Cheap and Efficient Coagulants

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What are other cheap and efficient coagulants apart from Aluminium Sulphates?

We are investigating some of the worse unsafe water sources (muddy water from rivers, ponds and wells) being used by some communities in some parts of Nigeria and how they treat the water before use.

We discovered that some of them use Alum (Aluminum Sulphate) as the cheapest available solution to clarify the water and use bleach to disinfect.

Our laboratory analysis of most of the "treated water" showed the presence of Aluminium at higher values than Nigeria Industrial Standard (NIS) and WHO guidelines for drinking water.

Is there a cheaper chemical solution that coagulates and clarifies such water?

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25 Answers

  1. Ferric Chloride is best among the best, based on alkalinity. e.g. if alkalinity = 20mg/l meaning dosing rate is 20mg/l/ L/s depend on type of process.

     

    Thank you,

    Mangena P

  5. Ferrous Chloride FeCl2 ?

  6. Try raising the pH slightly with quick or slaked lime. However if you raise it too much the aluminum will go back into solution. Alternatively just use lime without  aluminium sulfate.

  7. Choice of a Coagulant is dependent on many things: The availability of the coagulant, the cost of the product, the storage of the product  etc.  Since it is alum they are using and the problem is the residual alumina my suggestion is; determine the optimum dose of that Alum where the residual alumina is within the standards you are looking for and teach/show the users what quantity Aluminum Sulphate to use that would not leave a very high residual alumina this can be achieved by determining  the alkalinity of the water, then conduct a jar test to determine the optimum dose of the alum that gives you a residual within the limit you're looking for. Do you need to change a coagulant, because the problem you described above is not impossible to solve, easily too.

  8. When I was in Spain I visited a Water Treatment Plant using a very fine powder made from finely ground up oyster shells---it is inexpensive and is a waste by-product--after settling it can be used as a soil amendment that provides minerals to the soils along with nutrients from the SS that were precipitated. I am holding a sample but unfortunately they didn't label the sample I have as they consider it proprietary, but I know they get the seashells for free and then have them ground up and packaged in fiber drums. I will ask EAZ in Pamplona what it is (constituents) and post a reply when I have an answer.

    1 Comment

  9. Ferric coagulants may be cheaper, it rather depends on what is available in the area. One advantage that they may have is that it is possible to have grades with different acid contents which may make getting the pH right easier. Also iron doesn't increase in solubility at higher pH as Al does. If you do get iron coming through it is often more visible. Ferric coagulants may be more corrosive though. To get a more pH tolerant coagulant though you may have to go to poly

    aluminium chloride or similar.

    1 Comment

    1. Ferric Chloride is not cheaper but worse ferric chloride absorbs moisture how do you store that? Also, what about the ferric Bacteria but worse the smell? Water Treatment is dependent on quality and economy .

  10. Ferric Sulphate, Ferric Chloride, polyaluminium chloride.... Everything depends on water quality, results of JAR tests (pH, dose).

    1 Comment

    1. Ferric chloride is out of the question for the same reasons I gace Steve above.

  15. Simplest to more challenging, combinations always a consideration for pH, charge and settling or flotation; acid- HCl, H2SO4, FeCl, AlSO4,FeSO4, Lime- CaO, Caustic - NaOH, CaOH, KOH, inorganic salts mentioned with Polyamines: DADDMAC & Epiamines, blended with inorganic 5-20℅ blends should be sufficient, all are Cationic except sodium alumina the which is snionic, other inorganic a are aluminum chloride, polyaluminum chloride and polyaluminum sulfate, once a pepper sized floc is formed and pH.is less than 7.0 add a Cationic Flocculant to make a large Flickr, when pH is over 8.0 use an Anionic flocculant to form a large Floc. Higher pH's tend to float where lower pH's tend to settle. Selecting the equipment to match the chemistry correctly reduces operational and capital costs.

  16. Dear Chinenye: I agree with Randal: go membrane. Best coagulant is "no coagulant". Today's technology does not use chemicals at all; maybe sometimes a clarifying process when turbidity is too high. Write to me at fsanchezmts@yahoo.com and I'll fill you in with information, tech and financing solutions.

