Search

The rapid development of swine farming has resulted in the generation of a large amount of swine wastewater (SW), and dissolved organic matter (DOM) has a crucial role in determining the efficiency and safety of SW treatment. In this study, the transformation and influential mechanisms of DOM on the quality of SW effluent during full-scale SW treatment in actual engineering were systematically investigated using multispectral analysis and the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) technique. The results showed that S-containing, reduced, saturated, and less aromatic molecules were preferentially removed in the C-AF, while C-S preferentially removed reduced, unsaturated, and aromatic molecules, as well as molecules with large molecular weights. And in the two-stage A/O, the degradation of organic matter and DOM transformation occurred mainly in the A/O-1, with the A/O-2 acting as a supplement to further enhance the humification of DOM. Furthermore, the AOP preferentially removed lignin-like and highly unsaturated compounds, replacing them with a new generation of substances such as proteins and tannins with low aromaticity and unsaturation. More deeply, oxygen addition reactions dominate in both A/O and AOP. Specifically, the most common types of reactions in the A/O were the corresponding potential precursor-product pairs based on methyl to carboxylic acid (-H 2  + O 2 ) and alcohol to carboxylic acid (-H 2  + O), while tri-hydroxylation (+O 3 ) and di-hydroxylation (+H 2 O 2 ) reactions were predominant in the AOP. Finally, the study's findings might suggest improving the actual engineering by prioritizing the AOP before the A/O-2 and using the C-S for safeguard treatment of the A/O-2 effluent. It is reliable that this kind of adjustment guarantees safe drainage indications and raises each process unit's efficiency in purifying., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Recovering high-value biomaterials from anaerobic digestion sludge (ADS) has attracted considerable attention. However, the molecular features and biological effects of abundant dissolved organic matters (DOMs) in ADS are still unclear, which limits the efficient recycling and application of these bioproducts. This study investigated the molecular composition and transformation of DOMs recovered from ADS through a mild-temperature alkali-hydrothermal treatment (AHT) with ultrahigh-resolution mass spectrometry and energy spectroscopy, and the fertilizing effects of DOMs were evaluated by rice hydroponics. The results indicated that AHT processes significantly promoted the solubilization and release of DOMs from ADS, where most of DOMs molecules remained unchanged and mainly consisted of N-containing compounds with 1-3 N atoms, featuring aromatic or N-heterocyclic rings. Furthermore, AHT processes at pH of 9-10 induced the hydrolysis of partial protein-like substances in DOMs, which was accompanied by formation of heterocyclic-N compounds. Under AHT at pH of 11-12, protein-like and heterocyclic-N substances were increasingly decomposed into amino-N compounds containing 1 or 5 N atoms, while numerous oxygenated aromatic substances with phytotoxicity were degraded and removed from DOMs. Rice hydroponic test verified that ADS-derived DOMs recovered by AHT process at pH of 12 exhibited the highest bioactivity for rice growth, which was attributed to the abundance of amino compounds and humic substances. This study proposed a novel process for the recovery of high-quality liquid organic fertilizer from ADS through AHT process, which can further enrich the technical options available for the safe utilization of sludge resources., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Baiyangdian Lake (BYD), a large shallow lake in North China, has complex water landscape patterns that are underlies spatial variations in water quality. In this study, we collected 61 water samples from three water landscapes (reed littoral zones, fish ponds, and open water) and analyzed them for water quality parameters, such as dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP). Water landscape distribution (determined using remote sensing imagery) was then used to assess correlations between water quality parameters and water landscape proportion in differently scaled buffer zones. There was substantial variation across all subareas, with TN and TP concentrations ranging from 0.90 to 4.10 mg/L and 0.06 to 0.18 mg/L, respectively, in class IV of water quality as a whole. Spatial variations in water quality were mainly caused by water landscape distribution and external nutrient inputs. There were negative correlations between DOC, TN, and TP concentrations and the area proportion of reed littoral zones in the 300 and 500 m buffers. In contrast, DOC, TN, and TP concentrations were significantly positively correlated with the area proportion of fish ponds in the 100 m buffer. Furthermore, compared with reed littoral zones, a lower ratio of nitrogen to phosphorus and a higher proportion of dissolved organic nitrogen and tyrosine-like proteins were found in fish ponds. These effects were mainly attributed to the development of internal sediment loadings due to nutrient exchange across the sediment–water interface. Therefore, dredging-based sediment removal from fish ponds should be considered to suppress internal phosphorus loading and accelerate recovery of the BYD ecosystem. [ABSTRACT FROM AUTHOR]

