Estimating the concentration and biodegradability of organic matter in 22 wastewater treatment plants using fluorescence excitation emission matrices and parallel factor analysis

Ecotoxicological risk assessment of triclosan, an emerging pollutant in a riverine and estuarine ecosystems: A comparative study

Triclosan (TCS), an antibacterial biocide, pervades water and sediment matrices globally, posing a threat to aquatic life. In densely populated cities like Mumbai, rivers and coastal bodies demand baseline TCS data for ecotoxicological assessment due to the excessive use of personal care products comprising TCS. This pioneering study compares spatiotemporal TCS variations and risks in freshwater and marine ecosystems employing multivariate analysis of physicochemical parameters. Over five months (January to May 2022), Mithi River exhibited higher TCS concentrations (water: 1.68 μg/L, sediment: 3.19 μg/kg) than Versova Creek (water: 0.49 μg/L, sediment: 0.69 μg/kg). Principal component analysis revealed positive correlations between TCS and physicochemical parameters. High-risk quotients (>1) underscore TCS threats in both water bodies. This study furnishes crucial baseline data, emphasizing the need for effective treatment plans for TCS in effluent waters released into the adjacent aquatic systems.

Exploring relationships among landfill leachate parameters through multivariate analysis for monitoring purposes

Elucidating the properties of landfill leachate and the relationships among leachate parameters is crucial for efforts to determine appropriate landfill leachate monitoring activity and management strategies. This study investigated the physical, chemical and optical parameters of leachate in an old Japanese landfill over a 13-month period. The parameters were explored based on their relationships with the maximum fluorescence (Fmax) of three components (microbial humic-like C1, terrestrial humic-like C2 and protein-like C3) deconvoluted from excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC), chemical oxygen demand (COD), Cl- and SO42- concentrations and pH ranged from 2.6 to 38.2 mg C L-1, 9 to 324 mg L-1, 14 to 972 mg L-1, 26 to 1554 mg L-1 and 6.9 to 11.6, respectively. Linear regression analysis suggested that the Fmax values of C2 and C3 represented DOC, whereas the Fmax value of C2 alone could serve as a COD indicator. Hierarchical cluster analysis and principal component analysis were employed to successfully categorise leachate samples based on their locations. Higher dissolved organic matter levels were observed in leachate within the old disposal area, whereas elevated levels of inorganic components such as SO42- and Cl- were found in leachate collected from the extended disposal area and at a treatment facility. Statistical analysis provides crucial tools for assessing and managing various areas of a landfill, supporting targeted and effective waste management strategies.

Monitoring of university wastewater within the sewage system and its performance evaluation through integrated constructed wetlands

Rapid increase in population and industrialization has not only improved the lifestyle but adversely affected the quality and availability of water leading to ample amount of wastewater generation. The major contribution towards wastewater production is from sewage. Regular monitoring and treatment of sewage water is necessary to conserve and enhance the quality of water. The present study focuses on monitoring of sewage water within the sewage system of a residential university. A total of 16 samples from different manholes were collected for physicochemical and heavy metals analysis and compared with final effluent collected from integrated constructed wetlands (ICWs) to assess its removal efficiency. The mean concentrations of influent and effluent were compared with national environmental quality standards (NEQS) for municipal discharge (pH 6-9, COD 150 mg/L, TSS 200 mg/L and TDS 3500 mg/L) and international agricultural reuse standards (IARS) (pH 6-8, COD <150 mg/L, TSS < 100 mg/L) respectively. Among all physicochemical parameters, influent values for chemical oxygen demand (COD) (169.56-258.36) mg/L exceeded the limit of NEQS for discharge into inland waters, whereas for total suspended solids (TSS) the concentration exceeded for discharge into STP (406 mg/L) and inland waters (202.33 mg/L). However, effluent concentrations for all the parameters were found within the permissible limit set by IARS. The removal efficiency for different parameters such as phosphate- phosphorus (PO43-P), COD, TSS, total dissolved solids (TDS) and total kjeldahl nitrogen (TKN) were 52, 53, 54, 35, and 36%, respectively. Heavy metal concentrations were compared with WHO guidelines among which lead (Pb) in effluent and chromium (Cr) in influent exceeded the limit (Pb 0.01 and Cr 0.05 mg/L). Interpolation results showed that zone 2 was highly contaminated in comparison to zone 1 & 3. Statistical analysis showed that correlation of physicochemical parameters and heavy metals was found significant (p < 0.05).

Artificial neural network implementation for dissolved organic carbon quantification using fluorescence intensity as a predictor in wastewater treatment plants

Although spectroscopic methods provide a fast and cost-effective means of monitoring dissolved organic carbon (DOC) in natural and engineered water systems, the prediction accuracy of these methods is limited by the complex relationship between optical properties and DOC concentration. In this study, we developed DOC prediction models using multiple linear/log-linear regression and feedforward artificial neural network (ANN) and investigated the effectiveness of spectroscopic properties, such as fluorescence intensity and UV absorption at 254 nm (UV₂₅₄), as predictors. Optimum predictors were identified based on correlation analysis to construct models using single and multiple predictors. We compared the peak-picking and parallel factor analysis (PARAFAC) methods for selecting appropriate fluorescence wavelengths. Both methods had similar prediction capability (p-values >0.05), suggesting PARAFAC was not necessary for choosing fluorescence predictors. Fluorescence peak T was identified as a more accurate predictor than UV₂₅₄. Combining UV₂₅₄ and multiple fluorescence peak intensities as predictors further improved the prediction capability of the models. The ANN models outperformed the linear/log-linear regression models with multiple predictors, achieving higher prediction accuracy (peak-picking: R² = 0.8978, RMSE = 0.3105 mg/L; PARAFAC: R² = 0.9079, RMSE = 0.2989 mg/L). These findings suggest the potential to develop a real-time DOC concentration sensor based on optical properties using an ANN for signal processing.

Composition of dissolved organic matter (DOM) in wastewater treatment plants influent affects the efficiency of carbon and nitrogen removal

Wastewater treatment plants (WWTPs) play a critical role in receiving, removing, and discharging dissolved organic matter (DOM) in aquatic systems. To date, understanding the composition and fate of DOM in different WWTPs with various environmental and socioeconomic conditions is limited. This study analyzed DOM components in the influent and effluent samples from 49 WWTPs in China using EEM-PARAFAC and ESI-FT-ICR-MS methods. The influencing factors of DOM components in the influent were also analyzed. Geographic location and GDP showed significant (p < 0.05) correlations with DOM components in the influent. The removal efficiency of DOM in WWTPs was closely related to the DOM compositions, where carbohydrates, lipids, and protein-like components (removal efficiencies > 75 %) were more readily decomposed than the humic-like components, lignin, and tannin. The relative fraction of humic-like compound C3 in the influent was correlated negatively with total nitrogen (TN) and chemical oxygen demand (COD) removal in WWTPs (p < 0.05). Besides, the relative fraction of DOM containing the element sulfur also showed significant negative correlations with the humification of DOM (p < 0.05). The results from EEM-PARAFAC and ESI-FT-ICR-MS methods showed no obvious correlation for the DOM characterizations except for humic-like fluorescent fraction C3 and lignin, while significant positive correlations (p < 0.05) between the aromatic index (AI_mod) from the ESI-FT-ICR-MS analysis and the humification index (HIX) from spectrofluorimetry. This supports the use of these spectral indexes as simple surrogates to represent part chemical compositions in further research.

