Use of fluorescence EEM to monitor the removal of emerging contaminants in full scale wastewater treatment plants

Development of dissolved organic matter-based indicators to understand the degradation of organic contaminants in reverse osmosis concentrate from potable reuse systems

Reverse osmosis (RO)-based treatment of municipal wastewater effluent allows for potable reuse, but this process generates reverse osmosis concentrate (ROC) that needs further treatment before disposal. This study investigated the application of UV-based advanced oxidation processes (AOPs) to degrade nine contaminants of emerging concern (CECs) from real ROC waste streams, using UV-only and UV-AOPs with hydrogen peroxide, free chlorine, and persulfate. Dissolved organic matter (DOM) in ROC was characterized using fluorescence excitation emission matrix data and analyzed by a four-component parallel factor (PARAFAC) analysis model. UV-only treatment showed considerable removal of CECs that displayed high values of quantum yields and molar absorption coefficients. UV-AOP treatment of ROC exhibited heavy scavenging of reactive species during CEC degradation. A probe-based approach established that hydroxyl radical was the dominant reactive species in all UV-AOPs. A kinetic analysis of PARAFAC components of DOM showed that the visible humic-like and protein-like components exhibited the higher reaction kinetics compared to UV humic-like and nutrient-like components. The strong linear correlation of protein-like component and seven of the nine CECs across multiple AOPs indicated that they have similar reactivity, enabling the establishment of chemical-reactivity based surrogates for prediction CEC fate in ROC wastes.

Machine learning modeling of fluorescence spectral data for prediction of trace organic contaminant removal during UV/H2O2 treatment of wastewater

Dynamic feedback of the removal performance of trace organic contaminants (TrOCs) is essential towards economical advanced oxidation processes (AOPs), whereas the corresponding quick-response feedback methods have long been desired. Herein, machine learning (ML) multi-target regression random forest (MORF) models were developed based on the fluorescence spectra to predict the removal of TrOCs during UV/H2O2 treatment of municipal secondary effluent as a typical AOP. The predictive performance of the developed MORF model (R2 = 0.83-0.95) exhibited higher accuracy over the traditional linear regression models with R2 increased by ∼0.15. Furthermore, through feature importance analysis, the spectral regions of high importance were identified for different groups of TrOCs, thus enabling faster data acquisition due to remarkably reduced size of required fluorescence spectral scanning region. Specifically, the fluorescence regions Ex(235-275 nm)/Em(325-400 nm) and Ex(240-360 nm)/Em(325-450 nm) were found highly correlated with the removal of the TrOCs susceptible to both photodegradation and •OH degradation and those primarily subject to •OH degradation, respectively. In addition, the spectral regions of high importance were also individually identified for the investigated TrOCs during the AOP. Through providing an efficient ML-based feedback method to monitor TrOC removal during AOP, this study sheds light on the development of dynamic feedback-based strategies for precise and economical advanced treatment of wastewater.

Effects of photoaging on structure and characteristics of biofilms on microplastic in soil: Biomass and microbial community

Understanding of the environmental behaviors of microplastics is limited by a lack of knowledge about how photoaging influences biofilm formation on microplastics in soil. Here, original microplastics (OMPs) and photoaged-microplastics (AMPs) were incubated in soil to study the effect of photoaging on formation and characteristics of biofilm on the poly (butylene succinate) microplastics. Because photoaging decreased the hydrophobicity of the microplastic, the biomass of biofilm on the OMPs was nearly twice that on the AMPs in the early stage of incubation. However, the significance of the substrate on biomass in the biofilm declined as the plastisphere developed. The bacterial communities in the plastisphere were distinct from, and less diverse than, those in surrounding soil. The dominant genera in the OMPs and AMPs plastispheres were Achromobacter and Burkholderia, respectively, indicating that photoaging changed the composition of the bacterial community of biofilm at the genus level. Meantime, photoaging decreased the complexity and stability of the plastisphere bacterial community network. Results of Biolog ECO-microplate assays and functional prediction from amplicons showed that photoaging treatment enhanced the carbon metabolic capacity of the microplastic biofilm. This study provides new insights into the formation of plastispheres in soil.

Analysing N-nitrosamine occurrence and sources in karst reservoirs, Southwest China

N-nitrosamines in reservoir water have drawn significant attention because of their carcinogenic properties. Karst reservoirs containing dissolved organic matter (DOM) are important drinking water sources and are susceptible to contamination because of the fast flow of various contaminants. However, it remains unclear whether N-nitrosamines and their precursor, DOM, spread in karst reservoirs. Therefore, this study quantitatively investigated the occurrence and sources of N-nitrosamines based on DOM properties in three typical karst reservoirs and their corresponding tap water. The results showed that N-nitrosamines were widely spread, with detection frequencies > 85%. Similar dominant compounds, including N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosopyrrolidine, and N-nitrosodibutylamine, were observed in reservoirs and tap water, with average concentrations of 4.7-8.9 and 2.8-6.7 ng/L, respectively. The average carcinogenic risks caused by these N-nitrosamines were higher than the risk level of 10-6. Three-dimensional fluorescence excitation-emission matrix modeling revealed that DOM was composed of humus-like component 1 (C1) and protein-like component 2 (C2). Fluorescence indicators showed that DOM in reservoir water was mainly affected by exogenous pollution and algal growth, whereas in tap water, DOM was mainly affected by microbial growth with strong autopoietic properties. In the reservoir water, N-nitrosodiethylamine and N-nitrosopiperidine were significantly correlated with C2 and biological indicators, indicating their endogenously generated sources. Based on the principal component analysis and multiple linear regression methods, five sources of N-nitrosamines were identified: agricultural pollution, microbial sources, humus sources, degradation processes, and other factors, accounting for 46.8%, 36.1%, 7.82%, 8.26%, and 0.96%, respectively. For tap water, two sources, biological reaction processes, and water distribution systems, were identified, accounting for 75.7% and 24.3%, respectively. Overall, this study presents quantitative information on N-nitrosamines' sources based on DOM properties in typical karst reservoirs and tap water, providing a basis for the safety of drinking water for consumers.

Response of dissolved organic matter (DOM) and microbial community to submerged macrophytes restoration in lakes: A review

Microorganisms play a crucial role in the biogeochemical processes of Dissolved Organic Matter (DOM), and the properties of DOM also significantly influence changes in microbial community characteristics. This interdependent relationship is vital for the flow of matter and energy within aquatic ecosystems. The presence, growth state, and community characteristics of submerged macrophytes determine the susceptibility of lakes to eutrophication, and restoring a healthy submerged macrophyte community is an effective way to address this issue. However, the transition from eutrophic lakes dominated by planktic algae to medium or low trophic lakes dominated by submerged macrophytes involves significant changes. Changes in aquatic vegetation have greatly affected the source, composition, and bioavailability of DOM. The adsorption and fixation functions of submerged macrophytes determine the migration and storage of DOM and other substances from water to sediment. Submerged macrophytes regulate the characteristics and distribution of microbial communities by controlling the distribution of carbon sources and nutrients in the lake. They further affect the characteristics of the microbial community in the lake environment through their unique epiphytic microorganisms. The unique process of submerged macrophyte recession or restoration can alter the DOM-microbial interaction pattern in lakes through its dual effects on DOM and microbial commu-----nities, ultimately changing the stability of carbon and mineralization pathways in lakes, such as the release of methane and other greenhouse gases. This review provides a fresh perspective on the dynamic changes of DOM and the role of the microbiome in the future of lake ecosystems.

