2 research outputs found
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<sub>C</sub>), <i>N</i>-nitrosopyrrolidine
(NPYR, 14 ng/mg<sub>C</sub>), <i>N</i>-nitrosopiperidine
(NPIP, 3.7–5.5 ng/mg<sub>C</sub>), and <i>N</i>-nitrosomethylethylamine
(NMEA, 2.1–2.6 ng/mg<sub>C</sub>). 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 (<sup>•</sup>OH) rate constants and normalizing the applied ozone dose to the
dissolved organic carbon concentration (i.e., g O<sub>3</sub>/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 <sup>•</sup>OH exposure by the decrease of
the probe compound <i>p</i>-chlorobenzoic acid. The average
molar <sup>•</sup>OH yields (moles of <sup>•</sup>OH
produced per mole of ozone consumed) were 21 ± 3% for g O<sub>3</sub>/g DOC = 1.0, and the average rate constant for the reaction
of <sup>•</sup>OH with effluent organic matter was (2.1 ±
0.6) × 10<sup>4</sup> (mg C/L)<sup>−1</sup> s<sup>–1</sup>. 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 <sup>•</sup>OH, and the measurement of the <sup>•</sup>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