Coagulation with Rock Alum and an Alum Cage 1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars). 

Forum for discussion on chlorination, slow sand filtration, micro filtration, nano filtration, UV irradiation, desalination, reverse osmosis, roughing filtration, charcoal filtration, sedimentation, coagulation and flocculation, solar distillation, compact water treatment unit performance, etc.

Re: Coagulation with Rock Alum and an Alum Cage

Postby Tkay » 09 Feb 2010 14:59

Thanks Happy plumber, the article is useful and seems its gamble on the disposal hoping you don't get into trouble with the authorities.

Tkay!

1 Ratings (5.0 Stars out of 6.0) 1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars). 
09 Feb 2010 14:59

User avatar
Tkay
 
Posts: 5
Reputation:

Joined: January 2010
Years of WASH Experience: 5
WASH Country Experience: Kenya, DRC, Somalia
WASH Work Experience: Oxfam, NRC

Re: Coagulation with Rock Alum and an Alum Cage

Postby Caetano Dorea » 10 Feb 2010 16:16

Dear HappyPlummer,
Correct for the most part... but I'm a he not a she :-)
Anyhow, the issue with sludge disposal in receiving waters is a bit tricky. I worked in Canada for a while and a major water treatment plant I worked with up until recently disposed of its alum sludge back into the river. This is not saying that you should do the same, but the circumstances and priorities during emergencies may be such that there is no other viable alternative.
That said, what is seen as a problem by some is used as a solution by others. It is not rare to read about alum being used directly in lakes as an algal bloom control measure. Alum controls phosphorus levels which and is used for lake water quality management. However, this does not mean that there isn't any associated toxic "side effects" to this type of practice.
Just to be clear... you should avoid disposal of alum sludge in rivers and lakes unless there is no viable alternative.
Cheers,
Caetano

1 Ratings (5.0 Stars out of 6.0) 1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars). 
User avatar
Caetano Dorea
 
Posts: 40
Reputation:

Joined: November 2009

Re: Coagulation with Rock Alum and an Alum Cage

Postby janheeger » 09 Jul 2010 06:53

Though it looks easy I have some concerns on the dosing. This method seems to be a bit rough and compromises on the rapid mixing. The rapid mixing of aluminium sulphate has an influence on your final results. Iddeally Rapid uniform mixing for coagulation should occur within 30 to 90 sec and not much longer (when a floc has formed and breaks hereafter it can not be built again)

To do a jar test to determine the right dose wont be easy as the jar test should be a mimic of the real situation, otherwise the advised dose is not optimal and the applied dose can be far too much.

According to studies published in the l newspaper of the AWWA (1995) contrary to iron,
aluminium has no direct beneficial effect on health. It is known that the adverse effects of aluminium
are much more chronic (long term) that acute (short term) it was shown that aluminium is a neurotoxic
compound when it penetrates in blood circulation
• Aluminium fixed in the brain
• accelerates the aging brain
• the analogies with Alzheimer's disease

1 Ratings (5.0 Stars out of 6.0) 1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars). 
User avatar
janheeger
 
Posts: 7
Reputation:

Joined: December 2009
Years of WASH Experience: 0
WASH Country Experience: Albania, Algeria, DRC, Kenya, Rwanda, Sri Lanka, Tanzania, Uganda, Zambia
Short Missions in realtion to WASH:Afghanistan, Botswana, Burundi, Ethiopia, Guinea, Haiti, Ivory Coast, Kosovo, Lesotho, Liberia, Madagascar, Malawi, Namibia, Pakistan, Sierra Leone, Somalia, South Africa, Sudan (North and South), Tajikistan, Turkmenistan. Uzbekistan, Zimbabwe
WASH Work Experience: MSF-H, Oxfam GB, ICRC, UNICEF, WASTE

Re: Coagulation with Rock Alum and an Alum Cage

Postby Caetano Dorea » 09 Jul 2010 13:24

janheeger,
I'm glad you feel concerned, as simple solutions can be risky when they are not coupled with a good understanding of the underlying relevant principles. Anyhow, the doser is a makeshift solution to overcome the problem of rock alum dissolution. Notably other manufacturers use the same principle to dissolve tablets of either coagulants and disinfectants, but this one is at the fraction of the cost. There is no doubt that rapid mixing a coagulant solution in to the stream of raw water is probably more effective, but those that have attempted to dissolve rock alum for large emergency operations may tell you that it is far too time consuming.
You are also right that jar-testing should mimic the process in question... this is clearly stated in the article. Anyhow, as one can imagine many times (if not all the time) standard jar-testing equipment is not available in emergencies. Therefore one can only rely on simplified procedures for this test. The key is to try to keep it as standardised as possible and do the appropriate tests of whether the dosing has been above or below the optimal level. Again, not the ideal situation, but this is what can be done in an emergency with little to no lab infra-structure. Anyhow, I can send you more information on this if you are interested, as this is covered in more detail the abovementioned article.
With regards to aluminium residuals you are absolutely right: "aluminium is a neurotoxic compound when it penetrates in blood circulation." The key issue that perhaps you overlooked is the overwhelming evidence that the human body naturally absorbs very little of the ingested aluminium. Unless aluminium is being injected into the bloodstream (this is why we should pay more attention to aluminium that is used in vaccines), it must go through the gastrointestinal tract, where pH changes to near neutral conditions in the intestine causing most of the ingested aluminium to precipitate to a solid form that is then eliminated in the excreta (there is an excellent article in the Journal of the AWWA on this). The small proportion of aluminium that is absorbed is for the most part eliminated through urine, except those who have a compromised renal system. Such individuals may be at risk and is why they undergo dialysis for this and many other reasons. It is worth noting that most of the ingested aluminium does not come from water treatment chemicals. Due to its abundant nature it is found in many other food and pharmaceutical sources and sometimes in much higher concentrations that those typically found in drinking water. For example, if you were to test the aluminium content of a cup of tea, it would most likely not conform to WHO guidelines (and by the way those guidelines are not health based). Again, all of this is explained in more detail in the article, which I can send a copy to anyone interested (unfortunately I can't post it due to copyright reasons).
Anyhow, your points are all valid, but I just wanted to clarify some misconceptions that could be drawn from your comments. Aluminium sulfate is an excellent water treatment chemical that is extremely useful in emergencies due to its wide availability, relatively low cost and ease to use (as long as you know the fundamentals).
Cheers,
Caetano

1 Ratings (5.0 Stars out of 6.0) 1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars).1 Ratings (5.0 Stars). 
User avatar
Caetano Dorea
 
Posts: 40
Reputation:

Joined: November 2009

Previous

Return to 1.13 Water Treatment



 


  • Related topics
    Replies
    Views
    Last post

Who is online

Users browsing this forum: No registered users and 2 guests