Effect of two different intermediate landfill leachates on the ammonium oxidation rate of non-adapted and adapted nitrifying biomass

A widely employed approach to minimize the detrimental effect of landfill leachates (LL) on nitrifying biomass is to adapt it to these contaminated effluents prior to use. In the study reported here the impact of different intermediate landfill leachates (intermediate 1 (ILL1) and intermediate 2 (ILL2)) and synthetic medium (SM) on the nitritation rates of non-adapted and adapted nitrifying biomass were evaluated and modeled. The models, based on previously reported models (Haldane, Edwards and Aiba), considered the effect of three different heavy metals (Cu, Ni and Zn) present in both landfill leachates. The proposed models fitted well with the different biomasses. The highest specific substrate oxidation rate (q(s)) of the present study (41.85 +/- 1.09 mg N-NH4+ g TSS-1 h(-1)) was obtained by the non-adapted biomass using SM. The non-adapted biomass was characterized by similar to 5- and similar to 28-fold higher nitritation rates on using the different ammonium sources tested (SM, ILL1 and ILL2) when compared to the other biomasses adapted to ILL1 (similar to 9 mg N-NH4+ g TSS-1 h(-1)) and ILL2 (similar to 1.3 mg N-NH4+ g TSS-1 h(-1)), respectively. The calculated inhibition constants indicate that the inhibitory effect of the heavy metals followed the order Ni>Zn>Cu. The results reported here bring into question the commonly accepted idea that an adaptation period of the biomass is required to treat landfill leachate.

Automated summary

This study evaluated the impact of landfill leachates on nitrifying biomass and established models, showing that non-adapted biomass had higher nitritation rates with different ammonium sources. The inhibitory effect of heavy metals followed the order Ni>Zn>Cu.