Impact of different classification schemes on discrimination of proteins with noise-contaminated spectra using laboratory-measured fluorescence data

Biological agents are important to detect and identify with respect to environmental contamination and public health. Noise contamination in fluorescent spectra is one of the contributors to the uncertainties of identification. In order to investigate the noise-tolerant capability provided by laboratory-measured excitation-emission matrix (EEM) fluorescence spectra that are used as a database, fluorescence properties of four proteinaceous biotoxin samples and ten harmless protein samples were characterized by EEM fluorescence spectra, and the predicting performance of models trained by laboratory-measured fluorescence data was tested and verified from validation data with noise-contaminated spectra. By means of peak signal of noise (PSNR) as an indicator of noise levels, the potential impact of noise contaminations on the characterization and discrimination of these samples was evaluated quantitatively. Different classification schemes utilizing multivariate analysis techniques of Principal Component Analysis (PCA), Random Forest (RF), and Multi-layer Perceptron (MPL) coupled with feature descriptors of differential transform (DT), Fourier transform (FT) and wavelet transform (WT) were conducted under different PSNR values. We systematically analyzed the performance of classification schemes by the case study at 20 PSNR and by statistical analysis from 1-100 PSNR. The results show that the spectral features with EEM-WT decreased the demanding number of input variables while retaining high performances in sample classification. The spectral features with EEM-FT presented the worst performance although having the largest number of features. The distributions of feature importance and contribution were found sensitive to noise contaminations. The classification scheme of PCA prior to MPL with EEM-WT as input presented an improvement in lower PSNR. These results indicate that robust features extracted by corresponding techniques are critical to enhancing the spectral differentiation capabilities among these samples and play an important role in eliminating the noise effect. The study of classification schemes for discriminating protein samples with noise-contaminated spectra presents tremendous potential for future developments in the rapid detection and identification of proteinaceous biotoxins based on three-dimensional fluorescence spectrometry.

Fabrication and optimization of paper chips from calcinated Fe-MOFs for rapid and in situ visual detection of tetracyclines in water environments

Antibiotics such as tetracyclines (TCs) have become a major threat to ecosystem safety and human health, as their abuse has caused the occurrence and proliferation of antibiotic-resistant bacteria and genes. Currently, there is still a lack of convenient in situ methods for the detection and monitoring of TC pollution in actual water systems. This research reports a paper chip based on the complexation of iron-based metal organic frameworks (Fe-MOFs) and TCs for rapid and in situ visual detection of representative oxytetracycline (OTC) pollution in water environments. The optimized complexation sample NH₂-MIL-101(Fe)- 350 obtained by calcination at 350 °C exhibited the highest catalytic activity and was then used for paper chip fabrication by printing and surface modification. Notably, the paper chip demonstrated a detection limit as low as 17.11 nmol L^-1 and good practicability in reclaimed water, aquaculture wastewater, and surface water systems, with OTC recovery rates of 90.6-111.4%. More importantly, the presence of dissolved oxygen (9.13-12.7 mg L^-1), chemical oxygen demand (0.52-12.1 mg L^-1), humic acid (< 10 mg L^-1), Ca²⁺, Cl^-, and HPO₄^2- (< 0.5 mol L^-1) had negligible interference on the detection of TCs by the paper chip. Therefore, this work has developed a promising method for rapid and in situ visual monitoring of TC pollution in actual water environments.

Molecular probing of dissolved organic matter and its transformation in a woolen textile wastewater treatment station

Woolen textile industry produces enormous wastewater (WTIW) with high pollution loads, and needs to be treated by wastewater treatment stations (WWTS) before centralized treatment. However, WTIW effluent still contains many biorefractory and toxic substances; thus, comprehensive understandings of dissolved organic matter (DOM) of WTIW and its transformation are essential. In this study, total quantity indices, size exclusion chromatography, spectral methods, and Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) were used for comprehensively characterizing DOM and its transformation during full-scale treatments, including influent, regulation pool (RP), flotation pool (FP), up-flow anaerobic sludge bed (UA), anaerobic/oxic (AO) and effluent. DOM in influent featured a large molecular weight (5-17 kDa), toxicity (0.201 HgCl₂ mg/L), and a protein content of 338 mg C/L. FP largely removed 5-17 kDa DOM with the formation of 0.45-5 kDa DOM. UA and AO removed 698 and 2042 chemicals, respectively, which were primarily saturated components (H/C > 1.5); however, both UA and AO contributed to the formation of 741 and 1378 stable chemicals, respectively. Good correlations were found among water quality indices and spectral/molecular indices. Our study reveals the molecular composition and transformation of WTIW DOM during treatments and encourages the optimization of the employed processes in WWTS.

Linking pharmaceutical residues to dissolved organic matter and aquatic bacterial communities in a highly urbanized bay

Pharmaceuticals are causing environmental concerns associated with their widespread distribution in aquatic ecosystems. The environmental fate and behavior of pharmaceutical residues are related to dissolved organic matter and bacterial communities, both of which are strongly influenced by human activities. However, the relationships among pharmaceutical pollution, dissolved organic matter pool, and bacterial community structure under the pressure of human activities are still unclear, especially in highly urbanized bay areas. In this study, we investigated the occurrence and distribution of 35 pharmaceuticals in a typical urbanized bay (Hangzhou Bay) in Eastern China, and analyzed their relationships with dissolved organic matter and aquatic bacterial community structure. The target pharmaceuticals were ubiquitously detected in surface water samples, with their concentrations ranging from undetectable to 263 ng/L. The detected pharmaceuticals were mostly sulfonamides, macrolides, antidepressants, and metabolites of stimulants. Significant positive correlations were observed between the concentrations of pharmaceuticals and the intensity of human activities. Strong correlations also emerged between the concentration of antidepressants and the speed of urban expansion, as well as between the concentration of cardiovascular drugs and the population density or nightlight index. Three fluorescent components (protein-like C1, terrestrial humic-like C2, protein tryptophan-like C3) were significantly positively correlated with the total concentration of pharmaceuticals. Pharmaceutical pollution reshaped aquatic bacterial communities, based on the close correlation observed between pharmaceutical concentration and bacterial community structure. The results elucidate the potential dynamics of dissolved organic matter pool and aquatic bacterial communities in response to pharmaceutical pollution in urbanized bay ecosystems.

Using fluorescence index (FI) of dissolved organic matter (DOM) to identify non-point source pollution: The difference in FI between soil extracts and wastewater reveals the principle

Traceability and quantification of agricultural non-point source pollution are of great significance to water pollution management in watersheds. In this study, fluorescence components and indices of dissolved organic matter (DOM) in the river, wastewater and soil extracts from different land use types were analyzed to screen indicators that can identify non-point source pollution in 15 independent small watersheds located at the southern Qinling piedmont (China). The results showed that DOM fluorescence components in soil extracts among different land uses didn't have significant differences. The values of humification index (HIX) did not vary obviously between soil extracts and wastewater, with the mean values ranging from 3.4 to 3.9. However, the average value of fluorescence index (FI) of effluent wastewater was about 2.1 and did not change significantly through treatment. The FI values of soil extracts were generally between 1.5 and 1.7. The FI values in most river waters were just between the FI values of wastewater and soil extracts. This phenomenon indicated that FI could be used as an indicator to distinguish point source and non-point source pollution. Besides, the correlation analysis showed a significant positive relationship between the non-point source pollution calculated by FI and δ¹⁵N. The relationship was different in January and July, but further confirmed the reliability of using FI to quantify non-point source pollution. This study demonstrated the feasibility of using FI to identify non-point source pollution. When combined with handheld fluorescence spectrometers and unmanned aerial vehicle-mounted fluorescence spectrometers, this method may be adopted more widely.

Remote sensing of fluorescent humification levels and its potential environmental linkages in lakes across China

The pollution or eutrophication affected by dissolved organic matter (DOM) composition and sources of inland waters had attracted concerns from the public and government in China. Combined with remote sensing techniques, the fluorescent DOM (FDOM) parameters accounted for the important part of optical constituent as chromophoric dissolved organic matter (CDOM) was a useful tool to trace relative DOM sources and assess the trophic states for large-scale regions comprehensively and timely. Here, the objective of this research is to calibrate and validate a general model based on Landsat 8 OLI product embedded in Google Earth Engine (GEE) for deriving humification index (HIX) based on EEMs in lakes across China. The Landsat surface reflectance was matched with 1150 pairs fieldtrip samples and the nine sensitive spectral variables with good correlation with HIX were selected as the inputs in machine learning methods. The calibration of XGBoost model (R² = 0.86, RMSE = 0.29) outperformed other models. Our results indicated that the entire dataset of HIX has a strong association with Landsat reflectance, yielding low root mean square error between measured and predicted HIX (R² = 0.81, RMSE = 0.42) for lakes in China. Finally, the optimal XGBoost model was used to calculate the spatial distribution of HIX of 2015 and 2020 in typical lakes selected from the Report on the State of the Ecology and Environment in China. The significant decreasing of HIX from 2015 to 2020 with trophic states showed positive control of humification level of lakes based on the published document of Action plan for prevention and control of water pollution in 2015 of China. The calibrated model would greatly facilitate FDOM monitoring in lakes, and provide indicators for relative DOM sources to evaluate the impact of water protection measures or human disturbance effect from Covid-19 lockdown, and offer the government supervision to improve the water quality management for lake ecosystems.

