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[Display omitted] • The coagulation behavior of low-coagulability organic matter (LCOM) was revealed. • LCOM could not form flocs using the charge neutralization of coagulant. • The removal of LCOM only relied on the weak adsorption of metal hydroxides. • PACl could not remove LCOM and even got decomposed in the presence of LCOM. Hydrophobic and high-molecular-weight dissolved organic matter (DOM) can be efficiently removed via coagulation, but DOM with a low hydrophobicity and low molecular weight cannot. These can be respectively classified as high-coagulability organic matter (HCOM) and low-coagulability organic matter (LCOM). Most coagulation studies have focused on HCOM (such as humic acid) but not LCOM. Therefore, the coagulation behavior and mechanism of LCOM were revealed by comparing with HCOM in this study. The removal efficiency of HCOM via coagulation was high (>75%), while that of LCOM was very low (<15%). Charge neutralization (CN) and sweep flocculation (SF) were the primary mechanisms of DOM coagulation. Based on the results of fluorescence measurements, zeta potential, and floc growth processes, the CN mechanism was very efficient in HCOM coagulation, but it did not apply to LCOM coagulation. Since LCOM has a smaller molecular size, it bound with coagulants to form soluble complexes in contrast to the flocs formed during HCOM coagulation. Both HCOM and LCOM could be removed via the SF mechanism, but the interaction between LCOM and coagulant was far weaker. According to the analysis of floc properties, HCOM strongly bound with the coagulant to form flocs with a loose structure and uneven surface. The properties of LCOM flocs were very similar to those of hydroxide flocs formed without organics in terms of surface charges, fractal structure, recoverability, surface morphology, and contents of Al/O components of flocs. In conclusion, HCOM coagulation was controlled by the interaction between HCOM and coagulant, while LCOM coagulation was dominated by coagulant hydrolysis and polymerization. This study complements the existing understanding of LCOM coagulation and provides insights into the enhancement strategy. [ABSTRACT FROM AUTHOR]

[Display omitted] • The high stability due to betaine and HPAM in PW limited coagulation performance. • Souring-related water quality deterioration also occurred after coagulation. • The addition of ozone decreased the stability of PW and oxidized S2− from souring. • HOC process achieved high-standard reinjection without water quality deterioration. • Accumulation of small molecular weight intermediates can be inhibited in the HOC. Surfactants and polymers are extensively being used to enhance oil recovery resulting in the generation of surfactant-polymer (SP) flooding produced water, which is more challenging to treat for reinjection compared with conventional produced water. Aiming at high-standard SP flooding produced water reinjection, this study investigated the coagulation-based treatment processes for the treatment of SP flooding produced water. The conventional coagulation process with two typical coagulants, poly-aluminum chloride (PAC) and poly-ferric sulfate (PFS), was applied. However, the effluent did not meet the reinjection requirements for suspended solids (SS) ≤ 2 mg/L, oil ≤ 6 mg/L and median diameter d 50 ≤ 1.5 μm according to the water quality standard for oilfield injecting waters in clastic reservoirs (SY/T 5329–2012). The presence of adsorbed surfactant (betaine) and polymer (hydrolyzed polyacrylamide, HPAM) on oil and suspended solids increased the difficulties in agglomeration and charge-neutralization. In addition, water quality deterioration occurred within 5 h leading to increased turbidity, suspended solids and d 50. X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis implied that water quality deterioration was caused by souring (producing sulfide), leading to the generation of suspended solids mainly containing sulfur and calcium carbonate (CaCO 3). To address these challenges, the pre-ozonation coagulation (POC) and hybrid ozonation-coagulation (HOC) processes were compared. The effluent from both processes, using either PAC or PFS, met the reinjection requirements while inhibiting water quality deterioration. Additionally, higher removal efficiency and significantly reduced optimal ozone dosage were also achieved in the HOC process compared with the POC process. The enhanced generation of hydroxyl radicals (•OH) and polymeric hydrolysed coagulant species in the HOC process contributed to higher removal efficiency of HPAM, betaine and COD. Kinetics analysis revealed that •OH oxidation and coagulation played important roles in betaine and HPAM removal, respectively. The reaction pathways of betaine and HPAM in the ozonation and HOC processes were also analysed. Furthermore, the HOC process can effectively inhibit the accumulation of small molecular weight organic matter, facilitating the simultaneous coagulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A CSTR equipped with internal and external electrolyzers was constructed. • In-situ and ex-situ electrolytic H 2 supply for methanogenesis was compared. • In-situ electrolysis resulted in higher H 2 dissolved concentration and K L a. • In-situ H 2 supply enabled higher productivity, CE, and energy efficiency. Both in-situ and ex-situ electrolytic H 2 supply have been used for biomethane production from CO 2. However, the pros and cons of them have not been systematically compared. The present study makes this comparison using a 20 L continuous stirred-tank reactor equipped with external and internal electrolyzers. Compared to the ex-situ H 2 supply, the in-situ electrolytic H 2 bubbles were one order of magnitude smaller, which resulted in improved H 2 mass transfer and biomass growth. Consequently, the methane production rate and the coulombic efficiency of the in-situ H 2 supply (0.51 L·L-1·d-1, 96%) were higher than those of the ex-situ H 2 supply (0.30 L·L-1·d-1, 56%). However, due to high internal resistance, the energy consumption for the in-situ electrolysis was 2.54 times higher than the ex-situ electrolysis. Therefore, the in-situ electrolytic H 2 supply appears to be more promising, but reducing energy consumption is the key to the success of this technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • An innovative Nucleation crystallization pelleting process (NCP) is proposed. • Seeds provided for crystallization of Mn ions active sites. • High purity of Mn ions in the crystals, which can be used directly after acid leaching. • No harmful sludge containing manganese is produced during NCP. • Pilot experiment validated the stablility of multi-stage NCP system. To address the issues of wasting manganese resources and generating hazardous chemical sludge during the removal of manganese (Mn) ions from acidic electrolytic manganese wastewater using conventional chemical precipitation, an innovative nucleation crystallization pelleting process (NCP) was proposed. The NCP aimed to recover Mn ions without generating hazardous sludge. By pre-adding seeds with active sites for Mn ions attachment into the NCP reactor, Mn ions were induced to adhere to the seed surfaces in the form of MnCO 3 by adjusting the Na 2 CO 3 dosage and hydraulic conditions. The results demonstrated effective Mn ion removal, with Mn ions being reduced from 3800 mg/L to about 20 mg/L after five-stage NCP reactors. The Na 2 CO 3 dosage for the first to fifth stage was 3.0, 2.6, 2.2, 1.65, and 1.2 g/L, respectively. Optimizing the hydraulic conditions facilitated enhanced mass transfer between Mn ions and seeds, with the optimum upward flow rate of the reactor determined as 60 m/h. In addition, the optimized seed filling ratio was found to be 15 %. The seeds exhibited stability as they were recycled three times, and the crystallization of Mn ions showed little variation. Moreover, after a 20-day operation, the crystal seeds reached a size of approximately 0.8 mm, exhibiting a moisture content below 3 %. The grade of manganese ions exceeded 44 %, in terms of ore, and the extraction rate of manganese ions reached 98.17 % after acid leaching of the crystals. These crystals can be directly reused in the electrolytic manganese production, thereby improving the utilization rate of manganese ions. In conclusion, the NCP technology shows promise for effective Mn ion removal and recover without generating hazardous sludge. [ABSTRACT FROM AUTHOR]

