Arbuscular mycorrhizal fungi and sponge iron enhanced the vertical flow construced wetlands on the purification of dimethyl phthalate-containing wastewater

The extent to which, and mechanisms by which, arbuscular mycorrhizal fungi (AMF) and sponge iron (SI) enhance wetlands purify on phthalate acid esters (PAEs)-containing wastewater are not well understood. In this study, AMF and/or SI were applied into micro vertical flow constructed wetlands (MVFCWs) to enhance their purification of dimethyl phthalate (DMP). The results showed that (1) Under the three hydraulic retention time (HRT) conditions, the average effluent DMP concentrations of control MVFCW were 21.36, 12.52, and 15.51 mu g/ L, respectively. The addition of AMF, SI, AMF and SI reduced the effluent DMP concentrations significantly by 48.01 %, 21.03 %, 78.25 % and 56.38 %, 66.24 %, 45.74 %, and 58.50 %, 37.35 %, and 59.47 %, respectively. (2) Microbial degradation was the main way of DMP removal in MVFCWs, accounting for 94.04-95.77 %, substrate adsorption and plant uptake accounted for 0.14-0.48 % and 1.30-2.58 %, respectively. (3) DMP stress, AMF inoculation, and SI addition all increased bacterial community richness and diversity in MVFCWs, and SI addition significantly altered the bacterial community structure (p < 0.05). The dominant phyla in MVFCWs were Proteobacteria, Epsilonbacteraeota, Bacteroidetes, Patescibacteria, and Chloroflexi. AMF inoculation increased the relative abundance of Epsilonbacteraeota and Bacteroidetes, while SI addition increased the relative abundance of Proteobacteria and Chloroflexi. (4) DMP removal was positively correlated with the abundance of Epsilonbacteraeota and Bacteroidetes, suggesting that AMF might promote DMP removal by enhancing the abundance of these phyla. We therefore conclude that inoculation with AMF and SI addition improves the purification of DMP-polluted wastewater, and the AMF/SI enchanced MVFCWs exhibit great potential for application in remediation of PAEs-polluted wastewater.