Spectral change of dissolved organic matter after extracted by solid-phase extraction and its feasibility in predicting the acute toxicity of polar organic pollutants in textile wastewater

Spectroscopic parameters can be used as proxies to effectively trace the occurrence of organic trace contaminants, but their suitability for predicting the toxicity of discharged industrial wastewater with similar spectra is still unknown. In this study, the organic contaminants in treated textile wastewater were subdivided and extracted by four commonly-used solid-phase extraction (SPE) cartridges, and the resulting spectral change and toxicity of textile effluent were analyzed and compared. After SPE, the spectra of the percolates from the four cartridges showed obvious differences with respect to the substances causing the spectral changes and being more readily adsorbed by the WAX cartridges. Non-target screening results showed source differences in organic micropollutants, which were one of the main contributors leading to their spectral properties and spectral variations after SPE in the effluents. Two fluorescence parameters (C1 and humic-like) identified by the excitation emission matrix-parallel factor analysis (EEM-PARAFAC) were closely correlated to the toxicity endpoints for Scenedesmus obliquus (inhibition ratios of cell growth and Chlorophyll-a synthesis), which can be applied to quantitatively predict the change of toxicity effect caused by polar organic pollutants. The results would provide novel insights into the spectral feature analysis and toxicity prediction of the residual DOM in industrial wastewater.

Linking fluorescent dissolved organic matters to microbial carbon metabolism in the overlying water during submerged macrophyte Potamogeton crispus L decomposition in the presence/absence of Vallisneria natans

Multi-species submerged plants grow with succession patterns in the same habit and play an important role in the aquatic ecosystems. The decomposition of submerged plants in aquatic environments was a disturbance that affected the water quality and microbial community structures. However, the responses of the microbial community function in surface water to the disturbance remain poorly understood. In this study, the effects of submerged macrophyte Potamogeton crispus L decomposition on the water quality and microbial carbon metabolism functions (MCMF) in the overlying water were investigated in the presence/absence of Vallisneria natans. The result showed that the decomposition rapidly released a large amount of organic matter and nutrients into the overlying water. The presence of Vallisneria natans promoted the removal of dissolved organic carbon and fluorescent component C3, resulting in lower values of the percentage content of C3 (C3%). Under various decomposition processes, the MCMF changed over time and significantly negatively correlated with C3%. The functional diversity of MCMF significantly correlated with the fluorescence organic matters, such as the richness and Simpson index correlated with the amount of C1, C1+C2+C3, and C3%. But UV-visible absorption indexes and nutrients in the overlying water had no relationship with the MCMF, except for the total nitrogen correlated with the richness. These results suggested that under various decomposition conditions, the fluorescent dissolved organic matter could be used as an indicator for quick prediction of MCMF in surface water.

EEM-PARAFAC as a convenient methodology to study fluorescent emerging pollutants degradation: (fluoro)quinolones oxidation in different water matrices

Commercial (fluoro)quinolones ((F)Qs), ciprofloxacin (CIP), enrofloxacin (ENR), ofloxacin (OFL), oxolinic acid (OA) and flumequine (FLU) (3 μM each), were degraded with solar-photo-Fenton in a compound parabolic concentrator photoreactor (total volume 5 L) in ultra-pure water at pH = 5.0, salty water at pH = 5.0, and simulated wastewater at pH = 5.0 and 7.5. Iron speciation (its hydrolysis and the complexation with (F)Qs 15 μM and/or chlorides 0.5 M) was calculated at pH 5.0, observing, negligible formation of Fe(III)-chloride complexes, and that >99 % of the total (F)Qs are forming complexes stoichiometry 1:1 with Fe(III) (which also increases the percentage of Fe(OH)²⁺), being minoritarian the free antibiotic form. On the other hand, EEM-PARAFAC (fluorescence excitation-emission matrices-parallel factor analysis) was employed to simultaneously study the behaviour of: i) 4 structure-related groups corresponding to parent pollutants and slightly oxidised by-products, ENR-like (including CIP), OFL-like, OA-like, FLU-like; ii) intermediates still showing (F)Q characteristics (exhibiting analogous fluorescent fingerprint to ENR-like one, but shifted to shorter wavelengths); iii) humic-like substances. The scores from the 4 PARAFAC components corresponding to the parent pollutants were plotted vs. accumulated energy, exhibiting slower decay than their individual removals (measured with HPLC-UV/vis) due to the contribution of the aforementioned by-products to the overall fluorescence. Moreover, thiabendazole (TBZ) 3 μM was added as fluorescence interference. The presence of (F)Qs greatly enhanced TBZ degradation due to (F)Q-Fe(III) complex formation, keeping iron active at pH = 5.0 for Fenton process. The EEM-PARAFAC model was able to recognise the former six components plus an additional one attributable to TBZ-like.

Alternative methods of monitoring emerging contaminants in water: a review

Anthropogenic activities have steadily increased the release of emerging contaminants (ECs) in aquatic bodies, and these ECs may have adverse effects on humans even at their trace (μg L^-1) levels. Their occurrence in wastewater systems is more common, and the current wastewater treatment facilities are inefficient in eliminating many of such persistent ECs. "Gold standard" techniques such as chromatography, mass spectrometry, and other high-resolution mass spectrometers are used for the quantification of ECs of various kinds, but they all have significant limitations. This paper reviews the alternative methods for EC detection, which include voltammetry, potentiometry, amperometry, electrochemical impedance spectroscopy (EIS) based electrochemical methods, colorimetry, surface-enhanced Raman spectroscopy (SERS), fluorescence probes, and fluorescence spectroscopy-based optical techniques. These alternative techniques have several advantages over conventional techniques, including low sample volume, excludes solid phase extraction procedure, high sensitivity, selectivity, portability, reproducibility, rapidity, low cost, and the ability to monitor ECs in real time. This review summarises each of the alternative methods for detecting ECs in water samples and their respective limits of detection (LODs). The sensitivity of each technique varied depending on the type of EC measured, type of electrochemical probe and electrode, substrates, type of nanoparticle (NP), the physicochemical parameters of water samples tested, and more. Nevertheless, this paper also focuses on some of the current challenges encountered by these alternative methods in monitoring ECs.

Transformation of dissolved organic matter during biological wastewater treatment and relationships with the formation of nitrogenous disinfection byproducts

Nitrogenous disinfection byproducts (N-DBPs) can be produced from dissolved organic matter (DOM) during the disinfection of secondary wastewater effluent. This study examined the transformation of DOM and the abatement of N-DBP precursors during different types of biological wastewater treatment (e.g., anaerobic/anoxic/oxic activated sludge processes and membrane bioreactor) using high-performance size exclusion chromatography (HPSEC) with dissolved organic carbon, UV, and fluorescence detectors. DOM with molecule weight (MW) larger than 3 kDa and protein-like substances smaller than 0.3 kDa was effectively bio-transformed, whereas DOM fractions with MW in the range of 0.3-3 kDa were the most bio-refractory. Complete nitrification was beneficial to the removal of small amino sugar-like and protein-like molecules (< 0.3 kDa). Haloacetonitrile (HAN) precursors were recalcitrant to biological treatment with a median removal of 17%. Halonitromethane (HNM) and N-nitrosamine (NA) precursors tended to be effectively removed in complete nitrification conditions. The abundance of low-molecular-size protein-like substances (< 0.3 kDa) was significantly correlated with the formation potential of HNM, NA, and total N-nitrosamine (TONO) in post-chloramination (r = 0.81, 0.62, and 0.68, respectively, p < 0.01). This study improved the understanding of DOM transformation and the removal of N-DBPs precursors in wastewater treatment and pointed out the benefit of provision of complete nitrification in removing low-molecular-size protein-like substances and NA and HNM precursors.