Distribution of sediment microbial communities and their relationship with surrounding environmental factors in a typical rural river, Southwest China

With rapid urbanization and industrialization, rural rivers in China are facing deterioration in water quality and ecosystem health. Microorganisms living in river sediments are involved in biogeochemical processes, mineralization, and degradation of pollutants. Understanding bacterial community distribution in rural rivers could help evaluate the response of river ecosystems to environmental pollution and understand the river self-purification mechanism. In this study, the relationship between characteristics of sediment microbial communities and the surrounding environmental factors in a typical rural river was analyzed using 16S rRNA gene sequencing technology. The results showed that the dominant bacterial groups in the river sediment were Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, Bacteroidetes, and Firmicutes, accounting for 83.61% of the total microbial load. Different areas have different sources of pollution which give rise to specific dominant bacteria. The upstream part of the river flows through an agricultural cultivation area where the dominant bacteria were norank_f_Gemmatimonadaceae, Haliangium, and Pseudolabrys, possessing obvious nitrogen- and phosphorus-metabolizing activities. The midstream section flows through an urban area where the dominant bacteria were Marmoricola, Nocardioides, Gaiella, Sphingomonas, norank_f_67-14, Subgroup_10, Agromyces, and Lysobacter, with strong metabolizing activity for toxic pollutants. The dominant bacteria in the downstream part were Clostridium_sensu_stricto_1, norank_f__Bacteroidetes_vadinHA17, Candidatus_Competibacter, and Methylocystis. Redundancy analysis and correlation heatmap analysis showed that environmental factors: ammonia nitrogen (NH₄⁺-N) and total nitrogen (TN) in the sediment, and pH, temperature, TN, electrical conductivity (EC), and total dissolved solids (TDS) in the water, significantly affected the bacterial community in the sediment. The PICRUSt2 functional prediction analysis identified that the main function of bacteria in the sediment was metabolism (77.3%), specifically carbohydrate, amino acid, and energy metabolism. These activities are important for degrading organic matter and removing pollutants from the sediments. The study revealed the influence of organic pollutants derived from human activities on the bacterial community composition in the river sediments. It gave a new insight into the relationship between environmental factors and bacterial community distribution in rural watershed ecosystems, providing a theoretical basis for self-purification and bioremediation of rural rivers.

A case study: The deployment of a novel in situ fluorimeter for monitoring biological contamination within the urban surface waters of Kolkata, India

The quality and health of many of our vital freshwater systems are poor. To tackle this with ever increasing pressures from anthropogenic and climatic changes, we must improve water quality monitoring and devise and implement more appropriate water quality parameters. Recent research has highlighted the potential for Peak T fluorescence (tryptophan-like fluorescence, TLF) to monitor microbial activity in aquatic systems. The VLux TPro (Chelsea Technologies Ltd., UK), an in situ real-time fluorimeter, was deployed in different urban freshwater bodies within Kolkata (West Bengal, India) during March 2019. This study is the first to apply this technology in surface waters within a densely populated urban area. Spot-sampling was also undertaken at 13 sampling locations enabling physicochemical analysis, bacterial enumeration and determination of nutrient (nitrate and phosphate) concentrations. This case study has demonstrated the ability of an in situ fluorimeter, VLux TPro, to successfully identify both biological contamination events and potential elevated microbial activity, related to nutrient loading, in complex surface freshwaters, without the need for expensive and time-consuming laboratory analysis.

DOM tracking and prediction of rural domestic sewage with UV-vis and EEM in the Yangtze River Delta, China

Compared with the urban sewage treatment plants, the operation of rural decentralized sewage facilities is trapped by the absence of professionals, thus having to be run dependently on the self-adaptive operation of the facilities, which makes timely monitoring particularly important. In this study, organic pollutants in rural domestic sewage and urban domestic sewage are analyzed using ultraviolet-visible (UV-vis) absorption spectroscopy, fluorescence excitation-emission matrix (EEM) and Fourier transform infrared reflectance (FTIR). Compared with the UV-vis absorption spectrum, EEM can not only make up the deficiency in the detection of some easily degradable organics in sewage, but also reveal the transformation of different components, thus indicating timely the treatment progress of rural sewage. Linear fitting of COD and spectrum shows that UV₂₅₄ combined with fluorescence excitation-emission at Ex/Em = 250/330 nm might be more suitable for the prediction of COD in rural water than the UV₂₅₄ alone. This is of great significance for guiding the self-adaptive operation of rural domestic sewage facilities, improving their stability and efficiency, so as to improve the rural living environment.

How does the pre-treatment of landfill leachate impact the performance of O3 and O3/UVC processes?

In this study, O₃ and O₃/UVC processes were evaluated for the treatment of landfill leachate after biological nitrification/denitrification, coagulation, or their combinations. The O₃-driven stage efficiency was assessed by the removal of color, organic matter (dissolved organic carbon (DOC) and chemical oxygen demand (COD)), and biodegradability increase (Zahn-Wellens test). Also, fluorescence excitation-emission matrix (EEM) and size exclusion chromatography coupled with OC detector (SEC-OCD) analysis were carried out for each strategy. The bio-nitrified-leachate (L_N) was not efficiently mineralized during the O₃-driven processes since the high nitrites content consumed ozone rapidly. In turn, carbonate/bicarbonate ions impaired the oxidation of the bio-denitrified-leachate (L_D), scavenging hydroxyl radicals (HO^•) and inhibiting the O₃ decomposition. For both bio-leachates, only O₃/UVC significantly enhanced the effluent biodegradability (>70%), but COD legal compliance was not reached. EEM and SEC-OCD results revealed differences in the organic matter composition between the nitrified-coagulated-leachate (L_NC) and denitrified-coagulated-leachate (L_DC). Nonetheless, the amount of DOC and COD removed per gram of ozone was similar for both. Cost estimation indicates the O₃-driven stage as the costliest among the treatment processes, while coagulation substantially reduced the cost of the following ozonation. Thus, the best treatment train strategy comprised L_DC (with methanol addition for denitrification and coagulated with 300 mg Al³⁺/L, without pH adjustment), followed by O₃/UVC (transferred ozone dose of 2.1 g O₃/L and 12.2 kJ_UVC/L) and final biological oxidation, allowed legal compliance for direct discharge (for organic and nitrogen parameters) with an estimated cost of 8.9 €/m³ (O₃/UVC stage counting for 6.9 €/m³).

Source identification and characteristics of dissolved organic matter and disinfection by-product formation potential using EEM-PARAFAC in the Manas River, China

Dissolved organic matter (DOM) is ubiquitous in natural water and reacts with disinfectants to form disinfection by-products (DBPs). The analysis of DOM in raw water is helpful in evaluating the formation potential of DBPs. However, there is relatively little research on the DOM identification of raw water in northern China. In this study, the sources and characteristics of DOM were investigated in the samples collected from the Manas River. Dissolved organic carbon (DOC), UV₂₅₄, specific ultraviolet absorbance, and fluorescence indices (fluorescence index, humification index, and biological index) were measured to characterize the DOM, and trihalomethanes (THMs) were quantified following formation potential tests with free chlorine. The maximum amount of total trihalomethane formation potential (THMsFP) was 225.57 μg L⁻¹. The DOM of the Manas River consisted of microorganisms and soil resources. The excitation–emission matrix combined with parallel factor analysis (EEM-PARAFAC) identified microbial humus (C1, 54%) and tryptophan-like protein (C2, 46%). PARAFAC components were evaluated as the precursor surrogate parameters of THMsFP. Additionally, the linear THMsFP correlation was stronger with C1 + C2 (r = 0.529, p < 0.01) than with C1 (r = 0.485, p < 0.01). Thus, C1 + C2 is an accurate THMsFP precursor surrogate parameter for the Manas River, and the use of fluorescence spectroscopy may be a robust alternative for predicting DOC removal.

Humic-like and protein-like components were identified by PARAFAC. THMs FP was significantly correlated with components C1 and C1 + C2. The source, types and humification degree of DOM affect the formation of DBPs.

