Importance of Chain Length in Propagation Reaction on OH Formation during Ozonation of Wastewater Effluent.

During the ozonation of wastewater, hydroxyl radicals (OH) induced by the reactions of ozone (O) with effluent organic matters (EfOMs) play an essential role in degrading ozone-refractory micropollutants. The OH yield provides the absolute OH formation during ozonation. However, the conventional "tert-Butanol (BuOH) assay" cannot accurately determine the OH yield since the propagation reactions are inhibited, and there have been few studies on OH production induced by EfOM fractions during ozonation. Alternatively, a "competitive method", which added trace amounts of the OH probe compound to compete with the water matrix and took initiation reactions and propagation reactions into account, was used to determine the actual OH yields () compared with that obtained by the "BuOH assay" (). The were significantly higher than , indicating that the propagation reactions played important roles in OH formation. The chain propagation reactions facilitation of EfOMs and fractions can be expressed by the chain length (). The study found significant differences in for EfOMs and fractions, precisely because they have different . The actual OH yield can be calculated by and as = (1 + )/( + 1), which can be used to accurately predict the removal of micropollutants during ozonation of wastewater.