In this work, a novel carbon-based hydrotalcite-like compounds materials (LDO-SBCs) were prepared by coupling layered double hydroxides (LDHs) conditioning and pyrolytic carbonization, and characterized by X-ray diffraction (XRD), Thermogravimetric Analyzer (TGA), X-ray photoelectron spectroscopy (XPS) and Brunner-Emmet-Teller (BET) measurements. The synthesized LDO-SBCs composites were used in wastewater treatment for simultaneous removal of phosphate and dissolved organic matter (DOM). The adsorption of DOM and phosphate were well conformed to pseudo-second-order mode. Adsorption equilibrium was better fitted by Langmuir model for phosphate, while Freundlich model for DOM. Compared with the raw sludge carbon, the removal efficiency of DOM and phosphate by LDO-SBCs were increased by 8% and 13%, respectively. Based on the fluorescence spectrum and parallel factor analysis (PARAFAC), LDO-SBCs performed well in promoting the removal of protein substances (TPN and APN). Pore filling, hydrogen bonding, electrostatic adsorption and surface complexation might be dominant in the adsorption of DOM, while, surface complexation and ion exchange between the LDO layers were mainly responsible for the adsorption of phosphate. The difference of adsorption capacity of LDO-SBCs was related to the superior channel structure of composite materials and the composition of interlayer anions of LDO. Image 1 • Carbon-based hydrotalcite-like compounds materials were synthesized. • LDO-SBCs showed good adsorption properties for DOM and phosphate. • Liquid membrane control of DOM and phosphate was dominant on the adsorption. • LDO-SBCs had an excellent performance on removal of protein substances. [ABSTRACT FROM AUTHOR]

• A total of 144 tire-related additives were identified in the TWP leachate. • High temperature increased the chemical complexity of the tire-derived compounds. • Tire-derived compounds conjugated with amino acids or Maillard products during HT. • TWP leachate showed strong acute toxicity and negative effects on plant growth. Tire wear particles (TWPs) are considered a significant contributor of microplastics (MPs) in the sludge during heavy rainfall events. Numerous studies have shown that hydrothermal treatment (HT) of sludge can accelerate the leaching of MP-derived compound into hydrothermal liquid, thus impairing the performance of subsequent anaerobic digestion and the quality of the hydrothermal liquid fertilizer. However, the leaching behavior of TWPs in the HT of sludge remains inadequately explored. This study examined the molecular composition of TWP-derived compounds and transformation pathways of representative tire-related additives under different hydrothermal temperatures using liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with mass difference analysis. The acute toxicity and phytotoxicity of TWP leachates were assessed using Vibrio qinghaiensis Q67 and rice hydroponics experiments. The results indicated that elevating the hydrothermal temperature not only amplified the leaching behavior of TWPs but also enhanced the chemical complexity of the TWP leachate. Utilizing both suspect and non-target screenings, a total of 144 compounds were identified as additives, including N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PDD), hexa(methoxymethyl)melamine (HMMM), dibutyl phthalate (DBP). These additives underwent various reactions, such as desaturation, acetylation, and other reactions, leading to the formation of different transformation products (TPs). Moreover, certain additives, including caprolactam and 2,2,6,6-tetramethyl-4-piperidinol, demonstrated the potential to form conjugate products with amino acids or Maillard products. Meanwhile, TWP-derived compounds showed significant acute toxicity and detrimental effects on plant growth. This study systematically investigated the environmental fate of TWPs and their derived compounds during the HT of sludge, offering novel insights into the intricate interactions between the micropollutants and dissolved organic matter (DOM) in sludge. [Display omitted] [ABSTRACT FROM AUTHOR]

• PAC conditioning inhibited composting microbiomes with a decreased enzymatic reaction. • PFS conditioning increased the content of humification intermediate-indole. • PFS conditioning increased humic acid and indoleacetic acid content in the compost. • PFS conditioning changed the dominant humification occurrence stage during composting. • PAC conditioning declined compost quality, while PFS dosage increased compost quality. Inorganic coagulants (aluminum and iron salt) are widely used to improve sludge dewaterability, resulting in numerous residues in dewatered sludge. Composting refers to the controlled microbial process that converts organic wastes into fertilizer, and coagulant residues in dewatered sludge can affect subsequent compost efficiency and resource recycling, which remains unclear. This work investigated the effects of two typical metal salt coagulants (poly aluminum chloride [PAC] and poly ferric sulfate [PFS]) conditioning on sludge compost. Our results revealed that PAC conditioning inhibited composting with decreased peak temperature, microbial richness, enzymatic reaction intensities, and compost quality, associated with decreased pH and microbial toxicity of aluminum. Nevertheless, PFS conditioning selectively enriched Pseudoxanthomonas sp. and resulted in more fertile compost with increased peak temperature, enzymatic reaction intensities, and humification degree. Spectroscopy and mass difference analyses indicated that PFS conditioning enhanced reaction intensities of labile biopolymers at the thermophilic stage, mainly comprising hydrolyzation (H 2 O), dehydrogenation (-H 2 , -H 4), oxidation (+O 1 H 2), and other reactions (i.e., +C H 2 , C 2 H 4 O 1 , C 2 H 6 O 1). Unlike the common composting process primarily conducts humification at the cooling stage, PFS conditioning changed the main occurrence stage to the thermophilic stage. Non-targeted metabolomics revealed that indole (a humification intermediate) is responsible for the increased humification degree and indoleacetic acid content in the PFS-conditioned compost, which then promoted compost quality. Plant growth experiments further confirmed that the dissolved organic matter (DOM) in PFS-conditioned compost produced the maximum plant biomass. This study provided molecular-level evidence that PFS conditioning can promote humification and compost fertility during sludge composting, enabling chemical conditioning optimization for sustainable management of sludge. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Dissolved BrC fractions account for approximately 1/3-1/2 of DOC formulae. • Dissolved BrC shows high levels of OS C , DBE, and AI mod than those of DOC. • CRAMs-like structures are the most abundant species in DOC and dissolved BrC. • Molecular compositions of DOC and dissolved BrC show similarities and differences. Recently, extreme wildfires occur frequently around the world and emit substantial brown carbon (BrC) into the atmosphere, whereas the molecular compositions and photochemical evolution of BrC remain poorly understood. In this work, primary smoke aerosols were generated from wood smoldering, and secondary smoke aerosols were formed by the OH radical photooxidation in an oxidation flow reactor, where both primary and secondary smoke samples were collected on filters. After solvent extraction of filter samples, the molecular composition of dissolved organic carbon (DOC) was determined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). The molecular composition of dissolved BrC was obtained based on the constraints of DOC formulae. The proportion of dissolved BrC fractions accounted for approximately 1/3–1/2 molecular formulae of DOC. The molecular characteristics of dissolved BrC showed higher levels of carbon oxidation state, double bond equivalents, and modified aromaticity index than those of DOC, indicating that dissolved BrC fractions were a class of organic structures with relatively higher oxidation state, unsaturated and aromatic degree in DOC fractions. The comparative analysis suggested that aliphatic and olefinic structures dominated DOC fractions (contributing to 70.1%-76.9%), while olefinic, aromatic, and condensed aromatic structures dominated dissolved BrC fractions (contributing to 97.5%-99.9%). It is worth noting that dissolved BrC fractions only contained carboxylic-rich alicyclic molecules (CRAMs)-like structures, unsaturated hydrocarbons, aromatic structures, and highly oxygenated compounds. CRAMs-like structures were the most abundant species in both DOC and dissolved BrC fractions. Nevertheless, the specific molecular characteristics for DOC and dissolved BrC fractions varied with subgroups after aging. The results highlight the similarities and differences in the molecular compositions and characteristics of DOC and dissolved BrC fractions with aging. This work will provide insights into understanding the molecular composition of DOC and dissolved BrC in smoke. [ABSTRACT FROM AUTHOR]

