Lime sludge recycling

Published on by in Technology

In the conventional Remineralization Technology that uses Hydrated lime to add Calcium hardness to Desalinated water significant quantity of Lime sludge is produced.

It is predominantly Calcium carbonate.

Is there a Technology to recycle this sludge to lay roads or to use in Building industry?

Taxonomy

10 Answers

  3. Depending on your process, lime softening (using hydrated lime) can precipitate calcium carbonate (at pH 10,3) and magnesium precipitation if the pH is in the region of 11,0 to 11,3. So it depends on your process as to what constituents will be in the sludge.  I would like to see if this sludge can be used for soil amelioration. But again this all depends on chemical analysis of the sludge. Farmers are always looking for lime (CaCO3). But I am not sure of the purity requirements. So can any agronomists out there give us some leads?

  4. Why to add excess lime and looking a process to recover back? Just add a little lime to raise the pH above neutral. There is no lower limit for Ca in the drinking water and hence excess addition is not at all required.

    1 Comment

    1. First we acidify the Distillate with CO2 injection and then add Lime water for calcium hardness addition and we have a regulation to have a minimum of 50ppm calcium hardness.The lime saturators produce the Lime water from the Lime milk which is the solution of water and  Hydrated Lime by continuous recirculation and also constant feeding of Lime milk and bleeding of Lime sludge.So there is no excess addition as the target is to meet 50ppm calcium hardness 

  5. Dear Soloman Prince,

    Depending on the volume of waste, it contamination and other characteristics, it is possible to use such waste in the production of portland cement by the wet method, or in the production of concrete and small-sized products from it, for example, for cottages. The use of waste for road construction will require lengthy testing and is hardly economically viable.

  6. Dear Solomon,

    One of the areas where it may be reused with lesser degree of risk  is in odor control in land-fill sites or pit latrines. The other application would be in neutralization of acid waste from mines, where again the by product (calcium salts) volume may be an issue.

    Having said that, the sludge should be tested for its hazard levels and approvals from the respective authorities (handling, transportation, storage etc) before any bulk or major application.

    Regards,

    Zain

  7. Adding hardness with lime is normally made using CO2 to dissolve CaCO3 as bicarbonate. This eliminates the CaCO3 sludge and adds the hardness with smaller lime dose....

  9. Dear Soloman

    The short answer is yes it is likely and I can reference some for you but you need to understand the risks associated with, for example, of replacing a conventional building material with a recovered water treatment sludge. 

    Toxicity comes to mind if exposed to humans or the environment, usually in the form of heavy metals that can accumulated in the sludge.

    Regulation, is the sludge an allowed product to be applied in the re-use application or not?

    Integrity of the material, when applied does it pass strength and construction tests where it has been re-used?

    i have some very useful references if you are interested, contact me directly

    Regards

    Gary

    gary@dikubu.co.za