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Problem with in-line neutralization

2003

Hi!

I'm working the environmental issues of a company that does stainless steel equipment for wineries. We have a waste water treatment plant with a storage tank, followed by coagulation/flocculation and activated carbon.

The neutralization (1% soda+lime) and chemicals injection is in-line, with 2 static mixers (the pH control is also in-line and about 2 meters after the injection point). The system works for a few hours a day.

I noticed that some hours after the system has stopped, the pH in the flocculation tank is approx. 11,50 when I want it at approx. 8,00. (my permit is between 6,5 and 8,5) I think that, may be, this is due to a short reaction time for the neutralization in continuous flow.

The neutralization is fully achieved in batch.

Thank you.

Milton Fontes
stainless steel equipment for wineries - Bustos, Oliveira do Bairro, Portugal

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First of two simultaneous responses --

A flow through reactor tank with a mixer and pH control and a retention time of > 10 minutes would work much better than an in line system.

Lyle Kirman
consultant - Cleveland Heights, Ohio
2003

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Second of two simultaneous responses -- 2003

Hi Milton,

I noticed that no one had replied to your query ... so I thought, being somewhat of a tyro regarding neutralization systems, that maybe I could shed a little bit of light.

Question. You mention STATIC mixers. Why static? Shouldn't a mixer rotate? On equipment I designed, the flow was in a rectangular tank. This had two baffles (sometimes 3) which were full width but one was an inch or so lower at the top and the other an inch or so higher (25.4 mm !) at the bottom, i.e., the incoming liquid (acidic in my case) had to cascade over the top one and force itself below the bottom opening... but the first baffle did have a few 'bleed' holes at the bottom in case it was ever necessary to clean up any solids. (see # 21077 in the archives)

But also, more often than not, an electrical mixer was used, too. How else can one thoroughly disperse an alkaline?

Perhaps you have too much of a delay on your timing set-up so that you get a high pH. ... and my pH meters were always at the far, far end. Does this help at all? ... hope so.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).