Physiological and ecological response of a simultaneous nitrification-denitrification process treating organic solid waste leachates in a sequential batch reactor

The physiology and microbial community behavior of a simultaneous nitrification-denitrification process (SNDP) treating organic solid waste (OSW) leachate in a sequencing batch reactor (SBR) was analyzed. The SBR was fed with synthetic medium (SNDP control, 102 ± 5 mg of NH ₄ ⁺ -N/L) and then with diluted leachates (62 ± 7 mg of NH ₄ ⁺ -N/L and 4845 ± 162 mg/L of chemical oxygen demand, COD). Physiology was evaluated by ammonium and nitrate consumption efficiencies (ENH ₄ ⁺ -N, ENO ₃ ⁻ -N) and nitrate and nitrogen production yields (YNO ₃ ⁻ -N, YN ₂ -N). Microbial community was determined by high-throughput sequencing. SNDP control reached ENH ₄ ⁺ -N of 99% and YNO ₃ ⁻ -N of 0.94 during nitrification and ENO ₃ ⁻ -N of 99% and YN ₂ -N of 0.86 during denitrification. SNDP with leachates reached ENH ₄ ⁺ -N of 92% and YNO ₃ ⁻ -N of 0.83 during nitrification and ENO ₃ ⁻ -N of 79% and YN ₂ -N of 0.69 during denitrification. COD consumption efficiencies of 92% were obtained. Nitrifying species such as Nitrosomonas europaea , Nitrosomonas nitrosa , and Nitrospira defluvii were predominant, with abundances of 0.04%, 0.02%, and 0.12%, respectively. Denitrifying species such as Azoarcus sp , Pseudoxanthomonas mexicana , and Pseudomonas stutzeri were predominant, with abundances of 0.07%, 5.41%, and 8.48%, respectively. These species were associated with the consumption of organic matter and ammonium, as well as with the production of N₂. The SNDP process was successfully developed in a simple reactor achieving high ammonium and COD removal efficiencies from OSW leachates.