Specific Ultraviolet Absorbance Values Research Articles

Seasonal variations of natural organic matter (NOM) in surface water supplied to two coal-fired power stations.

Global issues such as pollution and global warming have resulted in changes in water characteristics over the past 20years. Natural organic matter (NOM) which is a major component in water systems has shown an increase globally. This increase in NOM concentration has negatively affected both water treatment processes and drinking water quality. It is subsequently critical to understand the seasonal variations and composition of NOM to be able to address issues related to NOM. In this study, techniques such as ultraviolet-visible spectroscopy, total organic carbon and liquid chromatography-organic carbon detection (LC-OCD) were used for characterisation and quantification of NOM. Two coal-fired power stations were selected for this study with each power station receiving water from a different source, i.e. power station A receives water from the Vaal River and power station B from the Nkomati River. Results from this study demonstrated that composition and concentration of NOM from these two water sources varied seasonally. Characterisation of NOM using the LC-OCD indicated that the different fractions of NOM, i.e. low molecular weight neutrals, low molecular weight acids, building blocks, humic substances and biopolymers, varied seasonally. The dissolved organic carbon concentration and specific ultraviolet absorbance values of the raw water at both power stations showed an increment amid the wet seasons and a decrease amid the dry seasons.

Formation of regulated and unregulated disinfection byproducts during chlorination and chloramination: Roles of dissolved organic matter type, bromide, and iodide

Algal blooms and wastewater effluents can introduce algal organic matter (AOM) and effluent organic matter (EfOM) into surface waters, respectively. In this study, the impact of bromide and iodide on the formation of halogenated disinfection byproducts (DBPs) during chlorination and chloramination from various types of dissolved organic matter (DOM, e.g., natural organic matter (NOM), AOM, and EfOM) were investigated based on the data collected from literature. In general, higher formation of trihalomethanes (THMs) and haloacetic acids (HAAs) was observed in NOM than AOM and EfOM, indicating high reactivities of phenolic moieties with both chlorine and monochloramine. The formation of haloacetaldehydes (HALs), haloacetonitriles (HANs) and haloacetamides (HAMs) was much lower than THMs and HAAs. Increasing initial bromide concentrations increased the formation of THMs, HAAs, HANs, and HAMs, but not HALs. Bromine substitution factor (BSF) values of DBPs formed in chlorination decreased as specific ultraviolet absorbance (SUVA) increased. AOM favored the formation of iodinated THMs (I-THMs) during chloramination using preformed chloramines and chlorination-chloramination processes. Increasing prechlorination time can reduce the I-THM concentrations because of the conversion of iodide to iodate, but this increased the formation of chlorinated and brominated DBPs. In an analogous way, iodine substitution factor (ISF) values of I-THMs formed in chloramination decreased as SUVA values of DOM increased. Compared to chlorination, the formation of noniodinated DBPs is low in chloramination.

Temperature effects on sorption of dissolved organic matter on ferrihydrite under dynamic flow and batch conditions

AbstractAccurately predicting the effect of temperature on soil C storage remains a crucial objective in the effort to understand, mitigate, and adapt to climate change. Associations between soil organic C and short‐range order minerals like the iron hydroxide ferrihydrite contribute substantially to C sequestration, but little is known about how these associations respond to changes in temperature. We investigated the effects of temperature (7, 25, and 45 °C) and dissolved organic matter (DOM) source and fraction on DOM sorption to ferrihydrite‐coated sand in continuous flow and batch systems at circumneutral pH. Our findings demonstrate a positive relationship between temperature and adsorption, especially between 25 and 45 °C. For aquatic DOM, desorption also increased appreciably with temperature, whereas desorption of peat and soil DOM was less sensitive. More aquatic DOM adsorbed compared with soil DOM at all temperatures, but flow studies revealed that aquatic DOM also desorbed at higher rates. Modeling of DOM breakthrough curves using the advection‐diffusion equation with a modified Freundlich isotherm suggested the partition coefficient increased over time. Specific ultraviolet absorbance values of initial column effluents were low, suggesting that aromatic‐rich compounds preferentially adsorbed to the mineral surface. Our results indicate that some circumstances may favor the accumulation of DOM on iron mineral surfaces as temperature increases, potentially removing organic substrates from the accessible dissolved C pool. However, the stability of new associations likely depends on the chemical characteristics of DOM and the conditions under which it adsorbed.

