[Nitrogen Removal Performance of ANAMMOX Process with K⁺ Addition in Saline Surroundings]

In view of the poor performance of biological nitrogen removal in saline wastewater treatment, nitrogen removal of anaerobic ammonium oxidation(ANAMMOX) with K⁺ addition was studied. The results showed that K⁺ addition could strengthen nitrogen removal performance. The effect of K⁺ on ANAMMOX process was mainly divided into four stages. In the adaptive phase(0-2 mmol·L^-1), sudden addition of K⁺ destroyed the original equilibrium reaction, but ultimately ANAMMOX bacteria could adapt to the presence of K⁺. Because K⁺ had no obvious effects on anaerobic ammonia oxidation bacteria, the removal rates of NH₄⁺-N and NO₂^--N slightly increased. In the ascension phase(2-8 mmol·L^-1), K⁺ played a role in promoting anaerobic ammonia oxidation biological systems, with increasing concentration of K⁺, the removal rates of NH₄⁺-N and NO₂^--N significantly increased. In the stabilization phase(8-20 mmol·L^-1), the nitrogen removal rate decreased, but was still higher than the control without K⁺ addition. In the inhibition phase(more than 20 mmol·L^-1), K⁺ largely inhibited anaerobic ammonia oxidation, and its denitrification efficiency was lower than 0 mmol·L^-1. In the whole cycle, when the concentration of K⁺ was 8 mmol·L^-1, it achieved the best effect, the average removal rates of NH₄⁺-N and NO₂^--N were 89.24% and 84.87%, and NRR was 1.113 kg·(m³·d)^-1.