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Abstract: This study introduces the concept of consistent examination of changes of log-transformed absorbance spectra of dissolved organic matter (DOM) at incrementally increasing concentrations of heavy metal cations such as copper, cadmium, and aluminum at environmentally relevant concentrations. The approach is designed to highlight contributions of low-intensity absorbance features that appear to be especially sensitive to DOM reactions. In accord with this approach, log-transformed absorbance spectra of fractions of DOM from the Suwannee River were acquired at varying pHs and concentrations of copper, cadmium, and aluminum. These log-transformed spectra were processed using the differential approach and used to examine the nature of the observed changes of DOM absorbance and correlate them with the extent of Me-DOM complexation. Two alternative parameters, namely the change of the spectral slope in the range of wavelengths 325–375 nm (DSlope325–375) and differential logarithm of DOM absorbance at 350 nm (DLnA350) were introduced to quantify Cu(II), Cd(II), and Al(III) binding onto DOMs. DLnA350 and DSlope325–375 datasets were compared with the amount of DOM-bound Cu(II), Cd(II), and Al(III) estimated based on NICA-Donnan model calculations. This examination showed that the DLnA350 and DSlope325–375 acquired at various pH values, metal ions concentrations, and DOM types were strongly and unambiguously correlated with the concentration of DOM-bound metal ions. The obtained experimental results and their interpretation indicate that the introduced DSlope325–375 and DLnA35 parameters are predictive of and can be used to quantify in situ metal ions interactions with DOMs. The presented approach can be used to gain more information about DOM-metal interactions and for further optimization of existing formal models of metal-DOM complexation. [Copyright &y& Elsevier]

Abstract: The mechanism of natural organic matter (NOM) removal by AlCl3 and polyaluminum chloride (PACl) was investigated through bench-scale tests. The fraction distributions of NOM and residual Al after coagulation in solution, colloid and sediment were analyzed as changes of coagulant dosage and pH. The influence of NOM, coagulant dose and pH on coagulation kinetics of AlCl3 was investigated using photometric dispersion analyzer compared with PACl. Monomeric Al species (Ala) shows high ability to satisfy some unsaturated coordinate bonds of NOM to facilitate particle and NOM removal, while most of the flocs formed by Ala are small and difficult to settle. Medium polymerized Al species (Alb) can destabilize particle and NOM efficiently, while some flocs formed by Alb are not large and not easy to precipitate as compared to those formed by colloidal or solid Al species (Alc). Thus, Alc could adsorb and remove NOM efficiently. The removal of contaminant by species of Ala, Alb and Alc follows mechanisms of complexation, neutralization and adsorption, respectively. Unlike preformed Alb in PACl, in-situ-formed Alb can remove NOM and particle more efficiently via the mechanism of further hydrolysis and transfer into Alc during coagulation. While the presence of NOM would reduce Alb formed in-situ due to the complexation of NOM and Ala. [Copyright &y& Elsevier]

Abstract: Conventional coagulation is not an effective treatment option to remove natural organic matter (NOM) in water with high alkalinity/pH. For this type of water, enhanced coagulation is currently proposed as one of the available treatment options and is implemented by acidifying the raw water and applying increased doses of hydrolyzing coagulants. Both of these methods have some disadvantages such as increasing the corrosive tendency of water and increasing cost of treatment. In this paper, an improved version of enhanced coagulation through coagulant optimization to treat this kind of water is demonstrated. A novel coagulant, a composite polyaluminum chloride (HPAC), was developed with both the advantages of polyaluminum chloride (PACl) and the additive coagulant aids: PACl contains significant amounts of highly charged and stable polynuclear aluminum hydrolysis products, which is less affected by the pH of the raw water than traditional coagulants (alum and ferric salts); the additives can enhance both the charge neutralization and bridging abilities of PACl. HPAC exhibited 30% more efficiency than alum and ferric salts in dissolved organic carbon (DOC) removal and was very effective in turbidity removal. This result was confirmed by pilot-scale testing, where particles and organic matter were removed synergistically with HPAC as coagulant by sequential water treatment steps including pre-ozonation, coagulation, flotation and sand filtration. [Copyright &y& Elsevier]

Abstract: The characteristics of typical source waters in northern China and their enhanced coagulation features were studied in this paper. Through bench scale tests, a composite coagulant (HPAC) was selected for this kind of high alkalinity and pH water. It can be 30% more efficient in organic matter (OM) removal than the traditional coagulants (AlCl3, FeCl3), and polyaluminum chloride (PACl), especially more efficient in removing high SUVA, hydrophobic and high molecular weight dissolved organic matter (DOM). It is found that some DOM with low SUVA has precedence over that with high SUVA to be removed at conventional dosages in some seasons, and that the priority of DOM removal is in the same sequence for all the coagulants. DOM with high SUVA is not always more easily removed. When applying HPAC as coagulant, flotation process can remove hydrophobic OM more efficiently than sedimentation process in pilot scale tests. [Copyright &y& Elsevier]

A novel activated sludge (AS) conditioning method through permanganate/bisulfate (PM/BS) process was proposed. The method involved a new conditioner of reactive Mn(III) intermediate. Moreover, a Mn(III) conditioning–horizontal electro-dewatering (Mn(III) C–HED) process was established to improve AS dewatering performance. Underlying mechanisms were unraveled by investigating changes in physicochemical characteristics, scanning electron microscope (SEM) morphology, and transformation of water and organic matters. The optimum dewatering conditions for Mn(III) C–HED process with the final water content of 86.94% were determined as the combination of KMnO 4 0.01 mol/L AS and NaHSO 3 0.05 mol/L AS at 20 V for 120 min. Results showed that Mn(III) C–HED process effectively reduced free water and bound water with the corresponding removal ratios of 51.68% and 87.62% at the anode-side as well as 36.55% and 85.08% at the cathode-side, respectively. During the PM/BS process, the produced Mn(III), Mn 2+ , and MnO 2 exerted chemical and physical effects on AS conditioning and dewatering. Mn(III) disintegrated extracellular polymeric substances (EPS) fractions and cells in AS, as well as induced partial bound water release. Additionally, flocculation effect induced by Mn 2+ and MnO 2 skeleton building also benefited AS dewatering. AS cells were further disrupted under the effect of a horizontal electric field. Accordingly, EPS within the AS matrix was solubilized, tightly bound (TB)-EPS or loosely bound (LB)-EPS was converted to their corresponding outer EPS fractions, and AS dewaterability improved. Additionally, changes in pH and temperature at HED stage damaged the AS cells and changed the floc properties, thereby leading to easy separation of liquid and AS particles. [ABSTRACT FROM AUTHOR]

The effects of combined calcium peroxide (CaO 2 ) oxidation with chemical re-flocculation on dewatering performance and physicochemical properties of waste activated sludge was investigated in this study. The evolutions of extracellular polymeric substances (EPS) distribution, composition and morphological properties were analyzed to unravel the sludge conditioning mechanism. It was found that sludge filtration performance was enhanced by calcium peroxide oxidation with the optimal dosage of 20 mg/gTSS. However, this enhancement was not observed at lower dosages due to the absence of oxidation and the performance deteriorated at higher dosages because of the release of excess EPS, mainly as protein-like substances. The variation in soluble EPS (SEPS) component can be fitted well with pseudo-zero-order kinetic model under CaO 2 treatment. At the same time, extractable EPS content (SEPS and loosely bound EPS (LB-EPS)) were dramatically increased, indicating sludge flocs were effectively broken and their structure became looser after CaO 2 addition. The sludge floc structure was reconstructed and sludge dewaterability was significantly enhanced using chemical re-flocculation (polyaluminium chloride (PACl), ferric iron (FeCl 3 ) and polyacrylamide (PAM)). The inorganic coagulants performed better in improving sludge filtration dewatering performance and reducing cake moisture content than organic polymer, since they could act as skeleton builders and decrease the sludge compressibility. [ABSTRACT FROM AUTHOR]