Laboratory In-Situ Production of Autochthonous and Allochthonous Fluorescent Organic Matter by Freshwater Bacteria

This work investigates the origin and range of fluorescent organic matter (FOM) produced in-situ by environmentally sourced freshwater bacteria. Aquatic FOM is an essential component in global carbon cycling and is generally classified as either autochthonous, produced in-situ via microbial processes, or allochthonous, transported into aquatic systems from external sources. We have demonstrated that, within laboratory model systems, environmentally sourced mixed microbial communities and bacterial isolates can produce and/or export FOM associated with both autochthonous and allochthonous material. This study focuses on fluorescence peak B, T, M, C and C+, exploring (1) the cellular nature of FOM produced, (2) FOM exported as extracellular material into the water column and (3) the impact of physical cell lysis on FOM signature. For the laboratory model systems studied, Peak T fluorescence is retained within bacterial cells (>68%), while Peak C fluorescence is mainly observed as extracellular material (>80%). Peak M is identified as both cellular and extracellular FOM, produced by all isolated freshwater microorganisms investigated. The origin of Peak C+ is postulated to originate from functional metabolites associated with specific microorganisms, seen specifically within the Pseudomonas sp. monoculture here. This work challenges the binary classification of FOM as either allochthonous or autochthonous, suggesting that FOM processing and production occurs along a dynamic continuum. Within this study, fluorescence intensity data for the environmental bacteria isolate monocultures are presented as enumeration corrected data, for the first time providing quantitative fluorescence data per bacterial colony forming unit (cfu). From this, we are able to assess the relative contribution of different bacteria to the autochthonous FOM pool and if this material is cellular or extracellular.

Seasonal variation in fluorescence characteristics of dissolved organic matter in wastewater and identification of proteins through HRLC-MS/MS

In the present study, wastewater samples acquired from five wastewater treatment plants (WWTPs), located in western India were characterized using fluorescence spectroscopy, and resin-based fractionation was conducted to fractionate DOM into hydrophobic and hydrophilic base, acid, and neutral fractions. Among several fractions, the hydrophilic acid (HIA) and hydrophilic neutral (HIN) fractions were present in higher abundance (more than 50% of DOC) compared to the hydrophilic base (HIB) fraction in both influent and effluent wastewater stream obtained from WWTPs. Tryptophan-like and tyrosine-like substances were also abundant in the influent and effluent stream of WWTPs. Further, LC-MS/MS analysis could identify 235 and 288 DOM proteins in the influent and effluent stream of WWTP-1, respectively. These proteins revealed varying percentage of tryptophan and tyrosine residues. The tryptophan residues primarily contributed to protein-like fluorescence in wastewater. The proteins were further classified based on their role in biological processes, location in the cell, and molecular function. Among several proteins, Alzheimer's and Huntington disease biomarkers were identified at WWTP-1. Their presence in the surface water can serve as an early warning system for wastewater-based epidemiology.

Calibration of an in-situ fluorescence-based sensor platform for reliable BOD5 measurement in wastewater

Reliance on biochemical oxygen demand (BOD₅) as an indicator of wastewater quality has hindered the development of efficient process control due to the associated uncertainty and lag-times. Surrogate measurements have been proposed, with fluorescence spectroscopy a promising technique. Yet, assessment of in-situ fluorescence sensors across multiple wastewater treatment plants (WwTPs), and at different treatment stages, is limited. In this study a multi-parameter sonde (two fluorescence peaks, turbidity, temperature and electrical conductivity) was used to provide a BOD₅ surrogate measurement. The sonde was deployed at three WwTPs, on post primary settlement tanks (PST) and final effluent (FE). Triplicate laboratory measurements of BOD₅, from independent laboratories were used to calibrate the sensor, with high variability apparent for FE samples. Site and process specific sensor calibrations yielded the best results (R²_cv = 0.76-0.86; 10-fold cross-validation) and mean BOD₅ of the three laboratory measurements improved FE calibration. When combining PST sites a reasonable calibration was still achieved (R²_cv = 0.67) suggesting transfer of sensors between WwTPs may be possible. This study highlights the potential to use online optical sensors as robust BOD₅ surrogates in WwTPs. However, careful calibration (i.e. replicated BOD₅ measurements) is required for FE as laboratory measurements can be associated with high uncertainty.

Using excitation-emission matrix fluorescence to evaluate the performance of water treatment plants for dissolved organic matter removal

This study is aimed at assessing the performance of water treatment plants (both wastewater and drinking water treatment plants) for dissolved organic matter (DOM) removal using excitation-emission matrix fluorescence (EEMF) as the monitoring technique. The influent from the wastewater treatment plant (WWTP) of Burgos (Spain) is characterized from the presence of protein-like peaks (T1 and T2) and humic-like peaks (A and C), T2 and A showing the highest fluorescence intensity. The percentages of total removal in the effluent were in the following order: peak T1 (65%) > peak A (45%) > peak C (34%) > peak T2 (26%). The humic-like peaks were the most removed at the primary sedimentation stage, whereas peak T1 was by far the most removed in the biological reactor. Protein-like peaks T1 and T2 experienced a slight increase in the final effluent in comparison to their fluorescence at the previous stage (the exit of the biological reactor), an increase that can be explained by the release of SMP (soluble microbial products) from the biomass in the secondary clarifier. A poor correlation was obtained between peak T2 fluorescence and COD, BOD (r² = 0.34-0.38). The natural water from the Úzquiza reservoir in Burgos (Spain) is characterized by the only presence of humic substances: a majority peak A (fulvic-like) and a weak peak C (humic-like). The whole fluorescent DOM was removed by coagulation-flocculation but a low fluorescence peak T2 appeared at the final stage, coming from protein-like SMPs released by the biomass attached to the filters.

Assessing the priming effect of dissolved organic matter from typical sources using fluorescence EEMs-PARAFAC

Priming effect (PE) is increasingly recognized as an important mechanism in the microbial degradation of dissolved organic matter (DOM) from freshwater to the ocean. However, potential PE during the mixing of DOM from different sources and the effects on different DOM constituents are still largely unknown. This study examined the PE after adding DOM from typical natural and anthropogenic sources (rainwater, fresh plant, leaf litter, and wastewater) into pre-aged river DOM, using dissolved organic carbon (DOC) measurement, absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). The plant-derived DOM had a low humic content and was dominated by benzoic acid-like and tyrosine-like fluorescent components (C4 and C5), which showed a high DOC bioavailability of 80%. DOC in rainwater and wastewater also had high bioavailabilities (45%-50%), while DOM in the leaf litter leachate showed high aromaticity, average molecular weight, and humic content but low DOC bioavailability (12%). There was generally limited PE (<5% of the initial values) on the degradation of DOC and chromophoric DOM (CDOM) for most samples. Two humic-like components (C2 and C3) showed little PE, while the humic-like C1 and C6, tyrosine-like C5, and tryptophan-like C7 showed variable PE after adding rainwater, wastewater, and plant leachate. Overall, the results revealed that the DOM from typical natural and anthropogenic sources had different composition and bioavailability, and their inputs to aquatic environments would result in variable PE on the bulk DOC and different DOM components.

Distribution and removal of fluorescent dissolved organic matter in 15 municipal wastewater treatment plants in China

Fluorescent dissolved organic matter (FDOM), having complex structures like aromatic structure and double bond structure, is able to represent relatively refractory parts of dissolved organic matter (DOM). This study investigated the distribution of FDOM in the influents and the removal in the secondary effluents of 15 municipal wastewater treatment plants (WWTPs) in 15 provincial capitals of China. Eight components have been identified using excitation emission matrix combined with parallel factor analysis (EEM-PARAFAC). Tryptophan-like (C1 or C4), terrestrial humic-like (C2) and microbial humic-like (C3) fluorescent components were major FDOM components in municipal wastewater, appearing in 11 WWTPs simultaneously. The removal of total fluorescence was generally about 30%-40%, while hydrophobic humic-like compounds (C5 and C8) were the most refractory components with 4%-16% removal and C3 was the second most refractory with -11%-41% removal. The compositions of FDOM in municipal wastewater were different in northeast/west and middle/east regions according to the self-organized map (SOM) analysis. Wastewater sources had more important influence on fluorescent characteristics of secondary effluents than biological treatment processes. Besides, this study found that humification index (HIX) was the most suitable index to describe the bulk fluorescent character of wastewater since it had a good correlation with abundance, removal and ratios of main fluorescent components either in the influents or in the secondary effluents.

