Ozonation of Reverse Osmosis Concentrate from Municipal Wastewater Reclamation Processes: Ozone Demand, Molecular Weight Distribution, UV/Fluorescence Characteristics, and Microalgal Growth Potential

Yuchang Chi, Zibin Xu and Nan Huang ()
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Yuchang Chi: National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China
Zibin Xu: Liaoning Transportation Research Institute, Shenyang 110000, China
Nan Huang: National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China

Sustainability, 2025, vol. 17, issue 21, 1-19

Abstract: To address the challenge of treating reverse osmosis concentrate (ROC) in municipal wastewater reclamation processes, this study systematically investigated changes in ozone demand, organic compound molecular weight distribution, UV/fluorescence characteristics, and microalgal growth potential during ozone treatment of ROC. The ROC contained fast-reacting substances and had an instantaneous ozone demand of 6.3 mg/L. The chemical oxygen demand (COD) and total organic carbon were partially removed, and the COD/five-day biochemical oxygen demand ratio increased slightly during the ozonation process. The molecular weight components shifted considerably during ozonation: the 300 Da–1000 Da components became dominant (51.6–72.3%), while the 1000 Da–4000 Da and <300 Da components were partially or completely removed. The maximum absorbance of the ROC peaked at 270 nm. At an ozone dosage of 84 mg/L, the UV 254 and UV 270 removal rates reached 76.9% and 86.5%, respectively. The three-dimensional fluorescence spectra showed that ozone effectively removed tryptophan-type aromatic proteins, fulvic acid-type substances, aromatic proteins, soluble microbial metabolites, and humic acid-type substances from the concentrate (84.6–88.9%), but only removed a minimal amount of the tyrosine-type aromatic protein (7.4%). The UV 254 at different molecular weights and the fluorescence area integrals across regions declined rapidly initially, then slowed gradually, correlating with the rapid reaction of UV/fluorescence chromophore-containing substances in ROC. Studies on microalgal growth potential indicate that ozonation increased the maximum algal density ( K ) in ROC (48.9–91.7%), while ozone/coagulation effectively reduced K (35.1–76.6%). This occurs because ozone converts organic phosphonate antiscalants in ROC into more readily absorbable inorganic phosphorus, whereas ozone/coagulation effectively removes total phosphorus from water. These results can guide the safe disposal of ROC and facilitate sustainable reclamation of municipal wastewater.

Keywords: reverse osmosis concentrate; ozonation; organic matter; molecular weight distribution; UV/fluorescence characteristics; microalgal growth potential; municipal wastewater reclamation (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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