Extracellular polymeric substances (EPS) are highly hydrated biopolymers and play important roles in bioflocculation, floc stability, and solid-water separation processes. Destroying EPS structure will result in sludge reduction and release of trapped water. In this study, the effects of combined process of peracetic acid (PAA) pre-oxidation and chemical re-flocculation on morphological properties and distribution and composition of EPS of the resultant sludge flocs were investigated in detail to gain insights into the mechanism involved in sludge treatment. It was found that sludge particles were effectively solubilized and protein-like substances were degraded into small molecules after PAA oxidation. A higher degradation of protein-like substances was observed at acid environments under PAA oxidation. Microscopic analysis revealed that no integral sludge floc was observed after oxidation with PAA at high doses. The floc was reconstructed with addition of inorganic coagulants (polyaluminium chloride (PACl) and ferric chloride (FeCl 3 )) and PACl performed better in flocculation due to its higher charge neutralization and bridging ability. Combined oxidative lysis and chemical re-flocculation provide a novel solution for sludge treatment. [ABSTRACT FROM AUTHOR]

The feasibility of combined process of composite enzymatic treatment and chemical flocculation with inorganic salt coagulants was investigated in this study. The evolution of extracellular polymeric substances (EPS) distribution, composition and morphological properties were analyzed to unravel the sludge conditioning mechanism. It was found that sludge filtration performance was deteriorated due to release of a large amount of biopolymers after enzymatic treatment. The change in EPS followed the pseudo-first-order kinetic equation well under enzymatic treatment. The feeding modes of enzymes had a significant influence on sludge lysis efficiency under compound enzymes treatment. Alpha amylase + protease was more effective in solubilization than other two addition modes (protease + α-amylase or simultaneous addition). The sludge floc re-formed and macromolecule biopolymers were effectively removed through coagulation process. At the same time, both of filtration rate and cake solid content of sludge treated with enzymes were improved with increasing dosage of coagulants, and ferric iron (FeCl 3 ) had better performance in sludge dewaterability enhancement than polyaluminium chloride (PACl). In addition, sludge filtration property was slightly deteriorated, while the cake moisture reduction was favored at the optimal dosage of inorganic coagulants. [ABSTRACT FROM AUTHOR]

Waste activated sludge serves an important reservoir for antibiotics within wastewater treatment plants, and understanding the occurrence and evolution of antibiotics during sludge treatment is crucial to mitigate the potential risks of subsequent resource utilization of sludge. This study explores the degradation and transformation mechanisms of three typical antibiotics, oxytetracycline (OTC), ofloxacin (OFL), and azithromycin (AZI) during sludge hydrothermal treatment (HT), and investigates the influence of biopolymers transformation on the fate of these antibiotics. The findings indicate that HT induces a shift of antibiotics from solid-phase adsorption to liquid-phase dissolution in the initial temperature range of 25–90 °C, underscoring this phase's critical role in preparing antibiotics for subsequent degradation phases. Proteins (PN) and humic acids emerge as crucial for antibiotic binding, facilitating their redistribution within sludge. Specifically, the binding capacity sequence of biopolymers to antibiotics is as follows: OFL>OTC>AZI, highlighting that OFL-biopolymers display stronger electrostatic attraction, more available adsorption sites, and more stable binding strength. Furthermore, antibiotic degradation mainly occurs above 90 °C, with AZI being the most temperature-sensitive, degrading 92.97% at 180 °C, followed by OTC (91.26%) and OFL (52.51%). Concurrently, the degradation products of biopolymers compete for active sites to form novel amino acid-antibiotic conjugates, which inhibits the further degradation of antibiotics. These findings illuminate the effects of biopolymers evolution on intricate dynamics of antibiotics fate in sludge HT and are helpful to optimize the sludge HT process for effective antibiotics abatement. [Display omitted] [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]

• Flocs would absorb and release NOM during aging, aquatic humics is the primary releasing organic matter. • The flocs generated form Al 13 and AlCl 3 have the same organic release pattern during aging, but the release intensity of Al 13 is lower. • The flocs generated form nanoparticles and microparticles have different release and absorption pattern of NOM during aging. • The flocs will further generate Al hydrolysates with higher polymerization during aging. Most studies on the interaction between coagulation and NOM (natural organic matter) currently focus on pollutant removal and coagulant species distribution, while studies on floc aging are lacking. Investigation onto the effects of floc aging could guide further processes that utilize flocs, such as densadeg sludge recirculation, floc predeposition for ultrafiltration, sludge condensation, and other traditional sludge reflux processes. In this study, flocs generated by Al 13 and AlCl 3 in microparticle- and nanoparticle-containing water were investigated, and the effect of floc aging on NOM was quantified based on several organic matter characterization techniques. Flocs absorb and release organics during aging. The flocs generated from micro-SiO 2 have a significant absorbing effect for LWM-N (low-molecular-weight neutral substances) and protein-like substances, while the absorption of NOM by flocs generated from nano-SiO 2 is insignificant. HS (humic substances) with high aromaticity are released during floc aging. From the molecular perspective, the molecules released during floc aging are those with higher double bond equivalents and higher aromaticity, while the absorbed molecules are those with lower double bond equivalents and lower aromaticity. 2D-COS (two-dimensional correlation spectroscopy) demonstrated that the flocs generated by Al 13 and AlCl 3 had the same organic release patterns but different intensities, while the flocs generated in the micro-SiO 2 and nano-SiO 2 systems had different organics release patterns. Abundant aluminum hydrolysates with low polymerization and amorphous Al(OH) 3 would be produced from AlCl 3 during the coagulation process and then undergo hydroxyl‑bridging reaction and crystallization during floc aging, thus releasing more HS with high aromaticity into the supernatant; in comparison, prehydrolyzed Al 13 produces a more stable floc and releases less HS during aging. The flocs produced by nano-SiO 2 and Al-based coagulants release higher aromaticity HS into the water than those produced by micro-SiO 2 , which may be related to the formation of more highly polymerized degree hydrolysates and nanocrystalline Al(OH) 3 in the nano-SiO 2 system. The flocs generated in water with micro-SiO 2 may contain a large amount of Al-OH and have a loose structure, thus further absorbing NOM, such as protein-like substances and LWM-N. In contrast, the flocs generated from nano-SiO 2 possess abundant adsorbed water and a denser structure; thus, organic matter cannot be absorbed stably. [Display omitted] [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]

