Starting-up performances and microbial community shifts in the coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) and anammox treating nitrate and ammonium contained wastewater

A novel coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) (NO3--N -> NO2--N) and anaerobic ammonium oxidation (Anammox) was developed using anaerobic sequencing batch reactor (ASBR) in this work. The integrated process comprised two stages. Firstly, the starting-up of SAPD process succeeded by gradually increasing the influent nitrate and sulfide in 95 days. The average nitrate removal efficiency (NRE) and NO2--N accumulation rates were 71.24% +/- 0.21% and 46.44% +/- 0.53% at SAPD process (days 75-95). Then, successful coupling process (SAPD-A) was implemented in two stages (stage I and stage II of SAPD-A). In stage I, it is feasible to promote the successful construction of SAPD-A process by elevating influent ammonium only based on SAPD system, making the NRE increased from 44.45% +/- 0.46% (day 95) to 64.62% +/- 0.12% at the end of stage I in SAPD-A system (day 126). Meanwhile, the ammonium nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TN-RE) also rose up to 42.46% +/- 2.02% and 63.28% +/- 0.54% respectively. Furthermore, the average ARE, NRE and TN-RE during the stage II in the bioreactor could reach 65.17% +/- 1.45%, 74.50% +/- 0.81% and 77.81% +/- 0.37% by loading some biofilters (with of approximate 10% of the volume of the bioreactor) attached anaerobic ammonium oxidation bacteria (AnAOB). High-throughput sequencing results showed that the dominant genera concerning nitrogen removal were norank_f_norank_o_Fim-briimonadates (with the abundance of 2.88-8.54%), norank_ o_ norank _ c_ OM190 (2.48-4.41%), norank_f_nor-ank_o_norank_c_WWE3 (11.01-17.69%), subgroup_10 (1.97-3.81%), Limnobacter(2.17-3.49%), norank_f_n orank_ o_norank_ c_OLB14 (2.03-5.23%), norank-f-PHOS-HE36 (2.18-5.5%), Ellin6067 (1.34-2.24%) and Candi-datus_ Brocadia (1.95-2.42%) during the whole starting-up period of coupling SAPD-A process. Batch experi-ments revealed that the sulfide was fully oxidized within 2 h, with the maximum reaction rate of 38.30 +/- 1.53 mg (L h)-1 in the first 1 h. Simultaneously, the concentration of nitrate sharply decreased from 53.08 +/- 0.23 mg L-1 to 24.16 +/- 0.42 mg L-1 with the reaction rate of 66.41 +/- 2.12 mg (L h)-1 in 0.5 h. Also, the ammonium concentration significantly declined from 47.88 +/- 0.34 mg L-1 to 10.98 +/- 0.39 mg L-1 in 8 h. Anammox process was responsible for the dominant nitrogen removal in the coupling SAPD-A system.

Automated summary

In this study, a novel coupling process (SAPD-A) combining sulfide autotrophic partial denitrification (SAPD) and anaerobic ammonium oxidation (Anammox) was developed using an anaerobic sequencing batch reactor (ASBR). The process consisted of two stages, with the SAPD process successfully started by gradually increasing the inflow of nitrate and sulfide. The SAPD-A process achieved high removal efficiencies of nitrate, ammonium, and total nitrogen, and was dominated by Anammox for nitrogen removal.