Coagulation-ultrafiltration integrated process for membrane fouling control: Influence of Al species and SUVA values of water

Natural organic matter (NOM) pollution is a great challenge for the ultrafiltration (UF) process owing to the inevitable membrane fouling. In this study, three Al species coagulants (Ala/Alb/Alc) and their composites in combination with Poly dimethyl ammonium chloride (PolyDMDAAC) were used as a pretreatment strategy for the UF process. Then, test waters with different NOM fractions (i.e., humic acid, fulvic acid, protein, and polysaccharide) were prepared to analyze the effects of NOM characteristics on membrane fouling behaviors. The results indicated that compared with Alb and Alc, Ala showed higher removal efficiencies for hydrophobic NOM, aromatic organic matters, and suspended particles, but a limited effect on removing dissolved organic carbon (DOC). Ala or Ala-PolyDMDAAC effectively mitigated membrane fouling by removing the hydrophobic NOM in the coagulation process and forming the porous cake layer in the UF process. The test waters with higher specific ultraviolet absorbance (SUVA) resulted in more severe total and reversible membrane fouling but lighter irreversible fouling. After pretreatment by Ala or Ala-PolyDMDAAC, water samples with the medium SUVA value exhibited remarkable alleviation of membrane fouling due to the formation of large, compact, and robust flocs, as well as the construction of loose and poriferous cake layer on the membrane surface. Although hydrophilic NOM was challenging to be removed by coagulation, the interception and re-adsorption of porous cake layers contributed to the alleviation of irreversible fouling.

Quantification of biodegradable natural organic matter (NOM) fractions and its impact on bacterial regrowth in a South African Water Treatment Plant

Natural organic matter (NOM) contributes to bacterial regrowth during potable water treatment and supply. Most conventional water treatment plants insufficiently remove the biodegradable dissolved organic (BDOC) NOM fraction. The presence of labile BDOC in water creates conducive conditions for bacterial regrowth. To reduce NOM and the bacterial regrowth potential (BRP) in water, the study aimed at establishing which of the NOM polarity fractions are biodegradable and if the BRP (enumerated according to the heterotrophic plate count [HPC]) method) can be correlated to biodegradability. Specific ultraviolet absorbance (SUVA) was used to characterise source and treated water NOM fractions (i.e. hydrophilic [Hpi], transphilic [Tpi] and hydrophobic [Hpo]) obtained through the modified polarity rapid assessment method (m-PRAM). The source and treated water SUVA values of the Hpi and Hpo were on average, 3.88 L/mg.m and 2.04 L/mg.m, respectively. The Hpi and Tpi fractions on the source and treated were the most biodegradable fractions, with mean BDOC values ranging between 29.22%, and 35.75 %. The high BDOC of the Tpi and Hpi NOM substantially contributed to BRP by up to 121.4 × 103-197.4 × 103 CFU/mL, respectively. The strong correlation (R2 > 0.96) between BRP and BDOC allows for the effective management of water treatment and supply processes, particularly for microbial control.

Exploring the complex removal behavior of natural organic matter upon N-doped reduced graphene oxide-activated persulfate via excitation-emission matrix combined with parallel factor analysis and size exclusion chromatography

Metal-free oxidative degradation by persulfate (PS) is an emerging process as green chemistry without any toxic metal leaching to aquatic environments but has never been explored for natural organic matter (NOM) removal to date. In this study, nitrogen-doped reduced graphene oxide (NrGO) was applied as a catalyst first to investigate the degradation behavior of NOM. A parallel system was also examined without PS for non-oxidative interaction. For three tested NOM, the extent of the removal increased with the addition of NrGO, and the removal rates were consistently higher for the systems with versus without PS (by 25–102%). Specific ultraviolet absorbance (SUVA) exhibited declining trends with NrGO for both oxidative and non-oxidative systems. Up to 86.9%, 59.9%, and 60.3% reduction in SUVA values were found for the oxidative removal of Suwannee River natural organic matter, Suwannee River humic acid, and Suwannee River fulvic acid, respectively. The excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) decomposed fluorescent NOM into two fulvic-like (C1 and C2) and two humic-like (C3 and C4) components. Results implied that more hydrophobic and more condensed aromatic NOM constituents might be preferably removed by both oxidation and adsorption with the greater removal tendency shown for the humic versus the fulvic-like components. Size exclusion chromatography (SEC) demonstrated that large size molecules were more effectively removed by the oxidative versus the non-oxidative interactions with NrGO. Comparative results revealed that adsorption likely played a critical role in determining the preferential removal tendency of the metal-free oxidation toward heterogeneous NOM structures.

