Effect of arbuscular mycorrhizal fungi on agricultural runoff treatment with different C/N ratios in lab scale continuous flow constructed wetlands

Bc. arch. Francisco Virgilio Machuca Saldaña

Master's thesis

Abstract:

Constructed wetlands (CWs) have turned into an eco-friendly alternative for the treatment of agricultural runoff with the ability to enhance ecosystem services. This study evaluated the performance of Vertical Subsurface Flow Constructed Wetlands (VSF CWs) in the removal of nitrogen compounds, phosphorus, carbon, and sulphates under varying carbon-to-nitrogen (C:N) ratios and varying hydraulic retention times. The present study is an assessment of the symbiotic relationship of Arbuscular Mycorrhizal Fungi (AMF) rhizophagus irregularis, with Iris Prseudacorus’ plants. The AMF effect on plant’s health, nutrient transformation and on the overall system performance of VSF CWs was evaluated. Eight lab-scale reactors were set-up and assigned a defined C:N ratio (1:6, 1:3, 3:1, and 6:1), with four reactors inoculated with AMF (AMF+) and four without (AMF−). Over the course of the experiment, water samples were collected at multiple retention times ranging from 0 (inflow) to 384 hours. Physicochemical parameters (pH, ORP, DO) and nutrient concentrations (TN, NO₂⁻, NO₃⁻, PO₄³⁻, SO₄²⁻, TOC, TC, IC) were monitored and analyzed. Results showed that (AMF+) systems consistently outperformed(AMF−)systems in terms of nutrient removal and system stability, particularly under higher C:N ratios and longer retention times. Nitrogen and phosphorus reductions were more effective in (AMF+) reactors, with denitrification supported by improved organic carbon availability and buffered redox conditions. Early surges in sulphate and phosphate were attributed to substrate leaching and redox-driven mobilization, gradually controlled as microbial dynamics and AMF symbiosis matured. Carbon analysis revealed that (AMF+) reactors maintained higher TOC percentages relative to TC, suggesting improved microbial uptake and stabilization of organic matter. These findings reflect the potential and importance of integrating AMF into CW design to improve treatment performance and resilience. This study highlights the importance of optimizing both carbon availability and retention times to achieve improved efficiency in nutrient cycling and removal in VSF CWs systems.

Keywords

Nutrient Removal, Constructed Wetlands, AMF, Rhizophagus irregularis, C, N Ratio, Denitrification, Phosphorus, Organic Carbon, Nitrogen

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 4. 4. 2025

Obhajoba závěrečné práce

• Obhajoba proběhla 20. 5. 2025
• Vedúci: doc. Zhongbing Chen
• Oponent: Tereza Dvořáková Březinová, Ph.D.

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Master programme:
Landscape Planning