Effects of pH on nitrogen transformations in media-based aquaponics

Yina Zou (1) , Zhen Hu (1) , Jian Zhang (2) , Huijun Xie (3) , Christophe Guimbaud (4) , Yingke Fang (1)

1 National laboratory for infrared physics,
2 Novartis Pharmaceutical Corporation
3 IFPRI - International Food Policy Research Institute [Washington]
4 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

•Aquaponics could tolerate a wide range of pH from 6.0 to 9.0.•Higher nitrogen utilization efficiency and N2O emission were achieved at pH 6.0.•Denitrification accounted for 75.2–78.5% of N2O emission from aquaponics.•Unfavorable conditions for denitrifiers led to higher N2O emission at pH 6.0. To investigate the effects of pH on performance and nitrogen transformations in aquaponics, media-based aquaponics operated at pH 6.0, 7.5 and 9.0 were systematically examined and compared in this study. Results showed that nitrogen utilization efficiency (NUE) reached its maximum of 50.9% at pH 6.0, followed by 47.3% at pH 7.5 and 44.7% at pH 9.0. Concentrations of nitrogen compounds (i.e., TAN, NO2−-N and NO3−-N) in three pH systems were all under tolerable levels. pH had significant effect on N2O emission and N2O conversion ratio decreased from 2.0% to 0.6% when pH increased from 6.0 to 9.0, mainly because acid environment would inhibit denitrifiers and lead to higher N2O emission. 75.2–78.5% of N2O emission from aquaponics was attributed to denitrification. In general, aquaponics was suggested to maintain pH at 6.0 for high NUE, and further investigations on N2O mitigation strategy are needed.

Keywords: Aquaponics; pH; Nitrogen transformations; N2O emission; Microbial abundance

Domains: Sciences of the Universe [physics]

Yina Zou, Zhen Hu, Jian Zhang, Huijun Xie, Christophe Guimbaud, et al.. Effects of pH on nitrogen transformations in media-based aquaponics. Bioresource Technology, 2016, 210, pp. 81-87. ⟨10.1016/j.biortech.2015.12.079⟩. ⟨insu-01320656⟩