Soil Biogeochemical Changes in Response to Irrigation with Treated Wastewater
Start Date
3-11-2024 4:00 PM
Abstract
Elevated summer water temperatures in the Tualatin River are a major concern for salmonids and other temperature-sensitive species. One significant heat source is the input effluent from wastewater treatment plants. Clean Water Services, a water utility in Washington County, aims to reduce the amount of heat entering the river by recycling treated wastewater to irrigate restored wetlands near their Wastewater Resource Recovery Facilities. In addition to lessening the amount of heat discharged into receiving waters, irrigation with recycled water could provide ecosystem benefits, such as carbon (C) sequestration, increased biodiversity, and improved habitat quality. On the other hand, recycled water irrigation could have detrimental effects such as increased emissions of greenhouse gases [GHG; carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4)]. In this study, we measured aspects of soil C and nitrogen (N) cycling including soil GHG emissions. My hypothesis is that the wet conditions and elevated N caused by irrigation will increase N2O emissions but will not become anoxic enough to produce CH4.
The 26-acre project site is irrigated with recycled wastewater at agronomic rates throughout the dry summer months. In 2022 and 2023, we installed four replicate soil chambers in Irrigated and Control areas in three different soil types. Every two weeks, we collected gas samples to estimate fluxes of CO2, N2O and CH4. Preliminary results indicate no significant differences in GHG emissions between control and irrigated sites, likely owing to low rates of irrigation to avoid surface ponding.
Subjects
Climate Change, Soil science, Water quality
Persistent Identifier
https://archives.pdx.edu/ds/psu/41401
Creative Commons License
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Soil Biogeochemical Changes in Response to Irrigation with Treated Wastewater
Elevated summer water temperatures in the Tualatin River are a major concern for salmonids and other temperature-sensitive species. One significant heat source is the input effluent from wastewater treatment plants. Clean Water Services, a water utility in Washington County, aims to reduce the amount of heat entering the river by recycling treated wastewater to irrigate restored wetlands near their Wastewater Resource Recovery Facilities. In addition to lessening the amount of heat discharged into receiving waters, irrigation with recycled water could provide ecosystem benefits, such as carbon (C) sequestration, increased biodiversity, and improved habitat quality. On the other hand, recycled water irrigation could have detrimental effects such as increased emissions of greenhouse gases [GHG; carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4)]. In this study, we measured aspects of soil C and nitrogen (N) cycling including soil GHG emissions. My hypothesis is that the wet conditions and elevated N caused by irrigation will increase N2O emissions but will not become anoxic enough to produce CH4.
The 26-acre project site is irrigated with recycled wastewater at agronomic rates throughout the dry summer months. In 2022 and 2023, we installed four replicate soil chambers in Irrigated and Control areas in three different soil types. Every two weeks, we collected gas samples to estimate fluxes of CO2, N2O and CH4. Preliminary results indicate no significant differences in GHG emissions between control and irrigated sites, likely owing to low rates of irrigation to avoid surface ponding.