Evaluation of disinfection by-product formation during chlor(am)ination from algal organic matter after UV irradiation.

This study evaluated the effect of low-pressure ultraviolet (UV) irradiation on the formation of disinfection by-products (DBPs) from algal organic matter of Microcystis aeruginosa during subsequent chlorination and chloramination. The algal organic matter includes extracellular organic matter (EOM) and intracellular organic matter (IOM). The fluorescence excitation-emission matrix spectra indicated that the humic/fulvic acid-like organics of EOM and the protein-like organics of IOM may be preferentially degraded by UV treatment. UV irradiation with low specific UV absorbance values was effective in reducing the formation of trihalomethanes and dichloroacetic acid from EOM and IOM during the subsequent chlorination. During the UV-chloramine process, higher UV dose (1000mJ/cm2) led to the decrease of the formation of dichloroacetic acid, trichloroacetic acid, and haloketones from IOM by an average of 24%. Furthermore, UV irradiation can slightly increase the bromine substitution factors (BSFs) of haloacetic acids from EOM during chlorination, including dihaloacetic acids and trihaloacetic acids in the presence of bromide (50μg/L). However, UV irradiation did not shift the formation of DBPs from IOM to more brominated species, since the BSFs of trihalomethanes, dihaloacetic acids, trihaloacetic acids, and dihaloacetonitriles almost kept unchanged during UV-chlorine process. As for UV-chloramine process, UV irradiation decreased the BSFs of trihalomethanes, while increased the BSFs of dihaloacetic acid for both EOM and IOM. Overall, the UV pretreatment process is a potential technology in treating algae-rich water.

Characterization and sources of colored dissolved organic matter in a coral reef ecosystem subject to ultramafic erosion pressure (New Caledonia, Southwest Pacific)

The eastern lagoon of New Caledonia (NC, Southwest Pacific), listed as a UNESCO World Heritage site, hosts the world's second longest double-barrier coral reef. This lagoon receives river inputs, oceanic water arrivals, and erosion pressure from ultramafic rocks, enriched in nickel (Ni) and cobalt (Co). The aim of this study was to characterize colored dissolved organic matter (CDOM), as well as to determine its main sources and its possible relationships (through the use of Pearson correlation coefficients, r) with biogeochemical parameters, plankton communities and trace metals in the NC eastern lagoon. Water samples were collected in March 2016 along a series of river/lagoon/open-ocean transects. The absorption coefficient at 350nm (a350) revealed the influence of river inputs on the CDOM distribution. The high values of spectral slope (S275–295, >0.03m−1) and the low values of specific ultraviolet absorbance (SUVA254, <4Lmg-C−1m−1) highlighted the photodegradation of CDOM in surface waters. The application of parallel factor analysis (PARAFAC) on excitation-emission matrices (EEMs) allowed the identification of four CDOM components: (1) one humic- and one tyrosine-like fluorophores. They had terrestrial origin, exported through rivers and undergoing photo- and bio-degradation in the lagoon. These two fluorophores were linked to manganese (Mn) in southern rivers (r=0.46–0.50, n=21, p<0.05). (2) A tryptophan-like fluorophore, which exhibited higher levels offshore. It would be potentially released from the coral reef. (3) A second tyrosine-like (“tyrosine 2-like”) fluorophore. Linked to Prochlorococcus cyanobacteria (r=0.39, n=47, p<0.05), this fluorophore would have an oceanic origin and enter in the lagoon through its southern and northern extremities. It also displayed relationships with Ni and Co content (r=0.53–0.54, n=21, p<0.05). This work underlines the diversity of CDOM sources in the NC eastern lagoon.

