|Ask The Expert: Hot and cold of lime softening
|Question: Q: I am doing some research on the market for lime in Mexico. At the moment the amount used in water treatment seems very low (when compared with the USA for example) and I am trying to find out if this represents a potential growth area for lime producers. I came across a reference to your magazine on the web and hoped you would be able to help me understand this market a little.
I would very much appreciate the opportunity to talk to you about some of the following points:
1.) To what extent is lime used in the purification of drinking water and the treatment of waste water?
2.) Under what conditions is the use of lime advised? Does it depend on the source of the water—or the type of waste?
3.) Are there any disadvantages in using lime—or are there other chemicals that are preferred?
4.) Do you think that the quantity of lime used in water treatment will increase, decrease or stay about the same over the next five years?
If you are prepared to spend a few minute talking about the use of lime in this market in Mexico, I would be most grateful. I look forward to hearing from you.
Judith Chegwidden, Director
Roskill Information Services Ltd.
Answer: A: Our Technical Review Committee suggests the following:
1) The Water Quality Association has a number of technical papers and other information that can assist you. Generally, there are two methods—hot and cold lime softening.
2) Use of lime in Mexico is dying off, but hot lime softening is still used on some industrial applications because of the high silica content of some water. More specifically, on waters with high hardness and alkalinity, lime softening will lower hardness, alkalinity and TDS. Hot lime processing is favored for silica removal as well, aside from accomplishing everything done with the cold system. It's more complicated to manage it and there are few, if any, promoting or servicing it in Mexico.
Among main applications, beverage makers like Coca-Cola (and other soft drink producers) and breweries use this process all over the world as it assures them of a similar water quality effluent. RO units displacing this process. Other applications were for municipal water, which isn't too common but still used occasionally. There are other U.S. applications, about which chemical companies have information.
3) To answer more specifically, you can look at the Spanish or English version of the old NALCO handbook. If that's not handy, the relevant article, "Conditioning Water Chemically," can be found online at the following ONDEO Nalco industrial water treatment website: www.onlinewatertreatment.com/literature/Nalco/docs/Tf-016.pdf
4) You can also track shipments of lime from the United States to Mexico at the National Trade Data Bank (NTDB)—see: http://govpubs.lib.umn.edu/stat/tool_ntdb.phtml
5) Lastly, the National Drinking Water Clearinghouse at West Virginia University offers a fact sheet on the subject: www.nesc.wvu.edu/ndwc/pdf/OT/TB/TB8_lime_softening.pdf
Hope that helps.
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