Catalytic versus Pure Ozonation: Insights from Real Wastewater Treatment Performance

The performance of pure (i.e., noncatalytic) ozonation and heterogeneous catalytic ozonation (HCO) in treating a range of real wastewater streams with varying organic compositions is investigated in this study. While HCO is often proposed as a promising approach for treating real wastewaters, our results reveal that its benefits over ozonation are very case-specific. Wastewaters rich in fulvic/humic-like, surface-active organic compounds, such as membrane concentrate, respond favorably to HCO, showing improved ozone utilization compared to the pure ozonation process. In contrast, coking wastewater shows minimal improvement with HCO compared to pure ozonation, indicating a limited catalytic benefit in such matrices. Similarly, alkaline electroplating wastewaters rich in ozone reactive compounds showed no improvement in organic removal by HCO compared to that of pure ozonation. In contrast, acidic Fenton-treated chemical wastewaters showed significant improvement in organic removal by HCO compared to pure ozonation due to limited hydroxyl radical (HO^•) generation via ozone self-decay under these conditions. Overall, our findings suggest that the inherent reactivity of ozone and sustained HO^• generation on ozone decay, particularly under alkaline conditions that are typical of many wastewaters, diminish the added value of the catalyst.