The integrated approach of carbon capture, utilization, and storage via CO2 mineralization for the removal of fly ash, bottom ash, and exhaust gas-A case study of circulating fluidized bed combustion.

Despite efforts to reduce dependence on coal-fired power generation due to climate concerns, continued usage for energy stability is anticipated. This study was conducted to address environmental issues associated with coal-fired power generation and promote its persistent utilization. we aimed to establish both eco-friendly and economically sustainable practices by mitigating waste such as fly ash (FA) and bottom ash (BA) emissions while recycling them in circulating fluidized bed combustion (CFBC). Initially, we conducted a literature review to analyze the global and domestic trends in coal-fired power generation. Subsequently, we performed experimental research on CO2 crystallization as a multifaceted approach for treating exhaust gases and waste materials such as FA and BA simultaneously. Throughout this research, we implemented a simple process to ensure scalability. In the context of carbon capture, utilization, and storage (CCUS) technology, we conducted experimental research on mineralizing CO2 targeting FA and BA by applying ambient temperature, atmospheric pressure, and simulated exhaust gas. The empirical findings demonstrated that 12.28 kg CO2/ton and 58.14 kg CO2/ton of CO2 were immobilized for BA and FA, respectively. The economic evaluation was measured based on the experimental results obtained from the techno-economic analysis (TEA). The B/C ratio stands at 1.07, with the cost of composite carbonate estimated at USD 159.6 per ton. With an internal rate of return (IRR) of 7.78 % and a net present value (NPV) of USD 7294.59, the economic viability demonstrates considerable promise. Ultimately, this study aims to mitigate the impact of coal-fired power plants on climate change and enhance environmental sustainability through CO2 removal and waste recycling.

Sludge-based candidate reference materials for enhanced quality control of particulate processes in total organic carbon analysis for wastewater1.

Accurate analyses of total organic carbon (TOC) encompassing particulate organic carbon in wastewater are key for evaluating the behavior of particulate organic contaminants and maintaining the carbon mass balance throughout the wastewater treatment process. This study was conducted to develop candidate reference materials of environmental origin from excess sludge collected from wastewater treatment facilities, primarily receiving industrial wastewater and livestock manure as the main sources. Homogeneity and stability assessments for total carbon (TC) and TOC were conducted in the particle samples following the standardized procedures of ISO Guide 35 and ISO 13258. The results showed that high inorganic carbon (IC) content in particles, such as YJ(500) (IC: 29%), rendered them unsuitable for TOC quality control (QC), as they increased uncertainty in both homogeneity and stability assessments. Additionally, a13C NMR analysis revealed that samples with a high (O-alkyl)/(C-H-alkyl) ratio in their carbon structures exhibited relatively low stability. Through the homogeneity and stability assessments, a particle sample, YJ(100), was selected as the reference material (RM); the assigned values were as follows: 30.78% for TC and 27.94% for TOC, with uncertainties of 0.01% and 1.1%, respectively. Furthermore, considering sample transportation conditions, the safe storage period for the RM particles was determined to be 2 weeks under harsh conditions (at 40 °C). In our inter-laboratory test (n = 8) using the particle samples, we confirmed that the particle samples can effectively enhance particle processing QC and validate a proposed suspended solids pretreatment method. This study showcases valuable environmental particle sample production and evaluation, offering potential advancements in the QC of TOC analysis for wastewater samples.

Investigating the different transformations of tetracycline using birnessite under different reaction conditions and various humic acids.

Prior studies have successfully used manganese oxides to facilitate the transformation of tetracycline in aqueous solution. To further understand the kinetic and the transformation pathway of tetracycline via birnessite (δ-MnO2) under different conditions, experiments were conducted at pH levels of 3, 6, and 9 in the presence or absence of Aldrich humic acid (ADHA). Tetracycline removal followed the pseudo-second-order reaction model in all investigated cases, and the removal efficiency (g mg-1 h -1) followed the following trend: pH 3 (0.45/0.27) > pH 6 (0.036/0.087) > pH 9 (0.036/0.103) in the absence/presence of ADHA. Liquid chromatography-mass spectrometry/mass spectrometry results identified five main transformation products at m/z 495, 477, 493, 459, and 415, produced by the transformation reactions, including hydration, oxidation, desaturation, and oxy reduction. Notably, in the presence of ADHA at pH 3, products with higher toxicity secondary (m/z 477 and 495) were reduced, while less toxicity products (m/z 459 and 415) were enhanced. The experiments utilizing tetracycline and δ-MnO2 with varied humic acids (HA) revealed that HA with high polar organic carbon groups, such as O-alkyl, exhibited higher removal efficiency at pH 6. This research offers the first comprehensive insights into the pathway transformations of tetracycline via δ-MnO2 under different pH conditions and HA types. For further understanding, future work should investigate the binding of HA, TTC, and/or Mn2+ and the oxidation capacity of MnO2 after the reaction to clarify Mn2+ elution mechanisms.

