Ammonia oxidation from landfill leachate by batch reactors with biological additive and subject to low pH

The use of a biological additive could improve the treatment of some recalcitrant wastewaters. Hence, this study evaluated the effect of biological additive (Component E) inoculation in the aerobic biological treatment of domestic sewage combined with landfill leachate. Two sequential batch reactors (SBR) were employed, and samples were collected at three aeration times: 8, 24, and 48 h. A total of 13 aeration batches were analyzed, and samples were then collected to evaluate pH, electrical conductivity (EC), turbidity, apparent colour, Chemical Oxygen Demand (COD), alkalinity, and ammoniacal nitrogen. At the end of the assay, sludge samples were collected for 16S rRNA sequencing. Aeration for 48 h yielded the highest ammoniacal nitrogen (87-93%) and COD (82-86%) removals, but low pH values (4.5∼5.0). Biomolecular analyses presented 61.2% similarity, with the predominance of bacteria from the genus Rhodanobacter and the family Xanthomonadaceae, the presence of which was associated with the reactors' lower pH at the end of the cycles. Rhodanobacter tolerates low pH and metals, and can carry out denitrification at low pH. Biological additive inoculation did not influence the removal of the organic or ammoniacal nitrogen load in the SBR but accentuated the pH condition, which resulted in the greater dominance of Rhodanobacter.