Organic removal from coal-to-chemical brine by a multistage system of adsorption-regeneration and electrochemically driven UV/chlorine processes

Treatment of coal-to-gas brine (CGB) is a great challenge since it contains elevated inorganic salts and a high level of toxic and bio-accumulative organics. In this study, CGB treatment was conducted by adsorptionregeneration and electrochemically driven UV/chlorine (E-UV/Cl₂) processes. LS-109D macroporous resin was optimal adsorbent primarily due to unique pore structure, which preferably adsorbed the aromatic fluorescent components with quenching Cl∙ effect and low molecular weight acids recalcitrant to ∙OH. The E-UV/Cl₂ process outperformed the UV photolysis process and electrochemical advanced oxidation processes (EAOPs) for oxidation of organic compounds due to its full utilization of Cl^- in CGB to produce highly active oxidation agents. Thanks to the synergy between process units in organic matter removal, dissolved organic carbon (DOC) of CGB was reduced from 163.41 mg/L to 26.58 mg/L by the multistage system. Furthermore, the CGB with characteristics of high fluorescence and molecular weight (MW) distribution was converted to effluent with low fluorescence and MW distribution. The exhausted LS-109D was regenerated by ultrasound-assisted hot water elution at 363 K. After pretreated by ozonation, the eluate can be easily treated by biological process. The study suggests that the multistage system can provide an effective treatment option for removing organics from CGB.

Enhancement of membrane fouling mitigation and trace organic compounds removal by electric field in a microfiltration reactor treating secondary effluent of a municipal wastewater treatment plant

Applying an electric field in the membrane filtration was an effective method to alleviate membrane fouling and enhance the trace organic compounds (TrOCs) removal. The secondary effluent of a municipal wastewater treatment plant was used as feed water to evaluate the performance of the electric field coupled microfiltration system. Applying a 1.25 V voltage reduced 22.9% membrane fouling by electrophoretic force, and the membrane fouling was alleviated by 70.8% at 3 V by electrochemical oxidation and electric field force. At 3 V, active chlorine and hydroperoxide generated on the electrodes and the acidic environment formed around the anode significantly inhibited the growth of microorganisms and their attachment on the membrane surface, and thus reduced the membrane fouling formed by microorganisms. Electrochemical oxidation also removed the protein in wastewater and changed the main organic components of membrane fouling from microorganisms, protein, and polysaccharide to humic substances and polysaccharide. Furthermore, the electrophoretic force and acidic environment reduced the electrostatic repulsion of humic substances and made them tend to aggregate and form hydrophilic porous fouling structures, which obviously lowered filtration resistance and showed significant membrane fouling mitigation. Also, the electric field effectively enhanced the removal of target TrOCs through electrochemical oxidation and electric field force improving the elimination of TrOCs from 8.5% ~ 26.1% at 0 V to 35.9% ~ 84.8% at 3 V.

Application Progress of O3/UV Advanced Oxidation Technology in the Treatment of Organic Pollutants in Water

Organic pollution is a significant challenge in environmental protection, especially the discharge of refractory organic pollutants in chemical production and domestic use. The biological treatment method of traditional sewage treatment plants cannot degrade such pollutants, which leads to the continuous transfer of these pollutants into the water environment. Therefore, it is necessary to study clean and efficient advanced treatment technologies to degrade organic pollutants. The ozone/UV advanced oxidation process (O3/UV) has attracted extensive attention. This paper summarizes the reaction mechanism of O3/UV and analyzes its application progress in industrial wastewater, trace polluted organic matter and drinking water. The existing research results show that this technology has an excellent performance in the degradation of organic pollutants and has the characteristics of clean and environmental protection. In addition, the control of bromate formation and its economy is evaluated, and its operating characteristics and current application scope are summarized, which has a practical reference value for the follow-up in-depth study of the O3/UV process.

Effect of colloidal fluorescence properties on the complexation of chloramphenicol and carbamazepine to the natural aquatic colloids

The complexation mechanism between pharmaceuticals and natural colloids is still uncertain due to the complexity, heterogeneity, and polydispersity of colloids. Therefore, this study investigated the effect of fluorescence properties on the complexation of chloramphenicol (CAP) and carbamazepine (CBZ) to the colloids from Poyang Lake Basin based on the multiple spectroscopic techniques and methods. Three-dimensional excitation-emission matrix fluorescence spectroscopy-parallel factor analysis results illustrated that two humic-like components and two protein-like components of colloids from the rivers and lakes were identified, with the much higher fluorescence intensity of the protein-like substance observed in lake samples. The protein-like substance decreased dramatically with the addition of CAP and CBZ, suggesting its higher binding capacity towards these drugs, especially for CBZ. In addition, the fluorescence quenching titration was proceeded to explore the binding mechanism between the colloids and the pharmaceuticals. Results of synchronous fluorescence spectra and two-dimensional correlation spectroscopy demonstrated that the fluorescence quenching effect occurred preferentially between the protein-like substances and the pharmaceuticals, with the stronger complexation for CBZ. Ryan-Weber model fitting results showed that the stability constant ranged from 4.02 to 5.04 with the higher binding capacity observed for the tryptophan-like substance. Combined, the fluorescence components in aquatic colloids could be significantly impacted the complexation of the pharmaceuticals. This study provides deep insights into the fate and pollution protection of pharmaceuticals.

Fluorescence Characteristics of Coalbed Methane Produced Water and Its Influence on Freshwater Bacteria in the South Qinshui Basin, China

Production of coalbed methane (CBM) resources commonly requires using hydraulic fracturing and chemical production well additives. Concern exists for the existence of chemical compounds in CBM produced water, due to the risk of environmental receptor contamination. In this study, parallel factor method analysis (PARAFAC), fluorescence index, and the fluorescence area integral methods were used to analyse the properties of CBM produced water sampled from Shizhuang Block (one of the most active CBM-producing regions in the Qinshui Basin). A culture experiment was designed to determine the effect of discharged CBM produced water on microorganisms in freshwater. Water quality analysis shows the hydrochemistry of most water samples as Na-HCO₃ type produced water of CBM appears as a generally weak alkaline (pH 8.69 ± 0.185) with high salinity, high alkalinity, and a high chemical oxygen demand (COD) value. Three individual components were identified by using parallel factor method analysis as humic-like components (C1), fulvic-like components (C2), and amino acid-like substances (C3). The fluorescence characteristic index comprehensively explains that the fluorescent substances in CBM produced water has the characteristics of a low degree of humification and a high recent self-generating source. The region integration results of characteristic peaks show that tyrosine-like and tryptophan-like materials account for more than 67% of fluorescent substances in CBM produced water. The addition of produced water from coalbed methane promotes the growth of freshwater bacteria, and this process is accompanied by the decrease of the proportion of fulvic acid, humic acid, and the increase of the proportion of soluble microbial metabolites. This paper proposes a convenient method for organic matter identification of CBM produced water and provides some theoretical support and reference for the improvement of CBM water treatment and utilization.

Glucose Addition Enhanced the Advanced Treatment of Coking Wastewater

Biological processes have high removal efficiencies and low operational costs, but the secondary effluent of coking wastewater (CWW), even at a low concentration, is difficult for microorganisms to degrade directly. In this study, glucose was used as a carbon source and co-metabolic substrate for microbial acclimation in order to enhance the advanced treatment of coking wastewater (CWW). The removal performance of the pollutants, especially recalcitrant compounds, was studied and the changes in the microbial community structure after activated sludge acclimation were analyzed. The effect of glucose addition on the secondary biochemical effluent of coking wastewater (SBECW) treatment by the acclimated sludge was further studied by a comparison between the performance of two parallel reactors seeded with the acclimated sludge. Our results showed that the concentrations of chemical oxygen demand (COD), total organic carbon (TOC), and UV absorption at 254 nm (UV254) of the wastewater decreased in the acclimation process. Refractory organic matter, such as polycyclic aromatic hydrocarbons and nitrogen-containing heterocyclics, in the SBECW was effectively degraded by the acclimated sludge. High-throughput sequencing revealed that microbes with a strong ability to degrade recalcitrant compounds were enriched after acclimation, such as Thauera (8.91%), Pseudomonas (3.35%), and Blastocatella (10.76%). Seeded with the acclimated sludge, the reactor with the glucose addition showed higher COD removal efficiencies than the control system without glucose addition (p < 0.05). Collectively, glucose addition enhanced the advanced treatment of coking wastewater (CWW).

