Insight into the Organic Micropollutants in MSWI Fly Ash Eluate: Toward a Molecular-Level Risk for Marine Discharge

Municipal solid waste incineration fly ash washing has emerged as a promising pretreatment strategy for resource utilization, yet molecular-level characterization of the organic micropollutants of fly ash eluate (FAE) remains lacking. Organic micropollutants in the FAE from simulated washing were identified by nontarget analysis, coupled with priority pollutant quantification and acute toxicity evaluation using Vibrio fischeri. Volatile/semivolatile (29–80 kinds) and nonvolatile organic compounds (78–136 kinds) are identified in the FAE, demonstrating substantial chemical diversity influenced by waste composition and high ionic strength. Polychlorinated dibenzo-p-dioxins/furans are not discovered in the FAE, while polycyclic aromatic hydrocarbons, herbicides, and antibiotics have been found in the FAE, with concentrations up to mg·L–1 levels. Acute toxicity assessment yields IC50 values of 1.19–2.39%, primarily attributed to Pb, organic micropollutants, their interactive effects, and limited pH stress under the test conditions. While salinity and pH would be neutralized upon marine discharge, the fate and transformation of heavy metals and organic micropollutants during rapid pH/salinity transitions represent critical concerns. Current wastewater regulatory frameworks using static concentration limits are inadequate for assessing dynamic fate processes in FAE discharge. This molecular-level characterization establishes the foundation for developing site-specific fate-based risk assessment and treatment strategies for FAE marine discharge.