In this work, blast furnace slag was successfully used to prepare five kinds of polymeric titanium aluminium flocculant (PTAC) with different polymerization degrees by two-step acid leaching method, which were applied as the effective dredged sludge conditioners. The results indicated that PTAC can obviously improve the sludge dewaterability. Compared with other four types of PTAC, PTAC 0.6 showed the best sludge conditioning efficiency under the optimum dosage of 4 mg Al + Ti/g TSS. It can reduce the capillary suction time of the sediment by 81.4%, the specific resistance to filtration by 65.1%, and the moisture content of the mud cake from 81.9% to 45.81%. PTAC can significantly increase the zeta potential of the dredged sludge, while it has no obvious effect on the floc size D 0.5. The electric neutralization substantially contributed to the conditioning of PTAC on dredged sludge dewatering. The concentration of dissolved organic carbon, total phosphorus in the residual water was significantly reduced after PTAC conditioning. PTAC can also remove large molecular weight components in dissolved organic matter by flocculation, or hydrolyze large molecular components into small and medium molecular weight components, furthermore reduce the concentration of these organic components. 3D-EEM analysis results showed that PTAC can effectively remove fulvic acid-like substances and some protein-like substances by flocculation, especially the removal effect of fulvic acid-like substances was more prominent. [Display omitted] • Blast furnace slag was used to prepare various polymeric titanium aluminum flocculant. • PTAC showed good dewatering performance for dredged sludge. • The electric neutralization substantially contributed to the conditioning process. • PTAC conditioning could effectively improve the quality of residual water. [ABSTRACT FROM AUTHOR]

• During sludge AHT treatment, leaching of MP-DOM hindered HA formation. • The inhibition of Maillard reaction was vital for the reduction of HA content. • Amino reactant consumption was the main way for inhibition of Maillard reaction. • MPs released organic acids that reduce pH, causing protonation of amino groups. • Oxidation of lipid-like compounds yielded fatty aldehydes, reducing amino reactants. Alkali-hydrothermal treatment (AHT) of sewage sludge is often used to recover value-added dissolved organic matters (DOM) enriched with artificial humic acids (HA). Microplastics (MPs), as emerging contaminants in sewage sludge, can leach organic compounds (MP-DOM) during AHT, which potentially impact the characteristics of thermally treated sludge's DOM. This study employed spectroscopy and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR-MS) to explore the impacts of MPs on DOM composition and transformation during AHT. The biological effects of DOM were also investigated by hydroponic experiments. The results showed that the leaching of MP-DOM led to a substantial increase in DOC content of DOM of thermally treated sludge. Conversely, the HA content significantly decreased in the presence of MPs, resulting in a decline of plant growth facilitation degree. FT-ICR-MS analysis revealed that the reduction in HA content was characterized by a notable decline in the abundance of O 6–7 and N 1–3 O 6–7 molecules. Reactomics results indicated that the leaching of MP-DOM inhibited the Maillard reaction but bolstered oxidation reactions. The inhibition of Maillard reaction, resulting in a decrease in crucial precursors (dicarbonyl compounds, ketoses, and deoxyglucosone), was responsible for the decrease of HA content. The primary mechanism responsible for inhibiting the Maillard reaction was the consumption of reactive amino reactants through two pathways. Firstly, the leaching of organic acids in MP-DOM caused decrease of sludge pH, leading to the protonation of amino groups. Secondly, the lipid-like compounds in MP-DOM underwent oxidation (-2H+O), producing fatty aldehydes that consumed the reactive amino reactants. These discoveries offer enhanced insights into the specific contribution of MPs to the composition, transformation, bioactivity of DOM during AHT process. [Display omitted] [ABSTRACT FROM AUTHOR]