Statistical correlation of ecotoxicity and water quality parameters in slaughterhouse wastewater

The major causes of toxicity in slaughterhouse wastewater are identified by analyzing the relationship between representative pollutants and the acute toxicity of Daphnia magna. Experimental results demonstrate that organic matters are strongly associated with the acute toxicity. Among many organic pollutants, proteins and carbohydrates were found to be the main toxicity inducers that cause metabolic transformation of D. magna. Statistical correlation between biodegradable soluble organics and the acute toxicity further explains how principal pollutants play potential toxin roles. Also, this study verifies that the variations of biochemical oxygen demand over total chemical oxygen demand (BOD TCOD^-1) as well as total organic carbon over total carbon (TOC TC^-1) can be indirect indicators explaining the acute toxicity of D. magna because the removal of non-degradable and non-soluble organic matters is connected to the toxicity removal. Overall, these results provide how the acute toxicity of D. magna is attributed to pollutants and what is the potential source of threats to society in slaughterhouse wastewater.

Characterization of urban and industrial wastewaters using excitation-emission matrix (EEM) fluorescence: Searching for specific fingerprints

Excitation-emission matrix (EEM) fluorescence spectroscopy has been applied to characterize several urban and industrial wastewaters (effluents from different types of industries: brewery, winery, dairy, biscuit, tinned fish industry, slaughterhouse, pulp mill, textile dyeing and landfill leachates), searching for specific fluorescence fingerprints. Tryptophan protein-like peaks (T₁ and T₂) are the predominant fluorescence in urban and food industry wastewaters (brewery, winery, dairy/milk, biscuit and fish farm industries) but no special fingerprint has been found to discriminate among them. Protein-like fluorescence also dominates the spectra of meat/fish industries (effluents from a tinned fish industry and a slaughterhouse), but in this case tyrosine protein-like peaks (B₁ and B2) also appear in the spectra in addition to tryptophan-like peaks. This fact might constitute a specific feature to differentiate these wastewaters from others, since the appearance of peaks B is quite uncommon in wastewaters. The textile dyeing effluent shows a characteristic triple humic-like fluorescence (peaks A, C₁ and C₂) that may represent a specific fingerprint for this kind of effluent. Leachates from medium-aged and old landfills might also show a specific fingerprint in their EEM spectra: the sole presence of the humic-like peak C with very high fluorescence intensity. This feature also allows differentiating them from young landfill leachates, which show predominance of protein-like peaks. The fluorescence index (FI) does not seem to be very appropriate to characterize wastewaters and its usefulness might be limited to the study of humic substances in natural waters, although further studies are needed on this topic. However, the humification index (HIX) and the biological index (BIX) do seem to be useful for studying wastewaters, since they have provided consistent results in the present work. This study shows the potential of EEM fluorescence to identify the origin of some industrial effluents, although more research is needed to check these preliminary results.

Using EEM-PARAFAC to probe NF membrane fouling potential of stabilized landfill leachate pretreated by various options

Pretreatment processes substantially modify the organic composition of landfill leachate, which affect the fouling behavior in the post-treatment of membrane filtration. In this study, the changes in the chemical composition of stabilized landfill leachate upon various pretreatments, which encompassed coagulation/flocculation (C/F), ion exchange resins (MIEX), granular activated carbon (GAC) adsorption, and their combinations, were tracked via excitation emission matrix - parallel factor analysis (EEM-PARAFAC), and the membrane fouling potentials were assessed in the subsequent processes of nanofiltration (NF). Fluorescence components, fulvic-like (C1), protein-like (C2), and humic-like (C3), were identified and validated using EEM-PARAFAC. MIEX and C/F pretreatments were not effective to remove C1 and C2, which were associated with relatively small sized and hydrophilic molecules. GAC adsorption did not show any preference with the removal towards different components. These differences in the chemical heterogeneity among the variously pretreated leachates led to the discrepancies in membrane fluxes at a similar leachate concentration. The result also signified the importance of probing the chemical composition of pretreated leachate for the optimization of the post membrane filtration. The sum of C2 and C3 in the pretreated leachate showed a good correlation with reversible membrane fouling resistance (r = 0.93; p < 0.05), while C1 was highly correlated with irreversible membrane resistance (r = 0.872; P < 0.05). These findings provided a new insight into the applicability of fluorescence spectroscopy for tracking the changes in the membrane fouling potential of stabilized landfill leachate after various pretreatments.

Characterization of aquatic organic matter: Assessment, perspectives and research priorities

Organic matter (OM) refers to the largest reactive reservoir of carbon-based compounds on Earth. Aside of its role as a source of carbon, OM is also actively involved in a wide range of ecological functions. It also plays an important role in the solubility, toxicity, bioavailability, mobility and distribution of pollutants. Therefore, OM is a key component in the local and global carbon cycle. About 12,000 articles containing organic matter in the title were published during the past decade, with a continuous increasing number each year (ISI Web of Science). Although this topic was widely explored and its interest has significantly increased, some limitations remain. These limitations can be technical (e.g., pre-treatment processes, low-resolution instrument, data handling) and can be related to the current approach. In this review, we first present the current strategies and tools to characterize the organic matter in the aquatic environment, then we tackle several aspects of current characterization limitations. Finally, we suggest new perspectives and priorities of research to improve the current limitations. From our point of view, simultaneous studies of particulate and dissolved OM fractions should be prioritized and multi-disciplinary approach, creation of databases, controlled experiments and collaborative works should be the next targets for future OM research priorities.

Targeted removal of organic foulants in landfill leachate in forward osmosis system integrated with biochar/activated carbon treatment

Forward osmosis (FO) has been adopted to treat complex wastewater such as landfill leachate due to its high rejection of organics. In this study, the in-line adsorptive process using biochar (BC) or powdered activated carbon (PAC) was applied to a cross flow FO system to enhance the mitigation of the FO membrane fouling from landfill leachate. The changes in the leachate composition along the treatments were tracked by excitation emission matrix-parallel factor analysis (EEM-PARAFAC) to identify tryptophan-like (C1), fulvic-like (C2), and humic-like (C3) components. After a single operation of FO, the C1 was found to be the main constituent responsible for membrane fouling irrespective of varying operation conditions regarding draw solute concentrations and flow rates. Both sorbents (i.e., BC and PAC) exhibited the preferential removal behavior towards C1 > C2 > C3, which was well supported by their individual adsorption isotherm model parameters. The addition of in-line adsorption treatment to FO resulted in substantial improvements in the filtered volume (>57%) and the flux recovery (>80%) compared to the single FO operation. Without chemical cleaning of membrane, the flux was fully recovered at a dose of 10 g/L BC or 0.3 g/L of PAC. A significant and negative correlation was found between the flux recovery and the C1 of the feed leachate or the corresponding spectral peak intensity (p < 0.05) for the integrated FO system, suggesting the potential of using on-line fluorescence monitoring for the performance of the integrated system in terms of fouling mitigation. This study provided a new insight into the effectiveness of BC or PAC adsorption as the in-line integration with an FO system for the targeted removal of FO membrane foulants in landfill leachate.

Enhancement of anaerobic digestion effluent treatment by microalgae immobilization: Characterized by fluorescence excitation-emission matrix coupled with parallel factor analysis in the photobioreactor

The bacterial-microalgal consortium has been investigated to anaerobic digestion effluent (ADE) treatment in the photobioreactor (PBR). However, the high concentrations of nutrients reduced the ADE treatment efficiency and the transformation of organic pollutants in PBR was still unclear. In this study, two-sequencing batch PBRs were operated with suspended Microcystis aeruginosa (M. aeruginosa, SMA) and immobilized M. aeruginosa (IMA) to compare the ADE treatment performance. Fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) was conducted to identify organics degradations. The results showed that the proportion of living M. aeruginosa cell (86.4%) in PBR (IMA) was highly significant (p < 0.05) higher than that in PBR (SMA) (75.2%). This indicated immobilized microalgae beads enhanced the resistance to the high concentration of nutrients in PBR (IMA). EEM-PARAFAC analysis displayed the biodegradation order in the bacterial-microalgal consortium system was humic-like substances > tyrosine-like substances > tryptophan-like substances. The removals of humic-like matters (94.05 ± 0.92%) and tyrosine-like matters (91.13 ± 2.49%) in PBR (IMA) were significantly (p < 0.01) higher than those in PBR (SMA). Notably, the average removals of nutrients in PBR (IMA) were significantly (p < 0.05) higher than those in PBR (SMA). This result verified that microalgae immobilization benefitted nutrients removals with 93.05 ± 1.45% of NH₄⁺-N and complete PO₄^3--P removal in PBR (IMA). Moreover, the enrichment of functional genera Flavobacterium and Opitutus contributed to decreasing the organics loadings and strengthening the ADE treatment performance. Therefore, this study verified microalgae immobilization enhanced the actual ADE treatment. Additionally, fluorescent organic pollutants degradations were further evaluated by EEM-PARAFAC analysis in the bacterial-microalgal consortium.

