Advanced Water Management Centre, The University of Queensland, Brisbane, 4072, QLD, Australia.
Centre for Solid Waste Bioprocessing, Schools of Civil and Chemical Engineering, The University of Queensland, 4072, QLD, Australia.
Water Res. 2018 Oct 15;143:127-135. doi: 10.1016/j.watres.2018.06.021. Epub 2018 Jun 14.
Inhibition by ammoniacal nitrogen, consisting of free ammonia (NH) and ammonium ion (NH), has been widely investigated for anaerobic digestion. However, despite the large amount of research on the subject, ammoniacal nitrogen inhibition still threatens many anaerobic digesters. This paper presents (i) a method to reliably characterise ammoniacal nitrogen inhibition and (ii) a robust inhibition modelling approach. Results showed that NH and NH inhibition need to be jointly determined, which can only be done by performing inhibition tests at various total ammoniacal nitrogen (TAN) concentrations and pH values. These test conditions were reliably achieved using the salts NHHCO and NHCl without pH adjustment, rather than by using NHCl with pH adjustment. The use of only salts showed a lower pH change during the inhibition test (∼1.5 days), thereby decreasing the uncertainty in TAN speciation and strengthening the test and model outputs. A threshold inhibition function satisfactorily described (R > 0.99) the joint inhibition of NH and NH on three distinct inocula, and provided a better description of the inhibition testing results than a non-competitive inhibition function (R ∼0.70). The key advantage of the proposed threshold inhibition function is its capacity to identify the inhibition lower limit (concentration where inhibition starts; KI) and upper limit (concentration where inhibition is complete; KI). The threshold inhibition function also identifies the 50% inhibition concentration (KI) at the midpoint of KI and KI. Finally, experimental and model results show that at pH 7.3-7.7 and TAN concentrations above 2000 mgN·L, both NH and NH contribute significantly to overall inhibition.
氨氮抑制作用，包括游离氨（NH）和铵离子（NH），已被广泛应用于厌氧消化。然而，尽管对这一主题进行了大量的研究，氨氮抑制作用仍然威胁着许多厌氧消化器。本文提出了（i）一种可靠地表征氨氮抑制作用的方法和（ii）一种稳健的抑制建模方法。结果表明，需要联合确定 NH 和 NH 的抑制作用，这只能通过在不同的总氨氮（TAN）浓度和 pH 值下进行抑制测试来完成。这些测试条件可以通过使用 NHHCO 和 NHCl 盐而不是使用 NHCl 盐和 pH 调整来可靠地实现。仅使用盐在抑制测试期间显示出较低的 pH 值变化（约 1.5 天），从而减少了 TAN 形态的不确定性，并增强了测试和模型输出。一个阈值抑制函数令人满意地描述了 NH 和 NH 对三种不同接种物的联合抑制作用，并且比非竞争性抑制函数（R ∼0.70）更好地描述了抑制测试结果。所提出的阈值抑制函数的主要优势在于其能够识别抑制的下限（抑制开始的浓度；KI）和上限（抑制完全的浓度；KI）。该阈值抑制函数还可以确定 KI 和 KI 的中点处的 50%抑制浓度（KI）。最后，实验和模型结果表明，在 pH 值为 7.3-7.7 和 TAN 浓度高于 2000 mgN·L 时，NH 和 NH 都对整体抑制作用有显著贡献。
