Enhancement of low C/N wastewater treatment and plant growth in sulfur-based constructed wetlands through arbuscular mycorrhizal fungi inoculation

Sulfur (S)-based constructed wetlands (CWs) are effective in removing pollutants from low carbon to nitrogen (C/N) wastewater, though nitrogen removal efficiency is limited. Additionally, by-products of sulfur may adversely affect plant growth. This study investigated the effects of arbuscular mycorrhizal fungi (AMF) inoculation on wastewater treatment across different C/N ratios (1, 5, 10) alongside evaluating the growth of Iris pseudacorus in S-based CWs. Results showed that AMF colonization in I. pseudacorus increased with rising C/N ratios in S-based CWs. AMF and sulfur jointly enhanced pollutant removal efficiencies, particularly at C/N ratios of 1 and 5. The NO3--N, COD, and TP removal efficiencies were improved by 19.9-34.1 %, 1.8-8.0 %, and 1.3-6.6 %, respectively, in AMF-inoculated S-based CWs (ASCW) compared to controls. Although NH4+-N removal was reduced in S-based CWs, AMF inoculation boosted NH4+-N removal by 3.5-20.7 %. Additionally, AMF inoculation enhanced the antioxidant response and photosynthesis in I. pseudacorus within S-based CWs, increasing SOD, POD, and CAT activities increased by 6.9-16.5 %, 0.7-10.7 %, and 1.1-3.9 %, respectively, while reducing MDA concentrations by 14.5-22.0 %. Mantel test analysis revealed a positive correlation between plant growth and wastewater purification under low C/N conditions. This study highlights AMF's significant role in improving low C/N wastewater treatment and promoting wetland plant growth in S-based CWs.