Treatment of high TDS water: Is RO feasible?

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Hello All,

 

Can the RO system refine the mine wastewater with the specifications given in the table below ?

Water type: Mine wastewater – 2500 m3/d

Goal

Results

Unit

Constituent

6.5-8.5

6.5

-

pH

-

117800.0

(µs/cm)

EC

1000.0

824000.0

(mg/l)

TDS

-

0.0

(mg/l)

CO32-

-

37.1

(mg/l)

HCO3-

250.0-400.0

57752.9

(mg/l)

Cl-

250.0-400.0

394.5

(mg/l)

SO42-

300.0

15833.3

(mg/l)

Ca2+

30.0

250.0

(mg/l)

Mg2+

200.0-500.0

40613.3

(mg/l as CaCO3)

TH(Total Hardness)

200.0

22831.0

(mg/l)

Na+

-

1580.0

(mg/l)

K+

0.01

0.1

(mg/l)

Pb2+

0.3

1.2

(mg/l)

Fe2+

0.3

2.0

(mg/l)

Mn2+

3.0

0.1

(mg/l)

Zn2+

1.0

0.2

(mg/l)

Cu2+

0.003

0.2

(mg/l)

Cd2+

Taxonomy

20 Answers

  2. Your salt content is astronomical. My suggestion is that you should not be seduced by expensive technical solutions, The simplest and by far least expensive solution is lined evaporation ponds, if you have the land and climate for it.

    1 Comment

  3. Dear Mr. Arsalan,

        If you are intending to reach Zero Liquid Discharge ZLD, then there is no ground to refer to Reverse Osmosis. To achieve ZLD you are intending to buy a flash evaporator and a crystallizer, all you have to do is to implement an accurate flash evaporator, and your situation is already fine to bypass any reverse osmosis as long as your wastewater is already of high TDS.

     

    1 Comment

    1. Yes, I agree with you too.
      - But for the ZLD process, the TDS should be high, for example, the TDS is 82000, and I do not think it is worthwhile to refine this wastewater directly to the LDP process, but our waste should have at least a TDS of over 150000 ppm.

      - On the other hand, we export reverse osmosis waste because in our country (Iran), unfortunately, there is currently no possibility of reverse osmosis.

      - Please provide it if you have any suggestions.

      - Thank you very much for your guidence and suggestions.

  4. I read all comments and in agreement. Pre-treatment with electrochemical water treatment techniques will not only reduce brine volume but will simplify and reduce cost of the rest of the desalination process. In all, I project higher recovery of treated water with lower CAPEX and OPEX.

    1 Comment

  5. Dear Mr. Arsalan,

       As we are receiving many similar requests, I would like to clarify one much more important question: Now you and your management are looking to treat a high TDS flow, fine. The result of any treatment process will include 2 exit flow streams: One is the refined water, and the other is a stream which will be carrying a much more saline water with higher TDS, which will impose another question: Do you and your management have the capacity to handle and find a way to dispose safely this highly saline flow stream??

       If you have an affirmative answer for this question, then we have a better process than Reverse Osmosis which is Room Temperature Desalination described in naturalseawaterdesalination.com.

     

    1 Comment

  6. It could be done very expensively and with great thought about where the reject water is to be sent.  As with all the comments below the scale-forming would mean that a pre-treatment would be required and something to control the manganese and iron.  Overall RO would not be the choice treatment for this water.  I do agree that the anomolies of the analyses need to be resolved.

    Answered on by

    1 Comment

  7. Dear Arsalan

    The Maximum guaranteed value of the high quality membranes made by reputable manufacturers is 80,000 ppm on reject line. So considering 40% recovery, you can have max. 50,000 ppm on inlet. That is why some software will stop calculation over 50,000 ppm

    This is the first reason. there are also pressure and material limitations in high TDS values for RO unit desalination design. 

    Hope with new coming technologies , these problems would be solved

    1 Comment

  8. Hi

    The relation between TDS and EC is equal 82,400ppm.

    I agree with others comments. RO is  ​not a proper ​ solution  ​whether the TDS ​is 84,000 or ​840,000

    1-please check your analysis

    2- Use pretreatment system similar lime softener

    3- After softener you can use EDR system or evaporator with crystallizer for reduction of TDS.

