Occurrence, removal and ecotoxicological assessment of halogenated dissolved organic matter in waste leachates

Halogenated organic compounds (HOCs) from plastics and electronics enter waste streams and leach into the environment. This study analyzed halogenated dissolved organic matter (DOM) in leachates from incineration, composting, and landfill processes using Fourier transform ion cyclotron resonance mass spectrometry. Incineration leachate contained significantly more halogenated species (879) than composting (548) and landfill leachates (439). The dominant compounds were monohalogenated CHOCl (33.72 %) and CHOBr (45.26 %), classified as aliphatic and highly unsaturated low-oxygen molecules. Compared to non-halogenated DOM, these exhibited higher aromaticity, lower oxidation levels, and smaller molecular weights. In membrane bioreactor systems with nanofiltration (NF) and reverse osmosis (RO), activated sludge adsorption outperformed biodegradation for removal. NF effectively reduced brominated DOM (65.49 % in compost, 92.16 % in incineration, 27.03 % in landfill leachates), while RO eliminated most 500-800 Da compounds. Toxicity analysis revealed incineration leachate had the highest developmental toxicity, whereas landfill leachate showed greatest mutagenicity. Rat oral toxicity was higher in incineration and landfill leachates than in compost leachate. Crucially, biological and membrane treatments increased effluent toxicity relative to influents. These findings demonstrate the environmental persistence of halogenated DOM and highlight limitations of current treatment methods. The study provides critical data for optimizing leachate treatment to reduce halogenated DOM toxicity.