[Display omitted] • The addition of Fe3+ and PS to the DOM solution significantly improved the catalytic performance. • Ligand-to-metal charge transfer resulted in enhanced Fe3+ reduction and PS activation. • More than 56% of the PS was decomposed via Fe2+ generated by the LMCT effect. • SO 4 − and OH were identified as the dominant reactive species present in the DOM-Fe3+-PS-Vis process. • The highly hydrophobic moieties with more aromatic carbon in DOM are beneficial for promoting catalytic performance. The activation of persulfate (PS) in dissolved organic matter (DOM) solution using visible light has demonstrated potential for advanced wastewater treatment. This study presents a novel visible light-assisted homogeneous Fenton-like process (DOM-Fe3+-PS-Vis) for the efficient DOM degradation, based on the ligand-to-metal charge transfer (LMCT)-induced enhanced Fe3+ reduction and PS activation. The simultaneous addition of Fe3+ and PS to DOM-enriched solutions under visible light significantly improved PS activation, leading to the degradation of DOM and coexisting organic contaminants. The PS decomposition rate constant in the DOM-Fe3+-PS-Vis process was calculated to be 3.5–20.69 times higher than that of the DOM-PS-Vis, Fe3+-PS-Vis, and DOM-Fe3+-PS-Dark systems. Notably, over half of the decomposed PS in the DOM-Fe3+-PS-Vis process was activated by Fe2+ generated via the LMCT between DOM and Fe3+. SO 4 − and OH were identified as the dominant reactive species present in the DOM-Fe3+-PS-Vis process with the steady-state concentration of 1.63–4.11 × 10−13 M and 0.07 × 10−13 M, respectively, which were 2.4–81.5 and 0.5–7 times higher than those in the DOM-PS-Vis, Fe3+-PS-Vis, and DOM-Fe3+-PS-Dark systems. Additionally, hydrophobic components with more aromatic carbon in DOM were found to promote the catalytic performance of the DOM-Fe3+-PS-Vis process. This study highlights the efficiency and promise of LMCT-induced enhanced Fe3+ reduction and PS activation in DOM-enriched solutions under visible light for advanced wastewater treatment. [ABSTRACT FROM AUTHOR]

Sulfate Radical-Advanced Oxidation Processes are considered an efficient way for purifying dyeing wastewater, which commonly resists conventional treatment processes owing to the complex components, low biodegradability and high toxicity. However, this emerging technique is associated with issues of secondary pollution and great energy consumption during peroxymonosulfate (PMS) or persulfate (PS) activation processes. Herein, a dye pollutant/PS/visible light self-catalytic system was constructed, based on the photosensitive property of organic dyes for PS activation without catalyst and energy input. In this system, the degradation ratio of 100 mL 10 mg L−1 basic fuchsin, rhodamine B and eosin Y significantly increased by 60%, 76% and 50%, compared with the process without light irradiation. Such improvements were attributable to an efficient photo-induced electron transfer from photo-excited dyes to PS, which has the precondition that the lowest unoccupied molecular orbital (LUMO) energy level of the dye is higher than that of PS, thereby generating oxidizing species like ·SO 4 −, ·OH and 1O 2 for pollutants degradation. Due to the high performance of pollutants simultaneous removal, wide pH adaptability and anti-interference, the complex self-catalytic system consisted of nine dyes and bis -phenol A exhibited the possibility for practical application. Expectedly, the actual dyeing wastewater self-purification system featured a decolorization efficiency of 54% accompanied by the removal of co-existing aromatic proteins and tryptophan-like substances; moreover, the acute bio-toxicity of the raw wastewater greatly decreased by 61.6%. Owing to its high efficiency, eco-friendliness and low consumption, the constructed "using waste to treat waste" system provides a promising way for wastewater treatment. [Display omitted] • A novel PS activation system without catalyst and energy input was constructed. • Well-matched energy level between photosensitive dye and PS leads to activation. • Dye and co-existing pollutants were simultaneously removed with high efficiency. • Actual dyeing wastewater was purified in a novel way of using waste to treat waste. • The eco-friendly and low-cost method has great potential in wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • An impregnation–calcination route is proposed to prepare FeQDs/TiO 2−x. • The obtained FeQDs/TiO 2−x exhibited quasi−full visible light absorption. • The lifetime of the photogenerated electrons in the catalyst was greatly prolonged. • Efficient Fe3+/Fe2+ cycling was observed on the surface of Fe3+/Ti3+ co−doped TiO 2. • Synergistic effects between Fe3+/Ti3+ doping improved the catalytic performance. In this work, a facile impregnation–calcination route was proposed for the synthesis of Ti3+ self−doped TiO 2 anchored with iron oxide quantum dots (FeQDs/TiO 2−x) as an efficient visible light−derived persulfate catalyst for organic degradation. After the successful co−doping of Fe3+ and Ti3+, the obtained FeQDs/TiO 2−x exhibited quasi−full visible light absorption, with the maximum absorption edge broadened to 791 nm; furthermore, its charge separation and interfacial transport capacity were significantly enhanced, as evidenced by the fact that the lifetime of the photogenerated electrons was prolonged from 6.17 to 10.34 ns. In addition, the surface Fe3+ species on FeQDs/TiO 2−x can be effectively reduced to Fe2+ by the separated electrons, establishing an efficient cycle between Fe3+ and Fe2+. Therefore, the obtained FeQDs/TiO 2−x nanocomposite exhibited enhanced catalytic performance for the degradation of phenolic pollutants via PS activation under visible light. Specifically, 50 mg/L bisphenol A (BPA) and acetaminophen (AAP) can be completely degraded by FeQDs/TiO 2−x with faster reaction rate constants and higher mineralization rates compared to its counterparts, including TiO 2 , TiO 2−x , and FeQDs/TiO 2. Based on the results of material characterization, degradation experiments, identification of reactive oxidizing species, and chemical quenching experiments, the mechanism of the enhanced photocatalytic activity of FeQDs/TiO 2−x was elucidated. Our results demonstrated the high potential of FeQDs/TiO 2−x for wastewater treatment. [ABSTRACT FROM AUTHOR]

This paper proposes a new system of multilevel reuse with source separation in printing and dyeing wastewater (PDWW) treatment in order to dramatically improve the water reuse rate to 35%. By analysing the characteristics of the sources and concentrations of pollutants produced in different printing and dyeing processes, special, highly, and less contaminated wastewaters (SCW, HCW, and LCW, respectively) were collected and treated separately. Specially, a large quantity of LCW was sequentially reused at multiple levels to meet the water quality requirements for different production processes. Based on this concept, a multilevel reuse system with a source separation process was established in a typical printing and dyeing enterprise. The water reuse rate increased dramatically to 62%, and the reclaimed water was reused in different printing and dyeing processes based on the water quality. This study provides promising leads in water management for wastewater reclamation. [ABSTRACT FROM AUTHOR]