Stokes Shift and Specific Fluorescence as Potential Indicators of Organic Matter Hydrophobicity and Molecular Weight in Membrane Bioreactors

Hydrophobicity and molecular weight (MW) are two fundamental properties of dissolved organic matter (DOM) in wastewater treatment systems. This study proposes fluorescence Stokes shift and specific fluorescence intensity (SFI) as novel indicators of hydrophobicity and MW. These indicators originate from the energy gap and photon efficiency of the fluorescence process and can be readily extracted from a fluorescence excitation-emission matrix (EEM). The statistical linkages between these indicators and hydrophobicity/MW were explored through investigation of DOM across 10 full-scale membrane bioreactors treating municipal wastewater. Stokes shift was found to exhibit a general rule among the hydrophobicity components in the order of hydrophilic substances (HIS) < hydrophobic acids (HOA) < hydrophobic bases (HOB). The Stokes shift of 1.2 μm^-1 is a critical border, above which the relative fluorescence correlated significantly with the HOA-related content (Pearson's r = 0.8). With regard to MW distribution (<1, 1-10, 10-100, and >100 kDa), SFI was found to be the most sensitive to the change of MW of <1 kDa proportion, especially at the excitation/emission wavelengths of 200-320/310-550 nm (r > 0.9). Hydrophobicity-related π conjugation and MW-dependent light exposure might be responsible for the correlations. These fluorescence indicators may be useful for convenient monitoring of DOM in wastewater treatment systems.

An environmentally friendly surrogate method for measuring the soluble chemical oxygen demand in wastewater: use of three-dimensional excitation and emission matrix fluorescence spectroscopy in wastewater treatment monitoring

Gaining rapid knowledge of dissolved organic matter (DOM) proves to be decisive for wastewater treatment plant operators in efforts to achieve good treatment efficiency in light of current legislation. DOM can be monitored by application of fluorescence spectroscopy both online and in real time in order to derive an assessment of DOM oxidation potential. This work presents an eco-friendly alternative method for measuring the soluble chemical oxygen demand (COD) in raw sewage by means of three-dimensional fluorescence spectroscopy. A peak-picking approach has been developed based on a previous parallel factor analysis (PARAFAC) model dedicated to Paris raw sewage. Fluorescence spectroscopy parameters were used to obtain a good prediction model of soluble COD (r² = 0.799; p < 0.0001; n = 80) for raw sewage. The approach employed in this study serves as a guideline for purposes of implementing online wastewater monitoring and conducting environmentally friendly soluble COD measurements in the laboratory.

Unraveling complex removal behavior of landfill leachate upon the treatments of Fenton oxidation and MIEX® via two-dimensional correlation size exclusion chromatography (2D-CoSEC)

The complex removal behavior of stabilized landfill leachate was explored for the treatments of Fenton oxidation (FnO) and magnetic ion exchange (MIEX^®) resin using two-dimensional correlation size exclusion chromatography (2D-CoSEC) and fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC). The overall removal rates of the bulk parameters (∼45% for dissolved organic carbon and ∼78% for UV absorbance) were similar between the two treatment options, while distinct differences were found with respect to different molecular sizes and chemical composition. The resin treatment eliminated humic substances (HS) and low molecular weight acid (LMWA) fractions to a greater extent than other fractions (i.e., HS: 62% and LMWA: 99%), while low molecular weight neutral (LMWN) and biopolymers (BP) fractions were more effectively treated by the FnO with the removal rates of 56% and 92%, respectively. The 2D-CoSEC further revealed that the sequential or preferential changes of different size fractions with increasing the resin or H₂O₂ were opposite between the two treatment options in the order of HS → LMWA → LMWN → BP for MIEX^®. Due to their complementary roles in treating leachate, the combined processes removed a wider ranges of different molecular sizes compared to the single operation.

Efficiency of sequential UV/H2O2 and biofilm process for the treatment of secondary effluent

In response to the shortage of water resources, multiple processes have been applied to turn wastewater secondary effluent (SE) into potable water. However, trace organic contaminants (TOrCs) and high concentrations of organic matter contained in SE pose a significant challenge to the reclamation. In this manuscript, combined UV-based and biofilm processes were used to treat the SE spiked with ibuprofen (IBU) and clofibric acid (CA). The efficiency of these sequential treatments was characterized in terms of changes in dissolved organic carbon (DOC), absorbance at 254 nm (A₂₅₄), fluorescence excitation-emission matrix (FEEM), the concentration of IBU and CA, and molecular weight of SE. Parallel factor (PARAFAC) was applied as the analysis method for FEEM of the samples and two fluorescent components were successfully identified: humic-like substances (C1) and protein-like matter (C2). Large reductions in A₂₅₄, C1, C2, IBU, and CA were observed during the UV-based processes, especially with the addition of H₂O₂. Nearly 50% of A₂₅₄, 80% of the component C1 were decreased and almost complete removal of the component C2 and TOrCs was achieved by UV/2.0 mM H₂O₂ after 90-min treatment. During the oxidation processes, the formation of lower molecular weight (LMW) compounds was detected, and the biodegradability of the organic matters was greatly increased. Although no significant DOC reduction was obtained in UV-based processes, an obvious further DOC reduction (30~60%) was achieved by biofilm treatment following UV-based processes, especially after UV/H₂O₂ treatments. In the meantime, large amounts of LMW were removed in the biofilm treatment process. This manuscript provides an effective advanced treatment of SE for the removal of DOC and TOrCs, facilitating the wastewater reclamation.

The Fate of Dissolved Organic Matter (DOM) During Bank Filtration under Different Environmental Conditions: Batch and Column Studies

Dissolved organic matter (DOM) in source water highly influences the removal of different contaminants and the dissolution of aquifer materials during bank filtration (BF). The fate of DOM during BF processes under arid climate conditions was analysed by conducting laboratory—scale batch and column studies under different environmental conditions with varying temperature (20–30 °C), redox, and feed water organic matter composition. The behaviour of the DOM fractions was monitored using various analytical techniques: fluorescence excitation-emission matrix spectroscopy coupled with parallel factor analysis (PARAFAC-EEM), and size exclusion liquid chromatography with organic carbon detection (LC-OCD). The results revealed that DOM attenuation is highly dependent (p < 0.05) on redox conditions and temperature, with higher removal at lower temperatures and oxic conditions. Biopolymers were the fraction most amenable to removal by biodegradation (>80%) in oxic environments irrespective of temperature and feed water organic composition. This removal was 20–24% lower under sub-oxic conditions. In contrast, the removal of humic compounds exhibited a higher dependency on temperature. PARAFAC-EEM revealed that terrestrial humic components are the most temperature critical fractions during the BF processes as their sorption characteristics are negatively correlated with temperature. In general, it can be concluded that BF is capable of removing labile compounds under oxic conditions at all water temperatures; however, its efficiency is lower for humic compounds at higher temperatures.

Immobilized microalgae for anaerobic digestion effluent treatment in a photobioreactor-ultrafiltration system: Algal harvest and membrane fouling control

A photobioreactor (PBR) coupled with ultrafiltration (UF) system was developed with goals of microalgae cultivation, harvest, and membrane fouling control in the anaerobic digestion effluent purification. Firstly, three-sequencing batch PBRs were started-up with suspended Chlorella vulgaris (C. vulgaris, SCV), immobilized C. vulgaris (ICV) and immobilized C. vulgaris with powdered activated carbon (ICV + PAC). The results exhibited high DOC degradation (66.61%-84.35%) and completely nutrients (nitrogen and phosphorus) removals were attained in PBRs. This indicated bacterial-microalgal consortiums enhanced biodegradation and PAC adsorption accelerated photodegradation. During the microalgae harvest by UF, immobilized microalgae beads protected cells integrity with less debris and intracellular/extracellular organic matters lysis. Moreover, the cake layer in ICV + PAC could even serve as a dynamic layer to entrap the residual pollutants and control membrane fouling. Hence, membrane fouling mitigation and ADE purification were realized during the microalgae harvest process in the ICV + PAC.

