Intracellular Organic Matter from Cyanobacteria as a Precursor for Carbonaceous and Nitrogenous Disinfection Byproducts

The formation of total organic halogen (TOX), carbonaceous disinfection byproducts (DBPs) (trihalomethanes (THMs) and haloacetic acids (HAAs)), and nitrogenous DBPs (trichloronitromethane (TCNM) or chloropicrin, haloacetonitriles (HANs), and nitrosamines) was examined during the chlorination or chloramination of intracellular organic matter (IOM) extracted from <i>Microcystis aeruginosa</i>, <i>Oscillatoria </i>sp. (OSC), and <i>Lyngbya </i>sp. (LYN). The percentage of unknown TOX (22–38%) during chlorination indicated that the majority of DBPs were identified among THMs, HAAs, TCNM, and HANs. Bromide was readily incorporated into DBPs with speciation shifting slightly from dihalogenated species to trihalogenated species. During formation potential testing with chloramines, nitrosamine yields from IOM were measured for <i>N</i>-nitrosodimethylamine (NDMA, 10–52 ng/mg_C), <i>N</i>-nitrosopyrrolidine (NPYR, 14 ng/mg_C), <i>N</i>-nitrosopiperidine (NPIP, 3.7–5.5 ng/mg_C), and <i>N</i>-nitrosomethylethylamine (NMEA, 2.1–2.6 ng/mg_C). When IOM was added to a natural water matrix, the nitrosamine yields were not realized likely due to competition from natural organic matter. Ozonation increased NDMA and NMEA formation and reduced NPYR and NPIP formation during subsequent chloramination. In addition, ozone oxidation of IOM formed detectable concentrations of aldehydes, which may contribute to DBP formation. Finally, bioluminescence-based test results showed that >99% of the IOM extracted from OSC and LYN was biodegradable. Therefore, a biological treatment process could minimize this source of DBP precursor material during drinking water treatment

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 <i>p</i>-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