This study aimed to explore the adsorption performance of sludge-based activated carbon (SBC) towards dissolved organic matters (DOMs) removal from sewage, and investigated the modification effect of different types of chemicals on the structure of synthesized SBC. Waste activated sludge (WAS) was used as a carbon source, and HCl, HNO 3 , and NaOH were used as different types of chemicals to modify the SBC. With the aid of chemical activation, the modified SBC showed higher adsorption performances on DOMs removal with maximum adsorption of 29.05 mg/g and second-order constant (k) of 0.1367 (L/mol/sec) due to the surface elution of ash and minerals by chemicals. The surface elemental composition of MSBC suggested that the content of C-C and C-O functional groups on the surface of modified sludge-based activated carbon (MSBC) played an important role on the adsorption capacities of MSBC towards DOMs removal in sewage. Additionally, the residual molecular weight of DOMs in sewage was investigated using a 3-dimension fluorescence excitation-emission matrix (3D-EEM) and high-performance size exclusion chromatography (HP-SEC). Results showed that the chemical modification significantly improved the adsorption capacity of MSBC on humic acids (HA) and aromatic proteins (APN), and both of NaOH-MSBC and HCl-MSBC were effective for a wide range of different AMW DOMs removal from sewage, while the HNO 3 -MSBC exhibited poorly on AMW organics of 2,617 Da and 409 Da due to the reducing content of macropore. In brief, this study provides reference values for the impact of the chemicals of the activation stage before the SBCs application. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Pyrolysis carbonisation is a promising technology to convert organic waste into valuable carbon-based materials. However, sludge is generally highly compressible and difficult to dewater because of its high concentrations of biopolymers; the bound water of sludge is trapped in a network composed of biopolymers. Therefore, chemical conditioning is an indispensable step for improving sludge dewaterability performance. In the present work, the effects of different chemical conditioning agents (polymeric aluminium chloride (PACl), iron(III) chloride (FeCl 3), KMnO 4 –Fe(II) and Fenton's reagent) on the physicochemical properties of sludge-based carbons (SBCs) were systematically studied and the SBCs were further used in advanced wastewater treatment. The adsorption mechanisms of dissolved organic matters (DOMs) by different SBCs were also investigated. The results showed that conditioning with KMnO 4 –Fe(II) and Fenton's reagent improved the specific surface area of the SBCs, whereas inorganic salt flocculation conditioning reduced the porosity of the SBCs. In addition, we found that the Fenton-SBC and Mn/Fe-SBC performed better than the other investigated SBCs in the removal of organic compounds from secondary effluent and that the pseudo-second-order kinetic model could better describe the process of DOMs adsorption by all of the investigated SBCs. Moreover, three-dimensional fluorescence excitation–emission matrix spectroscopy in combination with an analysis of the physical and chemical fractionation of DOMs showed that all of the SBCs performed well in the adsorption of aromatic substances, hydrophobic acids and hydrophobic neutrals, whereas the Mn/Fe-SBC and Fenton-SBC performed better than the other SBCs in the removal of weakly hydrophobic acids. Image 1 • Fenton's reagent and KMnO 4 –Fe(II) conditioning improved porosity of SBCs. • Fenton-SBC and Mn/Fe-SBC performed better in DOMs removal. • SBCs were effective in removing aromatic and high molecular weight of substances. • Pore structure and carbon content affected the adsorption capacities of SBCs. [ABSTRACT FROM AUTHOR]

This work examined the transformation pathways of sludge biochar-derived dissolved organic matters (SBC-derived DOMs) under sludge pyrolysis via FT-ICR-MS-based reactomics and molecular network analysis. Lignin/carboxylic-rich alicyclic molecules, proteins/aliphatic, and lipids of SBC-derived DOMs did not contribute equally to the overall pyrolytic reactions. Reactomics suggested that the pyrolysis reactions of SBC-derived DOMs consist of multiple cascade reactions involving the elimination of assemblages of reactive fragments during each pyrolysis reaction region, and the overall pyrolysis process was divided into three stages according to cascade reaction variations. Especially, cascade reactions at 400–500 °C produced potential environmental risk substances of N-containing, carbonyl-containing, and phenolic compounds. Besides, network analysis unraveled the complexity and number of molecular reaction pairs of SBC-derived DOMs decreased with the increase in pyrolytic temperatures. Keystone molecules and pathways results indicated that the pyrolytic temperature of the sludge pyrolysis process should be controlled at temperatures above 500 °C according to the harmful substances generation pattern in reaction products. Overall, the possible transformation pathways of SBC-derived DOMs during sludge pyrolysis treatment were proposed. This study elucidated the underlying mechanisms in generating SBC-derived DOMs and provided theoretical support for process optimization and harmful substances control of sludge pyrolysis. [Display omitted] • DOM molecular composition did not contribute equally to the overall pyrolytic reactions. • Increases in pyrolytic temperatures induced the decrease in reaction complexity. • Harmful substances produced by N 1-2 Ox should be controlled above 500 °C. • A possible transformation pathway of SBC-derived DOMs was proposed. [ABSTRACT FROM AUTHOR]