Evaluation of Sample Preparation Methods for Non-Target Screening of Organic Micropollutants in Urban Waters Using High-Resolution Mass Spectrometry

Non-target screening (NTS) has gained interest in recent years for environmental monitoring purposes because it enables the analysis of a large number of pollutants without predefined lists of molecules. However, sample preparation methods are diverse, and few have been systematically compared in terms of the amount and relevance of the information obtained by subsequent NTS analysis. The goal of this work was to compare a large number of sample extraction methods for the unknown screening of urban waters. Various phases were tested for the solid-phase extraction of micropollutants from these waters. The evaluation of the different phases was assessed by statistical analysis based on the number of detected molecules, their range, and physicochemical properties (molecular weight, standard recoveries, polarity, and optical properties). Though each cartridge provided its own advantages, a multilayer cartridge combining several phases gathered more information in one single extraction by benefiting from the specificity of each one of its layers.

A Review on Emerging Pollutants in the Water Environment: Existences, Health Effects and Treatment Processes

Emerging pollutants (EPs), also known as micropollutants, have been a major issue for the global population in recent years as a result of the potential threats they bring to the environment and human health. Pharmaceuticals and personal care products (PPCPs), antibiotics, and hormones that are used in great demand for health and cosmetic purposes have rapidly culminated in the emergence of environmental pollutants. EPs impact the environment in a variety of ways. EPs originate from animal or human sources, either directly discharged into waterbodies or slowly leached via soils. As a result, water quality will deteriorate, drinking water sources will be contaminated, and health issues will arise. Since drinking water treatment plants rely on water resources, the prevalence of this contamination in aquatic environments, particularly surface water, is a severe problem. The review looks into several related issues on EPs in water environment, including methods in removing EPs. Despite its benefits and downsides, the EPs treatment processes comprise several approaches such as physico-chemical, biological, and advanced oxidation processes. Nonetheless, one of the membrane-based filtration methods, ultrafiltration, is considered as one of the technologies that promises the best micropollutant removal in water. With interesting properties including a moderate operating manner and great selectivity, this treatment approach is more popular than conventional ones. This study presents a comprehensive summary of EP’s existence in the environment, its toxicological consequences on health, and potential removal and treatment strategies.

Tracking spatio-temporal dynamics of fluorescence characteristics of Huangpu River, China by parallel factor analysis: Correlation with disinfection by-product precursor and pesticide level variations

The components and characteristics of dissolved organic matter (DOM), the main precursor of toxic disinfection by-products (DBPs), have attracted increasing attention in water sources. In this study, fluorescence excitation-emission matrix (EEM) coupled with parallel factor (PARAFAC) analysis was used to investigate the DOM fluorescence characteristics of river water along the Huangpu River, China. Four fluorescence components were identified, including two protein-like components (C1 and C2) and two humic-like components (C3 and C4). The fluorescence characteristics showed spatial and temporal variations with the highest total fluorescence intensities observed in autumn, and the increased relative abundance of humic-like substance in the metropolitan area of Shanghai. Fluorescence index and biological index indicated that the DOM of Huangpu River water had both terrestrial and microbial origins and mainly autochthonous characteristic. Moreover, the formation potentials (FPs) of DBP for Huangpu River water were determined, and trihalomethanes were the predominant species formed in all samples. The correlation analysis further showed that PARAFAC C4 (microbial humic-like fluorescence) significantly correlated with the FP of N-DBPs, providing an insight for drinking water treatment to control specific DBPs precursor. In addition, the humic-like components also correlated with the concentrations of triazole and organophosphate pesticides detected in the Huangpu River. These results indicated that fluorescence-PARAFAC analysis is a promising tool to assess the DBPFPs and pesticide occurrence in surface waters.

Characterization and biogeochemical implications of dissolved organic matter in aquatic environments

Dissolved organic matter (DOM) is viewed as one of the most chemically active organic substances on earth. It plays vital roles in the fate, bioavailability and toxicity of aquatic exogenous chemical species (e.g., heavy metals, organic pollutants, and nanomaterials). The characteristics of DOM such low concentrations, salt interference and complexity in aquatic environments and limitations of pretreatment for sample preparation and application of characterization techniques severely limit understanding of its nature and environmental roles. This review provides a characterization continuum of aquatic DOM, and demonstrate its biogeochemical implications, enabling in-depth insight into its nature and environmental roles. A synthesis of the effective DOM pretreatment strategies, comprising extraction and fractionation methods, and characterization techniques is presented. Additionally, the biogeochemical dynamics of aquatic DOM and its environmental implications are discussed. The findings indicate the collection of representative DOM samples from water as the first and critical step for characterizing its properties, dynamics, and environmental implications. However, various pretreatment procedures may alter DOM composition and structure, producing highly variable recoveries and even influencing its subsequent characterization. Therefore, complimentary use of various characterization techniques is highly recommended to obtain as much information on DOM as possible, as each characterization technique exhibits various advantages and limitations. Moreover, DOM could markedly change the physical and chemical properties of exogenous chemical species, influencing their transformation and mobility, and finally altering their potential bioavailability and toxicity. Several research gaps to be addressed include the impact of pretreatment on the composition and structure of aquatic DOM, molecular-level structural elucidation for DOM, and assessment of the effects of DOM dynamics on the fate, bioavailability and toxicity of exogenous chemical species.

Removal of disinfection by-product precursors in drinking water treatment processes: Is fluorescence parallel factor analysis a promising indicator?

This work investigated the removal efficiency of disinfection by-product (DBP) precursors by different drinking water treatment processes and evaluated the feasibility of using fluorescence components removal as an indicator. A four-component (including tryptophan-like, protein-bound, tyrosine-like, and humic-like components) parallel factor analysis model was developed basing on 288 fluorescence excitation-emission matrices. Among all treatment processes, coagulation-sedimentation process showed the best performance, with mean removal ratios of 30% in total fluorescence intensity and 31% in total formation potential (FP) of DBPs, respectively. It preferentially removed humic-like component C4 (43%). Advanced treatment processes were less effective in comparison. Ozone and biological activated carbon (BAC) combined process reduced 20% of total fluorescence intensity, while ultrafiltration process reduced < 3%. Ozonation and BAC filtration preferentially removed free amino acids (i.e., C1 and C3) and protein-bound (i.e., C2) components, with mean removal ratios of 12% and 17%, respectively. Significant correlations (p < 0.01, double-tailed) were observed between four fluorescence components removal and FPs reduction of three trihalomethanes, dichloroacetonitrile (DCAN), and 1,1-dichloropropanone (1,1-DCP). Specifically, the correlation coefficients for three trihalomethanes and 1,1-DCP followed the order of C4 > C1 > C2 > C3, while the order for DCAN was C2 > C4 > C1 > C3.

Formation and control of disinfection by-products from iodinated contrast media attenuation through sequential treatment processes of ozone-low pressure ultraviolet light followed by chlorination

Different groups of disinfection by-products (DBPs) were studied through the degradation of iopamidol by the sequential oxidation process of ozone-low pressure ultraviolet light (O₃-LPUV) followed by chlorination. This paper investigates the attenuation of iopamidol under this sequential treatment and the effect of chlorine contact time (30 min versus 3 days) to control the formation potential of DBPs: trihalomethanes (THMs), haloacetonitriles (HANs) and haloacetamides (HAMs). Thirty target DBPs among the 9 iodinated-DBPs (I-DBPs), were monitored throughout the sequential treatment. Results showed that O₃-LPUV removed up to 99% of iopamidol, while ozone and LPUV alone removed only 90% and 76% respectively. After chlorine addition, O₃-LPUV yielded 56% lower I-DBPs than LPUV. Increasing chlorine contact time resulted in higher concentrations of all DBP groups (THMs, HANs, and HAMs), with the exception of I-DBPs. One new iodinated-haloacetamide, namely chloroiodoacetamide (CIACM) and one iodoacetonitrile (IACN) were detected. These results suggest the iodine incorporated in iopamidol may be a precursor for iodinated-nitrogenous-DBPs, which are currently not well studied.

