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.