Nonradical activation of peroxydisulfate (PDS) is promising for wastewater decontamination but suffers from insufficient decomposition efficiency toward organics. Herein, NiO nanospheres with hollow multi-shelled structure (HoMS) and tunable shell numbers are designed as a nanoreactor of PDS activation to enhance the decomposition efficiency. Study on bis-phenol A (BPA) degradation reveals that 3-shelled NiO HoMS exhibits enhanced kinetic rate (0.08 min 1) and mineralization degree (79.2%) compared to 2-shelled NiO HoMS (0.04 min−1, 50%) and NiO nanoparticles (0.01 min−1, 29.8%). The degradation of BPA over NiO HoMS follows electron transfer regime with oxygen vacancy (V O) acted as the active site. The hollow multi-shelled structure not only increases the accessibility of V O but also enriches local concentration of reactants in the void spaces due to the nanoconfinement effect, and thus mainly contributes to the enhanced catalytic efficiency. This work provides a distinct case for developing efficient nonradical oxidation technique for water purification. [Display omitted] • NiO with hollow multi-shelled structure (HoMS) was employed as a nanoreactor of PDS activation. • BPA was degraded in NiO HoMS nanoreactors via an electron transfer mechanism. • Nanoconfinement effect was mainly contributed to the enhanced catalytic efficiency. • HoMS increased the accessibility of active sites and enriched local concentration of reactants. [ABSTRACT FROM AUTHOR]

• A novel CM-E-HOC was firstly put forward to apply in produced water treatment. • The CM-E-HOC showed higher removal efficiency than the CM-EC processes. • Both reversible and irreversible membrane fouling were mitigated in the CM-E-HOC. • Alternating filtration in the CM-E-HOC can realize higher water production rate. • Excellent flux recovery can be achieved in the CM-E-HOC via in situ self-cleaning. Polymer-flooding produced water is more difficult to treat for reinjection compared with normal produced water because of the presence of residual hydrolyzed polyacrylamide (HPAM). A novel cathode membrane integrated electro-hybrid ozonation-coagulation (CM-E-HOC) process was proposed for the treatment of polymer-flooding produced water. This process achieved in situ self-cleaning by generated microbubbles in the cathode membrane. The CM-E-HOC process achieved a higher suspended solid (SS), turbidity and PAM removal efficiency than the CM-EC process. The SS in the CM-E-HOC effluent was ≤ 20 mg/L SS, which met the reinjection requirements of Longdong, Changqing Oilfield, China (Q/SYCQ 08,011–2019) at different current densities (3, 5 and 10 mA/cm2). The CM-E-HOC process greatly mitigated both reversible and irreversible membrane fouling. Therefore, excellent flux recovery was obtained at different in situ self-cleaning intervals during the CM-E-HOC process. Furthermore, alternating filtration achieved continuous water production during the CM-E-HOC process. On one hand, the effective removal of aromatic protein-like substances and an increase in oxygen-containing functional groups were achieved due to the enhanced oxidation ability of the CM-E-HOC process, which decreased membrane fouling. On the other hand, the CM-E-HOC process showed improved coagulation performance because of the increased oxygen-containing functional groups and polymeric Fe species. Therefore, larger flocs with higher fractal dimensions were generated, and a looser and more porous cake layer was formed on the membrane surface during the CM-E-HOC process. Consequently, the CM-E-HOC process exhibited better in situ self-cleaning performance and lower filtration resistance than the CM-EC process. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe/Mn co-doped biochar (Fe-Mn-C) was prepared and used as an ozonation catalyst. • The obtained Fe-Mn-C showed excellent catalytic activity and stability. • Fe-Mn-C promoted the decomposition of ozone into reactive oxidizing species (ROS). • Recycling of Fe/Mn redox pairs enhanced ozone decomposition and ROS generation. The fabrication of efficient, stable, and low-cost catalysts is crucially important for the catalytic ozonation process for the removal of recalcitrant pollutants. In this study, we present a facile impregnation-pyrolysis method for the preparation of novel porous Fe/Mn co-doped biochar (Fe-Mn-C) with excellent catalytic activity and reusability for the catalytic ozonation of ibuprofen (IBP). The incorporation of Fe/Mn heteroatoms into the carbon skeleton of biochar not only produced more defective sites and promoted the charge transfer on the materials surface but also created active Fe/Mn species with multi-valence states for ozone activation. As a result, >95% of IBP (50 mg/L) and 80.5% of total organic carbon can be rapidly removed within 9 min in the Fe-Mn-C/O 3 process at a pH of 7, ozone dosage of 4.93 mg/min, and Fe-Mn-C dosage of 0.5 g/L. The catalytic reaction rate in Fe-Mn-C/O 3 was 6.58 times higher than that of sole ozonation and 2.3–4.1 times higher than that of catalytic ozonation with other catalysts (e.g., biochar, Fe-doped biochar, Mn-doped biochar, activated carbon, Fe 3 O 4 and MnO 2). Moreover, the obtained Fe-Mn-C can be reused for multiple cycles; the performance is not significantly reduced in subsequent cycles, and there is no significant metal leaching. Further studies suggested that the radical pathways (superoxide radicals and hydroxyl radicals) were mainly responsible for the degradation of IBP in the Fe-Mn-C/O 3 system. Furthermore, the contributions of the surface functional groups, doped atoms, and delocalized π electrons of Fe-Mn-C to the decomposition of ozone and the formation of reactive species were identified by correlation analysis between the catalytic ozonation rate and the physiochemical properties of Fe-Mn-C to clarify the mechanism underlying the improved performance. [ABSTRACT FROM AUTHOR]

• Pre-ozonation had low range of dosages for improved organic removal in coagulation. • Overdose in pre-ozonation was detrimental to coagulation due to over-oxidation. • Over-oxidation of organic matter can be notably inhibited in the HOC process. • Immediate entrapment by coagulant occurred once organic intermediates formed in HOC. • C11-C20 organics accumulated in the flocs in the HOC rather than C1-C10. Pre-ozonation coagulation process had a very low and narrow range of ozone dosages for enhancing the dissolved organic matter (DOC) removal efficiency, in which over-oxidation may occur if the ozone dosage was not strictly controlled. In contrast, the proposed hybrid ozonation-coagulation (HOC) process with higher oxidation ability notably inhibited over-oxidation in this study, and exhibited improved DOC removal efficiency compared with coagulation at a much wider range of ozone dosages at different initial pH for the treatment of WWTP effluent. The HOC process also had a higher DOC removal efficiency than pre-ozonation coagulation. According to zeta potential analysis, a rising trend indicated that complexation between organic matter and metal coagulants persisted throughout the HOC process. However, the zeta potential remained almost unchanged during subsequent coagulation after pre-ozonation at high ozone dosages. Synchronous fluorescence spectroscopy analysis revealed that immediate entrapment and complexation between hydrolysed coagulants and oxidized intermediate organic matter occurred in the HOC process. Furthermore, FT-IR analysis showed that more oxygen-containing functional groups were generated, which were effectively trapped by metal coagulants and readily flocculated. To further prove the immediate entrapment and complexation during the HOC process, UPLC-Q-TOF-MS was applied to analyze the intermediate organic matter in the supernatant and flocs. The results implied that C21- organic matter was oxidized and decomposed into C11-C20, and C11-C20 intermediate organic matter was trapped and complexed by metal coagulants once formed, which led to the increase of C11-C20 in the flocs. Nevertheless, the catalytic ozonation process (γ-Al 2 O 3 /O 3) with the same oxidation ability as the HOC process decomposed the organic matter into C1-C10. XPS analysis further confirmed the immediate entrapment and removal of aliphatic/aromatic carbon and oxygen-containing functional groups during the HOC process. Therefore, over-oxidation can be effectively inhibited, and wide range of ozone dosages was obtained during the HOC process, which facilitate the application of the HOC process. [Display omitted] [ABSTRACT FROM AUTHOR]

