Exploring the fate and chemical transformation of organics by UV/H2O2-GAC and UV/H2O2-BAC based on pilot-scale systems in the treatment of micro-polluted surface water

UV/H2O2 is commonly used to remove organic micropollutants and frequently paired with activated carbon for further removal of pollutants, addressing issues such as H2O2 residuals, uncontrollable by-products, and energy consumption reduction. Here, we report the changes in the removal characteristics of organic contaminants during the operation of a pilot system based on UV/H2O2 coupled granular activated carbon (GAC) after in situ biofilm formation to generate biologically activated carbon (BAC). We completed the screening of unknown organic matter and molecular-level chemical transformation of 100-1600 Da dissolved organic matter (DOM) using Fourier transform high-resolution mass spectrometry (FT-ICR MS). The FT-ICR MS results indicated that BAC differs from GAC in terms of DOM removal behavior and mechanisms. GAC primarily produces free radicals through synergistic residual H2O2 to further oxidize and remove organics. Low molecular weight (LMW) organics undergo general molecular chemical changes but have modest removal effects. BAC considerably lowered the chemical variety of DOM and eliminated LMW organics through biodegradation and activated carbon adsorption. According to the study findings, UV/H2O2-BAC can more effectively compensate for the drawbacks of individual technologies than UV/H2O2-GAC, with superior removal efficiency of organic pollutants, no residual H2O2, controllable effluent products, and robust performance in real environmental matrices.