An agricultural waste lagoon has a total volume of 500 m3 and has an initial dissolved oxygen (DO) level at the saturation for 20 °C. This waste lagoon receives a discharge of 1,750 L of runoff containing an ammonium loading of 500 mg as N per liter. Assuming nitrification occurs in the waste lagoon, what is the final dissolved oxygen concentration (in mg/L) in the waste lagoon after all of the ammonium (NH4+) is converted to nitrate? Recall that 4.57 mg of O2 is need per mg of ammonium (as N) oxidized during nitirification. After all of the ammonium is converted to nitrate, would the waste lagoon be considered hypoxic.