Seepage well, as an ancient facility for sewage collection and treatment in China, still has reference significance for effective treatment of source-separated greywater in rural China under the background of rural revitalization. This study surveyed the discharge characteristic of rural greywater, and proposed onsite treatment of decentralized rural greywater using a novel ecological seepage well (ESW). In northwestern China, four rural households produced greywater with an average quantity of 128–146 L/d, with chemical oxygen demand (COD) of 213.6–235.9 mg/L as the main pollutant. For treating greywater, ESW with ceramsite and zeolite mixed in the packing layers and metallic corrugated plates (MCPs) set in the aeration zone achieved higher removal efficiencies of COD, total phosphorous (TP), total nitrogen (TN) and ammonia nitrogen (NH 4 +-N). When the influent C/N ratio was 16, the enhanced removal performance was realized by cutoff duration of 9 h, and the effluent met the Chinese standard for irrigation water quality with COD, TP, TN and NH 4 +-N removal efficiencies of 88.58%, 65.60%, 92.94% and 93.65%, respectively. Under the optimal condition, mechanism of pollutant removal by ESW was investigated. The variation of EPS and microbial morphology along the height illustrated that a micro-aerobic environment was formed in the lower layer of ESW. High throughput sequencing indicated plentiful denitrifying bacteria (DNB) and denitrifying phosphate accumulating organisms (DNPAOs), together with a higher relative abundance of ammonia oxidizing bacteria (AOB) than nitrite oxidizing bacteria (NOB) in the lower layer, which was relative to simultaneous nitrification, denitrification and phosphorous removal. This study provided theoretical and practical support for effective treatment mode of rural sewage. [Display omitted] • Four rural households produced 61–210 L/d greywater with COD as the main pollutant. • The effluent of ESW met the Chinese standard for irrigation water quality. • The use of mixed filler substrates and MCPs helped ESW to remove pollutants better. • The influent cutoff duration greatly affected the removal performance of ESW. • Simultaneous carbon, nitrogen and phosphorous removal occurred inside ESW. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified organics can be captured real time by microbubble flocs in HOC process. • The modified oxygenated intermediates retain macro aromatic structure of organics. • Real time complexation behavior of organics by Al species was verified by DAS. • The C O Al bonds in Al-organics complex limited low molecular products formation. • Formation of hydroxyl bridges by ozone resulted in more-efficient coagulation performance. The over-oxidation of organic pollutants by pre-ozonation leads to a decreased removal efficiency of coagulation. In this study, it was demonstrated that organics modified by ozonation can be captured in real time by microbubble flocs mediated by the interaction among ozone, Al species, and other organics using the hybrid ozonation-coagulation (HOC) process, which avoids further oxidation of the modified organics. Compared with the pre-ozonation-coagulation process, this real-time capture strategy during the HOC process can increase organics removal efficiency, and broaden the ozone dosing range. The synergistic effect of Al species and ozone enhanced hydroxyl radicals (·OH) formation, which increased the content of carboxyl and hydroxyl groups in the modified intermediates while retaining their original macro aromatic structure. That modified intermediates can be captured and complexed by Al species in the HOC process in real time was verified by differential absorbance spectroscopy (DAS). Al species are complexed with carboxyl and hydroxyl groups of organic compounds to form Al-organic complexes that have C O Al coordination bonds. These complex structures protect the modified organic compounds during immediate contact with and decomposition by ozone. The existence of ozone can increase the formation of poly Al species via hydroxyl bridges, thus causing the soluble small-scale metal complex to form insoluble flocs. The surface of flocs can be oxidized and modified, thus strengthening the surface coordination of residual organics in water and further improving their removal efficiency. [ABSTRACT FROM AUTHOR]

• The discharge characteristics of rural sewage in Shaanxi Province were investigated. • The effects of rural sewage discontinuity on A2/O process was investigated. • An intermittent aeration and DO regulation optimal operation strategy was developed. • Advanced nutrient removal based on PN and DPR was achieved in A2/O process. • Consumption reduction and efficiency enhancement were achieved in a rural WWTP. Rural wastewater treatment has become an important issue in China. This study investigated 76 rural wastewater treatment plants (WWTPs) in Shaanxi over a one-year period. We found that although rural sewage is suitable for biological treatment (BOD 5 /COD = 0.38–0.41), it has an obvious intermittent flow cutoff (5–19 h/d) characteristic, resulting in low sewage loading and poor pollutant removal in rural WWTPs. In order to improve operation efficiency and increase economic benefits of the existing rural WWTPs, a pilot-scale A2/O bioreactor was established, and the effect of rural sewage discontinuity (cutoff duration 10 h/d) on A2/O process was studied. An intermittent aeration and dissolved oxygen (DO) regulation operation strategy was developed. The results demonstrated that ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB), and polyphosphate accumulating bacteria (PAOs) were all enriched when T aeration : T stop = 5 h:5h and DO = 2.0–3.0 mg/L. During the subsequent process of reducing DO concentration to 0.5–1.0 mg/L, AOBs (2.43 %) and PAOs (1.91 %) were enriched and NOBs (1.61 %) were panned. The transformation of functional bacteria in the system stimulated partial nitrification and denitrification phosphorus removal (DPR) (nitrite accumulation rate = 46.56 ± 6.88 %, DPR rate = 43.15 ± 3.54 %), which improved the nutrient removal rates. Finally, the optimal operation strategy was applied to a typical town-level WWTP in Ankang, China. The removal rates of NH 4 +-N, TN, and TP increased from 85.85 ± 1.31 %, 59.77 ± 2.86 %, and 23.91 ± 1.77 % to 94.17 ± 2.02 %, 65.32 ± 4.75 % and 61.05 ± 2.34 %, respectively, and the operating cost was reduced by 118,600 CNY (17,541 USD) per year. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel 20 L E-CSTR is designed for microbial electrosynthesis. • The reactor enables high CE (99.4%) under high j (119.94 A·m−2). • A high methane production rate of 407.80 L·m−2·d−1 (0.68 L·L−1·d−1) is achieved. • The reactor exhibits excellent stability and robustness in 67 days of operation. Microbial electrosynthesis (MES) is a promising technology for CO 2 utilization and renewable electricity storage. The practical application of MES requires high current density and scalable reactor design. Here, we reported a novel 20 L electrochemical continuous stirred-tank reactor (E-CSTR) for methane production from CO 2. The E-CSTR was constructed by inserting a tubular electrochemical cell into a CSTR. At 4 A (119.94 A·m−2), the average and maximum methane production rates achieved in the reactor were 317.84 L·m−2·d−1 (0.53 L·L−1·d−1) and 407.8 L·m−2·d−1 (0.68 L·L−1·d−1), respectively, and the average coulombic efficiency was about 98%. The reactor outperformed most reported MES reactors. Increasing the current to 6 A resulted in a deterioration of the performance because O 2 across the membrane changed the microbial community composition. However, the reactor quickly recovered when the current was switched back to 4 A, which indicated the excellent robustness of the reactor. These results demonstrated that the E-CSTR holds great potential for scaling up and practical application. [ABSTRACT FROM AUTHOR]