Exploring the fate and oxidation behaviors of different organic constituents in landfill leachate upon Fenton oxidation processes using EEM-PARAFAC and 2D-COS-FTIR

In this work, the changes of different organic constituents in landfill leachate were tracked in Fenton oxidation processes with different operation parameters including H₂O₂ doses, pH, and the ratios of [H₂O₂]/[Fe] via fluorescence excitation emission matrix - parallel factor analysis (EEM-PARAFAC) and two-dimensional correlation spectroscopy (2D-COS). One tryptophan-like (C1), one fulvic-like (C2), and one humic-like (C3) components were identified in the leachates. The removal behaviors of the individual fluorescent components were dependent upon the operation conditions, suggesting the existence of unique characteristics with respect to the responses to the oxidation mechanisms, which were likely altered by different operation conditions. For all tested conditions, a greater extent of removal was consistently found for C3 versus C1 and C2 except for the relatively high pH ranges (>6.0), in which C2 presented the highest removal rates. 2D-COS combined with synchronous fluorescence spectra exhibited the preferential oxidation sequence in the order of C3 > C1 > C2 with higher H₂O₂ doses. 2D-COS coupled with Fourier transform infrared (2D-COS-FTIR) showed that aromatic functional groups were initially oxidized, followed by the removal of carboxylic groups and the formation of inorganic functional groups and aldehyde or ketonic groups. Hetero 2D-COS maps further revealed the close association between the aromatic groups and C3, and between the carboxylic groups and C1. This study utilizing 2D-COS provided new insights into the dynamic behavior of heterogeneous landfill leachate in Fenton oxidation processes under varying operation conditions.

Towards a better control of the wastewater treatment process: excitation-emission matrix fluorescence spectroscopy of dissolved organic matter as a predictive tool of soluble BOD5 in influents of six Parisian wastewater treatment plants

The online monitoring of dissolved organic matter (DOM) in raw sewage water is expected to better control wastewater treatment processes. Fluorescence spectroscopy offers one possibility for both the online and real-time monitoring of DOM, especially as regards the DOM biodegradability assessment. In this study, three-dimensional fluorescence spectroscopy combined with a parallel factor analysis (PARAFAC) has been investigated as a predictive tool of the soluble biological oxygen demand in 5 days (BOD₅) for raw sewage water. Six PARAFAC components were highlighted in 69 raw sewage water samples: C2, C5, and C6 related to humic-like compounds, along with C1, C3, and C4 related to protein-like compounds. Since the PARAFAC methodology is not available for online monitoring, a peak-picking approach based on maximum excitation-emission (Ex-Em) localization of the PARAFAC components identified in this study has been used. A good predictive model of soluble BOD₅ using fluorescence spectroscopy parameters was obtained (r² = 0.846, adjusted r² = 0.839, p < 0.0001). This model is quite straightforward, easy to automate, and applicable to the operational field of wastewater treatment for online monitoring purposes.

Using Two-Dimensional Correlation Size Exclusion Chromatography (2D-CoSEC) and EEM-PARAFAC to Explore the Heterogeneous Adsorption Behavior of Humic Substances on Nanoparticles with Respect to Molecular Sizes

The adsorption behaviors of different constituents within bulk humic substances (HS) on two nanoparticles, TiO₂ and ZnO, were examined by using two-dimensional correlation size exclusion chromatography (2D-CoSEC) and excitation emission matrix-parallel factor analysis (EEM-PARAFAC), which separated bulk HS into different size fractions and fluorescent components, respectively. Subtle changes in the size distributions of HS with increasing adsorbents were successfully identified and tracked via the 2D-CoSEC. From adsorption isotherm experiments, three different HS constituent groups with respect to sizes and fluorescence features were identified by the 2D-CoSEC and EEM-PARAFAC, respectively. The chromatographically separated HS size groups presented dissimilar adsorption behaviors in terms of adsorption affinity and isotherm nonlinearity. The sequence orders of adsorption, interpreted from the 2D-CoSEC, was consistent with those of the isotherm model parameters individually calculated for different HS size subfractions, signifying the promising application of 2D-CoSEC in obtaining an insight into the heterogeneous adsorption of HS in terms of molecular sizes. EEM-PARAFAC results also supported the major finding of the 2D-CoSEC as shown by the preferential adsorption of the fluorescent components associated with large molecular sizes.

Membrane electro-oxidizer: A new hybrid membrane system with electrochemical oxidation for enhanced organics and fouling control

The synergistic combination of membrane filtration with advanced oxidation is of particular interest for next-generation wastewater treatment technologies. A membrane electro-oxidizer (MEO) hybridizing a submerged microfilter and an electrochemical cell was developed and investigated for tertiary treatment of secondary industrial (textile) wastewater effluent. Laboratory- and pilot-scale MEO systems were designed and evaluated for treatment efficiency and membrane fouling control. The MEO achieved substantial removal of color (50-90%), turbidity (>90%), and bacteria (>4 log) as well as chemical oxygen demand (13-31%) and 1,4-dioxane (∼25-53%). Fluorescence-based parallel factor analysis disclosed the degradation of humic-like organics with fluorophores. Size exclusion chromatograms with organic carbon detection confirmed the removal of specific organic molecules with ∼100 Da. While investigating the effects of oxidant quenching agents, reactive chlorine species and hydrogen peroxide were found to be most responsible for the anodic oxidation of secondary effluent organics. The efficacy of membrane fouling mitigation by the MEO was greater when higher electric current densities were applied, but was not dependent on the number of electrochemical cells installed. The MEO is a promising technology for enhanced organics removal with simultaneous fouling control due to its multifunctional active oxidants.

Characterisation of landfill leachate by EEM-PARAFAC-SOM during physical-chemical treatment by coagulation-flocculation, activated carbon adsorption and ion exchange

The combination of fluorescence excitation-emission matrices (EEM), parallel factor analysis (PARAFAC) and self-organizing maps (SOM) is shown to be a powerful tool in the follow up of dissolved organic matter (DOM) removal from landfill leachate by physical-chemical treatment consisting of coagulation, granular activated carbon (GAC) and ion exchange. Using PARAFAC, three DOM components were identified: C1 representing humic/fulvic-like compounds; C2 representing tryptophan-like compounds; and C3 representing humic-like compounds. Coagulation with ferric chloride (FeCl₃) at a dose of 7 g/L reduced the maximum fluorescence of C1, C2 and C3 by 52%, 17% and 15% respectively, while polyaluminium chloride (PACl) reduced C1 only by 7% at the same dose. DOM removal during GAC and ion exchange treatment of raw and coagulated leachate exhibited different profiles. At less than 2 bed volumes (BV) of treatment, the humic components C1 and C3 were rapidly removed, whereas at BV ≥ 2 the tryptophan-like component C2 was preferentially removed. Overall, leachate treated with coagulation +10.6 BV GAC +10.6 BV ion exchange showed the highest removal of C1 (39% - FeCl₃, 8% - PACl), C2 (74% - FeCl₃, 68% - PACl) and no C3 removal; whereas only 52% C2 and no C1 and C3 removal was observed in raw leachate treated with 10.6 BV GAC + 10.6 BV ion exchange only. Analysis of PARAFAC-derived components with SOM revealed that coagulation, GAC and ion exchange can treat leachate at least 50% longer than only GAC and ion exchange before the fluorescence composition of leachate remains unchanged.

