Nickel (ii) effects on Anammox reaction: reactor performance, dehydrogenase, sludge morphology and microbial community changes

ABSTRACT

Nickel (ii) (Ni²⁺) is considered as one of the necessary trace elements in the process of Anammox culture, but it may have toxic effects at high concentration. This study explored the long-term influence of Ni²⁺ on the denitrification efficiency of Anammox bioreactors. The results showed that when the concentration of Ni²⁺ was 0.5 mg/L, the bioreactor had the highest denitrification efficiency, while the removal efficiency of ammonia nitrogen and nitrite nitrogen gradually decreased at concentrations higher than 2 mg/L, and the removal rates of ammonia nitrogen and nitrite nitrogen were 26% and 39.81% at the end of the experiment, respectively. The NRR was decreased from 7.47 kg N/m³ d to 3.28 kg N/m³ d during the whole process. The highest concentration of microbial dehydrogenase was attained in about 40 days; in the meantime, its ability to consume organic matter was also maximized. The sludge morphology was changed from granular cluster to loose flocculant with a small number of spherical and filamentous bacteria and bacilli distributed on the surface. At the end of the experiment, both species richness and community diversity were reduced, and the proportion of the dominant bacteria Candidatus Kuenenia was also decreased from 59.89% to 36.72%.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ni²⁺
• Anammox
• denitrification performance
• dehydrogenase
• sludge morphology

Data availability statement

All figures and tables of raw data are provided on request and available on figshare (DOI: 10.6084/m9.figshare.14784753).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by National Natural Science Foundation of China [grant number 51978654, 52004274].