• In-sewer physiobiochemical processes cause wastewater quality variation. • Microbial activities in stabilized sewer deposits are spatiotemporally organized. • In-sewer processes are intertwined with the dynamic wastewater discharge. • Detection and control of volatile compounds and bioaerosols are still challenging. • Relationships among microbiome, water quality, and sediment erosion are not clear. In-sewer physio-biochemical processes cause significant variations of wastewater quality during conveyance, which affects the influent to a wastewater treatment plant (WWTP) and arguably the microbial community of biological treatment units in a WWTP. In wet weather, contaminants stored in sewer deposits can be resuspended and migrate downstream or be released during combined sewer overflows to the urban water bodies, posing challenges to the treatment facilities or endangering urban water quality. Therefore, in-sewer transformation and migration of contaminants have been extensively studied. The compiled results from representative research in the past few decades showed that biochemical reactions are both cross-sectionally and longitudinally organized in the deposits and the sewage, following the redox potential as well as the sequence of macromolecule/contaminant degradation. The sewage organic contents and sewer biofilm microorganisms were found to covary but more systematic studies are required to examine the temporal stability of the feature. Besides, unique communities can be developed in the sewage phase. The enrichment of the major sewage-associated microorganisms can be explained by the availability of biodegradable organic contents in sewers. The sewer deposits, including biofilms, harbor both microorganisms and contaminants and usually can provide longer residence time for in-sewer transformation than wastewater. However, the interrelationships among contaminant transformation, microorganisms in the deposits/biofilms, and those in the sewage are largely unclear. Specifically, the formation and migration of FOG (fat, oil, and grease) deposits, generation and transport of contaminants in the sewer atmosphere (e.g., H 2 S, CH 4 , volatile organic compounds, bioaerosols), transport and transformation of nonconventional contaminants, such as pharmaceuticals and personal care products, and wastewater quality variation during the biofilm rehabilitation period after damages caused by rains/storms are some topics for future research. Moreover, systematic and standardized field analysis of real sewers under dynamic wastewater discharge conditions is necessary. We believe that an improved understanding of these processes would assist in sewer management and better prepare us for the challenges brought about by climate change and water shortage. [Display omitted] [ABSTRACT FROM AUTHOR]

Simultaneous generation of methane and sulfide is a major concern affecting sewer system operations, and the methanogenic archaea and sulfate-reducing bacteria may increase methane and sulfide production via their symbiotic activities. However, interactions between methane and sulfide metabolism are unclear. In this study, 18 high-quality draft genomes from sewer biofilms were obtained via genome-resolved metagenomics (Binning). The assembled bins 1, 5, 10, 12 and 15 contained abundant ackA , mcrA, mtsA , mtsB and serA genes were involved in methane generation, sulfide consumption via methane metabolism and sulfide metabolism to promote methane generation. Because of the independent and single functionality of these bins, they formed a bio-symbiotic system to promote methane and sulfide generation. Interestingly, for bins 2, 3, 8 and 9, the functions of methane generation, sulfide generation and sulfide consumption via methane metabolism occurred simultaneously. The community affiliations of the assembled bins were also unusual. For instance, bin 9 (Ignavibacteria bacterium) was derived from the Ignavibacteriae supercluster that was not been detected in sewer biofilms, but participated in both methane generation and sulfide consumption. Therefore, these bins formed another biological system with multiple functional aggregates. Two types of ecosystems integrating methane and sulfide generation in sewers were proposed. Our results improve the understanding of toxic gas emissions in sewers and provide a theoretical foundation for studies on gas suppression. [Display omitted] • Detection value and theoretical estimation of CH 4 and H 2 S generation were analysed. • Potential players to connect methane and sulfide metabolism was determined. • Symbiosis and multiple aggregates of methane and sulfide metabolism was uncovered. • Two kinds of ecosystem integrating CH 4 and H 2 S generation in sewer were proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel heterogeneous Fenton-like process driven by visible light is proposed. • Reactivity is strongly enhanced without the use of reducing agents and TiO 2 modification. • Fe(III) reduction for PS activation can be accomplished via LMCT in organic-TiO 2 -Fe(III). • It can be operated at low iron dosage and neutral conditions against Fenton system. • The excellent and long-lasting catalytic performance is mediated via synergistic effect. Efficient transformation of Fe(III) to Fe(II) enhances the efficiency of persulfate-based Fenton-like process (e.g., Fe(II)-PS system). Here, we developed a novel heterogeneous Fenton-like system driven by visible light (organic-Fe(III)-PS-TiO 2 -Vis) for effective reduction of Fe(III), activation of PS and degradation of organic pollutants without the need for external reducing agents or modifications in TiO 2. The visible light-induced ligand-to-metal (organic-to-TiO 2) charge transfer (LMCT) remarkably boosting Fe(III) reduction to increase reactive oxygen species (ROS) via PS activation, and further enhanced the self-degradation and mineralization of various organics, including phenolics (bisphenol A and phenol), antibiotics (ibuprofen and tetracycline), and dyes (methylene bule and rhodamine B). Compared with traditional Fe(II)-PS and Fe(II)–H 2 O 2 systems, the organic-Fe(III)-PS-TiO 2 -Vis process requires a lower dosage of iron salt. The effective pH range has been broadened to neutral conditions due to effective prevention of Fe(III) precipitation and rapid circulation of Fe(III)/Fe(II). The comprehensive mechanistic study indicated that a synergistic effect was generated via Fe(III) reduction, PS activation, ROS generation and organic decomposition, resulting in sustainable and excellent catalytic performance of this novel Fenton-like process. Further, the results of cycling experiments and tests involving real industrial wastewater highlight the enormous potential of the proposed LMCT-mediated heterogeneous Fenton-like process in environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • CDC process exhibited enhanced phosphorus removal compared to CC process. • CDC process had steady PO 4 3- removal in the presence of organics and various ions. • Low pH and low Al3+ concentration benefited the co-precipitation of Al3+ and PO 4 3- • Coral reef -like flocs had enhanced adsorption ability towards AlPO 4 and phosphate. In order to meet stricter phosphorus discharge standards for wastewater treatment plant effluent and better protect natural aquatic environments, this study investigated the coagulation performance and mechanisms of coral reef -like flocs formed in a continuous dosing coagulation (CDC) process. The CDC process exhibited enhanced phosphorus removal compared to the conventional coagulation (CC) process. To meet the 0.3 mg/L total phosphorus discharge standard, the CDC dosage (2 mg Al/L) was half the CC dosage (4 mg Al/L). Furthermore, at 4 mg Al/L, the CDC process obtained a very low total phosphorus concentration (0.035 mg/L). The CDC process had better phosphate removal performance when the initial pH was 6 or 5, and exhibited steady phosphate removal in the presence of organics and various ions. The CDC process enhanced phosphate removal in the following two ways. First, the "low pH and low Al3+ concentration" environment in the early stage benefited the co-precipitation of monomeric Al species and phosphate to form insoluble AlPO 4 particles. Second, the coral reef -like flocs formed in the continuous dosing process had a stronger positive charge (2.3 mV) and larger specific surface area (264.11 m2/g). The enhanced absorption ability towards undissolved AlPO 4 particles and dissolved phosphate anions promoted the overall phosphate removal of the CDC process. The coral reef -like flocs formed by a continuous dosing method provided new insights into the advanced treatment of dissolved contaminants in wastewater. [ABSTRACT FROM AUTHOR]

