Selective Inhibition of Nitrite Oxidation by Methanoic Acid Dosing in Sequencing Batch Reactor

Abstract

Shortcut nitrification can be successfully achieved by dosing methanoic acid in the sequencing batch reactor (SBR) system. While processing stable shortcut nitrification, influent pH value was kept at 7.5–8.5. However, dissolved oxygen and temperature were not controlled in the SBR. When influent NH4+−N was 50 mg/L, NH4+−N removal efficiency reached 98.77% and 98.92% in the reactor when we dosed 0.25 and 0.35 mL/L methanoic acid. Moreover, when we dosed 0.25 and 0.35 mL/L methanoic acid in the reactor, NO2−−N removal reached 77.88% and 79.63% of the NO2−−N/(NO2−−N + NO3−−N) in the effluent, respectively. We also discovered that when we dosed 0.35 mL/L methanoic acid, effluent NH4+−N was more volatile. Scanning electron microscopy showed that the main composition of the activated sludge was bacilli and coccus bacteria. High throughput sequencing analysis revealed that after methanoic acid was dosed, the dominant bacteria were Blastocatella, Brevundimonas, Ferruginibacter, Paracoccus, Pseudoxanthomonas, and Thermomonas. Methanoic acid can be used to control the development and maintenance for shortcut nitrification.