Fluorescence spectroscopy in the detection and management of disinfection by-product precursors in drinking water treatment processes: A review.

Monitoring and prevention of the formation of disinfection by-products (DBPs) is paramount in drinking water treatment plants (DWTP) to ensure human health safety. This review provides an overview of how fluorescence techniques are developed to predict DBP formation and to evaluate the reduction of fluorescence components and DBPs following individual DWTP processes. Evidence has shown that common DBPs, nitrogenous DBPs and specific emerging DBPs exhibit positive linear relationships with terrestrial, anthropogenic, tryptophan-like, and eutrophic humic-like fluorescence. Due to the interrelationships of both regulated and emerging DBP types with fluorescence components, the limitations arise when attempting to predict emerging DBPs solely through linear relationships. Monitoring the reduction of DBP precursors after each treatment process can be achieved by studying the relationship between fluorescence components and DBPs. During the coagulation process, highest reduction rates are observed for terrestrial humic-like fluorescence. Advanced treatments such as granular, powdered, silver-impregnated activated carbon, magnetic ion exchange resins, and reverse osmosis, have revealed a significant reduction of fluorescent DBP precursors, ranging from 53% to 100%. During chlorination, the reduction rate follows the order: terrestrial humic-like > microbial humic-like > protein/tryptophan-like fluorescence. This review provides insights into the reduction of fluorescence signatures following individual DWTP processes, which offers information regarding DBP formation. These insights could assist in optimizing the treatment process to more effectively manage DBP formation. For the identification of emerging DBP generation, the utilization of advanced models is imperative to precisely predict emerging DBPs and to more accurately trace DBP precursors within DWTPs.

Identification of the cause of the difference among TOC quantitative methods according to the water sample characteristics.

Total organic carbon (TOC) analysis with accurate determination of particulate organic carbon (POC) content in suspended solids (SS) containing water is critical for evaluating the environmental impact of particulate organic pollutants in water and calculating the carbon cycle mass balance. TOC analysis is divided into the non-purgeable organic carbon (NPOC) and differential (known as TC-TIC) methods; although the selection of method is greatly affected by the sample matrix characteristics of SS, no studies have investigated this. This study quantitatively evaluates the effect of SS containing inorganic carbon (IC) and purgeable organic carbon (PuOC), as well as that of sample pretreatment, on the accuracy and precision of TOC measurement in both methods for various environmental water sample types (12 wastewater influents and effluents and 12 types of stream water). For influent and stream water with high SS, the TC-TIC method expressed 110-200 % higher TOC recovery than that for the NPOC method due to POC component losses in SS owing to its conversion into PuOC during sample pretreatment (using ultrasonic) and subsequent loss in the NPOC purging process. Correlation analysis confirmed that particulated organic matter (POM, mg/L) content in SS directly affected this difference (r > 0.74, p < 0.01, n = 24); for POC water samples (those containing >10 mg/L of POM) featuring purgeable dissolved organic matter, TC-TIC was appropriate in securing TOC measurement accuracy. In constrast, in effluent and stream water with low SS (i.e., < ∼5 mg/L) and high IC (> 70 %) contents, the TOC measurement ratios (TC-TIC/NPOC) of both methods were similar, between 0.96 and 1.08, suggesting that NPOC is appropriate for improving precision. Our results provide useful basic data to establish the most reliable TOC analysis method considering SS contents and its properties along with the matrix characteristics of the sample.

Separately tracking the sources of hydrophobic and hydrophilic dissolved organic matter during a storm event in an agricultural watershed.

