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wastewater neutralization



Good morning everyone,

	I hope someone can give some help with the following:

	The question comes from a high quality woolen mill.  They use citric
acid to lower the pH in their wastewater but citric acid has a very high BOD
(and cost).  They've heard you can bubble CO2 through water forming Carbonic
acid which would also neutralize the effluent but without the BOD problem.
Further, CO2, unlike other acids is not a RCRA hazardous material/waste.
Here's a little more process info:

	The initial process water is LOW (acidic) in pH.  They strain out
the fiber flox (with dyes intact) and then "hit" the process water with
caustic soda to neutralize the effluent.

	Occasionally they overshoot the "7" pH range they try and maintain
for discharge..this is when they add the powdered citric acid that is costly
and carries the large BOD load.

	It is the replacement of this that they are interested in.  It is
their understanding that when the CO2 gas is forced into a solution under
high pressure it creates a carbonated solution which is carbonic acid (Not
Carbolic)

	Brent Clement
	p2 Technician
	NHDES
	bclement@des.state.nh.us