[micro]

Hi everybody,

I was wondering what people recommend for pH control in a bacterial fermentation vessel? I have considered Hydrochloric and Sulphuric acid - both have their drawbacks. I am shying away from Sulphuric acid though as i dont want sulphate reduction by the bacteria to form H2S... any thoughts? I have a dosing system in place with a set point of between pH 7.5 - 7.8

[eugenedakin]

Hi Micro,

As a general rule of thumb, if any of the molecules (Sulphuric acid for one) contains sulphur, then you will produce H2S to some degree. Hydrochloric acid also has its negative aspects, as it is quite corrosive to metal (albeit, in its neutralized form, it is forming a salt - which could be Calcium Chloride, sodium chloride, or any one of  a number of salts). Salts are usually less corrosive than the acid, but when you look at automobiles that drive through winter roads that have been salted, you will see corrosion at work on the fenders of older (and some newer) automobiles.

Most bacteria are very sensitive to pH changes. Check the preferred pH range of the microbes that you are planning on using.

I wish you well,

Eugene

[micro]

Thanks for your reply Eugene,

The pH parameters for the organisms are between 7.5 - 7.8 preferably... the reaction in small scale lab based tests proceeds rapidly to ~pH9.5 so i definitely need an acid that will not impact on the organisms but also adequately maintain the pH in the range necessary for the denitrification of ammonia and VOC, COD & BOD reduction

[eugenedakin]

Hello Micro,

Since you are going to be using very small amounts of acid, either chemical would probably be fine. For your piece of mind, run two identical samples with the two different acids, and see what numbers you attain.

Best wishes,

Eugene