Modeling and characterization of natural organic matter and its relationship with the THMs formation

&lt;p&gt;Natural organic matter (NOM) has been identified as the prominent precursor for disinfection by-products (DBPs) formation during chlorination. Various studies have shown that the characteristics of NOM influence the Trihalomethanes (THMs) formation mechanism. The present study represents NOM categorization in terms of total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm wavelengths (UV&lt;sub&gt;254&lt;/sub&gt;) and specific ultraviolet absorbance (SUVA) to investigate the effects of NOM on THMs formation mechanism. The high rate of dependency was found for each representative of NOM with respect to water quality characteristics and operational condition of disinfection process. Values of SUVA and UV&lt;sub&gt;254&lt;/sub&gt; is drastically reduced with respect from higher to a moderate chlorine dose which represent the chlorine contact is more predominant with hydrophobic fractions of NOM. The value of SUVA is decreasing with respect to temperature and reaction time, which reveled higher rate of utilization for hydrophobic fractions of NOM. Predictive modeling approach was carried out using multiple regression analysis with the combination of two surrogates at each stage of modeling with help of operational condition of disinfection process and water quality characteristics. The R&lt;sup&gt;2&lt;/sup&gt; value of the model was found in the range of 0.927 to 0.937 from the developed model and a model could be recommended for prediction of THMs in drinking water.&lt;/p&gt;&#x0D;

Probing Coagulation Behavior of Individual Aluminum Species for Removing Corresponding Disinfection Byproduct Precursors: The Role of Specific Ultraviolet Absorbance.

Coagulation behavior of aluminum chloride and polyaluminum chloride (PACl) for removing corresponding disinfection byproduct (DBP) precursors was discussed in this paper. CHCl3, bromine trihalomethanes (THM-Br), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) formation potential yields were correlated with specific ultraviolet absorbance (SUVA) values in different molecular weight (MW) fractions of humic substances (HS), respectively. Correlation analyses and principal component analysis were performed to examine the relationships between SUVA and different DBP precursors. To acquire more structural characters of DBP precursors and aluminum speciation, freeze-dried precipitates were analyzed by fourier transform infrared (FTIR) and C 1s, Al 2p X-ray photoelectron spectroscopy (XPS). The results indicated that TCAA precursors (no MW limits), DCAA and CHCl3 precursors in low MW fractions (MW<30 kDa) had a relatively good relations with SUVA values. These DBP precursors were coagulated more easily by in situ Al13 of AlCl3 at pH 5.0. Due to relatively low aromatic content and more aliphatic structures, THM-Br precursors (no MW limits) and CHCl3 precursors in high MW fractions (MW>30 kDa) were preferentially removed by PACl coagulation with preformed Al13 species at pH 5.0. Additionally, for DCAA precursors in high MW fractions (MW>30 kDa) with relatively low aromatic content and more carboxylic structures, the greatest removal occurred at pH 6.0 through PACl coagulation with aggregated Al13 species.

Using regression models to evaluate the formation of trihalomethanes and haloacetonitriles via chlorination of source water with low SUVA values in the Yangtze River Delta region, China

The purpose of this study was to develop the multiple regression models to evaluate the formation of trihalomethanes (THMs) and haloacetonitriles (HANs) during chlorination of source water with low specific ultraviolet absorbance (SUVA) in Yangtze River Delta, China. The results showed that the regression models of THMs exhibited good accuracy and precision, and 86-97% of the calculated values fell within ±25% of the measured values. While the HANs models showed relatively weak evaluation ability, as only 75-83% of the calculated values were within ±25% of the measured values. The organic matter [dissolved organic carbon (DOC) or UV absorbance at 254nm] and bromide exerted the most important influence on the formation of HANs. While for THMs, besides the organic matter and bromide, reaction time was also a key factor. Comparing the models for total THMs (T-THMs) in this study with others revealed that the regression models from the low SUVA waters may have low DOC coefficients, but high bromide coefficients as compared with those from the high SUVA waters.

