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

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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.