Comparison of AOPs at pilot scale: Energy costs for micro-pollutants oxidation, disinfection by-products formation and pathogens inactivation

This work evaluated different advanced oxidation processes (AOPs) operated at pilot-scale as tertiary treatment of municipal wastewater in terms of energy efficiency, disinfection by-products formation and pathogens inactivation. Investigated AOPs included UV/H₂O₂, UV/Cl₂, O₃, O₃/UV, H₂O₂/O₃/UV, Cl₂/O₃/UV. AOPs were operated using various ozone doses (1.5-9 mg L^-1), and UV fluences (191-981 mJ cm^-2). Electrical energy costs necessary for the oxidation of contaminants of emerging concern (CEC) (i.e., carbamazepine, fluoxetine, gemfibrozil, primidone, sulfamethoxazole, trimethoprim) were calculated using the electrical energy per order (E_EO) parameter. Ozonation resulted by far the most energy efficient process, whereas UV/H₂O₂ and UV/Cl₂ showed the highest energy costs. Energy costs for AOPs based on the combination of UV and ozone were in the order O₃/UV ≈ Cl₂/O₃/UV > H₂O₂/O₃/UV, and they were significantly lower than energy costs of UV/H₂O₂ and UV/Cl₂ processes. Cl₂/O₃/UV increased bromate formation, O₃/UV and O₃ had same levels of bromate formation, whereas H₂O₂/O₃/UV did not form bromate. In addition, UV photolysis resulted an effective treatment for NDMA mitigation even in combination with ozone and chlorine in AOP technologies. Ozonation (doses of 1.5-6 mg L^-1) was the least effective process to inactivate somatic coliphages, total coliform, escherichia coli, and enterococci. UV irradiation was able to completely inactivate somatic coliphages, total coliform, escherichia coli at low fluence (191 mJ cm^-2), whereas enterococci were UV resistant. AOPs that utilized UV irradiation were the most effective processes for wastewater disinfection resulting in a complete inactivation of selected indicator organisms by low ozone dose (1.5 mg L^-1) and UV fluence (191-465 mJ cm^-2).

A year-long cyclic pattern of dissolved organic matter in the tap water of a metropolitan city revealed by fluorescence spectroscopy

Delivering drinking water with stable quality in metropolitan cities is a big challenge. This study investigated the year-long dynamics of dissolved organic matter (DOM) in the tap water and source water of a metropolitan city in southern China using fluorescence spectroscopy. The DOM detected in the tap water, and source water of Shenzhen city was season and location-dependent. A year-long cyclic trend of DOM was found with predominate protein-like fluorescence in the dry season compared to the humic-like enriched DOM in the wet season. A general DOM pattern was estimated by measuring the shift in dominant fluorescence regions on the excitation-emission matrix (EEM). The difference in fluorescent DOM (FDOM) composition (in terms of the ratio of protein-like to humic-like fluorescence) was above 200% between wet and dry seasons. The taps associated with reservoirs receiving water from the eastern tributary of Dongjiang River showed significant changes in protein-like contents than the taps with source water originating from the western part of the river. This study highlights the importance of optimizing drinking water treatment plants' operational conditions after considering seasonal changes and source water characteristics.

Comparison of the new Cl2/O3/UV process with different ozone- and UV-based AOPs for wastewater treatment at pilot scale: Removal of pharmaceuticals and changes in fluorescing organic matter

This work critically compared the removal of fluorescing PARAFAC components and selected pharmaceuticals (carbamazepine, fluoxetine, gemfibrozil, primidone, sulfamethoxazole, trimethoprim) from a tertiary wastewater effluent by different UV- and ozone-based advanced oxidation processes (AOPs) operated at pilot-scale. Investigated AOPs included UV/H₂O₂, UV/Cl₂, O₃, O₃/UV, H₂O₂/O₃/UV, and the new Cl₂/O₃/UV. AOPs comparison was accomplished using various ozone doses (0-9 mg/L), UV fluences (191-981 mJ/cm²) and radical promoter concentrations of Cl₂ = 0.04 mM and H₂O₂ = 0.29 mM. Chlorine-based AOPs produced radical species that reacted more selectively with pharmaceuticals than radical species and oxidants generated by other AOPs. Tryptophan-like substances and humic-like fluorescing compounds were the most degraded components by all AOPs, which were better removed than microbial products and fulvic-like fluorescing substances. Removal of UV absorbance at 254 (UV₂₅₄) nm was always low. Overall, chlorine-based AOPs were more effective to reduce fluorescence intensities than similar H₂O₂-based AOPs. The Cl₂/O₃/UV process was the most effective AOP to degrade all target micro-pollutants except primidone. On the other hand, the oxidation performance of pharmaceuticals by other ozone-based AOPs followed the order H₂O₂/O₃/UV > O₃/UV > O₃. UV/Cl₂ process outcompeted UV/H₂O₂ only for the removal of trimethoprim and sulfamethoxazole. Correlations between the removal of pharmaceuticals and spectroscopic indexes (PARAFAC components and UV₂₅₄) had unique regression parameters for each compound, surrogate parameter and oxidation process. Particularly, a diverse PARAFAC component for each investigated AOP resulted to be the most sensitive surrogate parameter able to monitor small changes of pharmaceuticals removal.

Surrogates for on-line monitoring of the attenuation of trace organic contaminants during advanced oxidation processes for water reuse

The large number of trace organic contaminants (TrOCs) in wastewater has resulted in severe concerns to human health. Ozonation and UV/H₂O₂ are widely used to remove TrOCs in wastewater treatment process. Owing to the trace concentrations of TrOCs in wastewater, real-time monitoring of the abatement efficiency of TrOCs through ozonation and UV/H₂O₂ is quite challenging. Instead of a direct measurement of all the TrOCs, the research community has begun to use different surrogates to monitor the attenuation of TrOCs during AOPs. Various surrogates have been developed over the past few decades. In this review, the different types of surrogates are summarized, including ultraviolet spectroscopy and fluorescence spectroscopy. Strong linear correlations have been found for the removal of TrOCs using AOPs, and the abatement of UV absorption spectroscopy at 254 nm or total fluorescence (TF). Moreover, a two-phase linear correlation can better describe the ozone-resistant TrOCs compared with a single linear correlation. Two different kinds of predictive models exist that use surrogates as the input for ozonation: the regression model and kinetic model. The development of the models requires a further understanding of the impacts of water quality, seasonal variations, and storm events on the kinetic parameters. For the in situ monitoring system, the light-emitting diode (LED) is one of the most promising light sources, although the sensitivity and accuracy still need to be improved.

A review of the biotransformations of priority pharmaceuticals in biological wastewater treatment processes

Wastewater effluent discharges have been considered as one of the main sources of synthetic chemicals entering into the aquatic environment. Even though they occur at low concentrations, pharmaceutically active compounds (PhACs) can have an impact on ecological toxicity that affects aquatic organisms. Moreover, new regulations in development toward preserving water quality reinforces the increasing need to monitor and abate some PhACs in wastewater treatment plants (WWTPs), where they are typically only partially eliminated. Unlike most previous reviews, we have focussed on how the main biological and chemical molecular factors impact the biotransformations of key PhACs in biological WWTP processes. Biotransformations have been found to be an important contributor towards the removal of PhACs from WWTP effluents. This review paper critically assesses these aspects and the recent advances that have been achieved in wastewater treatment processes for biodegradation of 7 PhACs; namely the non-steroidal anti-inflammatory drug (NSAID) diclofenac (DCF); the macrolide antibiotics azithromycin (AZM), erythromycin (ERY) and clarithromycin (CLR); the two natural estrogens estrone (E1) and 17β-estradiol (E2), and the synthetic estrogen 17α-ethinylesradiol (EE2). These represent the micropollutants of the EU Watch list in Decision 2015/495/EU that are most relevant to WWTPs due to their frequent detection. The metabolic pathways, transformation products and impact of relevant factors to biological WWTP processes is addressed in this review. The biokinetics of PhAC biodegradation in different engineered bioprocesses is also discussed. Promising technologies and operational strategies that are likely to have a high impact on controlling PhAC releases are highlighted and future research needs are also proposed.