  18. Engr. Nwaogwugwu,

    Had you considered alternative treatment techniques to coagulation and sedimentation? Membrane filtration can be an economical substitute for conventional chemical treatment technologies. I would recommend that you take a look at membrane treatment as an alternative. One charity that provides membrane systems in various configurations for community water systems and emergency water supply is the     SkyJuice™ Foundation out of Australia. The founder of this charity, Rhett Butler, has long experience in the commercial membrane business and has been fully engaged with this charity for at least a decade. See their web site here: http://www.skyjuice.org.au/. They have provided manual and pressurized systems for communities up to 5,000 persons.

    Best wishes,

    Randal Samstag

    1 Comment

    1. Membranes will eventually need to be chemically cleaned or replaced. Although a well-designed membrane with adequate pretreatment should last 8 to 10 years. In any case, good to see charities looking into sustainable solutions.

  19. Good Morning Mr. Chinenye Justin Nwaogwugwu,

    Although aluminum based coagulants can be quite effective, I have found here at our water plants in Canada with similar conditions (it sounds like anyways) that iron based coagulants are much more effective...the downside is that they cost more money (at least where I live).   Coagulants as you already know are very finicky and require the right balance between pH, Temperature, and the size of particles in the water.  I am sorry that there isn't an easy answer for you but jar testing as the others have mentioned is crucial in determining which coagulant might work.  However, and this is the annoying part, the bench scale tests almost always need to be tweaked in the full scale system. 

    At one of our plants we were using an aluminum based coagulant and after a few years of finding increased aluminum in the treated water (there was zero aluminum in the raw water) we had determined that the coagulant had been carrying over through the treatment process into the treated water chamber.  Aluminum based coagulants (or any coagulant for that matter) must have some kind of detention system in order for the chemistry to take place and the detention time for us ranges between 30 - 90 minutes before we take that water to the second stage in the treatment process otherwise the aluminum will carry over.  I hope this helps.  Please feel free to contact me for further details as this is a complex issue that I could write pages and pages about!

    Respectfully,

    Kurt Rasmussen, P.Eng.

    SaskWater

  20. Have you considered mechanical coagulation and flocculation?

    For muddy river water, the process my company typically uses is fine and ultrafine bubble aeration which causes coagulation and flocculation due to the properties of the ultrafine bubbles. As well as oxidation to strip out iron, manganese, ammonia and other dissolved organics. This then goes through a static mixer which further provides further flocculation. By this stage the floc is large enough to be filtered out by a media filter. We typically use an Activated Filter Media which provides reliable filtration down to 1 micron with 99% efficiency. Biofilm does not develop on the media bed and hence chlorine demand is significantly reduced, I have seen up to 80% in some cases. This is a solution being used to provide clean drinking water for over 2,000,000 people in developing countries across Asia as of this year.

    Our company seeks to provide water treatment solutions that either eliminate or significantly reduce the use of toxic chemicals. If you are interested in learning more about this process of water treatment, please email me at andrew@waterandoilsolutions.com.au

  21. There are other cheaper technologies to perform effluent coagulation. Here are some alternative, low-cost and natural examples: bentonite, fulvic and humic acids, moringa oleifera, among others. The important thing is to perform a jar test, to verify in the laboratory what would be the best application dosage in the effluent, in order to have a concentration of the coagulant agent, efficient and low cost.

  23. Aluminium sulphate is one of the better coagulants for the application.  The challenge in a community application is that pH is not maintained in the optimum range (6.5 to 7.5) and if it falls below the solubility pH range, aluminium carryover into the filtered water is experienced.

    If maintaining pH in the optimum range is difficult, can use ferric chloride that works in a wider pH range, between 4 and 10.

  24. Bonjour

    On arrive à un stade ou l'on fait n'importe quoi sans au préalable regarder ce qui est de nature -biologique- ou ce qui sera de nature -biochimique-.

    Toute action biochimique sur un liquide contenant des éléments chimiques dissous aura  un impact sur la caractéristique -biologique- de l'eau qui se répercutera autoamtiquement sur la santé des individus à qui on aura présenter cette eau comme une consommable

    Oui, on peut tout faire mais quelles en seron les conséquences ?

    Hello

    We get to a stadium or we do anything without first looking at what is - biological - or whatever - biochemical-.

    All biochemical action on a liquid that contains dissolved chemicals will have an impact on the feature - organic - water which will impact rupted on the health of individuals who will be presenting this water as a consumable

    Yes, we can all do, but what in seron consequences?

     

  25. Dear Engr. Chinenye,

    To my knowledge Alum is the cheapest Cooagulant readily available in the market. Other coagulant which would be more efficient in your above mentioned applications could be Ferric Chloride but it would be definitely costlier than Alum.

    Regards, Imad