Enrichment Of Marine Anammox Bacteria And Enhanced Nitrogen Removal Performances With Metal Ions Addition

Marine anammox,as the deepest branching genus of anammox,occupies a dominant position in marine environment for its profound influence on marine nitrogen cycle.It was applied into the nitrogen removal of nitrogen-rich saline wastewater according to high salinity tolerance of marine anammox bacteria(MAB),which could achieve higher nitrogen removal performance.In this work,MAB was successfully enriched by seeding sediment sludge from the Jiaozhou bay.The enhanced nitrogen removal performance and dynamic characteristics of MAB with Mn(?)and Ni(?)addition were studied:A sequencing batch reactor(SBR)was successfully used to enrich MAB by seeding sediment sludge from the Jiaozhou bay for 192 d.Experimental results showed that whole process could be divided into four phases: bacterial lysis phase(1–15 d),lag phase(16–152 d),exponential growth phase(153–183 d)and stationary phase(184–192 d).After successfully enriched,the ammonia removal efficiency(ARE)and nitrite removal efficiency(NRE)achieved 96.98% and 95.66%,respectively.Compared to the enrichment of freshwater-derived anammox bacteria(FAB),the lag phase(137 d)was longer,accounting for more than 2/3 of the enrichment.However,the exponential growth phase(30 d)was shorter,which was less than 1/6 of the enrichment.Besides,MAB were more sensitive to the variation of substrate concentration and HRT.The activity delay time resulting from the inflow and effluent was 5 h,which was far longer than that of FAB.As a result,the acclimatization of MAB was weaker and it was harder to enrich.During the operation of SBR,the sludge characteristics changed from black muddy to brown flocculation,finally turned to red granule.SEM observation confirmed that red granule was cenobium,which was consisted of closely spaced micrococcus with smooth surface and crateriform shape.An SBR was used to study the enhanced nitrogen removal performance of MAB treating nitrogen-rich saline wastewater with Mn(?)and Ni(?)addition.Besides,remodified Logistic model and modified Boltzmann model was used to describe the nitrogen removal process of MAB.It showed that lower Mn(?)and Ni(?)contents(?0.05 m M)could enhance nitrogen removal performance of MAB greatly.The maximum of ARE and NRE were 93.95% and 94.05% at 0.05 m M Mn(?)while 93.18% and95.32% at 0.025 m M Ni(?).However,higher contents of Mn(?)and Ni(?)(> 0.05 m M)could suppressed the activity of MAB severely.With the optimal Ni(?)(0.025 m M)addition,ARE,NRE,nitrogen removal rate(NRR)and the specific anammox activity(SAA)improved 14.52%,14.90%,14.64% and 57.88%,which was higher than 4.45%,6.69%,3.94% and 9.43% of 0.05 m M Mn(II).It seemed that the enhancement of Ni(?)to MAB was better than Mn(?),but the optimal content of Ni(?)was lower thanMn(?).And the sensibility of MAB to Ni(?)was stronger than Mn(?).Both Mn(?)and Ni(?)could serve as potential electron acceptor instead of NO2--N,participated in marine anammox process,which further resulted in lower ?NO2--N/?NH4+-N.The remodified Logistic model at higher contents of Mn(?)and Ni(?)and modified Boltzmann model at lower contents of Mn(?)and Ni(?)was used to describe the nitrogen removal process of MAB,which had higher R2.Besides,TNREmax,Rm and ?could also be predicted well.The fitted parameters had practical significance.Mn(?)and Ni(?)dosage should be controlled within 0.075 m M to achieve good nitrogen removal in nitrogen-rich saline wastewater treatment.