The hydrophobicity of dissolved organic matter (DOM) affects various aspects of its environmental impacts in terms of water quality, sorption behaviors, interactions with other pollutants, and water treatment efficiency. In this study, source tracking of river DOM was conducted separately for hydrophobic acid (HoA-DOM) and hydrophilic (Hi-DOM) fractions using end-member mixing analysis (EMMA) in an agricultural watershed during a storm event. EMMA with optical indices of bulk DOM revealed larger contributions of soil (24 %), compost (28 %), and wastewater effluent (23 %) to riverine DOM under high versus low flow conditions. Molecular level analysis of bulk DOM revealed more dynamic features, showing an abundance of CHO and CHOS formulae in riverine DOM under high- and low flow conditions. CHO formulae originated from soil (78 %) and leaves (75 %) and contributed to the increasing CHO abundance during the storm event, whereas CHOS formulae likely originated from compost (48 %) and wastewater effluent (41 %). The characterization of bulk DOM at the molecular level demonstrated that soil and leaves are the dominant contributors for the high-flow samples. However, in contrast to the results of bulk DOM analysis, EMMA with HoA-DOM and Hi-DOM revealed major contributions from manure (37 %) and leaf DOM (48 %) during storm events, respectively. The results of this study highlight the importance of individual source tracking of HoA-DOM and Hi-DOM for the proper evaluation of the ultimate roles of DOM in affecting river water quality and for a better understanding of DOM dynamics and transformation in natural and engineered systems.

Proposal for a new customization process for a data-based water quality index using a random forest approach.

As the water quality index (WQI) represents water quality, it is crucial to customize the WQI for a specific purpose. In this study, to better represent water quality data using WQI, a random forest (RF) approach was used to derive the parameter weight and calculate the WQI according to the watershed and its use. Eight parameters (water temperature, dissolved oxygen, pH, electrical conductivity, suspended solids, total nitrogen, total phosphorus, and total organic carbon) were evaluated using a total of 220,103 data points collected from 900 monitoring sites throughout South Korea between 2011 and 2020. The estimation of parameter weights, key elements in developing the WQI model, was performed through the variable importance estimation method that can be derived from the RF model. The parameter weights were derived based on various spatiotemporal datasets, and it was confirmed that the spatiotemporal differences in weights according to data characteristics represented the regional and seasonal water quality characteristics. Consequently, a customized WQI representing water quality characteristics could be calculated using data-based weights, and it is expected that a data-based customized WQI could be developed to better match the previous WQI to the purpose and target source.

Fluorine-functionalized reduced graphene oxide-TiO2 nanocomposites: A new application approach for efficient photocatalytic disinfection and algicidal effect.

Using surface functionalization and related applications to 2D materials as innovative solutions to environmental pollution has gained considerable attention among researchers. Fluorinated graphene has derivative-based synergistic components with high thermal and chemical stability because of its structure and bonding. Fluorine-functionalized reduced graphene oxide (rFGO-TiO2) demonstrated enhanced hydrophilicity and wettability, highly efficient photocatalytic disinfection, and an algicidal effect. This study presents the hydrothermal synthesis of rFGO-TiO2 to realize antibacterial properties with high stability, which was conducted against the gram-negative bacteria Escherichia coli. To optimize antibacterial performance, the effects of multiple synthetic conditions were investigated. The antibacterial performance was optimized at an rFGO content of 1 wt%, hydrothermal temperature of 200 °C, and hydrothermal time of 1 h. The rFGO-TiO2 composite demonstrated an antibacterial efficiency of 5.76 log under ultraviolet A irradiation for 10 min and around 2 log under visible light. In the absence of light, rFGO-TiO2 took 6 h to reach an antibacterial efficiency of 6 log. Increasing the rFGO content and hydrothermal temperature beyond the optimal conditions reduced the antibacterial efficiency because of the excess rFGO and disruption of rFGO-TiO2 binding. Measurements with electron spin resonance spectroscopy confirmed that hydroxyl radicals and superoxide ions caused stress and damaged the membrane of a cell, which led to cell death.

Photochemical and microbial transformation of particulate organic matter depending on its source and size.

