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Effect of Short‐term Exposure of Selected Aromatic Nitrogen Compounds on Wastewater Treatment

The biodegradation of melamine and p‐nitrophenol (PNP) and their impact on wastewater treatment was evaluated after a short‐term individual chemical loading in activated sludge treatment systems. Melamine was not degraded and quickly washed out of the system. PNP was degraded, but it led to a prolonged period of nitrification inhibition and deterioration of effluent quality. Both melamine and PNP loadings increased the effluent nitrogen concentrations, with their main contributors being melamine and NH4+, respectively. Nitrosomonas and Nitrospira were dominant in the activated sludge. Melamine did not affect the nitrifying assemblages, whereas PNP led to a reduced Nitrosomonas population size and complete washout of Nitrobacter. The results suggest that melamine is an inert compound if it enters the treatment facility for a short duration. Although the short‐term exposure of melamine or PNP decreased effluent water quality, the impact of such aromatic nitrogen compounds on wastewater treatment performance may vary significantly.