Control of organic acids in raw water 1

[22854]

Can anyone tell me if the Sodium Hypoclorite destroys the organic acids present in raw water (source = water dike) and then retained in a sand/anthracite or an activated carbon filter.

 

[vintage70]

Organic acids are weak thus they don't give up that H easily
I don't think the C in the HO-C=O would have an affinity for substitution either. You would need some agressive oxidation. Maybe ozone or peroxide.
But if you do modify the acid activated carbon may not be effective if the organic remains polar. And sand work best with solids in solutions. I'll try to look into this some more. Very interesting problem. Give me some feedback.

 

[22854]

Many thanks to Vintage70 for his answer.

A brief description of our water system is the following:
We receive the raw water directly from a surface water supply and we have problems with algae, silica and organic acids.
The water is introduced into a pond and then pumped to the filtration unit. Immediately after the pump we dose Sulfuric acid for pH adjustment, alum as coagulant, Sodium Hypoclorite as biocide and a commercial polyelectrolite as flocculant trying to do an inline clariflocculation. In this condition the water passes thru eight sand/anthracite filters, next goes to a reservoir tank (we will try to dose additional Sodium Hypoclorite before entering the tank so as to get 1 - 1.5 ppm at the exit.) Then the water is pumped in to directions. One goes directly to the Cooling Water make-up and the rest (approx 190 m3/hr) goes to a clariflocculation unit with additional dosing of coagulant and flocculation chemicals. After that the water passes thru another sand/anthracite filtration unit, we dosify sodium bisulfite to eliminate chlorine and then we have the demineralization plant.

Our intention is to include and Activated carbon unit after the second sand filters unit to eliminate excess chlorine and mechanical filters with 3 microns mesh before de demin water unit.

I am very interested in your comments about the use of ozone or peroxide but am aware about which will be the effect on the cation resins in the demineralizer and capital and operating costs.

Which would be your advise on where should we introduce them to succeed in eliminating the organic acids(maybe fraction of Humic and Fulvic acids formed from decaying vegetation)and where or how retain them.

thanks in advance.

You can also reach me at: jbertoni@prefertil.com.ar

 

[vintage70]

Ozone and peroxide require UV light, so the clearest water gets the greatest results. In theory the products of the reaction are carbon dioxide and water(combustion reaction). That's in theory. I think the oxygen introduced would react with metals, so I would use this as the final unit in the system. I haven't used one of these in a while. So not sure as to current costs and suppliers. The systems have been leased in the passed. That seems to be the most economical. Chemical costs are moderate. The manufacturer will determine the amount of UV light. Then you will know your power costs.

I'll try to look into this some more.

 

[vintage70]

Another thought. I think the sodium bisulfite will be more economical than the activated carbon to remove chlorine.
The chorine to carbon loading is low. You will be using alot of carbon with a cost increase for disposal.

 

[22854]

A supplier of Ozone treatment told me that we have to avoid killing the algae with hypoclorite because in that condition the free toxines that combines with water so when organic acids are in solution it is very difficult (or impossible) to eliminate them. Tehy say that preozonization (they think UV is needed in this case) kills algae without combining with the acids so in that condition is possible to eliminate algae by filtration with no presence of organic acids and then eliminate ozone with an oxygen scavenger before entering the boilers.

¿ Any comments ?

 

[vintage70]

This should be looked into some more. It may be effective. My greatest concern is not removing all the oxygen before the boilers. You could have a serious destruction problem. I like the idea of using the UV to kill the algae. Look into using activated carbon to remove the organic acids. If there are no isotherm data available. Have a lab do some jar tests.

 

[22854]

Yes the concern about eliminating de the oxygen before the boilers is true. which lab analysis do you think will permit to follow up (or determine) the presence (quantity, ecc.)of organic acids?

 

[vintage70]

I don't know, but these are high molecular weight compounds. The lab could scan that range. Doesn't water containing humic and fulvic acid have a distinct color? Could you run tests and have appearance as an indication of removal? If the activated carbon doesn't appear promising, would you consider membrane filtration?

I think I'm getting of the track here, and I don't want to drift away from the original question. Let me know where you stand.