Effects of anthraquinone combined with biochar on the long-term nitrogen removal efficiency and palliative inhibition of anaerobic ammonia oxidation process

Anthraquinone has an inhibitory effect on anaerobic ammonia oxidation (anammox) to some extent, but the effect of combined biochar is uncertain. Currently, most studies have focused on the effect of single exogenous substance addition on anammox. The effects of adding multiple exogenous substances on anammox need to be further explored. The effects of different concentrations of anthraquinone and biochar additions on anammox was investigated, and discovered that the reactor with 0.025 mmol center dot L- 1 anthraquinone and 10 g center dot L- 1 coconut shell biochar had the best nitrogen removal, with NH4+-N and NO2- -N removal efficiency stabilized above 90.0 % and 85.0 %, respectively, and the relative Candidatus Brocadia abundance increased. During long-term anthraquinone combined with biochar anammox process operation, each reactor exhibited different levels of inhibition with anthraquinone addition. In the coconut shell biochar-anthraquinone (0.05 mmol center dot L- 1) reactor augmented with low quantities of N2H4, nitrogen removal efficiency (NRE) increased by 9.7 %, while T-PN and T-PS rose by 9.3 and 16.94 mg center dot gVSS- 1, respectively. The abundance of Candidatus Brocadia increased from 17.22 % to 20.75 % after anthraquinone addition was stopped. This lays the foundation for future research on the potential role of exogenous substances in regulating the function of anammox systems and microbial community structure.