Response Characteristics Of Marine Anammox Bacteria To Trace Element Zn(?)

Anaerobic ammonium oxidation(anammox)plays an important role in the global nitrogen cycle,and has attracted more and more attention all over the world.Marine anammox bacteria(MAB)could be used as the main strain to treat nitrogen-rich saline wastewater with great nitrogen removal performance.In this study,real seawater was used to prepare synthetic wastewater with salinity of 35 g/L and the temperature maintained at room temperature(19±3 ^oC).Based on the stable operation of reactor,it was explored the response mechanism of MAB-dominated anammox process to trace element Zn(?).In the sequencing batch reactor(SBR),the long term dormant activated sludge has basically recovered nitrogen removal performance after 125 days of bacterial lysis phase,lag phase,exponential growth phase and stationary phase.The ammonium removal rate and nitrite removal rate could reach 0.56 and 0.59 kg/(m³·d),respectively.The total nitrogen removal rate(TNRR)could reach 1.02 kg/(m³·d).The relative abundance of MAB was 9.20%,and MAB could play a stable role in nitrogen removal in saline wastewater.The remodified Logistic model could be well applied to the activity recovery test of MAB,and the lag time obtained after fitted was 82.66 d.The results could provide a certain guiding significance for the activated sludge in the dormant state for a long term.Several 100 ml serum bottles were used to investigate the short term response characteristics of MAB to trace element Zn(?).The influent NH₄⁺-N and NO₂^--N were 100and 132 mg/L,and HRT was set at 6 h.When the dose of Zn(?)was not higher than 8 mg/L,it could promote the nitrogen removal performance of MAB.When Zn(?)dose was higher than 15 mg/L,the nitrogen removal performance was inhibited,and the inhibition increased with the improvement of Zn(?)dose.The half maximal inhibitory concentration of Zn(?)for MAB in saline wastewater was 127.41 mg/L at 6 h exposure time.The remodified Logistic model and modified Gompertz model could be applied to the nitrogen removal process of MAB in saline wastewater with different Zn(?)doses,and the fitted parameters could be well predicted the TNRR_max in anammox process.The SBR reactor was used to investigate the long term response characteristics of MAB to trace element Zn(?).The influent NH₄⁺-N and NO₂^--N were 100 and 132 mg/L,and HRT was set at 4 h.With the Zn(?)in the range of 0 to 3 mg/L,the TNRR of MAB was stimulated from 1.1 to 1.33 kg/(m³·d).At 3 mg/L Zn(?),the activity of nitrite reductase,nitrate reductase,hydrazine dehydrogenase and heme c were significantly enhanced.Under 4 mg/L Zn(?),MAB could secrete a large amount of extracellular polymeric substances to resist the invasion.After adding 5 mg/L Zn(?),the TNRR was rapidly collapsed to 0.22 kg/(m³·d).MAB was always the dominant strain,and the rapid collapse of nitrogen removal had not caused the decline of MAB abundance.In general,the supply of sufficient Zn(?)was the key to improve the activity of MAB in saline wastewater.