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Improved nitrogen removal efficiency by implementation of intermittent aeration.

The aim of the paper was to verify the possibility of using intermittent aeration to decrease outflow total nitrogen concentrations in municipal WWTPs of different capacities (15,780, 23,000 and 806,250 PE). A simple time-based intermittent aeration control was used in the experimental work. The results of WWTPs are compared with each other and with literature sources. The use of intermittent aeration led to a significant decrease of outflow total nitrogen concentration by up to 57% without the need of additional investment costs or the increase of operating costs. Nitrification kinetic tests and fluorescence in-situ hybridization observations proved that intermittent aeration has no negative impact on nitrifiers. The results proved that it is possible to utilize intermittent aeration for treatment plants initially designed with permanent aeration of nitrification sections if the current load is lower than the designed capacity. A necessary prerequisite for successful implementation of intermittent aeration is sufficient blower power. Although the time-based control is very simple and inexpensive to implement, the results are comparable to more complex systems such as systems based on rule-based systems for N-NH4+ and N-NO3- concentrations, on fuzzy logic or on mathematical models.