficult to meet if taken literally, however. 

4. Spent considerable time working on Se reduction and it is not as easy as folks try to make it. Se can exist in an oxidized or reduced form as well as elemental.

   Anyone that claims to have a solution and the 1st step in their solution is not to get your sample speciated doesn't have a working knowledge of Se.

   So in keeping with my own advice, you must get your sample speciated so you know what you have. 

   Here is a simple example. ferric precipitation works really well with selenite. Not so hot with selenate. So you can reduce selenate to selenite with ferrous and get a double benefit with the ferric formed when ferrous is oxidized the ferric. Now have a little selenothionate. It cannot be reduced since it is a reduced form. You can decrease the Se+3 and Se+4 to low ppb but 10ppm from Selenothionate stays 10ppm.

   Hope that helps.

5. Use Nanofiltration

6. Two main choices. RO or ion exchange. Concentration levels and flow rate help to choose.

   1 Comment

   1. Right way....IX could be the best

7. What concentration do you have.? It is usually not necessary to remove selenium from water unless it is well above the WHO Guideline or EPA standard (50 ppb is very conservative). Selenium  is actually beneficial and an anticarcinogen. If you must remove it do not use RO! Activated alumina works and is much cheaper.

8. In general, selenium can be removed by reverse osmosis on through the use of ion exchange resins.

   1 Comment

   1. No! Not RO.

9. Good Afternoon Naveed,

   Please provide the complete water analysis so that the professionals are able to provide the proper solution(s).

   Warmest regards,

    

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10. Hi Naveed I send you a connection request. If you dont want to change the chemical composition settling by gravity might be an option. To find out if that approach might work we will need some more information.