Prediction of micropollutant elimination during ozonation of municipal wastewater effluents: Use of kinetic and water specific information

Ozonation is effective in improving the quality of municipal wastewater effluents by eliminating organic micropollutants. Nevertheless, ozone process design is still limited by (i) the large number of structurally diverse micropollutants and (ii) the varying quality of wastewater matrices (especially dissolved organic matter). These issues were addressed by grouping 16 micropollutants according to their ozone and hydroxyl radical ( ^•OH) rate constants and normalizing the applied ozone dose to the dissolved organic carbon concentration (i.e., g O₃/g DOC). Consistent elimination of micropollutants was observed in 10 secondary municipal wastewater effluents spiked with 16 micropollutants (∼2 μg/L) in the absence of ozone demand exerted by nitrite. The elimination of ozone-refractory micropollutants was well predicted by measuring the ^•OH exposure by the decrease of the probe compound p-chlorobenzoic acid. The average molar ^•OH yields (moles of ^•OH produced per mole of ozone consumed) were 21 ± 3% for g O₃/g DOC = 1.0, and the average rate constant for the reaction of ^•OH with effluent organic matter was (2.1 ± 0.6) × 10⁴ (mg C/L) ^-1 s^-1. On the basis of these results, a DOC-normalized ozone dose, together with the rate constants for the reaction of the selected micropollutants with ozone and ^•OH, and the measurement of the ^•OH exposure are proposed as key parameters for the prediction of the elimination efficiency of micropollutants during ozonation of municipal wastewater effluents with varying water quality.