River pollution: Assessment of hydro-philic and phobic nature of persistent organic contaminants

Natural purification of persistent organics by sorption during riverbank filtration (RBF) depends on their hydrophilic or hydrophobic nature. It can be ascertained by octanol/water partition coefficient (KOW) and specific ultra violet absorbance (SUVA). This motivated the authors to analyze KOW and SUVA, firstly, of some mixed synthetic samples of organics and secondly, of polluted water samples from the River Hindon. Monthly water samples of the Hindon were collected from five locations (latitude 28°38′08.64″ to 29°36′42.55″N and longitude 77°23′38.27″ to 77°34′19.38″E) and were analyzed for cumulative water-quality parameters total organic carbon (TOC), UV-A, biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The low ratio of BOD5-COD (∼0.13) is indicative of persistent nature of organics in the river water. Organics in the water samples were also analyzed by GC–MS and their logKOW values were obtained from the literature ranged from −0.84 to 2.15. LogKOW values of the water samples from four locations were between 0.11 and 0.37 but were around −0.43 at the fifth locations. Similarly, SUVA values of water from the same four locations were between 0.64 and 0.80 whereas the SUVA of the fifth water sample varied from 0.49 to 0.59. Both SUVA and KOW values reveal hydrophilic nature of the Hindon water samples.

Identification and characterization of dissolved organic matter sources in Kushiro river impacted by a wetland

The characterization of dissolved organic matter (DOM) is an important parameter for the management of water resources. In this study, physical and chemical characteristics of DOM in Kushiro river, and its territory (Eastern Hokkaido, Japan) were analyzed using multiple analytical tools. Multiple samples were collected from diverse locations (Kushiro river, Kushiro wetland, compost fertilizer, forest and treated sewage) and compared them against their DOM characteristics. Among the samples, Kushiro wetland samples presented higher specific ultraviolet absorbance (SUVA) values demonstrating DOM derived from vascular plants which are rich in aromatic-components. The SUVA values of the two samples of the Kushiro river were relatively close to those of the wetland samples implying the fact that the river contains high amount of plant derived aromatic DOM compounds, originating from the wetland. The excitation–emission matrix (EEM) fluorescence results showed that generally all water samples have two peaks namely, A and C. These two peaks are related to humic-like substance typically derived from the breakdown of organic matters. The excitation–emission matrix (EEM) fluorescence results of the river samples were also similar to those of the wetland samples, characterized by no appearance of protein, amino acid, polysaccharide, and fluvic like matter, but more pronounced to the aromatic component rich humic acid. Principal component analysis revealed that approximately 88% of the variance in the DOM characteristics might be explained by the type of different sources. From the loadings on PC1 and PC2 in the scores plot, the properties of the DOM of the wetland appeared to be similar to those of the river DOM. Combined results exhibited that the quality of the Kushiro river water is fundamentally inherited from the Kushiro wetland, and the main structure of the river water is characterized by poly-aromatic humic like matter and higher molecular weight.

Characterization of Natural Organic Matter in Conventional Water Treatment Processes and Evaluation of THM Formation with Chlorine

This study investigates the fractions of natural organic matter (NOM) and trihalomethane (THM) formation after chlorination in samples of raw water and the outputs from ozonation, coagulation-flocculation, and conventional filtration treatment units. All the water samples are passed through various ultrafiltration (UF) membranes. UF membranes with different molecular size ranges based on apparent molecular weight (AMW), such as 1000, 3000, 10,000, and 30,000 Daltons (Da), are commonly used. The NOM fraction with AMW < 1000 Da (1 K) is the dominant fraction within all the fractionated water samples. Its maximum percentage is 85.86% after the filtration process and the minimum percentage is 65.01% in raw water samples. The total THM (TTHM) yield coefficients range from 22.5 to 42 μg-TTHM/mg-DOC in all fractionated samples, which is related to their specific ultraviolet Absorbance (SUVA) levels. As the molecular weight of the fractions decreased, the TTHM yield coefficients increased. The NOM fractions with AMW values less than 1 K had lower SUVA values (<3 L/mg·m) for all treatment stages and also they had higher yield of TTHM per unit of DOC. The NOM fraction with AMW < 1 K for chlorinated raw water samples has the highest yield coefficient (42 μg-TTHM/mg-DOC).

