Old landfill leachate can be characterized by high ammonia nitrogen concentrations and limited biodegradable carbon availability. A promising and cost-effective option for ammonia nitrogen removal involves ex situ nitrification and in situ denitrification.

This study aimed to investigate the denitrification capacity of old MSW in six landfill bioreactors with very low COD/NO₃⁻-N mass ratios that ranged between 0.12 and 3.99 g/g. In particular, this study is novel in that it tested COD/NO₃⁻-N mass ratios lower than previous studies. The experiment lasted 83 days. The results showed that denitrification occurred in all bioreactors and even at considerably low concentrations of biodegradable organic matter (BOD₅ ≤ 9 mg O₂/L). In all but one case, when nitrate removal stopped at 55% due to the absence of leachate recirculation, nitrate removal was higher than 95%.

The average nitrate removal rates (ANRRs), calculated under significantly different conditions, ranged from 33 to 135 mg NO₃⁻-N/L/d. The initial COD concentration and COD/NO₃⁻-N ratio did not appear to affect the ANRRs, which were influenced by the initial nitrate concentration and leachate recirculation. The maximum ANRR (135 mg NO₃⁻-N/L/d) was measured with the highest initial nitrate concentration (4491 mg NO₃⁻-N/L) and the lowest COD/NO₃⁻-N mass ratio (0.12 g COD/g NO₃⁻-N). The lowest ANRR (33 mg NO₃⁻-N/L/d) was calculated for a bioreactor with no leachate recirculation.

Sulphate production observed in some bioreactors may suggest that, together with the heterotrophic pathway, autotrophic denitrification contributed to the removal of nitrate, especially in bioreactors with low COD/NO₃⁻-N mass ratio.

旧的垃圾填埋场渗滤液的特征是氨氮浓度高，可生物降解的碳利用率有限。去除氨氮的一种有前途且具有成本效益的选择涉及异位硝化和原位反硝化。

这项研究的目的是调查六个MSD / NO ₃ ^-- N质量比非常低，介于0.12至3.99 g / g之间的垃圾填埋生物反应器中旧垃圾的反硝化能力。特别地，该研究是新颖的，因为它测试的COD / NO ₃ ^-- N质量比低于以前的研究。实验持续了83天。结果表明，发生在所有生物反应器并且甚至在相当低的浓度下的可生物降解的有机物（BOD脱氮₅  ≤9毫克邻₂ / L）。在除一种情况外的所有情况下，由于没有渗滤液再循环，硝酸盐去除率停止在55％时，硝酸盐去除率高于95％。

在明显不同的条件下计算出的平均硝酸盐去除率（ANRRs）为33至135 mg NO ₃ ^-- N / L / d。初始COD浓度和COD / NO ₃ ^-- N比似乎没有影响ANRR，这受初始硝酸盐浓度和渗滤液再循环的影响。在最高初始硝酸盐浓度（4491 mg NO ₃ ^-- N / L）和最低COD / NO ₃ ^-- N质量比（0.12 g ）下测量最大ANRR（135 mg NO ₃ ^-- N / L / d）COD / g NO ₃ ^-- N）。最低ANRR（33毫克NO ₃ ^--N / L / d）计算没有渗滤液再循环的生物反应器。

在某些生物反应器中观察到的硫酸盐生成可能表明，与异养途径一起，自养反硝化作用有助于去除硝酸盐，特别是在COD / NO ₃ ^-- N质量比低的生物反应器中。