Gregory V. Korshin

Monitoring the properties of natural organic matter through UV spectroscopy: A consistent theory

UV spectra of natural organic matter (NOM) can be represented by three bands, each a Gaussian function of energy. The bands, referred to as the local-excitation (LE), benzenoid (Bz) and electron-transfer (ET) bands, can be ascribed to three types of electronic transitions typical in aromatic compounds. At wavelengths from 200 to 400 nm, an adequate fit to the spectrum can be obtained by consideration of only the Bz and ET bands. The parameters of these two bands are sensitive to the composition of NOM and to alterations in NOM caused by coagulation and chlorination. Removal of NOM fractions with higher-than-average concentrations of carboxyl-, hydroxyl- and ester-substituted aromatic rings or oxidation of those fractions by chlorine decreases the intensity and width of the ET and Bz bands. The ratio of absorbances at the band maxima is an indicator of the average degree of activation of the aromatic rings and permits prediction of the reactivity of the aromatic moiety in chlorination reactions. In addition, measurements of absorbance changes induced by chlorination permit one to monitor certain aspects of chlorination reactions in situ and to evaluate the formation of disinfection by-products.

Adsorption of natural organic matter (NOM) on iron oxide: Effects on NOM composition and formation of organo-halide compounds during chlorination

A large fraction of the natural organic matter (NOM) in potable water sources can be extracted by adsorption onto iron-oxide-coated sand (IOCS). In this research, two water sources were characterized with respect to their hydrophobic/hydrophilic fractionation, their 13C NMR and UV absorbance spectra and their reactivity with chlorine, before and after the waters were contacted with IOCS. The IOCS preferentially adsorbs acidic fractions of NOM and NOM molecules that are enriched in aromatic and carboxylic carbon. The yield of chloro-organic compounds (quantified as total organo-halide) produced upon chlorination of the NOM or its major fractions correlates with the specific absorbance (As) at 254 nm. IOCS may be useful for removing disinfection by-product (DBP) precursors from potable waters and/or as a medium for NOM accumulation.

Development of surrogate correlation models to predict trace organic contaminant oxidation and microbial inactivation during ozonation.

The performance of ozonation in wastewater depends on water quality and the ability to form hydroxyl radicals (·OH) to meet disinfection or contaminant transformation objectives. Since there are no on-line methods to assess ozone and ·OH exposure in wastewater, many agencies are now embracing indicator frameworks and surrogate monitoring for regulatory compliance. Two of the most promising surrogate parameters for ozone-based treatment of secondary and tertiary wastewater effluents are differential UV(254) absorbance (ΔUV(254)) and total fluorescence (ΔTF). In the current study, empirical correlations for ΔUV(254) and ΔTF were developed for the oxidation of 18 trace organic contaminants (TOrCs), including 1,4-dioxane, atenolol, atrazine, bisphenol A, carbamazepine, diclofenac, gemfibrozil, ibuprofen, meprobamate, naproxen, N,N-diethyl-meta-toluamide (DEET), para-chlorobenzoic acid (pCBA), phenytoin, primidone, sulfamethoxazole, triclosan, trimethoprim, and tris-(2-chloroethyl)-phosphate (TCEP) (R(2) = 0.50-0.83) and the inactivation of three microbial surrogates, including Escherichia coli, MS2, and Bacillus subtilis spores (R(2) = 0.46-0.78). Nine wastewaters were tested in laboratory systems, and eight wastewaters were evaluated at pilot- and full-scale. A predictive model for OH exposure based on ΔUV(254) or ΔTF was also proposed.

Absorbance spectroscopy-based examination of effects of coagulation on the reactivity of fractions of natural organic matter with varying apparent molecular weights.

Absorbance spectra of fractions of natural organic matter (NOM) with varying apparent molecular weights (AMWs) were examined in this study. Size exclusion chromatography (SEC) was employed to obtain AMW distributions for three Australian water sources which represented low- and high-dissolved organic carbon (DOC) surface waters and a source with highly degraded NOM. These waters were coagulated with alum and other coagulants. Effects of coagulation on AMW distributions were quantified based on an absorbance slope index (ASI) calculated using NOM absorbance measured at 220, 230, 254 and 272 nm. This index can be calculated for any AMW fraction of NOM. Similarly to SUVA(254), ASI values decrease consistently in coagulated waters and are correlated with trihalomethane yields. Comparison of ASI indexes in different water sources indicates the presence of both common trends and differences indicative of NOM site-specificity.

Effects of Fenton treatment on the properties of effluent organic matter and their relationships with the degradation of pharmaceuticals and personal care products

This study examined effects of Fenton oxidation on trace level pharmaceuticals and personal care products (PPCPs) commonly occurring in wastewater. The tested PPCPs included acetaminophen, atenolol, atrazine, carbamazepine, metoprolol, dilantin, DEET, diclofenac, pentoxifylline, oxybenzone, caffeine, fluoxetine, gemfibrozil, ibuprofen, iopromide, naproxen, propranolol, sulfamethoxazole, bisphenol-A and trimethoprim. Transformations of effluent organic matter (EfOM) caused by Fenton oxidation were also quantified. All tested PPCPs, except atrazine and iopromide, were completely removed by Fenton treatment carried out using a 20mg/L Fe (II) concentration and a 2.5 H(2)O(2)/Fe (II) molar ratio. Up to 30% on the total carbon concentration was removed during Fenton treatment which was accompanied by the oxidation of EfOM molecules and formation of oxidation products such as oxalic, formic and acetic acids and, less prominently, formaldehyde, acetaldehyde, propionaldehyde and glycolaldehyde. The absorbance of EfOM treated with Fenton reagent at varying Fe (II) concentration and contact time underwent a consistent decrease. The relative decrease of EfOM absorbance was strongly and unambiguously correlated with the removal of all tested PPCPs.

