Seawater neutralization

[DentonM]

Does anyone know the general benefits/challenges for using seawater to neutralize alkaline leachate, as oposed to using sulfuric acid or CO2?

Thanks

 

[25362]

I may be wrong, but aren't most kinds of seawater alkaline with pH>7 and around 8 ? Please comment for my own education. Thanks.

 

[DentonM]

As I understand the process, magnesium and calcium in seawater react with hydroxide and carbonate alkalinity, which result in a decrease in pH. I think it is mainly used to treat municipal wastewater. I'm evaluating the use on leachate from holding ponds.

 

[m777182]

If your leachate is alkaline, how could you neutralize it with an alkaline seawater? The most you can do is to dilute it with seawater and in a limit-if the pH of your leachate is higher then 8- approach to the final pH of about 8. You should consider the equilibria of Ca and Mg hydroxide (as a stong base) with CO2 from the air (as a weak acid) that gives slightly alkaline well buffered reaction of seawater. NaCl as the main compound does not contribute to pH change because it is a salt of equaly strong acid (HCl)with base(NaOH)of the same strenght. Municipal wastewater is only diluted with sea water if there is not some effect of biological tretment involved but I do not know much about that.
m777182

 

[DentonM]

More info:

I should have mentioned that my pH is starting around 11 and my target is 9 or less. Also, the other options that I will consider are sulfuric acid addition and CO2 bubbling. I suspect that I'll end up going with sulfuric acid, but I was mainly looking to gain some insight about seawater addition.

Thanks