Method of controlling a wastewater treatment plant

A method of controlling a wastewater treatment plant and reducing N2O emissions from the plant where the plant comprises at least one process tank for containing wastewater, an aeration structure configured to aerate the wastewater in the process tank, at least one sensor for detecting a first tank parameter, a second tank parameter, and a third tank parameter wherein the first and second tank parameters are selected from a group consisting of nitrate concentration, nitrite concentration, and ammonium concentration determined in the wastewater in the process tank, and where the third tank parameter is N2O that is determined in the water of the process tank, a control unit for controlling the aeration structure wherein the control unit comprises a computer having a memory and configured to determine a first event and a second event, and wherein a first and second predetermined time period and first, second, and third threshold values for the first, second, and third tank parameters are stored in the memory, the method comprising:

• reducing the N2O emissions from the wastewater treatment plant while treating the wastewater in the at least one process tank by controlling the alternating frequency between phases of increased aeration and phases of decreased aeration by:
• increasing aeration to the wastewater in the process tank when the first event occurs, wherein the first event occurs:
• (1) when the first threshold value of the first tank parameter is reached, or (2) when the first predetermined time period has expired, whichever occurs first;
• and
• decreasing the aeration to the wastewater in the process tank when the second event occurs, wherein the second event occurs:
• (1) when the second threshold value of the second tank parameter is reached, or (2) when the second predetermined time period has expired, or (3) when the third threshold value of the third tank parameter is reached, whichever occurs first;
• and
• wherein the third threshold value of the third tank parameter is an initial third threshold value determined during a nitrification phase.