Front-face fluorescence excitation-emission matrix (FF-EEM) for direct analysis of flocculated suspension without sample preparation in coagulation-ultrafiltration for wastewater reclamation

Fluorescence spectroscopy has been suggested as a promising online monitoring technique in water and wastewater treatment processes due to its high sensitivity and selectivity. However, a pre-filtration is still indispensable in fluorescence measurement for removing ubiquitous particles and flocs in real samples to eliminate the strong light scattering that could attenuate fluorescence detection significantly. This study proposed a front-face fluorescence spectroscopy, which could characterize the liquid sample with suspended solids directly without pre-filtration. Front-face excitation-emission matrix (FF-EEM) coupled with parallel factor (PARAFAC) analysis was used for analyzing fluorescence components and to probe coagulation of secondary effluent and fouling in the subsequent ultrafiltration (UF), and conventional right-angle fluorescence EEM (RA-EEM) was also compared. The results showed that FF-EEM was less susceptible to turbidity (induced by standard particles) in the secondary effluent compared to RA-EEM. FF-EEM could successfully measure dissolved fluorophores in coagulated suspension without pre-filtration, while conventional RA-EEM was undermined significantly due to the existing flocs. FF-EEM coupled with PARAFAC could accurately probe dissolved organic matter and fouling in coagulation- UF wastewater reclamation processes. Therefore, it was demonstrated that this front-face fluorescence without any sample preparation step might be highly promising in real-time online fluorescence monitoring in multi water and wastewater treatment processes.

Characteristics of DOM in 14 AAO processes of municipal wastewater treatment plants

The characteristics of dissolved organic matter (DOM) such as chemical composition, molecular weight (MW) distribution and hydrophobic/hydrophilic distribution can affect wastewater treatment efficiency, effluent quality and ecological risk. Fluorescence spectroscopy could provide a quick estimate of DOM characteristics during the monitoring of wastewater treatment plants (WWTPs). In this study, the characteristic and quantitative correlation of DOM from 14 anaerobic-anoxic-oxic (AAO) processes of WWTPs located in different provinces (municipalities) of China were investigated. The results showed that DOM of MW <1 kDa was the largest group of DOM in influent and secondary effluent, and DOM removal increased as the MW increased. Hydrophilic (HPI) fraction and hydrophobic acid (HPO-A) comprised the major portion of DOM in influent and secondary effluent and exhibited the lowest rate of removal. In addition, DOM concentrations in the northern provinces were higher than in the southern provinces, which were related to the water quality, economy and population. There were positive correlations between specific fluorescence intensity (SFI) and the MW <1 kDa, 1-5 kDa and <10 kDa fractions. The smaller the molecular weight, the better the correlation. Strong positive correlations between regional fluorescence proportion (f_i) and HPI were found. SFI and f_i may be explored as potential indicators of the MW fractions and the hydrophobic/hydrophilic distribution of DOM in AAO processes WWTPs.

Leachability of endocrine disrupting chemicals (EDCs) in municipal sewage sludge: Effects of EDCs interaction with dissolved organic matter

In this study, experiments were performed to assess the significance of dissolved organic matter (DOM) on the leachability of four common EDCs, i.e., bisphenol A (BPA), 17α-ethinylestradiol (EE2), progesterone (PGT) and testosterone (TST), in municipal sewage sludge (MSS) under landfill conditions. The DOM was derived from two sources: MSS (MDOM), and natural soil represented by organic matter obtained from the Suwannee River (NDOM). Fluorescence excitation-emission matrix quenching combined with parallel factor analysis was adopted to characterize the interaction properties between the EDCs and DOM. The accumulative leachability of the target EDCs ranged from 0.09% (PGT) to 3.8% (TST). In particular, the leaching of BPA, EE2 and TST followed S-shaped curves, while PGT exhibited continuous leaching potential in untreated MSS. With the introduction of DOM, (i) the leachability of BPA and EE2 increased to 13.4% and 61.6%, respectively, whereas those of PGT and TST declined by 61.3% and 45.8%, respectively, and (ii) BPA, EE2 and PGT no longer reached leaching equilibrium but the S-shaped leaching property of TST persisted. The differential effects of MDOM and NDOM at identical concentrations on the EDCs leachability increased with curing time. BPA, EE2 and PGT quenched the MDOM fluorophores attributed to aromatic protein-like components. The fluorescence quenching of NDOM by BPA, EE2 and PGT was centered on soluble microbial by-product-like and humic-like substances. Compared with PGT, EE2 and BPA had greater capability for binding with DOM components largely via hydrophobic interactions, whereas PGT preferentially interacted with the DOM hydrophilic functionalities through specific interactions. TST had no binding capability but displayed potentials competing for sorption sites with DOM moieties. Our findings suggested that the management of MSS increased the risk of environmental contamination by EDCs for a long duration and that DOM was a useful indicator to predict the migration and transport properties of EDCs.

Development of fluorescence surrogates to predict the ferrate(VI) oxidation of pharmaceuticals in wastewater effluents

The removal of pharmaceuticals from wastewater effluents is an emerging concern for environmental scientists and engineers. Ferrate(VI) (Fe^VIO₄^2-, Fe^VI) is a promising oxidant and the removal of pharmaceuticals from wastewater effluents has been investigated in this study. Firstly, Fe^VI oxidation of selected pharmaceuticals was examined by determining the apparent second-order rate constants (k_app) in buffer solutions as a function of pH (5.0-9.5). At pH 8.0, k_app of cimetidine, famotidine, nalidixic acid, ronidazole, dimetridazole, tinidazole, and caffeine are (1.6 ± 0.2)×10³, (7.8 ± 0.3)×10², 2.6 ± 0.4, 1.7 ± 0.1, 0.9 ± 0.3, 0.2 ± 0.1, and < 0.1 M^-1 s^-1, respectively. However, k_app could not be directly employed to predict the removal of pharmaceuticals in the effluents due to the inhibited or enhanced effects of effluent organic matters (EfOM). Therefore, an alternative approach of spectroscopic surrogates was investigated since fluorophore was co-degraded with pharmaceuticals in the wastewater effluents. Particularly, the humic-like fluorescent peak correlated well with the pharmaceutical attenuation. The relationship of the reduction of fluorescence and the removal of pharmaceuticals could be described through a universal equation: [Formula: see text] . The practical utility of the fluorescence surrogate was validated by applying to field samples. Monitoring the changes of the fluorescence surrogate provides a promising, rapid, and inexpensive method for estimating the degradation of pharmaceuticals during Fe^VI treatment of wastewater effluents.

Monitoring Approaches for Faecal Indicator Bacteria in Water: Visioning a Remote Real-Time Sensor for E. coli and Enterococci

A comprehensive review was conducted to assess the current state of monitoring approaches for primary faecal indicator bacteria (FIB) E. coli and enterococci. Approaches were identified and examined in relation to their accuracy, ability to provide continuous data and instantaneous detection results, cost, environmental awareness regarding necessary reagent release or other pollution sources, in situ monitoring capability, and portability. Findings showed that several methods are precise and sophisticated but cannot be performed in real-time or remotely. This is mainly due to their laboratory testing requirements, such as lengthy sample preparations, the requirement for expensive reagents, and fluorescent tags. This study determined that portable fluorescence sensing, combined with advanced modelling methods to compensate readings for environmental interferences and false positives, can lay the foundations for a hybrid FIB sensing approach, allowing remote field deployment of a fleet of networked FIB sensors that can collect high-frequency data in near real-time. Such sensors will support proactive responses to sudden harmful faecal contamination events. A method is proposed to enable the development of the visioned FIB monitoring tool.

Seasonal occurrence of N-nitrosamines and their association with dissolved organic matter in full-scale drinking water systems: Determination by LC-MS and EEM-PARAFAC

N-nitrosamines have been identified as emerging contaminants with tremendous carcinogenic potential for human beings. This study examined the seasonal changes in the occurrence of N-nitrosamines and N-nitrosodimethylamine formation potential (NDMA-FP) in drinking water resources and potable water from 10 drinking water treatment plants in a southern city of China. The changes in N-nitrosamines are well correlated with dissolved organic matter (DOM), particularly fluorophores, which were measured and compared between traditional fluorescence indices and excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Four of N-nitrosamine species including N-nitrosodimethylamine (NDMA), N-Nitrosodibutylamine (NDBA), N-Nitrosopyrrolidine (NPYR), and N-Nitrosodiphenylamine (NDPhA) are found to be abundant compounds with an average of 29.5% (26.7%), 20.0% (25.2%), 18.9% (16.0%), and 9.0% (9.9%) in the source (and treated) water, respectively. The sum of N-nitrosamines concentration is recorded to be low in the wet season (July-September), whereas the dry season (October-December) provided opposite impacts. EEM-PARAFAC modeling indicated the predominance of humic-like component (C1) in the wet season while in the dry season the water was dominant in protein-like component (C2). All the N-nitrosamines excluding NDPhA and N-Nitrosomorpholine (NMOR) showed a strong association with protein-like component (C2). In contrast, humic-like C1, which was directly influenced by rainfall, was found to be a suitable proxy for NMOR and NDPhA. The results of this study are valuable to understand the correlation between different N-nitrosamines and DOM through adopting fluorescence signatures.