• Selective removal of DOM in common treatment processes was elucidated by FT-ICR MS. • Removal of reduced molecules (low O/C) during adsorption caused the lower DBPs yields. • Coagulation and adsorption were complementary for DOM removal at the molecular level. • Reduced molecules that are more reactive with chlorine can pass through the NF membrane. • BAF enhanced the removal of DBPs precursors in coagulation-adsorption process. Alterations in molecular composition of dissolved organic matter (DOM) during water treatments can influence the composition and toxicity of disinfection by-products (DBPs) in subsequent chlorination disinfection process. In this study, the impacts of DOM composition after various water treatment techniques (coagulation, adsorption, nanofiltration, biological aerated filter (BAF), and their integrated processes) on the generation mechanisms of DBPs were comprehensively explored by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in combination with GC–MS and LC-MS analysis. The results indicated that coagulation preferentially removed unsaturated (low H/C) and oxidized (high O/C) compounds, whereas adsorption was prone to remove the reduced (low O/C) component that was more reactive with chlorine, leading to lower yields (μg DBP/mg DOC) of trihalomethanes (THMs) and haloacetic acids (HAAs) during subsequent chlorination. The coagulation-adsorption technique exhibited a relatively high removal of both known and unknown DBPs, demonstrating that coagulation and adsorption were complementary for DOM removal at the molecular level. Nanofiltration selectively removed molecules with relatively high O/C, however, those with very low O/C that were more reactive with chlorine could pass through the nanofiltration membrane, resulting in the highest yields of THMs and HAAs. Although BAF was inefficient in removing DBPs precursors, it could convert molecules with low degree of oxidation and unsaturation into highly oxidized and unsaturated ones, thereby significantly enhancing the removal of DBPs precursors in the subsequent coagulation-adsorption process. These findings are instrumental in developing and selecting more effective techniques to minimize the formation of DBPs in water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) and microbes co-mediate the transformation of heavy metals in soil. However, few previous studies have investigated the effects of interaction between DOM and microbes on the transformation and bioavailability of heavy metals in tailings soil at the molecular level after the addition of organic wastes. This study used co-occurrence network analysis based on Fourier-transform ion cyclone resonance mass spectrometry and high-throughput sequencing to investigate the molecular mechanisms of different bio-stabilized sludge addition on arsenic fraction transformation and bioavailability in tailings soil. It was found that sludge amendments decreased the arsenic bioavailable fraction from 3.62% to 1.74% and 1.68% and promoted humification of DOM in soil. The extra inorganic salt ions introduced with sludge desorb the adsorbed As(V) into soil solution. Specifically, bio-stabilized sludge increased the contents of labile compounds that provided nutrients for microbial metabolism and shaped the microbial community composition into a more copiotrophic state, which increased the abundance of As(V)-reducing bacteria and then converted the As(V) into As(III) and precipitated as As 2 S 3. This work innovatively explores the transformation mechanisms of As fractions through the perspectives of microbial community and DOM molecular characterization, providing an important basis for the remediation of As-contaminated soil using biosolids. [Display omitted] • Synergistic role of DOM and microbe in arsenic transformation was revealed. • Sludge amendment decreased bioavailability of As and promoted humification of DOM. • Copiotrophic bacteria contributed to delignification of DOM transformation. • Bioavailable As was stabilized in the form of As 2 S 3 and residual fractions. • Proteins and amino sugar promoted the reproduction of As(V)-reducing bacteria. [ABSTRACT FROM AUTHOR]

• CHON is the most reactive component in DOM under sludge AHT process. • Deamination is the most frequent reaction in the whole sludge AHT process. • Reactive fragments (-C2H2O2, -C3H4O2, -C4H6O2) were potential precursors of humic acids. • DOM12h could stimulate energy metabolism and carbohydrate storage in rice seedlings. • Byproducts (pyrrole, pyridine, etc.) formed in AHT > 12 h displayed phytotoxicity. Understanding the composition, transformation and bioactivity of dissolved organic matter (DOM) at the molecular level is crucial for investigating the hydrothermal humification process of wastewater sludge and producing ecological fertilizers. In this study, DOM transformation pathways under alkali–thermal humification treatment (AHT) were characterized by Fourier transform–ion cyclotron resonance mass spectrometry (FT–ICR MS) in conjunction with molecular reaction network analysis. The effects of DOM on plant growth were examined using hydroponics and transcriptomic analysis. In the wastewater sludge humification process, AHT produced maximum amounts of protein (3260.56 mg/L) and humic acid (5788.24 mg/L) after 12 h. FT–ICR MS results indicated that protein-like structures were prone to continuous oxidation and were ultimately transformed into aromatic N-containing compounds resembling humic substances. Several reactive fragments (such as –C 2 H 2 O 2 , –C 3 H 4 O 2 , and –C 4 H 6 O 2) formed by the Maillard reaction (MR) were identified as potential precursors to humic acid (HA). In terms of biological effects, DOM 12h showed the highest rice germination and growth activity, whereas that produced by AHT for a longer period (> 12 h) displayed phytotoxicity owing to the accumulation of toxic substances. Plant biostimulants (such as amino acids and HAs) in DOM improved energy metabolism and carbohydrate storage in rice seedlings by upregulating the "starch and sucrose metabolism" pathways. Toxic substances (such as pyrrole, pyridine, and melanoidin) in DOM can activate cell walls formation to inhibit abiotic stimuli in rice seedlings through the biosynthesis of phenylpropanoid pathway. These findings provide a theoretical basis for optimizing sludge hydrothermal humification and recovering high-quality liquid fertilizers. [Display omitted] [ABSTRACT FROM AUTHOR]