Particulate organic matter (POM) in water systems can be converted into dissolved organic matter (DOM) through various pathways depending on its properties and transformation. Thus, information on the behavior of POM is crucial for fully understanding water systems and the carbon cycle. In this study, the effects of particle size and the source of POM, as well as photochemical and microbial changes in DOM characteristics subsequently released from POM were evaluated using various spectral indices, excitation-emission matrix combined with parallel factor analysis components, and principal component analysis. The amount of dissolved organic carbon (DOC) released from POM during suspension was significantly associated with the carbon content of POM (p < 0.05). The amount of DOC (mg-C/g-SS) decreased in mineral-bound POM as a result of microbial degradation but increased in biogenic POM as a result of microbial dissolution, owing to the structural differences in organic matter from different sources. Mineral-bound POM showed more DOC production by photochemical desorption than microbial degradation, whereas biogenic POM displayed the opposite trend. The DOM derived from fine POM had more humified terrestrial humic-like substances than those derived from coarse POM. Principal components 1 and 2 were associated with DOC production and degree of humification, respectively. The increase in the degree of aromaticity and humification of organic matter was higher in mineral-bound POM by photochemical desorption of highly humified organic matter and in the biogenic POM by microbial dissolution. In conclusion, this study was able to provide basic information on the transformation of POM, thus, it is expected to broaden the knowledge of the biogeochemical cycle of organic matter.

Prediction of polarity-dependent environmental behaviors of humic substances (HS) using a HS hydrophobicity index based on hydrophilic interaction chromatography.

A variety of analytical methods have been applied to describe the properties of aquatic humic substances (HS). However, there are only a few methods available to probe HS hydrophobicity because of the heterogeneous character of HS. In this study, hydrophilic interaction chromatography (HILIC) equipped with a UV detector was employed to describe the heterogeneous distribution of HS with respect to its hydrophobicity and to suggest a representative HS hydrophobicity index. To this end, various mobile phases were explored to achieve the optimal separation capability of HILIC. The highest resolution was obtained with a mobile phase comprising acetonitrile and water at a ratio of 70:30 (v:v). A calibration curve was successfully constructed using eight different HS precursor compounds, which allowed for the successful conversion of the retention time (RT) into the octanol-water partition coefficient (Kow) (log Kow = -2.83 × (RT) + 17.44, R2 = 0.950). Several possible HS hydrophobicity indices were derived from the HILIC chromatogram. Among those, the weight-average log KOW value exhibited the strongest negative correlation with the well-known polarity index, (O + N)/C ratios, of seven reference HS samples. This new HILIC-based index (i.e., average log KOW) also presented a good relationship with the HS binding coefficients with pyrene as well as the extent of HS adsorption onto kaolinite at a given solution chemistry (i.e., at a high ionic strength and a neutral pH), both of which are known to be largely governed by the hydrophobic nature of HS. This study demonstrated that the average KOW value based on HILIC is an intuitive and robust HS hydrophobicity index to fully represent the heterogeneous distribution of hydrophobicity within a bulk HS and could be applied to predict many environmental behaviors related to HS hydrophobicity or HS polarity.

Structural characteristics of sediment humins from South Korean lakes and their phenanthrene binding compared to other carbon sources.

Sediment humins are extremely important for binding hydrophobic organic contaminants in rivers and lakes. Nonetheless, little is known about their structure and binding. We, therefore, examined the structure and phenanthrene sorption affinity of sediment humin samples upstream, midstream, and downstream from two artificial lakes in South Korea by using the elemental 13C-NMR analysis, Freundlich model, and Langmuir model. The characteristics and phenanthrene sorption affinity of sediment humins were also compared with those of sediment humic acids from similar origins as well as soil humins/humic acids in South Korea from previous studies by using principal component analysis. In both lakes, downstream sediment humins exhibited lower N/C, O/C, and (N + O)/C ratios, lower internal oxidation, and higher aliphaticity due to the presence of long-chain aliphatic compounds generated during anaerobic decomposition. The principal component analysis results also showed that C,H-alkyl, O-alkyl, and polar organic carbon contents were significantly different when comparing the up-mid stream and downstream sediment samples in Daecheong Lake. In addition, midstream sediment humin in Andong Lake presented higher C,H-alkyl and lower polar organic carbon contents compared to those of up-downstream samples. In both lakes, the sorption coefficient and adsorption isotherm linearity were positively correlated with the C,H-alkyl content and negatively correlated with the O-aryl content. Similar to C,H-alkyl and POC, C,H-alkyl, and (N + O)/C had an extremely high correlation coefficient when predicting the sorption coefficient (Freundlich model) and the maximum adsorption capacity (Langmuir model) of sediment humins. Sediment humins had higher C,H-alkyl contents and lower sorption coefficients than those of sediment humic acids and soil humins/humic acids. These findings provide key information for monitoring water quality and polycyclic aromatic hydrocarbon contamination in South Korean lake sediments.