• Four rainfall patterns identified by intensity, duration, and cumulative rainfall. • Nutrient forms and concentrations entering reservoirs vary with rainfall patterns. • TN:TP variations arise from distinctive particulate and dissolved p & n transport. • Hysteresis analysis unveils algae shifts with p & n dynamics amid rainfall events. • Phytoplankton community succession driven by both nutrient levels and proportions. The escalation of global eutrophication has significantly increased due to the impact of climate change, particularly the increased frequency of extreme rainfall events. Predicting and managing eutrophication requires understanding the consequences of precipitation events on algal dynamics. Here, we assessed the influence of precipitation events throughout the year on nutrient and phytoplankton dynamics in a drinking water reservoir from January 2020 to January 2022. Four distinct precipitation patterns, namely early spring flood rain (THX), Plum rain (MY), Typhoon rain (TF), and Dry season (DS), were identified based on rainfall intensity, duration time, and cumulative rainfall. The study findings indicate that rainfall is the primary driver of algal dynamics by altering nutrient levels and TN:TP ratios during wet seasons, while water temperature becomes more critical during the Dry season. Combining precipitation characteristics with the lag periods between algal proliferation and rainfall occurrence is essential for accurately assessing the impact of rainfall on algal blooms. The highest algae proliferation occurred approximately 20 and 30 days after the peak rainfall during the MY and DS periods, respectively. This was influenced by the intensity and cumulative precipitation. The reservoir exhibited two distinct TN/TP ratio stages, with average values of 52 and 19, respectively. These stages were determined by various forms of nitrogen and phosphorus in rainfall-driven inflows and were associated with shifts from Bacillariophyta -dominated to Cyanophyta -dominated blooms during the MY and DS seasons. Our findings underscore the interconnected effects of nutrients, temperature, and hydrological conditions driven by diverse rainfall patterns in shaping algal dynamics. This study provides valuable insights into forecasting algal bloom risks in the context of climate change and developing sustainable strategies for lake or reservoir restoration. [Display omitted] [ABSTRACT FROM AUTHOR]

• An innovative pilot-scale staged PN/A process developed to treat MLL. • Stable nitrogen removal (TN < 40 mg/L) was achieved under continuous flow. • Stable inhibition of NOB by low oxygen in combination with FA and FNA. • Salt-tolerant Kuenenia (33.4 %) dominated the ecological niche in anammox biofilm. • Dual biofilm membrane designed to keep effluent SS stable below 5 mg/L. The start-up and stable operation of partial nitritation-anammox (PN/A) treatment of mature landfill leachate (MLL) still face challenges. This study developed an innovative staged pilot-scale PN/A system to enhance nitrogen removal from MLL. The staged process included a PN unit, an anammox upflow enhanced internal circulation biofilm (UEICB) reactor, and a post-biofilm unit. Rapid start-up of the continuous flow PN process (full-concentration MLL) was achieved within 35 days by controlling dissolved oxygen and leveraging free ammonia and free nitrous acid to selectively suppress nitrite-oxidizing bacteria (NOB). The UEICB was equipped with an annular flow agitator combined with the enhanced internal circulation device of the guide tube, which achieved an efficient enrichment of Candidatus Kuenenia in the biofilm (relative abundance of 33.4 %). The nitrogen removal alliance formed by the salt-tolerant anammox bacterium (Candidatus Kuenenia) and denitrifying bacteria (unclassified SBR1031 and Denitratisoma) achieved efficient nitrogen removal of UEICB (total nitrogen removal percentage: 90.8 %) and at the same time effective treatment of the refractory organic matter (ROM). The dual membrane process of UEICB fixed biofilm combined with post-biofilm is effective in sludge retention, and can stably control the effluent suspended solids (SS) at a level of less than 5 mg/L. The post-biofilm unit ensured that effluent total nitrogen (TN) remained below the 40 mg/L discharge standard (98.5 % removal efficiency). Compared with conventional nitrification-denitrification systems, the staged PN/A process substantially reduced oxygen consumption, sludge production, CO 2 emissions and carbon consumption by 22.8 %, 67.1 %, 87.1 % and 87.1 %, respectively. The 195-day stable operation marks the effective implementation of the innovative pilot-scale PN/A process in treating actual MLL. This study provides insights into strategies for rapid start-up, robust NOB suppression, and anammox biomass retention to advance the application of PN/A in high-ammonia low-carbon wastewater. [ABSTRACT FROM AUTHOR]

Abstract: The classic Langmuir isotherm equation was modified to describe phosphorus (P) adsorption on P-polluted sediments. The P adsorption characteristics of six sediment samples from Chinese Taihu Lake were studied by short-term isotherm batch experiments and related to sediment composition. The maximum P adsorption capacities (PAC) and P-binding energy constant (k) were obtained by nonlinearly fitting sorption data using the modified Langmuir isotherm model. Native adsorbed exchangeable phosphorus (NAP), the zero equilibrium P concentration value (EPC0), and partitioning coefficients (K p) were subsequently calculated by corresponding formulae. K p and PAC were linearly related to the contents of active Fe and Al in sediments by least squares regression analyses ( for both). The effect of pH in a wide range on adsorption process was investigated and H2PO4 − was presumed to be the preferential sorption species in overall sorption process. The fact that the amount of P sorbed and zeta potential of sediment particles have no necessary relationship reveals that a strong contribution to the P binding still comes from a ligand-exchange process on the Me–OH2 + and Me–OH sites rather than electrostatic attraction. In addition, the influence of oxidation–reduction potential (ORP) was investigated and discussed and the dual nature of sediments as a pool or source of P in natural waters was evaluated in site T1–T4. [Copyright &y& Elsevier]

• 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]

Sewage sludge, the major by-product during the primary treatment and subsequent biotreatment of wastewater, is increasingly generated around the world. KMnO 4 Fe(II) consists both oxidation properties of KMnO 4 and flocculation ability by in-situ formed Fe(III) and is widely used in water treatment. In this study, KMnO 4 Fe(II) was used as chemical conditioners to synchronously improve sludge dewatering performance and catalyze the biomass pyrolysis of waste activated sludge for preparing multi-functional material to remedy arsenic containing groundwater. The results showed that the sludge dewaterability was significantly improved due to the moderate pre-oxidation of extracellular polymeric substances by KMnO 4 , and then the sludge particles were re-flocculated by Fe(III) generated from KMnO 4 Fe(II). The conditioned sludge cake was then utilized for preparing sludge-based carbon (Fe-Mn-SBC) which was systematically characterized. The surface area of Fe-Mn-SBC was characteristic of high surface area (100.08 m2/g) which had a great adsorption capacity on arsenic. Besides, Fe-Mn-SBC could effectively oxidize As(III) to As(V), and addition of low dose of H 2 O 2 can further improve total arsenic removal due to catalytic peroxidation of Fe-Mn-SBC. Besides, it was found that the presence of humic acid could inhibit the hydroxy iron formation and compete for the active adsorption sites and then resulted in the decrease in arsenic removal, and the co-existing humic acid could also be removed by adsorption of Fe-Mn-SBC. This work proposed a novel sludge treatment process by combining enhanced sludge dewatering with catalytic pyrolysis for preparing multi-functional materials, and they are promising in treatment of water containing combined pollutants. Image 1 • KMnO 4 Fe(II) was effective in improving the sludge dewaterability. • Both oxidation and coagulation were responsible for KMnO 4 Fe(II) conditioning. • Fe-Mn-SBC performed well in combined pollutants (arsenic and HA) removal in groundwater. • Oxidation and adsorption showed synergetic effects in arsenic removal under Fe-Mn-SBC treatment. • HA inhibited the arsenic removal by competing adsorption sites and slowing down the hydrolysis of ferric ions. [ABSTRACT FROM AUTHOR]