Previous knowledge of dissolved organic matter leached from microplastics (MP-DOM) was mainly based on the aquatic environment. The molecular characteristics and biological effects of MP-DOM in other environments have rarely been examined. In this work, FT-ICR-MS was applied to identify MP-DOM leached from sludge hydrothermal treatment (HTT) at different temperatures, and the plant effects and acute toxicity were investigated. The results showed that the molecular richness and diversity of MP-DOM increased with rising temperature, accompanied by molecular transformation in the meantime. The oxidation was crucial whereas the amide reactions mainly occurred at 180–220 oC. MP-DOM promoted root development of Brassica rapa (field mustard) by affecting the expression of genes and the effect was enhanced with rising temperature. Specifically, the lignin-like compounds in MP-DOM down-regulated Phenylpropanoids biosynthesis, while CHNO compounds up-regulated the nitrogen metabolism. Correlation analysis presented that alcohols/esters leached at 120–160 oC were responsible for the promotion of root, while glucopyranoside leached at 180–220 oC was vital for root development. However, MP-DOM produced at 220 oC showed the acute toxicity to luminous bacteria. Considering the further-treatment of sludge, the optimum HTT temperature could be controlled at 180 oC. This work provides novel insight into the environmental fate and eco-environmental effects of MP-DOM in sewage sludge. [Display omitted] • MPs is a non-negligible source of DOM in sewage sludge during HTT. • Oxidation reaction is key to MP-DOM transformation while amide reaction mainly occurred at relatively high-temperature stage. • MP-DOM could promote plant growth by affecting gene expression. • Alcohol, esters and glucopyranoside compounds in MP-DOM are key to promote plant growth. • 180oC is the optimum HTT temperature to remove MPs and convert it into harmless active MP-DOM. [ABSTRACT FROM AUTHOR]

