Insights into the mechanism of naproxen inhibiting biohydrogen production from sludge dark fermentation

In order to explore the effect of emerging pollutant naproxen (NPX) on the hydrogen production from excess sludge(ES) dark fermentation, six groups of laboratory-scale sequencing batch anaerobic reactor were constructed. The biohydrogen production efficiency, the transformation characteristics of organic matter and the activities of key enzymes were analyzed to explore the effect of NPX on the ES dark fermentation hydrogen production. The effect of NPX on ES dark fermentation is closely related to its exposure content, that is, low-dose NPX had no obvious effect on biohydrogen production, while high-dose NPX inhibited biohydrogen production. 12.0 mg NPX/Kg reduced biohydrogen production to 14.6 mL/g, about 12.5 % of the control. NPX can be partially removed in the process of ES dark fermentation, and the removal efficiency was about 23.3 similar to 42.5 %. NPX promoted the release of dissolved chemical oxygen demand (COD) and increased the soluble organic matter in the fermentation broth. However, NPX significantly suppressed the acidification process, which was also the key reason for the decline of biohydrogen production. Enzyme activity analysis also verified the inhibition of NPX on key enzymes involved in volatile fatty acids (VFA) and biohydrogen production. The results of this study enriched the influence behavior of NPX in the environment, and provided a certain theoretical basis for the ES resource utilization.

Automated summary

This study investigated the impact of the emerging pollutant naproxen (NPX) on hydrogen production from excess sludge dark fermentation. The results showed that NPX had an inhibitory effect on biohydrogen production, especially at high doses. NPX could be partially removed during the fermentation process, but it also promoted the release of dissolved chemical oxygen demand (COD) and increased soluble organic matter. NPX significantly suppressed the acidification process and key enzyme activity, leading to a decline in biohydrogen production.