Abstract Waste activated sludge (WAS) contains many anionic functional groups which can interact with heavy metal ions through electrostatic action and complexation reactions. The transition metals adsorbed in WAS can catalyze sludge pyrolysis in anaerobic conditions and improve structural properties of organic matter. In this work, a multistage WAS utilization process for preparing the carbon-based Fenton-like catalysis materials is proposed. More specifically, WAS is firstly used as an adsorbent for heavy metals (Cu and Ni) removal, and then complexes are converted into heterogeneous Fenton-like carbon-based catalysts through oxygen-free pyrolysis. The mechanisms of interactions between extracellular polymeric substances (EPS) and metals are investigated, and the physicochemical properties of sludge-based carbons (SBC) are comprehensively characterized using varies techniques. It is found that WAS is an excellent adsorbent for Cu and Ni removal, which is mainly due to the coordination and electrostatic interactions between EPS and heavy metals. Cu and Ni adsorbed in WAS significantly improved the porous structure of SBC. Both adsorption and catalytic oxidization of Cu/Ni-SBC contribute the removal of E2 in real wastewater. The E2 removal mechanism is explored by electron-spin resonance spectroscopy (ESR) analysis, and it is found that both of .O 2 − and .OH radicals are responsible for E2 degradation in Cu(II)-SBC-H 2 O 2 , while .O 2 − radicals contributes to E2 degradation in Ni(II)-SBC-H 2 O 2 system, so the former performed better than the latter in total removal of E2. Besides, Cu(II) and Cu(I) are both formed in Cu(II)-SBC during the oxidation process, while only Ni(II) is found in the Ni(II)-SBC-H 2 O 2 process, confirming that different catalytic oxidation reactions are occurred in the Cu(II)-SBC-H 2 O 2 and Ni(II)-SBC-H 2 O 2 processes. This study facilitates a great strategy to the sludge multi-stage circulating utilization and a better understanding about the role of the Cu/Ni existed in SBC during the estrogens removal process. Graphical abstract Image 1 Highlights • Proposed multistage WAS process to initiate carbon-based Fenton-like catalysis for the first time. • Cu(II)/Ni(II) adsorbed in sludge improved the porous structure of SBC materials. • The coordination interactions mechanisms between EPS and heavy metals were determined. • The combination of Cu(II)/Ni(II) and sludge carbon (SBC) enhanced E2 removal from wastewater. [ABSTRACT FROM AUTHOR]

Abstract Sludge treatment and disposal have become critical environmental issues in China. Electro-dewatering (ED) is an attractive technology for enhancing dewaterability and improving the sustainability of waste activated sludge (WAS) handling. However, electrically assisted mechanical dewatering processes consume more energy and the extracellular polymeric substance (EPS) dissolution caused by electrochemical reactions can lead to clogging of the filter cloth. Carbon-based materials (CBMs) such as activated carbon and graphite have electrical conductivity and well-developed pore structures which can adsorb the biopolymers. Therefore, addition of CBMs is expected to improve WAS electro-dewatering performance for fuel treatment by enhancing sludge conductivity and filterability. In this study, we evaluated the effects of the three carbon materials (AC-0, AC-5, and graphite) on sludge electro-dewatering behavior and the flammability of sludge cakes. The results showed that CBMs promote the performance of WAS electro-dewatering, and the promoting effect of the carbon materials on the sludge electro-dewatering is proportional to the electrical conductivity of the carbon material, and carbon materials can increase the electrophoretic mobility of sludge flocs and the electro-osmotic effect. Moreover, CBMs can adsorb the dissolved EPS, thus alleviate the plugging and filtration resistance of the filter medium. The addition of CBMs also decreases the energy consumption for water removal during the electro-dewatering process and improves the calorific value and sustainable combustion time of the sludge cake. Our approach can facilitate the resource utilization of the dewatered sludge cake in electro-dewatering processes. Graphical abstract Image 1 Highlights • CBMs enhanced the sludge electro-dewatering performance. • CBMs increased the electrophoretic mobility and electro-osmotic effects of sludge flocs. • CBMs can adsorb the dissolved EPS and promote sludge filterability. • CBMs can improve the calorific value of sludge cake. [ABSTRACT FROM AUTHOR]

Abstract Anaerobic digestion (AD) has been widely used in sludge treatment for biogas recovery, organic fraction stabilization, and sludge reduction. However, after AD, sludge filterability is extremely deteriorated due to the release of biopolymers and the formation of fine particles. AD sludge is generally rich in nutrients, mainly ammonium nitrogen and phosphates, that result from biopolymer degradation. We designed a conditioning process that combines the in-situ crystallization of magnesium ammonium phosphate (MAP), as a skeleton builder, with organic polymer flocculation. We show that crystallized MAP can bind with extracellular polymeric substance fractions to increase sludge floc density. The molecular structure and electrical charge of organic polymers importantly influence sludge particle flocculation and aggregation. We found that cationic polyacrylamides form flocs that aggregate with branching structures which are characterized by a larger size and a more compact structure. Simultaneous crystallization and flocculation produced by a magnesium–organic polymer gel improved AD dewaterability more than the separate addition of magnesium ions and organic polymers. The method of sludge conditioning that we propose was tested by extensive use in different AD sludge conditioning protocols. The method reduces the ammonium nitrogen load in AD liquor and increases the suitability of the biosolids for use as land fertilizer. Graphical abstract Image 1 Highlights • A novel AD sludge dewatering improvement process was proposed. • In-situ formed struvite could function as skeleton builders. • Molecular structure and charge property of PAM had important effects on sludge conditioning. • Mg-CPAM gel exhibited a synergistic effect in improving AD sludge dewaterability. [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]

Proteins are the dominant organic component of extracellular polymeric substances (EPS) in waste activated sludge (WAS), and play an important role during sludge dewatering processes. Methanol is a polar hydrophilic reagent and can denature proteins, which suggested to us that the modification of protein configurations with methanol could improve sludge dewatering performance. In this study, methanol was used to precondition WAS prior to adding inorganic coagulants for dewatering enhancement. The morphology and EPS properties (especially of proteins) were investigated to analyze and explain the effects of methanol in the sludge conditioning process. The results show that methanol performed much better than traditional inorganic coagulants in improving sludge dewaterability in term of specific resistance to filtration (SRF) and cake solid content (CSC). Extractable proteins in EPS increased to a maximum when the concentration of methanol reached 40% (w/w) because cell membranes were destroyed and intracellular substances and water were released. Floc protein content was reduced with the further increase in methanol concentration due to protein precipitation. Confocal laser scanning microscopy analysis indicated that proteins precipitated and formed larger aggregates because methanol destroyed both the hydration shell and the hydrophobic clusters of proteins and expanded the protein tertiary structure to release interstitial water and bound water. The combination treatment of methanol and inorganic coagulants (PAC or FeCl 3 ) showed significant synergetic effects on enhancing sludge dewatering and cake drying. In practical applications, methanol from the dewatering sludge can be returned to the biochemical pool and used as the carbon source for nitrogen removal in the denitrification process. This integrated process is appropriate for sludge final disposal technologies that have high energy demands, such as incineration and pyrolysis. This paper describes a novel approach to improving sludge dewaterability through the alteration of protein properties by use of physiochemical techniques. [ABSTRACT FROM AUTHOR]

