Microbial mediated anoxic nitrification-denitrification in the presence of nanoscale oxides of manganese

The present study investigates the feasibility of anoxic nitrification-denitrification in the presence of nanoscale oxides of manganese (NSOM). A template-assisted co-precipitation method was employed to synthesize NSOM. XRD and FESEM data reveal that the composite is amorphous in nature, and the particles are in nano regime (15-28 nm). The use of NSOM as an electron acceptor for the microbial mediated anoxic nitrification and the feasibility of re-oxidation of reduced NSOM coupled to denitrification was demonstrated by laboratory scale sequencing batch reactor (SBR). SBR operation lasted for 343 days in 9 different phases by varying the initial NH4+-N (100-500 mg l(-1)) and cycle time (0.5-2.0 d). Maximum removals of NH4+-N and total nitrogen were 126.2 +/- 11.3 mg l(-1) d(-1) and 109.8 +/- 10.9 mg l(-1) d(-1) respectively, in 0.5 d cycle time. Separate batch experiments were conducted to study the effect of time, pH, temperature, COD/NH4+-N ratio, and inhibitory concentrations of NH4+-N, NO2--N, and S2-, on the anoxic nitrification process. The developed process is economical as it works in the absence of external supply of aeration and alkalinity, and reduces 70% of the requirement of COD compared to conventional nitrification-denitrification. (C) 2016 Elsevier Ltd. All rights reserved.