Photochemical Formation of Hydroxyl Radical from Effluent Organic Matter

The photochemical formation of hydroxyl radical (HO center dot) from effluent organic matter (EfOM) was evaluated using three bulk wastewater samples collected at different treatment facilities under simulated sunlight. For the samples studied, the formation rates of HO center dot (R-HO center dot) were obtained from the formation rate of phenol following the hydroxylation of benzene. The values of R-HO center dot ranged from 2.3 to 3.8 x 10(-10) M s(-1) for the samples studied. The formation rate of HO center dot from nitrate photolysis (R-NO3(HO center dot)) was determined to be 3.0 x 10(-7) M-HO center dot M-NO3(-1) s(-1). The HO center dot production rate from EfOM (R-EfOM(HO)) ranged from 0.76 to 1.3 x 10(-10) M s(-1). For the wastewater samples studied, R-EfOM(HO center dot) varied from 1.5 to 2.4 x 10(-7) M-HO center dot M-C(-1) s(-1) on molar carbon basis, which was dose to HO center dot production from nitrate photolysis. The apparent quantum yield for the formation of HO center dot from nitrate (Phi(a)(NO3-HO center dot)) was determined as 0.010 +/- 0.001 for the wavelength range 290-400 nm in ultrapure water. The apparent quantum yield for HO center dot formation in EfOM (Phi(a)(EfOM-HO center dot)) ranged from 6.1 to 9.8 x 10(-5), compared to 2.99 to 4.56 x 10-5 for organic matter (OM) isolates. The results indicate that wastewater effluents could produce significant concentrations of HO center dot, as shown by potential higher nitrate levels and relatively higher quantum yields of HO center dot fori-nation from EfOM.