Enhanced nitrogen removal through marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater with Fe(III) addition: Nitrogen shock loading and community structure

Marine anammox bacteria (MAB) were used to treat nitrogen-rich saline wastewater with Fe(III) addition under nitrogen shock loading. Ammonia loading rate (ALR) and nitrite loading rate (NLR) gradually increased from 0.033 and 0.039 to 0.68 and 0.89 kg/(m(3).d), respectively. With 5 mg/L Fe(III) addition, ammonia removal rate (ARR) and nitrite removal rate (NRR) reached maximal values of 0.56 and 0.60 kg/(m(3).d), respectively. The value of Delta NO2--N/Delta NH4+-N was lower than theoretical ratio due to existing marine Feammox process. The growth rate of MAB was accelerated by Fe(III) and it dominated the reactor (27.70%). Besides, MAB were synergized with Marinicella and Caldithrix to achieve higher total nitrogen removal. Haldane model was proper to analyze and predict the effect resulting from nitrite on the activity of MAB under nitrogen shock loading. Overall, this study provides novel insights into the effect of Fe(III) on MAB treating nitrogen-rich wastewater.