To achieve simultaneous organics and ammonia (NH 4 +-N) removal toward leachate treatment, this study designed a composite anode (CA+), in which iron powders were attracted to RuO 2 -IrO 2 /Ti tube surface by an inserted magnet and utilized in electro-hybrid ozonation-coagulation (E-HOC). The E-HOC (CA+) resulted in higher chemical oxygen demand (COD) and NH 4 +-N removal with most content of CO 2 /H 2 O and gaseous N in product compared with E-HOC (Fe+), electrolysis ozonation and single ozonation. Reactive chlorine species (RCS) and coagulants were co-produced by compositing RuO 2 -IrO 2 /Ti and Fe powders, resulting in multiple reactions including electrocoagulation, ozone oxidation, synergistic between ozone and coagulants (SOC), electrolytic chloride and synergistic oxidation between active chlorine and ozone (SCO) occurred. Hydroxyl radical (•OH) generated through SOC reaction was promoted due the RCS generation in E-HOC. The interaction between •OH and Cl-/ClO- also contributed to enhanced Cl•/ClO• production. Consequently, synergy of chlorine, coagulants and ozone enhanced reactive species generation which contributed to favorable organics and NH 4 +-N removal. Enhanced •OH and RCS are also attributed to conversion of bio-refractory organics like polyphenol, polycyclic aromatics and S-containing to biodegradable ones, e.g., aliphatic compounds and CHO. This study provides an easily operating strategy for leachate treatment with high content organics and NH 4 +-N. [Display omitted] • Organics and NH 4 +-N were simultaneously converted mainly into CO 2 /H 2 O and gaseous N. • RCS were greatly produced by composite anode while ROS generating in the E-HOC. • Coagulant and chlorine were co-produced by compositing DSA tube and magnetic powder. • The synergy from chlorine, coagulant and ozone improved •OH and Cl•/ClO• generation. • Enhanced •OH and RCS emerging also worked on bio-refractory organics conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe powder was fixed on RuO 2 –IrO 2 /Ti tube by inserted magnet to form a composite anode. • Removal rate of organic and NH 4 + were higher by composite anode than Fe in the EAO. • Multiple OH and RCS generation ways enhanced organic and NH 4 + removal in the EAO. • Composite anode also reduced the formation of iron sludge and alleviated passivation. Treatment of organics and NH 4 +-N containing wastewater has become a wide concern due to the difficulties for their removal in single technologies. In this study, a new composite anode (CA) was designed in which Fe powder was magnetically attracted by an internally inserted magnet onto a dimensionally stable anode (DSA) tube surface. The CA was utilized in the electrochemically assisted ozonation (EAO) process and the results were compared with the traditional Fe and DSA anode. Results showed that the CA-EAO process exhibited 9.46% and 53.40% higher efficiency for model organic oxalic acid (OA) removal compared to the Fe-EAO and DSA-EAO at optimal operating condition (current intensity 1 A, iron powder dosage 60 mg/cm2, initial pH 3 and Cl− concentration 50 mM). Besides, the removal efficiency of CA-EAO for NH 4 +-N removal was 72.61% higher than Fe-EAO although slightly lower than DSA-EAO. A series of trapping experiments and electron paramagnetic resonance (EPR) tests were also conducted and results showed that higher OH and reactive chlorine species (RCS) were generated by the CA-EAO compared to Fe-EAO, which is favorable for organic and NH 4 +-N removal, respectively. Corresponding mass transfer coefficients measurements demonstrated that attraction of iron powder on the DSA surface increased the mass transfer coefficients of the electrochemical system. Quantification of accumulated Fe illustrated that 68.99–76.64% reduction in the production of iron sludge was achieved by using CA in the EAO process compared with Fe anode. Moreover, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) mapping analysis proved that iron surface passivation was alleviated on the CA compared with Fe anode. The present study provides an implementable strategy for the treatment of wastewater containing organics and NH 4 +-N with high efficiency and less by-product generation. [ABSTRACT FROM AUTHOR]

The discharge of personal care products (PPCPs) to sewer systems increased due to the rapid expansion of cities, while PPCPs transformation in sewer and the potential threat to receiving water environments have been rarely revealed. In this study, six PPCPs (antibiotics, generic drugs and personal care products) were added continuously over a 90-day experimental period to investigate the effect of transformation in a pilot sewer. The results showed that the biological metabolism of carbon, nitrogen and phosphorus pollutants were restricted under the PPCPs stress condition. The genomic detection also confirmed that the diversity of microflora in sewer sediment were obviously decreased with the PPCPs transformation, and the total relative abundance of dominant phylum species (Firmicutes, Bacteroidetes and Proteobacteria) increased from 67.7% to 94.9%. In addition, principal coordinate analysis and metagenome showed that the two kinds of antibiotics were the most important inducement for the metabolic dysfunction in sewer systems, and led to the increase of functional gene of "Human Disease" (accounted for 0.97%) which could form more harmful metabolites to cause serious exposure hazards. Thus, this investigation provided the insights into the metabolic hazards of PPCPs bioconversions in sewers, which hoped to bring to the forefront of PPCPs emission to sewers by society. [Display omitted] • Biological metabolism of C, N and P was restricted under PPCPs stress condition. • TCY and SMX were the most important inducement for the metabolic dysfunction in sewer. • Exposure of TCY and SMX led to the increase of functional gene of "Human Disease". • ARGs can significantly affect the external environment under the exposure scenarios. [ABSTRACT FROM AUTHOR]

The separation zone in flotation is generally considered the site of solid-liquid separation of insoluble particles. However, the residual dissolved organic matter (DOM) can be effectively removed in the separation zone of the hybrid ozonation-coagulation (HOC) process was firstly discovered. DOM removal in the separation zone was mainly attributed to the in-situ formation of microbubble flocs mediated by the interaction between ozone and flocs. Ozone can regulate the oxygen containing groups on the surface of flocs, which induces formation of multilayer reaction sites. Hydrogen bonding to polar oxygen containing groups on microbubble flocs was the dominant driver of DOM removal, and –COOH and –OH were identified as the surface hydrogen bond donors. This indicated that the hydrogen bond reaction can be enhanced by the modification of ozone for flocs in the separation zone. Furthermore, surface hydroxyl groups formed by the Al acted as active sites for the connection between ozone and flocs. Ozone accelerated the transformation of tetrahedral Al to octahedral Al in flocs, which can enhance microbubble flocs generation. Moreover, microbubble floc-HA, a flotation product, exhibited higher surface hydrophobicity than conventional flocs, which resulted in high flotation efficiency. [Display omitted] • DOM removal in separation zone of HOC process was firstly discovered. • Regulation of carboxyl/hydroxyl groups of flocs by ozone aided hydrogen bond formation. • Functional flocs modified by ozone increased their affinity for residual DOM. • Ozone induced Al transformation in flocs and enhanced microbubble flocs generation. • Microbubble floc-HA as flotation products exhibited higher surface hydrophobicity. [ABSTRACT FROM AUTHOR]

Sulfide inhibition is a critical task for the secure operation of sewer systems, and oxidation is usually utilised to achieve this purpose. However, the effects and mechanism of oxidation during the transformation of sulfur-associated pollutants in gas-liquid-solid phases of sewers have not been extensively evaluated. In this study, a method for quantifying sulfur-associated pollutant exchange pathways in gas-liquid-solid phases of sewers was established. The results showed that although the concentration of sulfide decreased under different oxidation conditions, the consumption of sulfate in sewers clearly increased. The transformation strength of elemental sulfur was high (18.65 mg/L, 35.52% of sulfate from the influent) and the accumulation of sulfate in sediment was obvious (3.49 mg/L, 6.65% of sulfate from the influent). Higher concentrations of sulfate in the influent promoted the generation of sulfide in sediment (8.98 mg/L, 17.10%). Thus, the oxidation process led to the generation of more absolute sulfide. In addition, promoting the metabolism of sulfate-reducing bacteria enhanced the loss of organic carbon in sewers, which might weaken the efficacy of nitrogen and phosphorus removal in wastewater treatment plants. Based on the evaluation of the exchange pathways of sulfur-associated pollutants in sewers, further studies into sulfide inhibition in sewers should consider the above issues to enhance the safe management of urban sewers. [Display omitted] • Effect of oxidation of sulfur-pollutant on wastewater infrastructure were revealed. • An approach to quantify the sulfur-pollutant exchange pathways was established. • The consumption of SO 4 2− in sewers clearly increased under oxidation conditions. • Due to the high metabolism of SRB, the degradation of organics was also improved. [ABSTRACT FROM AUTHOR]