Spectroscopic study of degradation products of ciprofloxacin, norfloxacin and lomefloxacin formed in ozonated wastewater

This study addressed the formation and properties of degradation products of ciprofloxacin, norfloxacin and lomefloxacin formed during ozonation of secondary wastewater effluent containing these fluoroquinolone antibiotics. The generation of the degradation products was interpreted in the context of transformations of effluent organic matter (EfOM) tracked via absorbance measurements. The structures of 20 degradation products were elucidated for ciprofloxacin and norfloxacin, respectively. 27 degradation products were identified for lomefloxacin. The prevalent oxidation pathways were suggested based on the structures of the identified products formed in the absence and presence of the hydroxyl radical scavenger t-butanol. These pathways were largely similar for all studied fluoroquinolones and involved attacks on the piperazine ring and the quinolone structure. The quinolone ring remained intact in the presence of t-butanol thus indicating that this functional group could only be oxidized by OH radicals while the piperazine ring was readily oxidized by molecular ozone. The cleavage of the quinolone moiety that resulted in several identified degradation products occurred via the attack by hydroxyl radicals on the carbon-carbon double bond adjacent to the carboxylic acid group. Lomefloxacin had more diverse oxidation products due to the presence of a methyl group on its piperazinyl ring. The concentrations of the identified degradation products behaved non-monotonically as a function of ozone dose or treatment time, yet exhibited interpretable correlations versus changes of EfOM absorbance. Examination of these correlations allowed developing a novel approach for elucidating the transformations of fluoroquinolone antibiotics during ozonation.

The decrease of UV absorbance as an indicator of TOX formation

Abstract The decrease in UV absorbance (ΔUV) caused by chlorination of NOM correlates linearly with the amount of TOX formed, for a remarkably wide range of water quality conditions and reaction times. THM formation also correlates with ΔUV, but the relationship is more sensitive to solution pH and is probably not linear over the entire range of conditions/times relevant for water treatment. It appears that all Cl-DOC reactions that destroy UV absorbance generate TOX, but substantial amounts of THMs are formed only after a significant amount of reaction has occurred.

Characterization of elemental and structural composition of corrosion scales and deposits formed in drinking water distribution systems.

Corrosion scales and deposits formed within drinking water distribution systems (DWDSs) have the potential to retain inorganic contaminants. The objective of this study was to characterize the elemental and structural composition of extracted pipe solids and hydraulically-mobile deposits originating from representative DWDSs. Goethite (alpha-FeOOH), magnetite (Fe(3)O(4)) and siderite (FeCO(3)) were the primary crystalline phases identified in most of the selected samples. Among the major constituent elements of the deposits, iron was most prevalent followed, in the order of decreasing prevalence, by sulfur, organic carbon, calcium, inorganic carbon, phosphorus, manganese, magnesium, aluminum and zinc. The cumulative occurrence profiles of iron, sulfur, calcium and phosphorus for pipe specimens and flushed solids were similar. Comparison of relative occurrences of these elements indicates that hydraulic disturbances may have relatively less impact on the release of manganese, aluminum and zinc, but more impact on the release of organic carbon, inorganic carbon, and magnesium.

Correlations between differential absorbance and the formation of individual DBPs.

This study examined correlations between the differential absorbance at 272nm (deltaA272) and the formation of disinfection by-products (DBPs) in chlorinated water from the Tolt River, a water source for Seattle, WA. The DBPs investigated included chloroform (CHCl3), dichlorobromomethane (CHCl2Br), mono-, di- and trichloroacetic acids (MCAA, DCAA, and TCAA, respectively), chloral hydrate (CH), dichloroacetonitrile (DCAN) and 1,1,1-trichloropropanone (TCP). Whereas the kinetics of DBP formation are complex and are non-linear, the same DBP data represented as a function of deltaA272 are quite simple. Absorbance decreases when the water is chlorinated, i.e., deltaA272 is always negative. The DBP vs. -deltaA272 correlations can almost always be quantified by linear equations, at least above some threshold value of -deltaA272, with R2 values > 0.95. The only DBP that did not follow this trend was CH, for which an exponential relationship better described the data. TCP and DCAN were unstable at pH 7 and 8, but at pH 6 linear correlations between their concentrations and -deltaA272 were as strong as those for the more stable DBPs. The threshold -deltaA272 value is approximately the same for many of the DBPs studied, supporting the hypothesis that individual DBPs are released following the formation of a common intermediate, or at least a small group of similar intermediates. The DBP vs. -deltaA272 correlations may have practical value since they provide an alternative approach for monitoring the formation of individual DBP species on-line, but the generality of the relationships needs to be further examined.

Evolution of Absorbance Spectra of Ozonated Wastewater and Its Relationship with the Degradation of Trace-Level Organic Species

This study examined the evolution of absorbance spectra of wastewater ozonated using varying initial ozone concentrations or treatment times; concomitant changes of concentrations of trace-level pharmaceuticals were also quantified. The absorbance of ozonated wastewater decreased due to the degradation of chromophores in effluent organic matter (EfOM). The relative decrease of absorbance (DeltaA/A(0)) ranged from < 30% for lambda < 250 nm to > 80% for lambda > 320 nm. The removal of atenolol, carbamazepine, DEET, diclofenac, gemfibrozil, ibuprofen, iopromide, naproxen, propranolol, sulfamethoxazole, trimethoprim, and p-chlorobenzoic acid was strongly correlated with DeltaA/A(0) values. The observed features were hypothesized to correspond to the engagement of kinetically distinct groups of EfOM chromophores. Modeling of the evolution of EfOM absorbance and concurrent degradation of trace-level organic species based on this hypothesis confirmed its applicability and utility for practical applications and theoretical exploration.