Nitrate reduction by anaerobic sludge using glucose at various nitrate concentrations: ammonification, denitrification and methanogenic activities

A synthetic wastewater containing glucose as the sole source of carbon was used to assay glucose-acclimatized anaerobic digester sludge in batch-tests for its potential to carry out ammonification (nitrate- -> ammonium), denitrification (nitrate —>nitrogen gas) and to continue anaerobic digestion processes at various nitrate loads. Nitrate—>ammonium reduction activity was found to increase with decrease in the initial nitrate load. This activity appeared to take place principally during the acidogenesis of the glucose. Nitrate/nitrite loss after the fermentation process was essentially through denitrification. The denitrification capacity of the anaerobic sludge used was very high. Up to 80% of added nitrate was denitrified. The presence of nitrate or nitrite enhanced the fermentation of glucose to acetic acid but inhibited the production of propionic acid and methane. This inhibition was not observed after the complete reduction of nitrate and nitrite.