Effect of Fe(II) on simultaneous marine anammox and Feammox treating nitrogen-laden saline wastewater under low temperature: Enhanced performance and kinetics

A sequencing batch reactor (SBR) was used to study enhanced nitrogen removal of marine anammox bacteria (MAB) treating nitrogen-laden saline wastewater with Fe(II) addition. The reactor was operated at 15 degrees C with influent pH of 7.5 +/- 0.1. At 4 mg/L Fe(II), ammonia removal rate (ARR) and nitrite removal rate (NRR) increased to 0.85 and 0.90 kg/(m(3).d), respectively. Specific anammox activity (SAA) sharply increased to 0.76 kg/(kg.d). Both marine anammox and marine Feammox reaction occurred simultaneously. Delta NO2--N/Delta NH4+-N was lower than theoretical ratio due to marine Feammox. When Fe(II) was > 25 mg/L, the maximal substrate conversion rate increased from 2.97 to 3.47 kg/(m(3).d) within 1 h. High Fe(II) concentration (> 25 mg/L) had no negative effect on marine anammox but could inhibit marine Feammox process. The optimal Fe(II) dose was 25 mg/L for marine Feammox. The remodified Logistic model was appropriate to analyze nitrogen removal independent of Fe(II) concentration, and the modified Boltzmann model could only be used to analyze nitrogen removal at high Fe(II) concentration. At 10 mg/L Fe(II), the fitted A. value declined from 0.52 h to 0.34 h. The lag time of MAB was shorten greatly.