Saline Water Treatment at Household Level

We are working ​on the ​installation of ​hand pumps and ​we are faced ​with ​saline water ​with TDS over ​2000 ppm. ​

What is the ​low-cost ​solution for ​saline water ​treatment at ​household level?​ How can we ​reduce TDS and ​arsenic levels?​ ​

RO plants are ​not a ​sustainable ​solution due to ​maintenance ​since 80% of RO ​plants in ​this area ​are not working.​

Taxonomy

• Drinking Water Treatment
• Household Water Treatment
• Water Treatment & Control
• Water Treatment Solutions
• Saline Water
• Total Dissolved Solids (TDS)

12 Answers

1. Absolute low-cost, low tech would be small solar distillation units. Easy to design and manufacture, no moving parts so durable. You may need to consider remineralisation though if used extensively.

2. Have you thought about Electrodialysis? Consumes less energy than RO and with a good solar radiation could be used with solar energy. Normally, it does not work with higher salt concentrations with in literature has shown that could also work with sea water. 

3. Where in Pakistan do you work? Sindh? You may consider looking for deeper groundwater, which tends to be less mineralized; a household-level demineralization is hardly possible. Arsenic, depending on its chemical form in your specific water, may be removed by aeration (oxydation) and iron "saw dust" in the water, followed by a simple filtration; however, you have practically no control over the remaining As content on household level. You would have to test each shallow well inidividually and several time after starting to use it, since frequently As contents develop only after some months of operation. In Sindh, deep seated groundwater (explorable through handpumps) is frequently found, but it needs careful well construction for safe exploration. This is dafer and less costly on village level, than inividual purification installations on household level.

4. As is your biggest problem, as to the saline water the chipest way is to dilute them with pure water.

5. Roof Rain/ Rain Water Harvesting might be the alternate solution instead of installing the hand pumps for drinking as it is locally managed system which would be more sustainable and would not containing such ambiguities like TDS, Arsenic etc. and Rain Water can further filtered through normal Bio-Sand Filter to remove the bacteriological contamination. Both the interventions are cost effective too.  

6. Usually RO membranes in domestic units are not capable of handling TDS above 1000ppm. Only larger membranes are available for high TDS. 

   For arsenic you can look for Activated Alumina cartridges and for TDS there is no other membrane filtration method for high TDS water.

   Using solar distillation may not be practical as it cannot produce water in low sunlight. 

   You should look for distillation units with electrical heating. 

7. It is obvious that you can not allow Hand pump discharge to be consumed directly. Hand pump flows have to go to a storage tank where a dose of Potassium Permanganate is easily possible. There after, it needs to be filtered to remove Arsenic salts. Then various options are : 1. Let individual Households use it as input to their individual R.O. to remove TDS for Drinking water purposes and washing of hair/ skin etc. The RO reject should get used for toilet flushing, etc.(Individual ROs are better maintained than community RO.) Or

   2. Use Focused Sunlight Energy/ Power to heat water in tanks and collect the vapour/ steam condensate for drinking water purpose.

   3. Invest in Rain water harvesting to reduce the TDS of Ground water and dispose off Reject waters at far off locations.

8. Hi Ali,

   Our SaferEx - Multiaction Water Purifier solves the household water challenges you are battling with. It reduces TDS to acceptable level or negligible in some cases. Coagulates and sediments salts and heavy metals like Arsenic, etc.

   Read More:http://tinyurl.com/y79f3e96

   Regards

   Justin

9. For As you are likely to have As(III) to remove it you would be better to oxidise it to As(V) with ferric chloride or potassium permanganate Peroxide or Ozone should work too.  Then As(V) could be flocculated with Ferric sulphate the flock can be removed by MF. Not sure if this is feasible at household level. As to remove 2000ppm of dissolved solid NF or RO can be envisage alternative is to distil the water an condense the vapour into demineralised water add back so salt to make it drinkable. there are some hand pump RO system on the market.

10. I think the only feasible low cost solution is solar distillation. There are very different methods that you can easily find in the web (from very low cost solutions made by plastic sheets, to integrated plants that produce distilled water and electricity). It can be applied both at household and community level. The only you need is the sun. So it fits well in hot, dry climates.

    With respect to the arsenic content, I understand that there are succesfully attempts to remove arsenic from water using solar distillation. See for example:

    http://www.watertechonline.com/arsenic-the-great-chameleon/

    https://novascotia.ca/nse/water/arsenicremovaldistill.asp

     

    Good luck

     

    Giacomo

     

11. Dear Ali

    If the problem is electricity supply you may consider using a hand pump also for the RO as you do for the pumping

    It can be very efficient with Brackish Water Membrane and high recovery. It can be done batch wise, so the user may be instruct to pump it till certain level and then to withdraw the concentrate

    Good luck

    Ilan

12. Point of use low pressure RO might be the only solution. But it is very inefficient, about 80% reject. They have to be maintained, and cartridges replaced as needed.  Depending upon the type and concentration of arsenic, it might not work well for arsenic. +5 is removed better than +3. Would have to oxidize +3 first with chlorine.