Simultaneous nitrogen and sulfur removal using Anammox coupled sulfide-denitrification process: Impact of pH

Nitrogen and sulfur coexisted in many kinds of wastewaters, which could be simultaneously removed in the Anammox coupled sulfide-denitrification process. In this study, the pH suitable for the coupling process was analyzed in a biofilter. The results showed that the coupling process could operate normally at pH of 6.5-8.5, with the total nitrogen removal efficiency (TNRE) higher than 85.0 %. At pH 7.5, the TNRE reached the highest, the hydroxylamine oxidoreductase (HAO) activity and heme-c reached 0.998 EU center dot g(-1) SS and 0.0010 mmol center dot g(-1) SS, respectively, with the hzo and nosZ gene concentrations as 4.6 x 10(8) and 9.7 x 10(7) copies center dot mL(-1). At pH 6.0, the process was significantly deteriorated and it secreted more protein to resist the pH shock, the TNRE was 34.0 %, HAO, hzo and nosZ genes and abundance of Candidatus_Kuenenia decreased by 2.8, 4.2, 2.2, and 1.4 times, respectively. Thiobacillus reduced nitrate to nitrite and supplied for Candidatus_Kuenenia, but utilized nitrite in adverse environment

Automated summary

This study analyzed the suitable pH for the coupling process in a biofilter and found that the process could operate normally at pH of 6.5-8.5 with high total nitrogen removal efficiency. The highest TNRE was observed at pH 7.5. The variations in activity and gene concentration at different pH values revealed the response mechanism of the coupling process.