     

     

    1 Comment

  11. 1. As regards TDS & Conductivity figures, it is obvious that at that TDS range, conductivity is not linear & hence appears erroneous. Mine water can have high TDS. I suggest kindly recheck TDS by gravimetric method & send me feedback by email (drmodak2007@gmail.com)

    2. Very high TDS water can be processed by RO operating at higher pressure than 50bar.Such High Pressure RO is in existence & being used commercially. You can reduce volume, recover water compliant with your desired values on the capacity indicated i.e. 2500m3/day 

    3. Notwithstanding the above, high TDS water can also be processed by Forward Osmosis, which is also routinely being used on commercial level to reduce volume & recover water to the desired parameters. 

    If seriously interested, we can work out a guaranteed solution, by carrying out trials on pilot plant & set up a demonstration. Kindly recheck the analytical results i.e. TDS by Gravimetry & send your feedback to above email ID. Regards,  

    Dr. Harshvardhan Modak.  

    1 Comment

  12. Hi Arsalan,

    I agree with the other comments. The TDS should be less than the Conductivity. Based on your chemical species you may have added a '0' to your TDS value. Standard conductivity probes only go up to 20 mS/cm. Did you use a specialist probe for the test? For these high salinity applications, the TDS and/or TS (@105dC) would give a more accurate value. 

    In general RO desal systems can be designed and operated very efficiently for TDS

    1 Comment

  13. Good Afternoon Mr. Arsalan,

    I concur with Mr.  Alexandros Stefanakis that the EC and TDS are disproportionate.  And simply adding the higher contaminate values relates to neither of the aforementioned.   You should request the lab revisit their report.

    As Mr. Joe Cortuvo detailed, RO is not a proper solution whether the TDS is 84,000 or 840,000.   However, if it where, what would you do with the further highly concentrated mega gallon waste water?

    Over a hundred years, South Africa is sitting on an ever growing ocean of mine wastewater that is gradually percolating upwards ultimately affecting the ground water and soils.  Ultimately any reclamation will cost exponentially more than mining profits.

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    1 Comment

  14. The only answer that makes sense is Alexandre’s answer; the conductivity number must be bigger than the TDS number!, the analysis shows that conductivity number smaller than the TDS number, that is wrong.

    This water is impossible to treat with membranes because the osmotic pressure of this water is so high that you will not find a membrane, not pressure vessels for that matter that will tolerate such a high pressure.

    So the answer to your question, no membranes are not an option.

    Good Luck

    Luis Inarejo

    1 Comment

  15. I think there is a mistake with TDS concetration. It should be 84.000 mg/l, instead of 840.000 mg/l. Acordingto the data, you can use RO because your cl-  goal is not to stright. The hardness is too high, so you will need some preatreatment to reduce the total hardness, such as softening using resins or lime softening. You also have to check the suspended solid concentration to prevent some problems in the RO membranes. Depend of this, the turbidity  and the Silt Density Index (SDI), yo have to choose between Microfiltration or nanofiltration as a pretreatment. Finally, chemical treatment is needed to avoid problems during the RO operation.

  18. You would need pretreatments.  The pH and is not  aggressive, but the TDS is astronomical. Seawater runs from about 30,000 to 50,000 TDS.  You might think about nanofiltration to take out a lot of the +2 ions, followed by RO for the +1 ions. Maybe ceramic membranes?

    1 Comment

  19. Are you sure the data are correct? I see EC 110,000 μS/cm and TDS 824,000 mg/L? Maybe it is EC 110,000 mS/cm and TDS 84,000 mg/L?
    These seems like a brine. RO could in principle treat, but practically it will be too expensive and difficult...

    2 Comments

    2. It is brine, as it consist mainly from NaCl and CaCl, which easily dissolve any iron and manganese exist at that area, and it could become from salty underground mines. 

  20. There is too much Iron and Manganese, which have to be removed firstly with pretreatment (you can ask for that treatment). 

    Second stage pretreatment need for pH adjustmen, aand third stage for clarification (suspended solids removal).

    The RO unit has to be calculated using seawater membranes at high pressure operation. Depending on the use of the produced water it will maybe need a second stage RO unit pass. 

    2 Comments