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Precipitation in bulk storage tank for sodium hypochlorite?
Posted: Wednesday, August 4, 2010 9:04 AM
Joined: 8/4/2010
Posts: 6


Heard some operating experience at a recent conference where it was reported that it was not recommended to add new sodium hypochlorite product into a storage tank that already contained sodium hypochlorite.  The concern was the new mixing with the old could cause precipitation.  The guy telling me this said they were seeing clogging of strainers in their feed system from what was determined to be calcium carbonate.

Note, the precipitation was apparently occurring in the storage tank.  No water was added to the tank, the only thing that was supposed to be going in it were bulk deliveries of 12% hypo.


Has anyone else experienced this?  And can anyone shed any light on why precipitation would occur in the tank?



Posted: Tuesday, August 17, 2010 11:41 PM
Joined: 7/26/2010
Posts: 8

Mixing new loads of hypochlorite with existing is a very common practice, at least in all treatment plants I've been.


Never seen such thing.

James Royer
Posted: Wednesday, August 18, 2010 10:04 AM
Joined: 9/21/2009
Posts: 98

Hypochlorite solutions contain a sodium hydroxide so carbondioxide is absorbed and any Calcium will be precipitated out in the tank. The tank should be emptied as much as possible before refilling to avoid a buildup og precipitate.


It is common practice to mix loads at most WWTP but they do have problems with precipitate. I work in the lab so I have to titrate the hypochlorite solution all the time so that the chlorine concentration is correct. Mixed tanks seem to deteriorate faster than empty tanks that are filled. The precipitation lowers the pH which allows the chlorine to deteriorate.

Posted: Sunday, November 13, 2011 11:00 PM
Joined: 11/13/2011
Posts: 2

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