Importance of Chain Length in Propagation Reaction on (OH)-O-center dot Formation during Ozonation of Wastewater Effluent

During the ozonation of wastewater, hydroxyl radicals ((OH)-O-center dot) induced by the reactions of ozone (O3) with effluent organic matters (EfOMs) play an essential role in degrading ozone-refractory micropollutants. The (OH)-O-center dot yield provides the absolute (OH)-O-center dot formation during ozonation. However, the conventional tertButanol (t-BuOH) assay cannot accurately determine the (OH)-O-center dot yield since the propagation reactions are inhibited, and there have been few studies on (OH)-O-center dot production induced by EfOM fractions during ozonation. Alternatively, a competitive method, which added trace amounts of the (OH)-O-center dot probe compound to compete with the water matrix and took initiation reactions and propagation reactions into account, was used to determine the actual (OH)-O-center dot yields (F) compared with that obtained by the t-BuOH assay (f). The F were significantly higher than f, indicating that the propagation reactions played important roles in (OH)-O-center dot formation. The chain propagation reactions facilitation of EfOMs and fractions can be expressed by the chain length (n). The study found significant differences in F for EfOMs and fractions, precisely because they have different n. The actual (OH)-O-center dot yield can be calculated by n and f as F = f (1 + n)/(nf + 1), which can be used to accurately predict the removal of micropollutants during ozonation of wastewater.

Automated summary

During the ozonation of wastewater, the hydroxyl radicals ((OH)-O-center dot) formed by the reactions of ozone (O3) with effluent organic matters (EfOMs) are crucial for degrading ozone-refractory micropollutants. However, the conventional tertButanol (t-BuOH) assay cannot accurately determine the (OH)-O-center dot yield. A competitive method, considering initiation and propagation reactions, was used to determine the actual (OH)-O-center dot yields (F) compared with the t-BuOH assay (f). The study found that the chain propagation reactions facilitated by EfOMs and fractions, expressed by the chain length (n), significantly impacted the (OH)-O-center dot formation.