Modeling sustainable reuse of nitrogen-laden wastewater by poplar

ABSTRACT

Numerical 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.

KEYWORDS:

• HYDRUS 1D
• poplar
• sustainable water reuse
• nitrogen management

Acknowledgments

Funding provided by the Port of Morrow, Boardman, Oregon under UI Project #1186790. Research data and expertise provided by Hayden Ausland.