Thesis
Effect of wastewater irrigation onto forest land on grandwater phosphorus concentrations
Washington State University
Master of Science (MS), Washington State University
05/2020
DOI:
https://doi.org/10.7273/000004075
Handle:
https://hdl.handle.net/2376/125352
Abstract
Phosphorus (P) is commonly a limiting nutrient for aquatic plant and algal growth. Excess P can lead to eutrophication of surface waters. This study examined the potential effects on lake water quality from wastewater irrigation onto forest land. Total phosphorus, anthropogenic waste indicators, and stable water isotopes were monitored in the groundwater entering Kalispell Bay at Priest Lake, ID, where wastewater irrigation is the waste disposal method. Soil phosphorus sorption capacity was characterized by P isotherms for six soil depths. A phosphorus leaching experiment was conducted in the laboratory using undisturbed soil columns from the study area. Phosphorus transport through the vadose zone was simulated using the HYDRUS-1D model and compared to observed P concentration in groundwater. Phosphorus and anthropogenic waste indicators were found in the groundwater entering the lake. Phosphorus and caffeine concentrations were positively correlated (p = 0.016). Phosphorus in groundwater reached concentrations up to 0.14 mg P/L compared to the background concentration of 0.013 mg P/L. Soil layers to 30 cm depth were found to have high P sorption capacity. Sorption capacity greatly diminished below 60 cm due to coarse sandy layers. The column experiments showed P can potentially leach out of the irrigation field at its current state at concentrations ranging from 0.2 - 0.8 mg P/L. Model simulations over a 21 year time period showed potential P concentrations up to 0.04 mg P/L are reaching the groundwater. Phosphorus transport by preferential flow throughout the entire vadose zone along with low sorption capacity in the sandy soil enhanced P transport above the assumed homogeneous soil conditions in design of the wastewater irrigation system. These simulated concentrations are lower than those found entering the lake, however, documented leakage of the waste lagoons adds an additional P load. Findings of this study suggest that wastewater irrigation onto forest land can potentially contribute to elevated groundwater P concentrations.
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Details
- Title
- Effect of wastewater irrigation onto forest land on grandwater phosphorus concentrations
- Creators
- Joseph Galen Kornowske
- Contributors
- Jan Boll (Advisor) - Washington State University, Department of Civil and Environmental Engineering
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890789101842
- Language
- English
- Resource Type
- Thesis