Spatiotemporal Evaluation of Water Quality and Hazardous Substances in Small Coastal Streams According to Watershed Characteristics.

In this study, spatial and temporal changes of eight water quality indicators and 30 types of hazardous substances including volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), pesticides, and inorganic matters for the small coastal streams along the West Coast of South Korea were investigated. In coastal streams with clear seasonal changes in water quality, larger watershed areas led to greater contamination by particulate matter (i.e., suspended solids, r = 0.89), and smaller watershed areas led to greater contamination by organic matter (i.e., BOD, r = -0.78). The concentration of VOCs and pesticides was higher in agricultural areas, and those of SVOCs and metals were often higher in urban areas. According to the principal component analysis (PCA), during the wet season, the fluctuation in the water quality of coastal streams was higher in urban areas than in agricultural areas. Furthermore, coastal streams in residential areas exhibited higher levels of SVOCs, and those in industrial areas exhibited higher levels of metallic substances. Based on these results, the spatial and temporal trends of water quality and hazardous substances were obtained according to watershed characteristics, thereby clarifying the pollution characteristics of small-scale coastal streams and the major influencing factors.

Biochar-induced priming effects in soil via modifying the status of soil organic matter and microflora: A review.

Biochar (BC) application has the potential to be integrated into a carbon-trading framework owing to its multiple environmental and economic benefits. Despite the increasing research attention over the past ten years, the mechanisms of BC-induced priming effects on soil organic carbon mineralization and their influencing factors have not been systematically considered. This review aims to document the recent progress in BC research by focusing on (1) how BC-induced priming effects change the soil environment, (2) the factors governing the mechanisms underlying BC amendment effects on soils, and (3) how BC amendments alter soil microbial communities and nutrient dynamics. Here, we carried out a detailed examination of the origins of different biochar, its pyrolysis conditions, and potential interactions with various factors that affect BC characteristics and mechanisms of C mineralization in primed soil. These findings clearly addressed the strong linkage between BC properties and abiotic factors that leads to change the soil microclimate, priming effects, and carbon stabilization. This review offers an overview of a fragmented body of evidence and the current state of understanding to support the application of BC in different soil environments with the aim of sustaining or improving the agricultural crop production.

Source tracking of dissolved organic nitrogen at the molecular level during storm events in an agricultural watershed.

Accelerated export of nitrogen-containing dissolved organic matter (DOM) or dissolved organic nitrogen (DON) to streams and rivers from agricultural watersheds has been reported worldwide. However, few studies have examined the dynamics of DOM molecular composition with the attention paid to the relative contributions of DON from various sources altered with flow conditions. In this study, end-member mixing analysis (EMMA) was conducted with the optical properties of DOM to quantify the relative contributions of several major organic matter sources (litter, reed, field soil, and manure) in two rivers of a small agricultural watershed. DOC and DON concentration increased during the storm events with an input of allochthonous DOM as indicated by an increase in specific ultraviolet absorbance at 254 nm (SUVA254) and a decrease in biological index (BIX), fluorescence index (FI), and protein-like component (%C3) at high discharge. EMMA results based on a Bayesian mixing model using stable isotope analysis in R (SIAR) were more accurate in source tracking than those using the traditional IsoSource program. Manure (>30%) and field soil (also termed as "manure-impacted field soil") (>23%) end-members revealed their predominant contributions to the riverine DOM in SIAR model, which was enhanced during the storm event (up to 56% and 38%, respectively). The molecular composition of the riverine DOM exhibited a distinct footprint from the manure and manure-impacted field soil, with a larger number of CHON formulas and abundant polyphenols and condensed aromatics in peak flow samples in the studied rivers. The riverine DOM during peak flow contained many unique molecular formulas in both rivers (4980 and 2082) of which >60% originated from manure and manure-impacted field soil. Combining the EMMA with DOM molecular composition clearly demonstrated the effect of manure fertilizer on the riverine DOM of the watershed with intensive agriculture. This study provides insights into the source tracking and regulation of DON leaching from anthropogenically altered river systems worldwide.

Competitive adsorption of heavy metals onto modified biochars: Comparison of biochar properties and modification methods.

