Here are the details to the experiment
Innoculum : Thickened Sludge
Feed : Synthetic acetic acid and butyric acid
Reactors : CSTR reactor with working volume of 11L
pH at the start of my experiment : 7.4
I collect samples from the reactor everyday to check the pH of the system, and even though I'm feeding it synthetic organic acids around the pH of 3, the overall pH of the system steadily increased and now it's around 9.
My theory for the increase in pH is
1. The CO2 production caused production of bicarbonates
2. Some part of methanogenesis increases pH heavily.
If there's anyone who has had a similar experience please let me know.
Hello the methane fermentation is complex process and not only CO2 is forming during fermentation. During the fermentation you have also NH3 production which with water can became NH3-H2O or NH4OH which will increase the fermentation pH.
Organic nitrogen is converted to ammonia through ammonification by a process called hydrolysis. Subsequently, ammonia reacts with carbon dioxide produced during anaerobic digestion to form ammonium bicarbonate which contributes to alkalinity in the reactor (Shende and Pophali, 2020). I suggest you to check TKN and NH3 both in the thickened sludge (feed). Also, make sure that the VFA/Alkalinity ratio should be kept below 0.4 in the reactor.
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