광분해에 의한 용존 유기물질의 분자량 변화가 소독부산물 생성능에 미치는 영향

UV-induced transformations in the characteristics of dissolved organic matter (DOM) and the subsequent effects on the disinfection by-product formation potential (DBPFP) were investigated using the mixtures of the two humic substances with different sources, and two different size fractions of Suwannee River fulvic acid (SRFA). 7 day-photodegradation resulted in the decrease of specific ultraviolet absorbance (SUVA) of the mixtures as well as the specific DBPFP. After the irradiation, however, higher specific DBPFP values were consistently observed at the same range of the SUVA values. This suggests that non UV-absorbing components, generated by the UV-irradiation, may contribute to the formation of DBPs. Two different molecular size fractions of SRFA showed dissimilar responses to photodegradation. The behavior was also influenced by the types of the DBPs generated. Higher levels of trihalomethenes (THMs) were formed per organic carbon for the high molecular fraction compared to the low molecular fraction, whereas no differences were found in the formation of haloacetic acids (HAAs) between the two different size fractions. The formation of the two types of DBPs also differed by the irradiation times. Specific formation potential of THMs consistently increased upon the irradiation, whereas HAAs showed the initial increase followed by the decrease in their specific formation potential.

Effect of pre-ozonation on the formation and speciation of DBPs

The objective of this study was to quantitatively evaluate the effect of pre-ozonation on the formation and speciation of disinfection byproducts (DBPs) from subsequent chlorination and chloramination. Laboratory experiments were conducted on six diverse natural waters with low to medium bromide concentrations. Four groups of DBPs were investigated in this study: trihalomethanes (THMs), trihaloacetic acids (THAAs), dihaloacetic acids (DHAAs), and dihaloacetonitriles (DHANs). The results showed that the relative destructions of chlorination DBP precursors by ozone generally follow the order of DHANs > THMs & THAAs > DHAAs. Pre-ozonation substantially increased the DHAA precursors in the waters with low specific ultraviolet absorbance values. Pre-ozonation shifted the formation of DBPs to more brominated species. The bromine substitution factors (BSF) of different chlorination DBPs typically increased by 1–8 percentage points after ozonation. Pre-ozonation reduced the yields of chloramination DHAAs and THMs and increased the BSFs of chloramination DHAAs by 1–6 percentage points.

The response of typical South African raw waters to enhanced coagulation

Drinking water treatment plants in South Africa rely almost entirely on surface water sources, which are often compromised due to high return flows and indirect reuse. The typical treatment plants focus on the removal of physical and microbial contaminants which include turbidity, colour, chemical compounds and microorganisms. A relatively new concern to this list is natural organic matter (NOM) which has become a major concern in potable water treatment due to its recent regulation. In this study, eight different raw water samples from the various water types found in the country were seasonally collected and treated for the removal UV absorbance at a wavelength of 254 nm (UV254) using enhanced coagulation (EC). The efficacy of EC, which can be employed as a practical technology in the removal of both turbidity and NOM, was evaluated in remaining UV254 from these raw water sources. Jar tests were conducted, with ferric chloride used as the coagulant (due to its extensive use as a coagulant in the water treatment industry in South Africa) and specific pH values (initial water pH, 7.0, 6.0, 5.5, 5.0 and 4.5) were chosen as target values guiding the six different coagulant dosages for the jar tests. The pH of the low-alkalinity (&amp;lt;60 mg/L CaCO3) raw waters were adjusted and raised by the addition of sodium carbonate. The response parameters of the tests were turbidity (NTU), pH and UV254. Algorithms for finding the optimum coagulant dosage for UV254 removal were developed and consistently applied to all the results. Results showed large variations in the nature of NOM across the country from specific ultraviolet absorbance values. From the UV254 values, the concentrations of NOM also varied greatly geographically than temporally. The general trend observed in the EC results suggested that the pH should always be dropped to between 4.5 and 7.0 to lower the amounts of UV254 and turbidity to reasonable levels.

Variations in spectroscopic characteristics and disinfection byproduct formation potentials of dissolved organic matter for two contrasting storm events

Changes in disinfection byproduct (DBP) precursors during storm events have not been intensively studied to date despite their dramatic impact on downstream drinking water supplies. For this study, variations in dissolved organic matter (DOM) spectroscopic properties and DBP formation potentials (DBPFPs), and the correlations among these various parameters, were investigated in river water samples collected under two contrasting storm event conditions (a strong summer storm versus a weak fall event). Fluorescence excitation–emission matrices (EEMs) combined with parallel factor analysis revealed that a combination of two humic-like components (C1 and C2) dominated the EEM data of the storm samples. Measured DOM characteristics and DBPFPs varied over a wider range during the more intense summer storm, exhibiting higher values of specific ultraviolet absorbance and C1/C2 ratio at high flow conditions. Variations in the fluorescence index were less pronounced during the two storm events. The spectroscopic changes were well explained by the input of terrestrial DOM sources from the surrounding catchments during the storms. Different trends of the formation potentials for trihalomethanes and haloacetic acids on the recession limb of the hydrographs suggest that the structures responsible for DBP precursors during storm events may not be the same for the two classes of DBPs. The ultraviolet light-absorbing moieties in DOM appear to play major roles in generating DBPs, as evidenced by their strong positive correlations with DBPFPs. Higher correlations with DBPFP for C1 versus C2 suggest that humic-like substances associated with more aromatic and condensed structures have a greater proclivity to generate DBP upon chlorination.

