User:Dwyerbm/Anaerobic digestion

Total ammonia nitrogen (TAN) has been shown to inhibit the production of methane. Furthermore, it can also make the microbial community unstable and impact the synthesis of acetic acid. Acetic acid is one of the driving forces in methane production. In excess of 5000 mg/L TAN, pH adjustment is needed to keep the reaction stable. TAN at a concentration above 1700- 1800 mg/L will inhibit methane production and the yield will decrease at greater TAN concentrations. High TAN concentrations will cause the reaction to turn acidic and lead to a domino effect of inhibition. TAN is the combination of free ammonia and ionized ammonia. TAN is produced through degrading material high in nitrogen, typically proteins, and will naturally build in anaerobic digestion. This depends on the organic feedstock fed to the system. In typical wastewater treatment practices, TAN reduction is made with nitrification. Nitrification is an aerobic process where TAN is consumed by aerobic heterotrophic bacteria. These bacteria release nitrate and nitrite, which are later converted to nitrogen gas through denitrification. Hydrolysis and acidogenesis can also be impacted by TAN concentration. In mesophilic conditions, inhibition for hydrolysis was found to occur at 5500 mg/L TAN, where acidogenesis inhibition occurs at 6500 mg/L TAN.