Various biochars (BCs) have been developed to remove heavy metals contained in road runoff; however, there is insufficient information regarding the competitive adsorption efficiency of modified BC with regard to heavy metals due to a lack of comparative evaluation based on BC properties and modification methods. In this study, three different types of BC (RBC: rice husk, WBC: wood chip, MBC: mixture) were modified following five different methods: acidic, alkaline, oxidic, and manganese oxide (MnOx) and iron oxide (FeOx) impregnation. The changes in the physicochemical and morphological properties of the modified BC were investigated, and the adsorption characteristics of three heavy metals (Cd, Pb, and Zn) under single and mixed conditions were compared and evaluated. The improvements in the BC properties varied for different BC types and modification methods; in particular, alkaline and manganese modification caused substantial the changes in the surface area and functional groups (such as aromatic ring, -OH, and Mn-O groups). The BC prepared by manganese oxide impregnation absorbed a high amount of heavy metals (>9.15 mg/g) even under mixed conditions through cation exchange and surface complexation. The distribution coefficient (Kd) of heavy metals was high in the order of Pb > Cd > Zn; thus, the adsorption of Pb replaced that of Zn in competitive adsorption due to the difference in their affinity to BC. Therefore, the results suggest that BC prepared by manganese oxide impregnation is suitable for removing heavy metals from road runoff, as it maintained high heavy metals adsorption regardless of the BC material, even under competitive conditions.

Changes in structural characteristics of humic and fulvic acids under chlorination and their association with trihalomethanes and haloacetic acids formation.

The effects of chlorination on 16 humic and fulvic acids (HAs and FAs, respectively) extracted from six different soil samples from Korea and two purchased soil samples (Canadian peat moss, Elliott Silt Loam Soil) were investigated to identify the changes in their structural characteristics and their effects on trihalomethane formation potential (THMFP) and haloacetic acid formation potential. The effect of chlorination was also investigated in fractionated samples (Aldrich HA, F1-F5) based on molecular weight (MW). Total organic carbon (TOC), specific UV absorbance (SUVA), fulvic-like fluorescence (%FLF), terrestrial humic-like fluorescence (%THLF), weight-average molecular weight (MWw), and carbon structures (13C NMR) were measured for each sample before and after chlorination, and factors relating to the chlorination mechanism were examined using principal component analysis (PCA). The results showed that the changes in the structural characteristics and the disinfection by-product formation of chlorinated HA and FA differed critically. For chlorinated HA, TOC and %FLF decreased due to oxidation, whereas %THLF was reduced via incorporation; MW also affected the structural changes and THMFP generation. In the PCA results, high SUVA, low MW, low N/C, and low O groups of aromatic C were associated with high THMFP production in HA, whereas low O groups of aliphatic C in FA were associated with both oxidation and incorporation in terms of THMFP. These results elucidate the mechanisms associated with the effects of chlorination in HA and FA and will support the prediction of THMFP generation in HA and FA based on their specific structural characteristics.

Dynamic exchange between particulate and dissolved matter following sequential resuspension of particles from an urban watershed under photo-irradiation.

Particulate matter (PM) has long-term effects on water quality compared to dissolved matter (DM) during downstream transfer after inflows into an aquatic environment. In the present study, the characteristics, behavior, and effects of PM from an urban watershed under photo-irradiation were investigated through sequential resuspensions before being compared. Changes in the organic matter content, heavy metals (Mn, Fe, Zn, Pb), spectroscopic indices (SUVA254, slope ratio (SR), humidification index (HIX), fluorescence index (FI), and biological index (BIX)), excitation-emission matrix combined with parallel factor analysis components (EEM-PARAFAC), and disinfection by-product formation potential (DBPFP) were analyzed. According to our results, light enhanced the release of organic matter from PM but reduced dissolved heavy metals. The PMU affected by urban-derived pollutants (i.e., rainfall particles, road-deposited sediment, sewer-pipeline-deposited sediment) exhibited higher quantities of terrestrial humic-like organic matter than PMR, which contains base particles from riverines (i.e., soil, sediments). For the PMU, the humic-like fluorescent components (C1 and C2) enhanced under light conditions with every resuspension, whereas the components decreased in the PMR. Consistent with the PARAFAC results, the trihalomethane formation potential (THMFP) of the PMU was enhanced by approximately 2.8 times more than that of the PMR, and exhibited a high correlation with the fluorescent components (C1, r = 0.81, p < 0.001). The principal component analysis results also confirmed that the characteristics of dynamic exchanges between PM and DM were distinguished by PM sources and light, and the photo-released DM and their spectral characteristics displayed opposite behaviors depending on the PM sources during the sequential resuspensions.

