Modeling sustainable reuse of nitrogen-laden wastewater by poplar

Abstract

ABSTRACTNumerical modeling was used to simulate the leaching of nitrogen (N) to groundwater as a consequence of irrigating food processing wastewater onto grass and poplar under various management scenarios. Under current management practices for a large food processor, a simulated annual N loading of 540 kg ha−1 yielded 93 kg ha−1 of N leaching for grass and no N leaching for poplar during the growing season. Increasing the annual growing season N loading to approximately 1,550 kg ha−1 for poplar only, using “weekly”, “daily” and “calculated” irrigation scenarios, yielded N leaching of 17 kg ha−1, 6 kg ha−1, and 4 kg ha−1, respectively. Constraining the simulated irrigation schedule by the current onsite wastewater storage capacity of approximately 757 megaliters (Ml) yielded N leaching of 146 kg ha−1 yr−1 while storage capacity scenarios of 3,024 and 4,536 Ml yielded N leaching of 65 and 13 kg ha−1 yr−1, respectively, for a loading of 1,550 kg ha−1 yr−1. Further constraining the model by the current wastewater storage volume and the available land area (approximately 1,000 hectares) required a “diverse” irrigation schedule that was predicted to leach a weighted average of 13 kg-N ha−1 yr−1 when dosed with 1,063 kg-N ha−1 yr−1.