• Electrodialysis pretreatment showed high recovery efficiency for sludge-derived DOM. • Molecular number in DOM identified with dual ESI modes was increased by 200%. • DOM WAS mainly contained proteins/aliphatic and lipid-like compounds. • DOM ADS was composed of lipids, proteins/aliphatic, and lignins/CRAM-like compounds. • Two ESI analysis modes can recognize different emerging contaminants. High-resolution mass spectrometry was extensively applied in molecular composition and transformation pathways of dissolved organic matter (DOM) in wastewater sludge treatments. Sample pretreatment methods and electrospray ionization (ESI) modes significant affect the accuracy of molecular characterization for DOM. This study investigated the effects of pretreatment methods (styrene divinyl benzene polymer (PPL), octadecyl (C18), and electrodialysis (ED)) on molecular characteristics of DOM in two typical wastewater sludges (waste activated sludge (WAS) and anaerobic digestion sludge (ADS)) analyzed by FT-ICR MS in both positive ESI (ESI (+)) and negative ESI (ESI (−)) modes. The results indicated that ED pretreatment exhibited the highest recovery rate of 70% ‒ 95% for sludge-derived DOM. ED and PPL performed well in recovering the different sludge-derived DOM with a high similarity of molecular characteristics (e.g., lipids, proteins/aliphatic, and lignins/CRAM-like), and the C18 method was ineffective in extracting carbohydrates, unsaturated hydrocarbons, and amino sugars. In addition, compared with single ESI (−) analysis mode, the molecular number identified by ESI (+) analysis mode was increased by 200%, especially, more unsaturated hydrocarbons and N-containing compounds were detected. Except for biogenic DOM, plenty of emerging containments (ECs) in sludge-derived DOM were identified; ESI (−) mode was more effectively in recognizing the alkyl benzene sulfonic acids (e.g., anionic surfactants); and ESI (+) mode was more effectively for plasticizers identification, for example, dioctyl terephthalate and dibutyl phthalate. This study illustrated that ED pretreatment coupled with FT-ICR MS in dual ESI modes could give more insights in complexed molecular information for DOM in wastewater sludge, and provides a theoretical basis for subsequent sludge treatments and disposals. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • PHT was proposed to synchronously enhance dewaterability and biostimulants recovery from ADS. • Lignins/CRAM and proteins/aliphatic-like structure dominated in ADS-derived DOMs. • CHON compounds possessed highest reactivity due to carbonyl-related reactions. • DOM 160 containing high levels of N&O heterocyclic compounds showed phytotoxicity. • 200 °C was suggested to enhance ADS dewaterability and biostimulants recovery. In this study, we investigated the effects of hydrothermal temperature on molecular reaction pathways and the plant growth of dissolved organic matters (DOMs) in anaerobic digestion sludge (ADS) via post-hydrothermal treatment (PHT). ADS-derived DOMs mainly comprise lignins/carboxyl-rich alicyclic molecules-like and proteins/aliphatic-like compounds featured with enriched N 1-2 O 6-7 and O 8-10 fragments. With the increase in the hydrothermal (HT) temperature, the relative abundance of the compounds with < 7O atoms in DOMs gradually increased in HT-treated samples. Furthermore, based on Fourier transforms ion cyclotron resonance mass spectrometry (FT-ICR-MS)-based reactomics, we found that CHON compounds possessed the highest reactivity, and that reaction of carbonyl (loss of glyoxal (−C 2 H 2 O 2)) with unique reaction precursors possessed the largest number of high-frequency reactions at different HT temperatures. Consequently, DOM 160 contained higher levels of N&O heterocyclic compounds and acetic acid, inhibiting pakchoi growth, and causing an increase in superoxide dismutase activity in the roots. However, DOM 200 comprised a higher content of amino acids and humic/fulvic acids, increasing indole-3-acetic acid concentration and H+-ATPase activity in the pakchoi roots, thus exhibiting higher plant activity. Overall, the best HT temperature for ADS dewaterability and the recovery of organic matter was found to be 200 °C. These findings proposed a promising approach for synchronously recycling biostimulants, deep dewatering of ADS via PHT, and further improving the carbon–neutral operation of wastewater treatment plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-targeted mass difference analysis was used to clarify DON transformation pathways. • Nucleic acid (mainly RNA) contributed to deamidization and deamination at 30 °C–70 °C. • Aspartyl, serine, histidine, and glutamyl units were representative precursors at 160 °C–200 °C. • HT liquor at 70–120 °C showed the highest DON bioavailability (∼57.6 %). Hydrothermal (HT) treatment has been considered effectively to recover nitrogen-containing organic nutrients from wastewater activated sludge (WAS), and understanding the fate and distribution of dissolved organic nitrogen (DON) during HT process is of great importance to process optimization. Thus, this study aims to investigate molecular transformation pathway of DON during HT process using non-targeted mass difference network analysis and evaluate the bioavailability of DON with chlorella. Results suggested that HT treatment was superior in N -containing organic matter solubilization (DON /TN > 60 %), and DON in WAS underwent extensive transformation processes at various HT temperatures. From room temperature to 70 °C, nucleic acids were solubilized to HT liquor, accomplishing with deamidation (–CONH + H 2 /H 2 O). And a representative ribose nucleic acid with a 'PA–pentose (ribose)–uracil (U)' structure was identified. With temperature rising to 120 °C, large amounts of stable protein were solubilized and hydrolyzed into HT liquor. The non-targeted mass difference network analysis suggested that, from 160 °C to 200 °C, aspartyl, serine, histidine, and glutamyl units were representative precursors for a variety of reactions including Maillard reactions, deamidation, deamination and so on. Amino acids were deaminated (–NH) to produce organic acids and ammonia (ammonium) or decarboxylated (–COO) to produce amines and CO 2. Dicarbonyl compounds (–C 2 H 2 O 2) were identified as the most abundant fragments which could either form humic substances or Maillard reaction products. Chlorella growth bioassay indicated that org-N in HT liquor produced at 120 °C showed the highest bioavailability for Chlorella , while that generated in HT liquor above 160 °C inhibited the growth of Chlorella. This study provided molecular insights for DON transformation following HT process and promoted high-quality resource utilization of WAS. [ABSTRACT FROM AUTHOR]

[Display omitted] • N-compounds were transformed into aromatic and refractory oxygenated compounds. • N-compounds and lignin in dredging sludge were major precursors in humification. • CHON component showed the highest reactivity among different elemental categories. • Deamination was the dominant reaction among 23 reaction types of composting. Using Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) and molecular reaction network analysis, this study investigated molecular transformation of dissolved organic matter (DOM) and formation pathway of humic substances (HS) in dredged sludge during aerobic composting. The results showed that macromolecular N-containing compounds in dredged sludge are abundantly transformed into unsaturated and aromatic oxygenated compounds, exhibiting physicochemical properties similar to those of humus. Especially, N-containing compounds with one nitrogen atom are susceptible to oxidative deamination. Furthermore, assemblages of reactive fragments (e.g., –C 7 H 8 O 2 , –C 10 H 12 O 2 , –C 2 H 2 O 2 , and –C 4 H 6 O 2) were identified as potential precursors to HS formed by the following reactions: starting with protein deamination and desulfurization, lignin delignification cascaded, finally decarbonylation occurred. This work provides novel insight for optimizing the process of stabilization and humification of dredged sludge. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyphenols in DOM ACS and DOM ADS are responsible for their contrasting photoactivity. • High unsaturation/aromaticity compounds with heteroatom in DOM BSS are easily degraded. • Differences in reactants of DOM ACS and DOM ADS caused their different photolysis pathways. • Photochemical transformations reduced Cd (II) ion activity of DOM BSS. Bio-stabilization sludge contains numerous dissolved organic matter (DOM) that could enter aquatic environments by soil leaching after sludge land use, but a clear understanding of their photochemical behavior is still lacking. In this study, we systematically investigated the photoactivity and photochemical transformation of aerobic composting sludge-derived DOM (DOM ACS) and anaerobic digestion sludge-derived DOM (DOM ADS) by using multispectral analysis coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicated that DOM ACS and DOM ADS have a higher proportion of highly unsaturated and phenolic compounds (HuPh)with high DBE wa , but the different polyphenols (Polyph) abundance of them, causing the different photoactivity between them. DOM ACS had much higher apparent quantum yields (AQY) for triplet states of dissolved natural organic matter (3DOM*) and hydroxyl radical (•OH) but slightly lower AQY for singlet oxygen (1O 2) than DOM ADS under simulated sunlight conditions. As the irradiation time increased, HuPh and Polyph (associated with humic-like substances) contained in DOM ACS (DOM ADS) decreased by 12.0% (14.1%) and 3.0% (0.2%), respectively, with concurrent decrease in average molecular weight and aromaticity moieties, resulting in more generation of aliphatic compounds. Furthermore, based on 27 types of photochemical transformation reactions, DOM ACS containing higher fractions of O 10-15 and N 1-3 O y class preferred dealkyl group and carboxylic acid reactions, whereas DOM ADS composed of more N 4 O y and S 2 O y fragments preferred oxygen addition and anmine reactions. Consequently, photochemical transformations reduced the Cd (II) ion activity in the presence of DOM ACS (DOM ADS). This study is believed to unveil the photochemical transformation of bio-stabilization sludge-derived DOM and its impact on pollutants' fate in the aquatic environment. [ABSTRACT FROM AUTHOR]