Sludge treatment and disposal have become important environmental issues in China. Mechanical dewatering is widely used to reduce the amount of sludge to be disposed and relieve the rapid growth pressure of waste sludge. In comparison to traditional sludge dewatering processes, pressure electro-osmotic dewatering has many advantages on sludge dewatering efficiency, low conditioner dosage and concentrated cake are both beneficial to further recycling of waste sludge. In general, complex electrochemical effects (eg. electrochemical oxidation, ohmic heating and pH gradient effect) are accompanied by the pressure electro-osmotic dewatering process. These electrochemical effects will inevitably cause solubilization and/or degradation of key constituents of wastewater sludge - extracellular polymeric substances (EPS). In this study, the effects of voltage, pH and ionic strength on sludge electro-osmotic dewatering performance and electrochemical effects were investigated. The solubilization and degradation of EPS were analyzed by examining the variation of dissolved organic matter (DOM) in the filtrate, and the relationships between microstructural properties of sludge cake and DOM and electro-osmosis dewatering performance in electro-dewatering process was examined. It was found that electro-dewatering properties were improved by raising the operating voltage or decreasing the pH value, while dewatering rate initially increased at low ionic strength it decreases with increased ionic strength. In addition, the porous structure of cathodic cake was more plentiful than that at the anode. At the cathode, the EPS dissolution was mainly related to alkalization, while the oxidation and acidification were responsible for release of EPS at the anode. Meanwhile, electrophoresis effect was able to promote migration of EPS toward the anode. The average electro-osmotic dewatering rate at the anode (R 2 .>0.79, p < 0.02) and at the cathode (R 2 .>0.87, p < 0.03) strongly correlated with the volume of pore of sludge cake. There was no correlation between the total content of anodic DOM (R 2 <0.31, p>0.08) and electro-osmotic dewatering rate at the anode, however, the content of cathodic DOM (R 2 > 0.62, p < 0.09) negatively correlated with average electro-osmosis dewatering rate of cathode. Since cathode is the main water-permeable side in sludge electro-dewatering, and the sticky biopolymers (proteins and humic subtances) could not be converted into small molecules, higher EPS release was associated with worse sludge filterability. As for the anode, the biopolymers were degraded into small molecules due to electrochemical oxidation, which greatly reduced the impact of DOM on dewatering effect. Therefore, the operating conditions (voltage, pH and ionic strength) caused changes in electrochemical effects, which played a crucial role in compartmentalization of sludge EPS dissolution and consequently sludge electro-dewatering behavior. [ABSTRACT FROM AUTHOR]

An effective approach for eutrophication control and phosphate recovery remains a longstanding challenge. Herein, we present a new technique for phosphate sequestration in lake and phosphate recovery using novel magnetically recoverable magnetite/lanthanum hydroxide [M-La(OH) 3 ] hybrids that can be prepared using a simple one-pot synthesis method. Batch studies show that M-La(OH) 3 exhibits a strong sorption towards phosphate with sorption capacities of up to 52.7 mg-P/g at pH 7.0 in water. A simple model indicates that the efficiency of M-La(OH) 3 for phosphate sequestration in lake is significantly attenuated by 34–45% compared to that in water, due to interference from sediment particles. However, our results demonstrate that sediments suspensions mixed with a M-La(OH) 3 content of 1–3% exhibit a capability of up to 1.2 mg-P/g for sequestering external phosphate compared with that of 0.2 mg-P/g for pristine sediment at pH 7.3. M-La(OH) 3 -mixed sediment suspensions appear to effectively sequester phosphate over an environmentally relevant pH range from 4 to 8.5. Phosphorus (P) fractionation experiments indicate that the enhanced phosphate sorption by M-La(OH) 3 -mixed sediment suspensions is mainly due to the increased fractions of NaOH-P and inorganic P. This work indicates that the M-La(OH) 3 has the potential for phosphate sequestration and recovery from lake. [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]

• A molecular model was built to reveal the arrangements and dynamic characteristics of biopolymers in EPS. • Biopolymers form agglomerates spontaneously through electrostatic and hydrophobic interactions. • Rearrangement of EPS molecular conformation reduced the exposure of hydrophilic groups. • Contact of biopolymers promoted by multivalent cations enhancing the intermolecular forces and compactness of EPS. • The hydration of Al3+ and Mg2+ affect the stability of association with biopolymers. Interactions between cations and extracellular polymeric substances (EPS) play an important role in the formation of microbial aggregates and have key effects on the physical properties of activated sludge across wastewater and sludge treatment process. Here, a molecular model of EPS cluster in activated sludge was constructed and simulated by molecular dynamics (MD) to probe the structural properties of EPS and the interaction between EPS and prevalent multivalent cations (Ca2+, Mg2+, Al3+). Then the predicted changes in physical properties were validated against the dynamic light scattering, XAD resin fractionation and rheology test. The binding dynamics and interactions mechanisms between multivalent cations and EPS functional groups were further investigated using MD in combination with spectroscopic analysis. Results suggest that biopolymers are originally aggregated by electrostatic and intermolecular interactions forming dynamic clusters with negatively charged surface functional groups, which induced electrostatic repulsion preventing further agglomeration of biopolymer clusters. In the presence of multivalent cations, surface polar functional groups in biopolymers are connected, causing the rearrangement of EPS molecular conformation that forms larger and denser agglomerates. Reduced solvent accessible surface area, enhanced hydrophobicity, and increased binding free energy lead to a strong gel-like network of EPS. Ca2+ and Al3+ predominantly interact with functional groups in polysaccharides, promoting agglomeration of macromolecules. In contrast, Mg2+ and Al3+ disrupted the secondary structure of proteins, exposing hydrophobic interaction sites. Al3+ can better agglomerate biopolymers with its higher positive charge and shorter coordination distance as compared to Ca2+ and Mg2+, but compromised by the effect of hydration. This work offers a novel approach to explore the construction and molecular aggregation of EPS, enriching the theoretical basis for optimization of wastewater and sludge treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Hardness cations are ubiquitous and abundant in source water, while the effect of hardness on the performance of coagulation for dissolved organic matter (DOM) removal in water treatment remains unclear due to the limitation of methods that can characterise the subtle interactions between DOM, coagulant and hardness cations. This work quantified the competition between coagulant Al 3+ and hardness cations to bind onto DOM using absorbance spectroscopy acquired at different Al 3+ concentrations in the absence and presence of Ca 2+ or Mg 2+ . The results indicate that, in the presence of either Mg 2+ or Ca 2+ , an increasing depression of the binding of Al 3+ -DOM could be observed in the differential spectra of DOM with the increasing of Mg 2+ or Ca 2+ at a level of 10, 100 and 1000 μM, with the observation being more significant at higher pH from 6.5 to 8.5. The results of zeta potentials of DOM indicate that the competition of hardness cations results in the negative DOM being less efficiently neutralised by Al 3+ . This study demonstrates that the removal of DOM by coagulation would significantly deteriorate with the presence of hardness cations, which would compete with coagulant Al 3+ to neutralise the unsaturated sites in DOM. [ABSTRACT FROM AUTHOR]

Trace heavy metals accumulated in iron corrosion scales within a drinking water distribution system (DWDS) could potentially be released to bulk water and consequently deteriorate the tap water quality. The objective of this study was to identify and evaluate the release of trace heavy metals in DWDS under changing source water conditions. Experimental pipe loops with different iron corrosion scales were set up to simulate the actual DWDS. The effects of sulfate levels on heavy metal release were systemically investigated. Heavy metal releases of Mn, Ni, Cu, Pb, Cr and As could be rapidly triggered by sulfate addition but the releases slowly decreased over time. Heavy metal release was more severe in pipes transporting groundwater (GW) than in pipes transporting surface water (SW). There were strong positive correlations (R 2 > 0.8) between the releases of Fe and Mn, Fe and Ni, Fe and Cu, and Fe and Pb. When switching to higher sulfate water, iron corrosion scales in all pipe loops tended to be more stable (especially in pipes transporting GW), with a larger proportion of stable constituents (mainly Fe 3 O 4 ) and fewer unstable compounds (β-FeOOH, γ-FeOOH, FeCO 3 and amorphous iron oxides). The main functional iron reducing bacteria (IRB) communities were favorable for the formation of Fe 3 O 4 . The transformation of corrosion scales and the growth of sulfate reducing bacteria (SRB) accounted for the gradually reduced heavy metal release with time. The higher metal release in pipes transporting GW could be due to increased Fe 6 (OH) 12 CO 3 content under higher sulfate concentrations. [ABSTRACT FROM AUTHOR]

