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431 results on '"Rosario-Ortiz, Fernando"'

132. Impact of Light Screening and Photosensitization by Surface Water Organic Matter on Enterococcus Faecalis Inactivation.

Author

Mostafa, Simón, Rubinato, Matteo, Rosario-Ortiz, Fernando L., and Linden, Karl G.

Subjects
ENTEROCOCCUS faecalis, PHOTOSENSITIZATION, CARBON content of water, WASTEWATER treatment, MICROBIAL inactivation
Abstract

Sunlight irradiation is known to contribute to microbial inactivation in natural treatment systems (NTS) and surface waters via both direct and indirect processes. This study investigated the influence of various types of organic matter (OM) on endogenous and exogenous photoinactivation of Enterococcus faecalis. Solar simulator exposure experiments were conducted in surface waters and wastewater and in the presence of natural OM isolates and a singlet oxygen (1O2) sensitizer, methylene blue. Presence of both natural and anthropogenic OM resulted in increases in inactivation rates of 17-67% compared to sensitizer-free experiments. This suggests that, while direct and endogenous photoinactivation is hindered with increasing depth due to light screening by OM, its role as a photosensitizer in the formation of reactive intermediates (predominantly involving 1O2) is greater than its negative impact due to light screening at levels typically found in NTS. Specifically, increases in light absorbance (particularly at shorter wavelengths) are estimated to reduce direct and endogenous processes by up to 41% under our experimental conditions; however, presence of external photosensitizers enhances exogenous inactivation processes to a greater degree. A novel approach is presented to help estimate endogenous and exogenous inactivation rates of E. faecalis as a function of depth in the presence of OM based on common optical measurements. Implications of this knowledge in informing design parameters (e.g., depth and retention time) of NTS are discussed, thus contributing to both fundamental understanding of photoinactivation processes in surface waters and improvement of treatment unit design. [ABSTRACT FROM AUTHOR]

Published
2016
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148. Formation of Nitrogenous Disinfection By-products From Algal Organic Matter.

Author

HOHNER, AMANDA K., GHOSH, AMLAN, and ROSARIO-ORTIZ, FERNANDO L.

Subjects
ALGAL cells, DISSOLVED organic matter, ORGANIC compounds, BASE pairs, TRIHALOMETHANES, CHEMICAL precursors
Abstract

The article focuses on nitrogenous disinfection by-products (N-DBPs) formation from algal organic matter (AOM). It mentions that higher formation of N-DBP was associated with disinfection of water consisting dissolved organic nitrogen. Furthermore, it says that AOM was determined as precursors of C- and N-DBPs, in which the cells and proteins from an specific algae species form trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs).

Published
2013

149. Evaluating the Use of UV Absorbance for the Differentiation of Humified From Non-Humified Materials.

Author

Rahbari, Mohammad, Psutka, Jarrod, Lamar, Richard, and Rosario-Ortiz, Fernando L

Subjects
*HUMIC acid, *FULVIC acids, *ULTRAVIOLET-visible spectroscopy, *PEAT, *LIGHT absorbance
Abstract

Background Products containing humic acids (HA) and fulvic acids (FA) have significant commercial potential; however, unknown to the consumer, some products may be mislabeled or contain adulterants. The prevalence of mislabeling and adulterants is found primarily in FA products. Using UV-Vis spectroscopy to differentiate between real and fake FA products is practical and desirable. Objective The objective of this study was to expand the dataset generated using a UV-Vis-based method proposed by Mayhew et al. 2023. Methods In total, 30 test samples were used to generate 90 test portions (three replicates per test sample) for analysis using the UV-Vis methodology outlined in Mayhew et al. 2023, which in this study is referred to as the UVAC (UV absorbance confirmation) method. Results None of the 13 FA test samples investigated were determined as humified using the UVAC method. The FA samples studied consisted of two IHSS standards, five commercial FA products (CFAP), and six full FA fractions (SFA), which were isolated from six known solid humic material sources (SHMS). There was a leonardite, a humalite, and four peat sources used as the SHMS. Analysis of the neutralized extract of the SHMS found only 3/6 SHMS were determined as humified. Six HA (SHA) test samples were also generated by isolating the HA from the SHMS, and only 3/6 SHA were determined as humified. Conclusions Given the high prevalence of false determinations, more work is needed to improve the method so that it can be used by industry or regulators. Highlights The proposed method failed to determine IHSS FA standards as humified. Although the method is practical, it needs improvement and further study before it can be used for reliable differentiation of real from fake FA. [ABSTRACT FROM AUTHOR]

Published
2024
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150. Effects of Ozone on the Photochemical and Photophysical Properties of Dissolved Organic Matter

Author

Leresche, Frank, McKay, Garrett, Kurtz, Tyler, von Gunten, Urs, Canonica, Silvio, and Rosario-Ortiz, Fernando L.

Subjects
optical-properties, quantum yields, ms2 coliphage, charge-transfer interactions, waste-water treatment, disinfection by-product, aquatic environment, sunlight-mediated inactivation, singlet oxygen, surface waters
Abstract

This study focused on the effects of ozonation on the photochemical and photophysical properties of dissolved organic matter (DOM). Upon ozonation, a decrease in DOM absorbance was observed in parallel with an increase in singlet oxygen (O-1(2)) and fluorescence quantum yields (Phi(1O2) and Phi(F)). The increase in Phi(1O2) was attributed to the formation of quinone-like moieties during ozonation of the phenolic moieties of DOM, while the increase in Phi(F) can be explained by a significant decrease in the internal conversion rate of the first excited singlet state of the DOM ((DOM)-D-1*). It is a consequence of an increase in the average energy of the first electronic transition (S-1 -> S-0) that was assessed using the wavelength of maximum fluorescence emission (lambda(F,max)). Furthermore, ozonation did not affect the ratio of the apparent steady-state concentrations of excited triplet DOM ((DOM)-D-3*) and O-1(2), indicating that ozonation does not affect the efficiency of O-1(2) production from (DOM)-D-3*. The consequences of these changes for the phototransformation rates of micropollutants in surface waters were examined using photochemical model calculations. The decrease in DOM absorbance caused by ozonation leads to an enhancement of direct photolysis rates due to the increased transparency of the water. Rates of indirect photooxidation induced by O-1(2) and (DOM)-D-3* slightly decrease after ozonation.

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