Combined dual-size foam glass media filtration process with micro-flocculation for simultaneous removal of particulate and dissolved contaminants in urban road runoff.

In this study, a combined media filtration process with micro-flocculation (CMF) was developed, to simultaneously treat particulate and dissolved contaminants in urban road runoff. Dual-size foam glass media with stone and sand layers were applied and the efficiency of road runoff treatment was investigated according to filtration and micro-flocculation under various experimental conditions (stone/sand layer ratio, linear velocity, and coagulant types). Moreover, the removal efficiencies of suspended solids (SS), phosphorus, organic carbon, and heavy metals (Zn, Cu, Pb, Cd) by CMF were evaluated. The removal rate of SS was maintained to be above 84.1% for 1 h filtration by the dual-size foam glass, regardless of increasing pressure. The removal of phosphorus by micro-flocculation was more suitable in alum than ferric due to a higher initial floc growth rate and an increased particle size. The performance of the CMF was significantly improved over media filtration only process (MF) in removing both particulate and dissolved contaminants. The removal efficiency of all particulate pollutants by CMF was found to be more than 90%, and notably, the dissolved phosphorus, which was mostly not removed by MF, was also removed by 97.4%. Meanwhile, the backwash efficiency of CMF was half that of MF. Physical removal mechanisms, such as internal diffusion, dominated MF, whereas chemical removal mechanisms, such as adsorption and surface precipitation, dominated CMF. These results show the potential of the CMF process for the treatment of urban road runoff and identify the removal mechanisms of the filtration process that use micro-flocculation with dual-size foam glass.

Removal of 1,4-Naphthoquinone by Birnessite-Catalyzed Oxidation: Effect of Phenolic Mediators and the Reaction Pathway.

This study investigated the birnessite (δ-MnO2) catalyzed oxidative removal of 1,4-naphthoquinone (1,4-NPQ) in the presence of phenolic mediators; specifically, the kinetics of 1,4-NPQ removal under various conditions was examined, and the reaction pathway of 1,4-NPQ was verified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The removal rate of 1,4-NPQ by birnessite-catalyzed oxidation (pH = 5) was faster in the presence of phenolic mediators with electron-donating substituents (pseudo-first-order initial stage rate constant (k1) = 0.380-0.733 h-1) than with electron-withdrawing substituents (k1 = 0.071-0.244 h-1), and the effect on the substituents showed a positive correlation with the Hammett constant (Σσ) (r2 = 0.85, p < 0.001). The rate constants obtained using variable birnessite loadings (0.1-1.0 g L-1), catechol concentrations (0.1-1.0 mM), and reaction sequences indicate that phenolic mediators are the major limiting factor for the cross-coupling reaction of 1,4-NPQ in the initial reaction stages, whereas the birnessite-catalyzed surface reaction acts as the major limiting factor in the later reaction stages. This was explained by the operation of two different reaction mechanisms and reaction products identified by LC-MS/MS.

A Novel Procedure of Total Organic Carbon Analysis for Water Samples Containing Suspended Solids with Alkaline Extraction and Homogeneity Evaluation by Turbidity.

This study was conducted to develop and validate a more reliable total organic carbon (TOC) analytical procedure for water samples containing suspended solids (SS). The effects of the combined ultrasonic and alkaline pretreatment (CULA) on the TOC measurement were studied in water samples containing SS from three origins (algae, sewage particles, and soil) under different analytical conditions (SS concentration, oxidation methods, and sieve size). The applicability of turbidity as a homogeneity index was also evaluated. With CULA, TOC recovery remained high (> 80%) for SS concentration ranges up to four times larger than ultrasonic pretreatment alone (UL) due to enhanced particulate organic carbon (POC) solubilization, and did not significantly differ depending on the oxidation methods, at low SS concentrations, or with varying sieve sizes. In particular, the turbidity change rate (i.e., NTU5/NTU0) of the pretreated water sample showed a high correlation with TOC precision (r2 = 0.73, p < 0.01), which suggests that turbidity can be used as an indicator of sample homogeneity. A novel TOC analytical procedure is expected to be useful for more accurate assessments of the impact of particulate pollutants on water quality than current methods, and for the analysis of the carbon cycle, including POCs, in the environment.