In this study, the effects of chemical conditioning using titanium salt coagulants (TSCs) of different hydrolysis speciation in combination with magnetic nano-particles on dewatering performance of waste activated sludge were evaluated by means of specific resistance to filtration (SRF) and capillary suction time (CST). The morphological and extracellular polymeric substances (EPS) properties under chemical conditioning were investigated in detail to understand the reaction mechanisms involved. The results showed that the TSC with basicity of 0.5 performed better in improving sludge dewatering performance than other TSCs. Sludge floc formed by TSC 0.5 treatment was characterized by larger floc size and higher floc strength than that conditioned by other TSCs. EPS compression and densification were the major mechanisms of sludge conditioning, and TSC 0.5 had better performance in compressing EPS structure. In addition, reduction of soluble EPS concentration, especially protein-like substances contributed to improvement of sludge filterability under conditioning. Furthermore, addition of Fe 2 O 3 nanoparticles could further improve dewatering performance and decrease compressibility of sludge system by acting as skeleton builders and enhancing floc strength. The sludge particles aggregation efficiency was effectively improved with addition of nano-Fe 2 O 3 . They also were able to bind with protein-like substance in EPS component, which might contribute to promotion of sludge filterability. [ABSTRACT FROM AUTHOR]

Chemical conditioning is one of the most important processes for improve the performance of sludge dewatering device. Aluminum salt coagulant has been widely used in wastewater and sludge treatment. It is generally accepted that pre-formed speciation of aluminum salt coagulants (ASC) has an important influence on coagulation/flocculation performance. In this study, the interaction mechanisms between sludge particles and aluminum salt coagulants with different speciation of hydroxy aluminum were investigated by characterizing the changes in morphological and EPS properties. It was found that middle polymer state aluminum (Al b ) and high polymer state aluminum (Al c ) performed better than monomer aluminum and oligomeric state aluminum (Al a ) in reduction of specific resistance to filtration (SRF) and compressibility of wastewater sludge due to their higher charge neutralization and formed more compact flocs. Sludge was significantly acidified after addition Al a , while pH was much more stable under Al b and Al c conditioning due to their hydrolysis stability. The size of sludge flocs conditioned with Al b and Al c was small but flocs structure was denser and more compact, and floc strength is higher, while that formed from Al a is relatively large, but floc structure was loose, floc strength is relatively lower. Scanning environmental microscope analysis revealed that sludge flocs conditioned by Al b and Al c (especially PAC 2.5 and Al 13 ) exhibited obvious botryoidal structure, this is because sludge flocs formed by Al b and Al c were more compact and floc strength is high, it was easy generated plentiful tiny channels for water release. In addition, polymeric aluminum salt coagulant (Al b , Al c ) had better performance in compressing extracellular polymeric substances (EPS) structure and removing sticky protein-like substances from soluble EPS fraction, contributing to improvement of sludge filtration performance. Therefore, this study provides a novel solution for improving sludge dewatering property by controlling aluminum speciation. [ABSTRACT FROM AUTHOR]

Abstract: The chemical stability of iron corrosion scales and the microbial community of biofilm in drinking water distribution system (DWDS) can have great impact on the iron corrosion and corrosion product release, which may result in “red water” issues, particularly under the situation of source water switch. In this work, experimental pipe loops were set up to investigate the effect of sulfate on the dynamical transformation characteristics of iron corrosion products and bacterial community in old cast iron distribution pipes. All the test pipes were excavated from existing DWDS with different source water supply histories, and the test water sulfate concentration was in the range of 50–350 mg/L. Pyrosequencing of 16S rRNA was used for bacterial community analysis. The results showed that iron release increased markedly and even “red water” occurred for pipes with groundwater supply history when feed water sulfate elevated abruptly. However, the iron release of pipes with only surface water supply history changed slightly without noticeable color even the feed water sulfate increased multiply. The thick-layered corrosion scales (or densely distributed tubercles) on pipes with surface water supply history possessed much higher stability due to the larger proportion of stable constituents (mainly Fe3O4) in their top shell layer; instead, the rather thin and uniform non-layered corrosion scales on pipes with groundwater supply history contained relatively higher proportion of less stable iron oxides (e.g. β-FeOOH, FeCO3 and green rust). The less stable corrosion scales tended to be more stable with sulfate increase, which was evidenced by the gradually decreased iron release and the increased stable iron oxides. Bacterial community analysis indicated that when switching to high sulfate water, iron reducing bacteria (IRB) maintained dominant for pipes with stable corrosion scales, while significant increase of sulfur oxidizing bacteria (SOB), sulfate reducing bacteria (SRB) and iron oxidizing bacteria (IOB) was observed for pipes with less stable corrosion scales. [Copyright &y& Elsevier]

• High DOM chemodiversity is ubiquitous in all headwater streams and a large river. • S-containing and aliphatic compounds originate from rural domestic effluent. • Ecosystem respiration can be controlled by anthropogenic sources of DOM. • H/C of 1.07 and O/C of 0.37 were typical precursors of DBPs. • DOM with 151 to 635 Da was the main part that was hard to remove through degradation. Dissolved organic matter (DOM) is a complicated assembly of organic molecules, including thousands of molecules with various structures and properties. However, how the stream DOM sources respond to carbon compositions and the transformation processes remains unclear. In this study, the chemical characteristics and spectral and mass spectrometry (FT-ICR MS) of DOM were analyzed. Six sampling points of headwater stream (HWSs) were sampled, and an effluent polluted stream (WSR) and a main stream of the Changjiang River (DT) were also sampled for comparison. In situ degradation experiments and FT-ICR MS analysis were also performed to observe the dynamic processes of DOM in HWS. The results showed that the anthropogenic markers of sewage (i.e. sulfur (S) compounds and marker from antibiotics and estrogen) in HWS were higher than those in DT. The molecular weight decreased while the degradation products (S-containing compounds and unsaturated compounds (HU)) increased after in situ degradation due to the influence of both the photodegradation and biodegradation process. In addition, the KMD plots showed that the DOM homologue intensities in range 400–600 Da changed significantly after demethylation by biodegradation. The components of highly refractory substances and the degradation degree of DOM in DT was higher than that in HWS. We extracted the refractory DOM pool in HWS, which was mainly small molecular with molecular weights < 600 Da. These molecular will be difficult to remove in traditional drinking water treatment processes and easily produced disinfection byproducts (DBPs). This study emphasized the necessity of identifying the sources and transformation processes of DOM in HWS and clarified the types and characteristics of DOM that should be considered in future drinking water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

