Abstract
Fe(Ⅱ)is an essential trace element for anaerobic ammonium oxidation bacteria(AAOB)metabolism,and can improve the nitrogen removal efficiency of anaerobic ammonia oxidation(Anammox).Here we oper-ated two identical expanded granular sludge bed(EGSB)reactors at low temperature(15±3 ℃)for 154 days.Reactor 1(R1)received additional Fe(Ⅱ)(0.12mmol/L)during the late startup phase,while reactor 0(R0)served as the control and did not receive extra Fe(Il).Nitrogen removal in R1 became stable at 55 d of operation,ten days earlier than R0.The nitrogen removal rate(NRR)of R1 was 1.64kg N m-3 d-1 and its TN removal rate was as high as 89％,while R0 only reached 75％.The addition of Fe(Ⅱ)was fur-ther beneficial to aggregation and stability of the granular sludge,and the used sludge of both reactors showed enrichment for AAOB populations compared to the inoculum,for instance,increased abundance of Candidatus-Kuenenia and in particular of Candidatus-Brocadia(from 0.17％to 10.10％in R0 and 7.79％in R1).Diverse microbial species and complex microbial network structure in R1 compared to R0 promoted the coupled denitrogenation by Anammox,dissimilatory nitrate reduction to ammonium(DNRA),nitrate-dependent Fe oxidation(NDFO),and ferric ammonium oxidation(Feammox).In addition,the microbial community in R1 was more resistant to short-term low temperature(2-7 ℃)starvation,illustrating a further positive effect of adding Fe(Ⅱ)during the startup phase of an Anammox reactor.
维普
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