Use of spectroscopic indicators for the monitoring of bromate generation in ozonated wastewater containing variable concentrations of bromide

Time-resolved monitoring of bromate and other by-products formed into effluents treated with ozone or advanced oxidation processes in wastewater treatment plants (WWTPs) is time-consuming and expensive. This study examined whether concentrations of bromate formed in wastewater after ozonation in the presence of widely varying bromide levels (from ca. 0.7-21.2 mg/L) can be quantified based on measurements of changes in optical properties (differential UV absorbance (ΔUVA), spectral slopes, total or regional fluorescence) of the ozonated samples. Batch ozonation was carried out using a secondary effluent produced at a major wastewater treatment plant located in the Metropolitan Seattle Area. The tests involved raw and bromide-spiked samples treated with ozone doses from 0.1 to 1 mg O₃/mg DOC. Measurements of the absorbance at 254 nm (UVA254), fluorescence and bromate concentrations were performed on the treated samples. In the ozonated wastewater the concentration of bromate increased approximately linearly, from <10 ppb to ca. 200 ppb, without showing the lag phase characteristic for lower ozone doses (<0.4 mg O₃/mg DOC) that was observed in previous studies carried out with concentrations of bromide in the range of 0.05-0.5 mg/L. The highest bromide concentrations used in this study (>10 mg/L) tended to inhibit the generation of bromate. Relative reduction of UVA254 and total fluorescence (TF) were found to be good predictors of bromate generation. Specifically, exponential curves could adequately fit the non-linear relationships found to exist between the concentrations of bromate and the relative reductions of the UV254 and TF, for any initial bromide concentrations used in this study. Little formation of bromate was found to occur for reduction ranges for UVA254 and TF of 30-40% and 70-80% respectively. Conversely, rapid increases in bromate generation were observed when the decrease of UVA254 or TF exceeded these threshold values.

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.

Tracing the occurrence of organophosphate ester along the river flow path and textile wastewater treatment processes by using dissolved organic matters as an indicator

Organophosphate esters (OPEs) are frequently detected in wastewater and receiving river, but their occurrence is hard to be quickly and effectively responded. In this study, the relevant OPEs and dissolved organic matters (DOMs) data were obtained from two textile wastewater treatment plants (WWTPs) with different processes and a 15 km stretch of river receiving the treated textile wastewater. UV-Vis absorption and fluorescence spectroscopy combined with peak-picking and fluorescence regional integration (FRI) methods were used to characterize DOM components in these samples. The results showed that OPEs concentrations were not always consistent with that of DOM, but were related to their physico-chemical properties and sources. Correlation and regression analysis indicated that the FRI pattern could be considered for tracing the occurrence of organophosphate diesters derived from multiple pollutants in river water, and reflected the emerging of moderate or high removal organophosphate triesters in WWTPs. Difference in the sources and DOM compositions was the main contributor to the correlation difference of OPEs and DOM in the two types of processes. The treatment technique also played important roles in the co-occurrence of OPEs and DOM in different WWTPs. This study would be beneficial to develop in-situ monitoring for the dynamic change of emerging contaminants along with a river flow path and from WWTPs, respectively.

Paradigm shifts and current challenges in wastewater management

Wastewater is a significant environmental and public health concern which management is a constant challenge since antiquity. Wastewater research has increased exponentially over the last decades. This paper provides a global overview of the exponentially increasing wastewater research in order to identify current challenges and paradigm shifts. Besides households, hospitals and typical industries, other sources of wastewater appear due to emerging activities like hydraulic fracturing. While the composition of wastewater needs constant reassessment to identify contaminants of interest, the comprehensive chemical and toxicological analysis remains one of the main challenges in wastewater research. Moreover, recent changes in the public perception of wastewater has led to several paradigm shifts: i) water reuse considering wastewater as a water resource rather than a hazardous waste, ii) wastewater-based epidemiology considering wastewater as a source of information regarding the overall health of a population through the analysis of specific biomarkers, iii) circular economy through the implementation of treatment processes aiming at harvesting valuable components such as precious metals or producing valuable goods such as biofuel. However, wastewater research should also address social challenges such as the public acceptance of water reuse or the access to basic sanitation that is not available for nearly a third of the world population.

Monitoring NDMA precursors throughout membrane-based advanced wastewater treatment processes by organic matter fluorescence

This study investigates the potential of fluorescence excitation/emission matrices (EEM) measurement as a tool to predict N-Nitrosodimethylamine (NDMA) formation in water reuse applications. In particular, samples from a pilot-scale membrane biological reactor (MBR) followed by nanofiltration (NF) advanced water treatment plant, are used for the study. Concentrations of both, specific NDMA precursors and NDMA formation potential (FP) are correlated with different EEM peaks. The specific precursors investigated are: erythromycin, azithromycin, clarithromycin, venlafaxine, o-desmethylvenlafaxine, ranitidine and citalopram, while the NDMA FP is conventionally measured by the NDMA formation potential test. EEM peaks investigated are obtained by fluorescence regional integration as well as by the peak picking method generating I₁, I₂, I₃, I₄, and I₅ peaks. Results showed that protein-like materials are correlated with the bulk NDMA FP and specific NDMA precursors. Additionally, selected fluorescence peaks such as I₁, I₂ and I₄ are strongly correlated with NDMA precursors throughout the MBR-NF pilot plant. The removal of NDMA precursors and EEM peaks also correlated well (R² > 0.8). This data shows that fluorescence EEM can be a promising tool to monitor the concentration of NDMA precursors and their removal in water reuse application.

Inner filter effect, suspended solids and nitrite/nitrate interferences in fluorescence measurements of wastewater organic matter

In this study, it was assessed the effectiveness to correct for inner filter effect (IFE) the fluorescence spectra of several wastewaters (i.e., primary, secondary and tertiary wastewater effluents) and wastewater-impacted surface waters using a common method based on UV absorbance measurements. In samples of secondary/tertiary wastewater effluents and surface waters, IFE was severe at excitation wavelengths <240 nm, and it was low (4-11%) at excitation wavelengths >340 nm. On the contrary, IFE has always been significant in primary wastewater effluents. After IFE correction, linear relationship was observed between fluorescence and absorbance in dilution series across the full excitation-emission matrix (EEM), although some distortions were still present. Particularly, experimental data showed the presence of static/dynamic quenching of fluorescence due to nitrite/nitrate, which cannot be corrected by IFE correction methods. Indeed, after addition of different nitrate/nitrite concentrations in wastewater (3-40 mg/L as N), the estimated static/dynamic quenching error (QE) after IFE correction was often >20% for tyrosine and tryptophan-like fluorescence measured at excitation <240 nm. However, the QE was low (<5-10%) for fluorescence measured at excitation >240 nm. Overall, the QE increased with the increase of nitrite/nitrate concentration in wastewater. Total suspended solids (TSS) (i.e., particulate organic matter) in water produced intense fluorescence peaks in the tyrosine-like and tryptophan-like region of EEM, and TSS increased the absorbance values at all the excitation wavelengths of the UV-visible absorption spectra in unfiltered samples compared to 0.7 μm filtered samples. On the contrary, tertiary effluents employing full scale sand filtration (TSS < 2-4 mg/l) had similar UV absorbance and fluorescence spectra to 0.7 μm filtered samples. Finally, it was observed that uncorrected fluorescence intensities in the humic-like region of EEM were similar in both filtered and unfiltered samples, and it was independent of TSS concentration, dilution factor and water quality.