Nonradical oxidation based on singlet oxygen (1O 2) has attracted great interest in groundwater remediation due to the selective oxidation property and good resistance to background constituents. Herein, recoverable CuO nanoparticles (NPs) supported on mineral substrates (SiO 2) were prepared by calcination of surface-coated metal-plant phenolic networks and explored for peroxymonosulfate (PMS) activation to generate 1O 2 for degrading organic pollutants in groundwater. CuO NPs with a close particle size (40 nm) were spatially monodispersed on SiO 2 substrates, allowing highly exposure of active sites and consequently leading to outstanding catalytic performance. Efficient removal of various organic pollutants was obtained by the supported CuO NPs/PMS system under wide operation conditions, e.g., working pH, background anions and natural organic matters. Chemical scavenging experiments, electron paramagnetic resonance tests, furfuryl alcohol decay and solvent dependency experiments confirmed the formation of 1O 2 and its dominant role in pollutants removal. In situ characterization with ATR-FTIR and Raman spectroscopy and computational calculation revealed that a redox cycle of surface Cu(II)-Cu(III)-Cu(II) was responsible for the generation of 1O 2. The feasibility of the supported CuO NPs/PMS for actual groundwater remediation was evaluated via a flow-through test in a fixed-bed column, which manifested long-term durability, high mineralization ratio and low metal ion leaching. CuO nanoparticles were spatially monodispersed on the mineral substrates, allowing high-level exposure of active sites and thus leading to efficient PMS activation for groundwater remediation. A redox cycle of surface Cu(II)-Cu(III)-Cu(II) induced the activation of PMS and generation of 1O 2 that played a dominant role in pollutants removal. [Display omitted] • Recoverable CuO nanoparticles (NPs) immobilized on mineral substrates were prepared. • Supported CuO NPs were monodispersed rendering high-level exposure of active sites. • Supported CuO NPs manifested good catalytic performance for groundwater remediation. • Degradation of organics in groundwater followed a 1O 2 -dominated nonradical pathway. [ABSTRACT FROM AUTHOR]

Well dispersion of ultrafine CuO nanoparticles on layered MgO induces formation of oxygen vacancy and electron deficient Cu3+. Surface oxygen vacancy facilitated the adsorption of PDS while Cu3+ facilitated the activation of PDS, leading to a good catalytic performance for pollutants removal with high utilization efficiency of PDS. The activation of PDS by CuO/MgO hybrid catalysts followed an electron transfer mechanism. [Display omitted] • Well dispersion of CuO nanoparticles on layered MgO induces formation of surface defects. • Oxygen vacancy and electron deficient Cu3+ facilitated adsorption and activation of PDS. • PDS activation by CuO/MgO hybrid catalyst followed an electron transfer mechanism. • CuO/MgO hybrid shows selective oxidation capability and high utilization efficiency of PDS. Heterogeneous activation of peroxydisulfate (PDS) by transition metal oxides offers a promising strategy for organic pollutants removal but suffers from low electron transfer efficiency. Herein, layered MgO supported CuO nanoparticles was prepared by thermal conversion of metal-phenolic networks of Cu2+/Mg2+ and tannic acid. CuO nanoparticles (∼2 nm) were spatial monodispersed on layered MgO, inducing the formation of electron deficient Cu3+ and surface oxygen vacancies and thus facilitated adsorption and activation of PDS. The electron-rich CuO/MgO hybrid catalysts manifested good catalytic performance of PDS activation for organic pollutants removal. At 0.18 g/L of CuO/MgO hybrid catalyst and 0.2 mM of PDS, complete removal of bisphenol A (BPA) was achieved with a high kinetic constant (0.1 min−1, 50 min). Quenching experiments, electron paramagnetic resonance tests, PDS decomposition behaviors, electrochemical analysis and in situ ATR-FTIR and Raman spectroscopy revealed a nonradical pathway of electron transfer for PDS activation. The CuO/MgO hybrid catalysts exhibited wide working pH range from 3 to 11, selective oxidation capability, good resistance to halide ion and high utilization efficiency of PDS, and thus would be a promising candidate for wastewater remediation. [ABSTRACT FROM AUTHOR]

Abstract: A full scale anaerobic–anoxic–oxic (A2O) biological unit followed by a submerged MBR was applied for domestic wastewater treatment and reclaimed water production. Under a constant flux of 16L/m2h, TMP varied narrowly between 12 and 22KPa over the duration of 9 months with only enhanced flux maintenance (EFM) for restoring membrane permeability. By analyzing the particle size distribution (PSD) and extracellular substances (EPS) in the mixed liquor at different steps, it was found that fine particles, proteins and polysaccharides, as potential foulants, decreased along the A2O–MBR array. Fluorescent excitation–emission matrix (3DEEM) analysis further revealed the characteristics of dissolved organic substances throughout the treatment process. Nevertheless, the deposition of organic foulants was identified in the cake layer on the membrane surface by scanning electron microscopy and Fourier transform infrared spectroscopy. The advantage of the A2O–MBR system over the conventional MBR was not only in the effectiveness for high quality reclaimed water production, but also in the reduction of potential foulants through the A2O biological process prior to entering the MBR unit. [Copyright &y& Elsevier]

In this study, a novel iron and nitrogen co-doped biochar (Fe/N-biochar) was successfully prepared and employed as an efficient adsorbent for micropollutants. The maximum adsorption capacity of Fe/N-biochar for bisphenol A (BPA) was 54 mg/g, which is significantly better than that of commercial graphene (19 mg/g) and activated carbon (6 mg/g). Additionally, for eight other common micropollutants (e.g., phenol, acetaminophen, and sulfamethoxazole), Fe/N-biochar also exhibited highly enhanced adsorption performance. The results of adsorption kinetics and isotherms studies showed that the adsorption of micropollutants onto Fe/N-biochar is by monolayer coverage. Thermodynamic studies further suggested that the adsorption process is feasible, spontaneous, and chemical in nature. The adsorption mechanism was investigated by correlation analysis between the adsorption capacity and the physiochemical properties of Fe/N-biochar. The results demonstrated that the strengthening of π–π electron donor-acceptor interactions between the organics and the adsorbent caused by the co-doping of iron and nitrogen was the dominant driving force behind the efficient adsorption of micropollutants. Furthermore, graphitic N and Fe−N x were identified as the major adsorption sites. Simple heat treatment could effectively restore the adsorption capacity of Fe/N-biochar that had reached adsorption equilibrium. In view of its simple preparation method, highly enhanced adsorption capacity, and excellent recyclability, the prepared Fe/N-biochar can be regarded as a promising candidate for wastewater treatment. [Display omitted] • Fe/N-biochar exhibits enhanced adsorptive removal of micropollutants. • Fe/N-biochar has 10.8 times higher adsorption capacity than pristine biochar. • Strong π−π interactions are the main driving force for adsorption of organics. • Graphitic N and Fe−N x are identified to be the primary adsorption sites. • Heat treatment can effectively restore the adsorption ability of used adsorbent. [ABSTRACT FROM AUTHOR]