• The presence of MRPs significantly inhibited the activity of extracellular lysozyme. • The MRPs-lysozyme interaction is a spontaneous exothermic process. • Aromatic structures with polar N atoms in MRPs interacted strongly with proteins. • H-bond and aromatic stacking occurred simultaneously in MRPs-Lysozyme complex. • The changes in protein secondary structure mainly contributed to enzyme activity decrease. Thermal hydrolysis pretreatment (THP) is often used to improve the anaerobic digestion performance of waste activated sludge (WAS) in wastewater treatment plants (WWTPs). During the THP process, the proteins and polysaccharides in the biomass will undergo hydrolysis and Maillard reaction, producing biorefractory organic substances, such as recalcitrant dissolved organic nitrogen (rDON) and melanoidins. In this study, a series of spectroscopy methods were used to quantitatively analyze the Maillard reaction of glucose and lysine, and the interaction mechanisms of the Maillard reaction products (MRPs) and lysozyme were investigated. Results showed that the typical aromatic heterocyclic structures in MRPs, such as pyrazine and furan, were found to quench molecular fluorescence of lysozyme, resulting in an unfolding of standard protein structure and increase in lysozyme hydrophobicity. Significant loss of enzyme activity was detected during this process. Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) confirmed that the interaction between MRPs and lysozyme occurred both exothermically and spontaneously. Density functional theory (DFT) calculations suggested that the molecular interactions of MRPs and protein included parallel dislocation aromatic stacking, T-shaped vertical aromatic stacking, H-bond and H-bond coupled to aromatic stacking. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The corrosion scales on iron pipes could have great impact on the water quality in drinking water distribution systems (DWDS). Unstable and less protective corrosion scale is one of the main factors causing “discolored water” issues when quality of water entering into distribution system changed significantly. The morphological and physicochemical characteristics of corrosion scales formed under different source water histories in duration of about two decades were systematically investigated in this work. Thick corrosion scales or densely distributed corrosion tubercles were mostly found in pipes transporting surface water, but thin corrosion scales and hollow tubercles were mostly discovered in pipes transporting groundwater. Magnetite and goethite were main constituents of iron corrosion products, but the mass ratio of magnetite/goethite (M/G) was significantly different depending on the corrosion scale structure and water source conditions. Thick corrosion scales and hard shell of tubercles had much higher M/G ratio (>1.0), while the thin corrosion scales had no magnetite detected or with much lower M/G ratio. The M/G ratio could be used to identify the characteristics and evaluate the performances of corrosion scales formed under different water conditions. Compared with the pipes transporting ground water, the pipes transporting surface water were more seriously corroded and could be in a relatively more active corrosion status all the time, which was implicated by relatively higher siderite, green rust and total iron contents in their corrosion scales. Higher content of unstable ferric components such as γ-FeOOH, β-FeOOH and amorphous iron oxide existed in corrosion scales of pipes receiving groundwater which was less corroded. Corrosion scales on groundwater pipes with low magnetite content had higher surface area and thus possibly higher sorption capacity. The primary trace inorganic elements in corrosion products were Br and heavy metals. Corrosion products obtained from pipes transporting groundwater had higher levels of Br, Ti, Ba, Cu, Sr, V, Cr, La, Pb and As. [Copyright &y& Elsevier]

Abstract: In this study, the formulation of a novel polyaluminum chloride-chitosan composite coagulant that improves the coagulation process for natural organic matter (NOM) removal was investigated. The performance of the composite coagulant was tested using two water sources (synthetic and natural water) to develop a better understanding on the behaviour of the composite coagulant. Fourier Transform-Infra red (FT-IR) spectroscopy, ferron analysis and zeta potential studies were performed to characterise the composite coagulant. FT-IR analysis showed that there is an intermolecular interaction between Al species and chitosan molecules, while ferron analysis indicated that the distributions of Ala, Alb, and Alc in PACl-chitosan are different from those in PACl. At a low Al dosage (2.16 mg L−1), a much higher removal of NOM from synthetic water, as evidenced from UV254 and Dissolved Organic Carbon (DOC) measurements, was achieved by the composite coagulants in comparison to that removed by PACl or PACl and chitosan added separately. For natural water from the Myponga Reservoir, both polyaluminum chloride (PACl) and PACl-chitosan composite coagulants demonstrated similar dissolved organic carbon (DOC) percentage removal, whereas PACl-chitosan gave a slight improvement in removing the UV254 absorbing components of NOM. [Copyright &y& Elsevier]

Abstract: The coagulation behavior of Al13 aggregates formed in coagulation of kaolin was investigated by small angle static light scattering (SASLS), solid-state 27Al NMR and tapping mode atomic force microscope (TM-AFM). A kaolin suspension was coagulated by PACl containing high content of Al13 polycation (PACl-Al13). The results indicated that Al13 was predominant in destabilizing kaolin particles for PACl-Al13 coagulation even though at alkaline pH (pH 10). At such high pH, Al13 aggregates were observed when the dosage of PACl-Al13 was increased. In addition, the mechanism of coagulation by PACl-Al13 at alkaline pH was affected by dosage. When the dosage was insufficient, coagulation was caused by electrostatic patch, which led to compact flocs with high fractal dimension (D f). Interparticle bridging dominated the coagulation when the coagulant dosage approached the plateau of adsorption, which caused the looser flocs with low D f. The in-situ AFM scanning in liquid system proved that the existence of linear Al13 aggregates composed of a chain of coiled Al13 in coagulation by PACl-Al13 at a high dosage and alkaline pH. Meanwhile, several coiled Al13 aggregates with various dimensions were observed at such condition. [Copyright &y& Elsevier]

• OH− was consumed mainly to react with Al 13 at 2.46 < B < 3.02. • Most Al 13 keep structure unchanged during the aggregation process. • Al 13 became unstable after deprotonation and favored to lose more protons. • Deprotonated Al 13 preferentially aggregated via bridged by Al monomers. • Particles can promote the aggregation of Al 13 by adsorption effect. Unraveling the transformation of coagulants and their interaction with contaminants at the micro-level is vital to advancing our understanding of the coagulation mechanism. To the best of our knowledge, the coagulation effectiveness of [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ]7+ (Al 13), regarded as the dominant species in polyaluminum chloride (PACl), is highly related to its aggregation characteristic, but the detailed process of Al 13 aggregation in coagulation time scale was not well studies. Here we systematically studied the deprotonation and aggregation processes of Al 13 by alkaline titration to simulate the reaction in coagulation case. By reacting with OH−, Al 13 can continuously lose protons regardless of pH until its positive charge was well neutralized. The initial Al 13 aggregates (Al 13 agg) appeared at B of 2.70 and large Al 13 agg was generated by coalescence of small initial Al 13 agg. Most Al 13 polycations kept their main structure unchanged during aggregation and part was decomposed into monomers or oligomers. Density functional theory (DFT) results reveal that Al 13 becomes unstable after deprotonation, but the aggregation of Al 13 bridged by Al monomers can stabilize the polycations. Al 13 needs to be hydrolyzed before interacting with colloidal particles, but particles can promote the aggregation of Al 13 by weakening the repulsion force between the polymers. Strong and compact flocs can be generated induced by in-situ aggregation of Al 13 in neutral and alkaline conditions. This study can provide a deep understanding about the role of Al 13 agg in removing particles and instruct the development of new efficient coagulants against the various water qualities. [Display omitted] [ABSTRACT FROM AUTHOR]

• The basic principles/advances in adsorptive micellar flocculation (AMF) are summarized. • Interfacial phenomena and AMF process applied in water treatment are highlighted. • Factors affecting the performance of AMF are comprehensively discussed. • Emphasis is given to alternative surfactants and materials recycling/recovery. • Ways to enhance AMF efficiency and the future developing prospect are discussed. Among various aqua remediation technologies, separation aims at cleaning pollutants by isolating them despite their destruction; solutes can also be recovered after the process. Adsorptive micellar flocculation (AMF) has been known as an important surfactant-based technique to separate poorly water-soluble hazardous pollutants from aqua media as an efficient and energy-intensive replacement for other surfactant-based techniques, as such AMF should be known. AMF is based on the partitioning of solutes gradient from bulk solution into the nanosized smart anionic surfactant micelle followed by flocculation. However, unlike coagulation/flocculation or adsorption, AMF is not viable for the production of drinking water in water utilities due to the loss of surfactant monomers. Unfortunately, it can be used as a reservoir or for the recycling/recovery of organic pollutants (intermediates) (ions, organics/bioactive, dyes, etc.), even at high concentrations. The performance of AMF depends on various parameters, and this review briefly summarizes the existing researches on different pollutants removal by AMF and material recovery/recycling. This includes operating condition factors (surfactants, flocculants, surfactant-flocculant or surfactant-pollutant concentration ratio, and water conditions chemistry). Because varieties of micro interfacial phenomena other than physical interactions occur in a versatile micellar environment in the AMF process, emphases are given to adsorptive oxidation, micellar catalysis, selectivity. Furthermore, for the first time, this review gives an overview of understanding the state-of-the-art multifunctional nano amphiphile-based AMF that behaves mimetic to aquatic organisms in the process of pollutant removal. The efficiency of AMF, including recycling concentrated solution without noticeable deterioration, as an auxiliary resource/income for the next cycle, signifies economic viability, versatility, and manifold applications in aqua remediation. Significance, ways to achieve enhanced process efficiency, as well as challenges and future opportunities in wastewater treatment, are also highlighted. [Display omitted] [ABSTRACT FROM AUTHOR]