Monitoring natural organic matter and disinfection by-products at different stages in two South African water treatment plants

Natural organic matter (NOM) is a complex organic material present in natural surface water. NOM can cause problems during water treatment . most notably the formation of toxic disinfection by-products. This study was undertaken in order to assess the effectiveness of some of the water treatment techniques employed by selected water supply companies in South Africa in dealing with NOM. Total organic carbon (TOC) and ultra violet (UV) absorbance at wavelength of 254 nm were measured and used to calculate specific ultra violet absorbance (SUVA), which was used to determine the changes in NOM concentration throughout the water treatment train. Other parameters measured include pH, turbidity, chemical oxygen demand (COD) and conductivity. Water samples were collected from two water treatment plants in South Africa, namely Sedibeng (Balkfontein) and Midvaal. The overall TOC reduction after the water treatment processes was 33% and 30% at Midvaal and Sedibeng, respectively. SUVA values were generally low (<2 ..mg-1.m-1) indicating the presence of aliphatic compounds and less earomaticityf in NOM of the water samples. Water insoluble ƒA-cyclodextrin (ƒA-CD) polyurethanes were then applied to the water to compare TOC reduction in addition to enormalf water treatment processes, and were found to provide up to 19% additional TOC decrease, and UV absorbance reduction was up to 78%. Results obtained using gas chromatography-mass spectrometry (GC-MS) analysis after chlorination, revealed that the water had the potential to form halomethane compounds with chloroform being the most dominant. Again, water-insoluble ƒA-CD polyurethanes were applied to the water as a treatment to remove trihalomethanes (THMs) and were found to efficiently remove up to 95% of THMs formed during the disinfection step. The treatment processes studied have limited ability in dealing with NOM and are not individually effective in NOM removal. Results obtained indicate that the application of ƒA-CD polyurethanes in addition to the water treatment processes may enhance NOM removal in water and significantly reduce the THMs formed.

Dissolved Organic Carbon and Estrogen Transport in Surface Runoff From Agricultural Land Receiving Poultry Litter1

Dutta, Sudarshan, Shreeram Inamdar, Jerry Tso, Diana S. Aga, and J. Tom Sims, 2012. Dissolved Organic Carbon and Estrogen Transport in Surface Runoff from Agricultural Land Receiving Poultry Litter. Journal of the American Water Resources Association (JAWRA) 48(3): 558‐569. DOI: 10.1111/j.1752‐1688.2011.00634.xAbstract: Dissolved organic carbon (DOC) provides a reactive substrate for the transport of organic contaminants with runoff. Very few studies have investigated the export of DOC from agricultural land, especially those receiving manure applications. We investigated exports of DOC in surface runoff from agricultural fields receiving various treatments of poultry litter (raw vs. pelletized). In addition, we also investigated how estrogens in runoff were associated with DOC. Different forms of estrogens studied were: estrone, 17β‐estradiol, estriol, and their conjugates. Experimental agricultural plots were 12 m × 5 m long and had reduced tillage and no‐till management practices. The aromatic content of DOC was characterized using specific ultraviolet absorbance (SUVA). Flow‐weighted concentrations of DOC and SUVA in surface runoff from plots with poultry litter were significantly (p ≤ 0.10) greater than the control (no litter) plots. Compared to pelletized poultry litter, reduced‐tillage plots with raw litter yielded higher DOC concentrations and SUVA values. No significant differences (p ≥ 0.10) in DOC and SUVA were observed between litter treatments for plots with no‐till. Total estrogen concentrations (including all forms) were positively and significantly (p ≤ 0.10) correlated with DOC. These results can help select and guide agricultural management practices that can reduce the exports of DOC and associated contaminant from agricultural land receiving manure applications.