Fast tracking the molecular weight changes of humic substances in coagulation/flocculation processes via fluorescence EEM-PARAFAC

The removal of a commercial humic acid (HA) and changes in its chemical composition were examined for coagulation/flocculation (C/F) processes based on jar tests using two different coagulants at a wide range of pH. ZrCl₄ showed a better performance in eliminating HA than Al₂SO₄ with the same removal rates at lower dosages. The highest removal rates were found at a neutral pH range (5.0-6.5). The HA was further decomposed into three different humic-like components (C1, C2, and C3) by excitation emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Although the removal rates of all three components generally followed those of dissolved organic carbon, the relative removals of the individual components depended on the coagulant's doses and the solution pH. The fluorescent components of five ultrafiltered size fractions of the HA revealed that the peak with a longer emission wavelength could be associated with larger sized molecules. The C1/C3 ratios of the size fractions exhibited a significant linear relationship with the logarithmic values of the average molecular weight (MW) measured by size exclusion chromatography, which made it possible to predict the HA MW value changes upon the C/F using EEM-PARAFAC alone. Irrespective of the coagulant types and the pH, larger sized HA molecules were removed to a greater extent than smaller sized fractions. The preferential removal was more pronounced for ZrCl₄ versus Al₂SO₄ and at a neutral pH range. Our study suggests a great potential of EEM-PARAFAC in fast tracking the MW of humic substances in conventional C/F processes.

Unveiling the transformation and bioavailability of dissolved organic matter in contrasting hydrothermal vents using fluorescence EEM-PARAFAC

The submarine hydrothermal systems are extreme environments where active cycling of dissolved organic matter (DOM) may occur. However, little is known about the optical properties and bioavailability of hydrothermal DOM, which could provide valuable insights into its transformation processes and biogeochemical reactivity. The quantity, quality, and bioavailability of DOM were investigated for four very different hydrothermal vents east of Taiwan, using dissolved organic carbon (DOC), absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC). The DOC and absorption coefficient a₂₈₀ were both lower in the two hydrothermal vents off the Orchid Island and on the Green Island than in the surrounding seawater and the two vents off the Kueishantao Island, indicating effective removals of DOM in the former two hydrothermal systems owing to possible adsorption/co-precipitation and thermal degradation respectively. The four hydrothermal DOM showed notable differences in the absorption spectral slope S_275-295, humification index HIX, biological index BIX, EEM spectra, and the relative distributions of seven PARAFAC components. The results demonstrated a high diversity of chemical composition and transformation history of DOM under contrasting hydrothermal conditions. The little change in the hydrothermal DOC after 28-day microbial incubations indicated a low bioavailability of the bulk DOM, and different PARAFAC components showed contrasting bioavailability. The results have profound implications for understanding the biogeochemical cycling and environmental effects of hydrothermal DOM in the marine environments.

Evaluating Activated Carbon Adsorption of Dissolved Organic Matter and Micropollutants Using Fluorescence Spectroscopy

Dissolved organic matter (DOM) negatively impacts granular activated carbon (GAC) adsorption of micropollutants and is a disinfection byproduct precursor. DOM from surface waters, wastewater effluent, and 1 kDa size fractions were adsorbed by GAC and characterized using fluorescence spectroscopy, UV-absorption, and size exclusion chromatography (SEC). Fluorescing DOM was preferentially adsorbed relative to UV-absorbing DOM. Humic-like fluorescence (peaks A and C) was selectively adsorbed relative to polyphenol-like fluorescence (peaks T and B) potentially due to size exclusion effects. In the surface waters and size fractions, peak C was preferentially removed relative to peak A, whereas the reverse was found in wastewater effluent, indicating that humic-like fluorescence is associated with different compounds depending on DOM source. Based on specific UV-absorption (SUVA), aromatic DOM was preferentially adsorbed. The fluorescence index (FI), if interpreted as an indicator of aromaticity, indicated the opposite but exhibited a strong relationship with average molecular weight, suggesting that FI might be a better indicator of DOM size than aromaticity. The influence of DOM intermolecular interactions on adsorption were minimal based on SEC analysis. Fluorescence parameters captured the impact of DOM size on the fouling of 2-methylisoborneol and warfarin adsorption and correlated with direct competition and pore blockage indicators.

Effects of ozonation pretreatment on natural organic matter and wastewater derived organic matter - Possible implications on the formation of ozonation by-products

The aim of this study was to investigate possible implications of natural and wastewater derived organic matter in river water that is subsequently used following treatment for drinking purposes. River water was subjected to lab-scale ozonation experiments under different ozone doses (0.1, 0.4, 0.8, 1.0 and 2.0 mgO₃/mgC) and contact times (1, 3, 5, 8 and 10 min). Mixtures of river water with humic acids or wastewaters (sewage wastewater and secondary effluents) at different proportions were also ozonated. Dissolved organic carbon and biodegradable dissolved organic carbon concentrations as well as spectroscopic characteristics (UV absorbance and fluorescence intensities) of different types of dissolved organic matter and possible changes due to the ozonation treatment are presented. River water, humic substances and wastewater exhibited distinct spectroscopic characteristics that could serve for pollution source tracing. Wastewater impacted surface water results in higher formation of carbonyl compounds. However, the formation yield (μg/mgC) of wastewaters was lower than that of surface water possibly due to different composition of wastewater derived organic matter and the presence of scavengers, which may limit the oxidative efficiency of ozone.

Non-catalytic and catalytic degradation of effluent dissolved organic matter under UVA-and UVC-irradiation tracked by advanced spectroscopic tools

Non-catalytic and catalytic photodegradation of effluent dissolved organic matter (EfDOM) was examined under two different light sources (UVA and UVC). The degradation behavior was tracked by dissolved organic carbon (DOC), UV absorbance, and different fluorescent components. Catalytic UV irradiation resulted in much higher degradation rates than those without photocatalysts (TiO₂ and ZnO) regardless of the tracking variables. For non-catalytic degradation, the highest removal rates of UV absorbance were found at wavelengths close to the irradiation of either UVC or UVA, while the photocatalytic degradation rates were consistently higher at longer wavelengths. The pseudo first-order rates of UV absorbance individually calculated at several representative wavelengths were very consistent with the sequential orders interpreted from two-dimensional correlation spectroscopy (2D-COS). Excitation emission matrix - parallel factor analysis (EEM-PARAFAC) identified one tryptophan-like (C1) and two humic-like (C2 and C3) components from EfDOM samples. Among those, C1 exhibited the lowest adsorption extent and the highest degradation rates for both photocatalysts, suggesting that the photocatalysis is mainly governed by hydroxyl radicals in aqueous solution. All observed degradation behaviors were well explained by the irradiation wavelengths, the extent of adsorption onto catalysts, and the presumed structure of the tracked component. Our study demonstrated that EEM-PARAFAC and 2D-COS could provide further insights into both non-catalytic and catalytic degradation of EfDOM upon UV-irradiation.

Microalgal growth in municipal wastewater treated in an anaerobic moving bed biofilm reactor

Nutrient removal from the effluent of an anaerobic moving bed biofilm reactor (AnMBBR) treated with microalgae was evaluated. Algal treatment was highly efficient in removal of nutrients and discharge limits were met after 3days. Extending the cultivation time from 3 to 5days resulted in a large increase in biomass, from 233.3±49.3 to 530.0±72.1mgL(-1), despite nutrients in the water being exhausted after 3days (ammonium 0.04mgL(-1), orthophosphate <0.05mgL(-1)). Biomass productivity, lipid content and quality did not differ in microalgal biomass produced in wastewater sampled before the AnMBBR. The longer cultivation time resulted in a slight increase in total lipid concentration and a significant decrease in linolenic acid concentration in all treatments. Differences were observed in chemical oxygen demand, which decreased after algal treatment in wastewater sampled before the AnMBBR whereas it increased after algal treatment in the effluent from the AnMBBR.