• Ce/TiO 2 @LDH was prepared from waste Ti-BFS. • Ce greatly promoted the adsorption and visible light photodegradation. • Active surface oxygen and oxygen vacancies was distinctly increased. • The photodegradation pathway was studied. • The photocatalytic mechanism was proposed. [Display omitted] As a kind of bulk solid waste in iron and steel industry, titanium-bearing blast furnace slag (Ti-BFS) poses a serious threat to the environment, its disposal and reuse has been a hot and difficult spot. In this study, a new and high efficient hydrotalcite-like photocatalytic material (denoted CeTL) was prepared from Ti-BFS, and applied to the visible light catalytic degradation of antibiotics in water environment. The results showed that the degradation rate of tetracycline (TC) by the optimized CeTL reached 92.8% after 90 min of illumination. Dissolved organic matter with molecular weight 1–3 kDa was the most inhibiting to degradation rate. The introduction of Ce contributed to the nanopore structure and increased the specific surface area (302.58 m²/g), and effectively promoted the development of active surface oxygen and oxygen vacancies in the lattice, thus reducing the excited energy of photoelectron and expanding the spectral response range. Moreover, Ce acted as a medium to transfer photoelectrons, which successfully separates the reducing photoelectron in conduction band (CB) and the oxidized hole in valence band (VB), and generated·O 2 − and·OH with O 2 and OH−, respectively. These active species attacked TC molecules adsorbed on CeTL surface, degraded them into small molecules, and improved the antibacterial activity of CeTL. The good adsorption capacity and the enhanced visible light catalysis of CeTL synergistic realized the efficient removal of TC. This work enriched the research system of comprehensive utilization of Ti-BFS, and provided a new strategy for the preparation of efficient applied photocatalysts and the recycling of resources. [ABSTRACT FROM AUTHOR]

Sludge pyrolysis carbonization has shown potential to convert sludge biomass into multifunctional carbon materials. However, ecological risks of dissolved organic matters (DOMs) with obscure molecular characteristics retaining in sludge-based carbons (SBCs) have received little attention. This study investigated the impact of pyrolysis temperatures on the molecular conversion and biotoxicity effects of DOMs in SBCs. The results revealed that DOMs in SBCs 300–400 were mainly derived from depolymerization of biopolymers and the polycondensation and cyclization of small intermediate molecules, which mainly consisted of aromatic CHON compounds with 1–3 N atoms, featuring high unsaturation and molecular weights. High-temperature pyrolysis (500–800 °C) promoted the decomposition and ring-opening of aromatic CHON compounds into saturated aliphatic CHO compounds with 2–4 O atoms in SBCs 500–800. Noteworthily, SBCs 300–400 -derived DOMs showed relatively strong biotoxicity on the growth and development of wild-type zebrafish embryos, pakchoi seeds, and Vibrio qinghaiensis Q67, which was significantly related to aromatic amines, phenols, and heterocyclic-N compounds in DOMs of SBCs 300–400. SBCs 500–800 -derived DOMs were mainly straight-chain fatty acids and showed no observable acute biotoxicity. This study highlights the negative impact of DOMs in SBCs on the ecological environment, and provides the theoretical basis for controlling toxic byproducts in sludge pyrolysis process. [Display omitted] • DOMs in SBCs 300–400 mainly contained N-containing aromatic compounds. • DOMs of SBCs 500–800 were mainly composed of saturated aliphatic compounds. • Biotoxicity was related to aromatic amines, phenols, and heterocyclic-N compounds. • Increasing pyrolysis temperature can reduce the content and biotoxicity of DOMs in SBCs. [ABSTRACT FROM AUTHOR]