Research On The Stability Of Anammox Process And Its Coupling System With Autotrophic Desulfurization-denitrification

Anaerobic ammonium oxidation (anammox) allows significant saving in energy, reduces the need for organic carbon addition and lowers sludge production, becoming one of the most cost-effective, and environmentally friendly process especially for the treatment of wastewater with low C/N and high ammonium. However, the sensitivity of anammox process hindered its application. And the treatment of sulfide contained in high ammonium wastewater is always separately treated from ammonium, which leads to more complex process, higher energy consumption and more area needed. Thus, this research focuses on the influence of the seasonal change in temperatureon anammox performance, stability and sludge characteristics; different type, intensity and time of instantaneous shocks on the resistance stability and recovery of anammox; the start-up and operation strategies of the anammox autotrophic desulfurization-denitrification co-system, and the achievement of good performance in terms of nitrogen and sulfide removal. The conclusions are as follows:(1) The anammox process was comparatively operated for 330 days without temperature control. The results demonstrated that the nitrogen removal efficiency (NRE), nitrogen loading rate (NLR) and nitrogen removal rate (NRR) decreased from 91.2%,13.5 kg N m-3 d-1 and 11.7 kg N m-3 d-1 to 49.4%,1.34 kg N m-3 d-1 and 0.91 kg N m-3 d-1, respectively, as the temperature decreased from 31.2? to 2.5?. However, the nitrogen removal performance recovered as the temperature re-increased gradually. The stability turned to be the worst in winter, and the specific anammox activity (SAA) decreased to 52.8±2.2 mgTN g-1 VSS d-1. The settleability tended to worsen after low-temperature exposure, reaching a value of 57.8-63.5 m h-1, and granules appeared to be more irregular, with a lower diameter of 1.82±1.44 mm. The content of heme c decreased, while EPS content increased under the low temperature stress. In addition, the biomass of anammox granules is the key element for an efficient anammox process with seasonal temperature changes.(2) A 1.0- and 1.5-fold of substrate concentration,5.95 and 12.9 mg L-1 transient Cu(II) shock, and 2/3-and 1/2-fold decrease in hydraulic retention time (HRT) were applied either individually or in combination for durations of 2.00 and 4.00 h, to investigate the performance stability and resilience of anammox process. The stability was affected by FA and FNA, the reactor response to the shock loads was intensity-and time-dependent; the stability order of the system with different shocks was as follows:substrate shock> heavy metal shock> hydraulic shock; and the effects of the combined shocks on the anammox system were dependent on the types of combined shocks:(substrate+hydraulic shock)> (substrate+heavy metal shock)> (hydraulic +heavy metal shock); the anammox system recovered after normal conditions were applied certain days.(3) The combined anammox and autotrophic desulfurization-denitrification (AADD) process represents a promising innovative technology for biological nitrogen and sulfur removal. The co-system initiated with anammox and methanogenic granules, was operated for 245 days. The highest nitrogen removal rate and sulfide removal rate attained were 4.00 kg N m-3 d-1 and 2.39 kg S m-3 d-1, respectively. Besides, the influent NH4+-N:S2--S and NO2--N:S2--S ratios set at 1.74 and 2.20-2.27 were suitable for maintaining system stability. And the specific activities of anammox and autotrophic desulfurization-denitrification increased with the loading rate after the adaptive phase, and heme c reduced to 1.17?mol g-1 VSS. What's more, the dominant bacteria belonged to members of Brocadiaceae and Hydrogenophilaceae.