Heterogeneous adsorption behavior of landfill leachate on granular activated carbon revealed by fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC)

Heterogeneous adsorption behavior of landfill leachate on granular activated carbon (GAC) was investigated by fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (PARAFAC). The equilibrium adsorption of two leachates on GAC was well described by simple Langmuir and Freundlich isotherm models. More nonlinear isotherm and a slower adsorption rate were found for the leachate with the higher values of specific UV absorbance and humification index, suggesting that the leachate containing more aromatic content and condensed structures might have less accessible sites of GAC surface and a lower degree of diffusive adsorption. Such differences in the adsorption behavior were found even within the bulk leachate as revealed by the dissimilarity in the isotherm and kinetic model parameters between two identified PARAFAC components. For both leachates, terrestrial humic-like fluorescence (C1) component, which is likely associated with relatively large sized and condensed aromatic structures, exhibited a higher isotherm nonlinearity and a slower kinetic rate for GAC adsorption than microbial humic-like (C2) component. Our results were consistent with size exclusion effects, a well-known GAC adsorption mechanism. This study demonstrated the promising benefit of using EEM-PARAFAC for GAC adsorption processes of landfill leachate through fast monitoring of the influent and treated leachate, which can provide valuable information on optimizing treatment processes and predicting further environmental impacts of the treated effluent.

Angle-Polarization Estimation for Coherent Sources with Linear Tripole Sensor Arrays

We propose a parallel factor (PARAFAC) analysis-based angle and polarization estimation algorithm for multiple coherent sources using a uniformly-spaced linear tripole sensor array. By forming a PARAFAC model using the spatial signature of the tripole array, the new algorithm requires neither spatial smoothing nor vector-field smoothing to decorrelate the signal coherency. We also establish that the angle-polarization parameters of K coherent signals can be uniquely determined by PARAFAC analysis, as long as the number of tripoles L≥2K−1. In addition, the proposed algorithm can offer enhanced angle and polarization estimation accuracy by extending the interspacing of the tripoles beyond a half wavelength.

Wastewater compounds in urban shallow groundwater wells correspond to exfiltration probabilities of nearby sewers

Wastewater compounds are frequently detected in urban shallow groundwater. Sources include sewage or reclaimed wastewater, but origins are often unknown. In a prior study, wastewater compounds were quantified in waters sampled from shallow groundwater wells in a small coastal California city. Here, we resampled those wells and expanded sample analyses to include sewage- or reclaimed water-specific indicators, i.e. pharmaceutical and personal care product chemicals or disinfection byproducts. Also, we developed a geographic information system (GIS)-based model of sanitary sewer exfiltration probability--combining a published pipe failure model accounting for sewer pipe size, age, materials of construction, with interpolated depths to groundwater--to determine if sewer system attributes relate to wastewater compounds in urban shallow groundwater. Across the wells, groundwater samples contained varying wastewater compounds, including acesulfame, sucralose, bisphenol A, 4-tert-octylphenol, estrone and perfluorobutanesulfonic acid (PFBS). Fecal indicator bacterial concentrations and toxicological bioactivities were less than known benchmarks. However, the reclaimed water in this study was positive for all bioactivity tested. Excluding one well intruded by seawater, the similarity of groundwater to sewage, based on multiple indicators, increased with increasing sanitary sewer exfiltration probability (modeled from infrastructure within ca. 300 m of each well). In the absence of direct exfiltration or defect measurements, sewer exfiltration probabilities modeled from the collection system's physical data can indicate potential locations where urban shallow groundwater is contaminated by sewage.

To what extent can portable fluorescence spectroscopy be used in the real-time assessment of microbial water quality?

The intrinsic fluorescence of aquatic organic matter emitted at 350 nm when excited at 280 nm correlates widely with water quality parameters such as biochemical oxygen demand. Hence, in sewage-impacted rivers and groundwater, it might be expected that fluorescence at these wavelengths will also correlate with the microbial water quality. In this paper we use a portable fluorimeter to assess the relationship between fluorescence intensity at this wavelength pair and Escherichia coli enumeration in contrasting river catchments of poor water quality: in KwaZulu-Natal, S. Africa and the West Midlands, UK. Across all catchments we demonstrate a log correlation (r = 0.74) between fluorescence intensity and E. coli over a seven-log range in E. coli enumerations on non-perturbed (unfiltered) samples. Within specific catchments, the relationship between fluorescence intensity and E. coli is more variable, demonstrating the importance of catchment-specific interference. Our research demonstrates the potential of using a portable fluorimeter as an initial screening tool for indicative microbial water quality, and one that is ideally suited to simple pollution scenarios such as assessing the impact of faecal contamination in river or groundwater at specific sites.

Submersible Spectrofluorometer for Real-Time Sensing of Water Quality

In this work, we present a newly developed submersible spectrofluorometer (patent pending) applied to real-time sensing of water quality, suitable for monitoring some important indicators of the ecological status of natural waters such as chlorophyll-a, oil and protein-like material. For the optomechanical realization of the apparatus, a novel conceptual design has been adopted in order to avoid filters and pumps while maintaining a high signal-to-noise ratio. The elimination of filters and pumps has the advantage of greater system simplicity and especially of avoiding the risk of sample degradation. The use of light-emitting diodes as an excitation source instead of Xe lamps or laser diodes helped save on size, weight, power consumption and costs. For sensor calibration we performed measurements on water samples with added chlorophyll prepared in the laboratory. The sensor functionality was tested during field campaigns conducted at Albano Lake in Latium Region of Italy as well as in the Herzliya Harbor, a few kilometers North East of Tel Aviv in Israel. The obtained results are reported in the paper. The sensitivity achieved for chlorophyll-a detection was found to be at least 0.2 µg/L.

Characterizing treated wastewaters of different industries using clustered fluorescence EEM-PARAFAC and FT-IR spectroscopy: implications for downstream impact and source identification

The quantity and spectroscopic features of dissolved organic matter (DOM) in treated wastewaters were studied for up to 57 facilities across 12 industrial categories to evaluate the potential influences of the effluents on downstream ecosystems and the feasibility of spectroscopic techniques in discriminating pollution sources. The average dissolved organic carbon (DOC) concentration was 3.30±0.70-73.4±14.0 mg L(-1) for each category, high enough to pollute downstream waterbodies. The average specific UV absorbance at 254 nm (SUVA) for each category spanned a broad range between 0.79±0.24 and 5.35±1.41 L(mg m)(-1), suggesting a variable aromaticity of DOM. Fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC) identified four humic-like and two protein-like components. The EEMs were grouped into seven clusters, five of which were dominated by a single PARAFAC component in each cluster. Fourier transform infrared (FT-IR) spectroscopy revealed notable variations in relative intensities of several characteristic absorbance bands among different wastewaters. The large variability in SUVA, PARAFAC and FT-IR features indicated that the chemical composition of DOM greatly differ among industrial wastewaters, and further implied variable biogeochemical reactivity in downstream waterbodies. The results also suggested the potential of DOM features in discriminating different wastewaters, although the variations within each industrial category were also significant.

Occurrence and behaviors of fluorescence EEM-PARAFAC components in drinking water and wastewater treatment systems and their applications: a review

Fluorescence excitation emission matrices-parallel factor analysis (EEM-PARAFAC) is a powerful tool for characterizing dissolved organic matter (DOM), and it is applied in a rapidly growing number of studies on drinking water and wastewater treatments. This paper presents an overview of recent findings about the occurrence and behavior of PARAFAC components in drinking water and wastewater treatments, as well as their feasibility for assessing the treatment performance and water quality including disinfection by-product formation potentials (DBPs FPs). A variety of humic-like, protein-like, and unique (e.g., pyrene-like) fluorescent components have been identified, providing valuable insights into the chemical composition of DOM and the effects of various treatment processes in engineered systems. Coagulation/flocculation-clarification preferentially removes humic-like components, and additional treatments such as biological activated carbon filtration, anion exchange, and UV irradiation can further remove DOM from drinking water. In contrast, biological treatments are more effective for protein-like components in wastewater treatments. PARAFAC components have been proven to be valuable as surrogates for conventional water quality parameter, to track the changes of organic matter quantity and quality in drinking water and wastewater treatments. They are also feasible for assessing formations of trihalomethanes and other DBPs and evaluating treatment system performance. Further studies of EEM-PARAFAC for assessing the effects of the raw water quality and variable treatment conditions on the removal of DOM, and the formation potentials of various emerging DBPs, are essential for optimizing the treatment processes to ensure treated water quality.