• VTIS and 2D-COS was used to examine the response of EPS at varying temperatures. • The freezing treatment caused the destruction of hydrophilic functional groups. • The mild-hydrothermal treatment (80–100 °C) caused the increase in EPS hydrophilicity. • The α- helix and β -sheet content were reduced under high temperature condition. • Polysaccharides and HAs changed the protein stability under temperature variation. Extracellular polymeric substances (EPS) are important components of activated sludge, whose content and composition have important effects on the macro-physical properties of sludge. In this study, the response of EPS in sludge to temperature (−40–200 °C) was systematically investigated using XAD resin fractionation, variable-temperature infrared spectra (VTIS) and two-dimensional correlation spectroscopy (2D-COS). The relationships between the molecular structure of EPS and the macro-physical properties (rheological property and dewatering performance) of waste activated sludge (WAS) at varying temperature were also established. During the freezing treatment, the solubilization of biopolymers and destruction of the hydrophilic functional groups (hydroxy, amino and carboxyl) resulted in the production of small organic matters, which enhanced EPS hydrophobicity and reduced electrostatic repulsion of sludge, and subsequent dewaterability improvement. For the hydrothermal treatment, the EPS transformation showed a two-stages reaction including stage I (70–120 °C) and stage II (>120 °C). Stage I (70–120 °C), a plenty of hydrophilic functional groups (hydroxy, amino and carboxyl) in EPS were exposed via the solubilization of biopolymers, which enhanced electrostatic repulsion of sludge and EPS hydrophilicity, and subsequence in deterioration of sludge dewaterability and fluidity. However, at stage II (>120 °C), the high temperature caused hydrolyzation of macromolecular organic matters in completely, in which the secondary structure of the protein was destroyed, causing the peptide chain to unfold. In addition, the reduction of α- helix and β -sheet content and intensified Maillard reaction decreased electrostatic repulsion of sludge, thus resulted in the improvement of sludge dewaterability and fluidity. This study enriched the theoretical basis of the optimal control of sludge treatment based on temperature regulation. [ABSTRACT FROM AUTHOR]

• Sludge enhanced dewatering technologies are comprehensively reviewed. • Mechanisms of different sludge enhanced dewatering technologies are discussed. • Process adaptability of different sludge conditioning methods are analysed. • Sludge electro-dewatering and its coupled processes are discussed. • Sludge enhanced dewatering technology and its coupled processes are prospected. Sludge is an inevitable by product of sewage treatment, and it includes pathogens, heavy metals, organic pollutants and other toxic substances. The components of sludge are complex and variable with extracellular polymeric substances (EPS) being one. EPS are highly hydrophilic and compressible, and make sludge dewatering difficult. Therefore, the development of efficient sludge-dewatering technology is an important means of mitigating rapid sludge growth. At present, the main methods used for sludge deep-dewatering technology are chemical preconditioning with high-pressure filtration and electrical mechanical dewatering. The selection of chemical preconditioning directly determines the final efficiency of the sludge-dewatering process. In this paper, we conduct a comprehensive review of the problems related to sludge dewatering and systematically summarise the impact of different chemical conditioning technologies on the efficiency of sludge dewatering. Furthermore, the characteristics of different enhanced dewatering technologies are evaluated and analysed for their adaptability and final disposal methods. We believe that this review can clarify the chemical conditioner mechanism to improve sludge dewatering, provide reference debugging information for the sludge-dewatering process and promote the development of efficient and environmentally friendly sludge-dewatering technology. [ABSTRACT FROM AUTHOR]

• Six Gaussian bands comprise differential absorbance spectra of all examined waters. • Bands A1-A4 in the spectra of chlorinated compounds show dependence of conjugation. • Spectral parameters from long wavelength have high correlation with DBPs formation. This study compared chlorination-induced changes of the properties of natural organic matter (NOM) represented by standard humic substances and NOM present in pristine and anthropogenically-affect reservoirs, rivers, groundwater and seawater. The chlorination-induced changes of NOM properties were quantified using the differential absorbance spectra (DAS) which were processed via numeric deconvolution. Six Gaussian bands were found to comprise the DAS of all examined waters. These bands (denoted as A0, A1, A2, A3, A4 and A5, respectively) have maxima located at ca. 200, 240, 276, 316, 385 and 547 nm. The bands A1-A4 were observed in the DAS of representative model chlorinated compounds. Quantum chemical (QC) calculations were carried out to examine the intrinsic nature of these bands and electronic transitions associated with them. QC data demonstrate that bands A1 and A2 are present in almost all aromatic organic species, A3 is likely to be associated with acetophenone- and/or styrene-like groups. A4 can be attributed to the engagement of m-hydroxyaromatic and flavone-type groups typical for the polyphenolic moiety in NOM and known to be the key precursors of disinfection by-product (DBP) formation. Thus, the intensity of band A4 is predicted to be an especially strong predictor of DBP formation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Extracellular polymeric substances (EPS) in wastewater sludge form a network structure that is highly hydrophilic and compressible. Thus chemical conditioning is always required to improve sludge dewaterability by changing the gelatinous structure of sludge flocs. Layered double hydroxides (LDH) are generally characterized by large surface area and high anion exchange capacity, so we prepared three types of hydrotalcite-like compounds (Ca/Mg/Al-LDHs) from a typical solid waste, blast furnace slag, using NaOH precipitation (giving LDH a), a hydrothermal method (LDH b), and NaOH–Na 2 CO 3 precipitation (LDH c). The physicochemical properties of the three LDH were comprehensively characterized, and their effectiveness as sludge conditioners was evaluated. The results showed that LDH conditioning was able to promote sludge dewaterability, and conditioning efficiency was strongly dependent on LDH structural properties. LDH neutralized the negative charges onto sludge particles and interacted with EPS to increase floc strength. LDH also formed a skeletal structure that reduced sludge compressibility. In addition, there were interactions between the LDH surfaces and the O C–OH in EPS proteins, which altered the secondary structure of protein molecules, consequently increasing sludge dewaterability. The biomolecules of low-molecular-weight fractions (such as peptides and humic acids) in soluble EPS intercalated LDH. Both the surface complexation of organic matter containing carboxyl groups and the intercalation of small molecules in soluble EPS were responsible for EPS–LDH interactions. The combination of skeleton formation, electrostatic interaction, and EPS–LDH interactions resulted in compression of gel-like structure and improved sludge dewatering performance. We finally suggested a novel sludge treatment process that increases sludge dewaterability using slag-derived Ca/Mg/Al-LDH to condition the sludge, and it could be combined with pyrolysis to prepare multi-functional materials or bio-oil. Image 1 • Slag based LDH were used as chemical conditioners to improve sludge dewaterability. • LDH structural properties had important effects on sludge conditioning efficiency. • LDH conditioning reduced sludge cake compressibility by functioning as skeleton builders. • Charge neutralization and EPS-LDH interaction were responsible for sludge conditioning. • LDH interacted with EPS through surface complexation and intercalation. [ABSTRACT FROM AUTHOR]