● SMP and EPS could be used as denitrifying carbon sources by strain RT1901. ● Whole-genome sequence of Thauera sp. RT1901 revealed diverse metabolism. ● The abundance of traditional PAOs decreased with the enrichment of Thauera. ● The removal rates of COD and TN increased with the enrichment of Thauera. Thauera , as one of the core members of wastewater biological treatment systems, plays an important role in the process of nitrogen and phosphorus removal from low-carbon source sewage. However, there is a lack of systematic understanding of Thauera 's metabolic pathway and genomics. Here we report on the newly isolated Thauera sp. RT1901, which is capable of denitrification using variety carbon sources including aromatic compounds. By comparing the denitrification processes under the conditions of insufficient, adequate and surplus carbon sources, it was found that strain RT1901 could simultaneously use soluble microbial products (SMP) and extracellular polymeric substances (EPS) as electron donors for denitrification. Strain RT1901 was also found to be a denitrifying phosphate accumulating bacterium, able to use nitrate, nitrite, or oxygen as electron acceptors during poly-β-hydroxybutyrate (PHB) catabolism. The annotated genome was used to reconstruct the complete nitrogen and phosphorus metabolism pathways of RT1901. In the process of denitrifying phosphorus accumulation, glycolysis was the only pathway for glycogen metabolism, and the glyoxylic acid cycle replaced the tricarboxylic acid cycle (TCA) to supplement the reduced energy. In addition, the abundance of conventional phosphorus accumulating bacteria decreased significantly and the removal rates of total nitrogen (TN) and chemical oxygen demand (COD) increased after the addition of RT1901 in the low carbon/nitrogen (C/N) ratio of anaerobic aerobic anoxic-sequencing batch reactor (AOA-SBR). This research indicated that the diverse metabolic capabilities of Thauera made it more competitive than other bacteria in the wastewater treatment system. [Display omitted] [ABSTRACT FROM AUTHOR]

• Mesoporous metal oxidesensing materials from MOFs have been summarized. • The relationships between structures and gas sensing performance are discussed. • The prospects on MOFs-derived mesoporous metal oxides for gas sensor are proposed. Chemiresistive gas sensors based on semiconducting metal oxides (SMOs) have been widely used in medical diagnosis, industrial production and aerospace vehicles. It's challenging to develop gas sensor with high selectivity and low working temperature. Recently, metal-organic frameworks (MOFs) derived SMOs have been regarded as a promising candidate for developing high-performance gas sensors owing to their mesoporous structure, unique morphology, tunable architectures and compositions. Great progresses have been made in design and synthesis of SMOs with different nanostructures and compositions using MOFs as a precursor. However, there are few reviews to summarize the progresses of this fast-growing area. In this review, we systematically summarize the recent developments in the field of MOFs-derived mesoporous SMOs with different architectures and compositions for gas sensing application. In particularly, the influence of structure and composition of SMOs on the sensing performance in terms of sensitivity, selectivity, response/recovery speed and working temperature are summarized. Strategies including constructing novel nanostructures, building heterojunctions, decorating with noble catalysts and combining with highly-conductive materials for enhancing the sensing performance are discussed in this review. Furthermore, the current challenges and prospects in the application of MOFs-derived mesoporous SMOs for sensing application are proposed. This review may provide a guideline for rational design and development of high-performance gas sensors using MOFs-derived SMOs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Topological defects could be created through the nitrogen incorporation-evaporation process. • PMS could be effectively activated by topological defects. • The electron-transfer mechanism was the dominant way for pollutant degradation. Nitrogen was usually doped into carbon matrix to boost its catalytic activity owing to its electronic adjusting activity toward the topological carbon structure. Herein, an overlooked role of nitrogen dopant was unraveled. The nitrogen dopant was firstly incorporated into the carbon matrix and then partially evaporated, leaving the newly generated topological intrinsic defects under high temperature. It was confirmed that peroxymonosulfate (PMS) could be activated by topological defects-rich carbon catalysts. Surface-activated PMS complex was found to be the dominant reactive oxidation species for organic degradation through electron-transfer mechanism. The distinct current density attenuation revealed that N-rich carbon catalysts possessed more effective stoichiometric reaction between the surface-activated PMS and adsorbed organic than topological defects-rich carbon. Findings from this work confirmed the roles of topological defects and extrinsic defects in PMS activation and provided new insight into the synthesis of defects-rich carbon catalysts. [ABSTRACT FROM AUTHOR]

Via enlarging the specific surface area of sludge biochar to enhance the close contact of multiple reactants may be a simple route to improve the catalytic performance with reduced dosage of biochar and oxidant, benefitting for cost-effectiveness and eco-friendliness. Herein, PS activation ability of a reported sludge-derived biochar adsorbent was investigated. 80% TOC of 100 mL 10 mg/L BPA was removed within 40 min by 7 mg biochar and 0.5 mM PS mixed, with a relatively high PS activation efficiency close to 50%. Expectedly, the desired mineralization efficiency of complex actual wastewater was also identified. Eco-friendliness of the application mode was confirmed by the leaching toxicity and acute bio-toxicity tests. Physicochemical properties of the sludge biochar were comprehensively characterized by various techniques. Combined with a series of mechanism analysis, ·OH, SO 4 ·-, ·O 2 -, 1O 2 , free electron all participated in pollutants removal process and the non-radical pathway of electron transfer dominated the reaction. The generated metastable complex [SBC-PS*] confirmed by in situ FT-IR and Raman spectra was the most important active species for electron transfer and PS decomposition. Due to the high efficiency and stability, the sludge biochar adsorbent/PS catalytic system provides a promising way for waste reuse and advanced wastewater treatment. [Display omitted] • The proposed biochar adsorbent with large surface area promotes PS activation. • Desired mineralization efficiency is achieved by the small dosage of PS and biochar. • Toxicity of the biochar/PS catalytic system is relatively low with eco-friendliness. • Most important active species [SBC-PS*] is verified by FT-IR and Raman spectra. • Active sites for PS activation and pollutant degradation are systematically explored. [ABSTRACT FROM AUTHOR]

• The E-HOC with bipolar connection exhibited higher EfOM and IBP removal efficiency. • The E-HOC with dual-coagulants generated leads to higher organic removal efficiency. • Bipolar connection or dual-coagulants generation resulted in more active sites. • More polymeric al/fe species formed in bipolar connection or dual-coagulants mode. The electro-hybrid ozonation-coagulation process (E-HOC) integrates electrocoagulation (EC) and ozonation simultaneously in a single unit. Nevertheless, the performance of the EC process is highly dependent on the polar connection configuration (monopolar vs. bipolar connection) and the type of generated coagulants (single-coagulant vs. dual-coagulants). In this study, the removal efficiency of the E-HOC process with different connection configurations and types of coagulants was assessed. The E-HOC process with bipolar connection (BE-HOC) exhibited higher removal efficiency for wastewater treatment plant (WWTP) effluent organic matter and ibuprofen (IBP) compared with the E-HOC process with monopolar connection (ME-HOC). Furthermore, dual-coagulant generation (released from both Al and Fe electrodes) in the BE-HOC process greatly improved the WWTP effluent organic matter and IBP removal efficiency. Lower energy consumption was observed for the BE-HOC process compared with the ME-HOC process. It was found that ozonation promoted the polymerization reactions during coagulant hydrolyzis in the E-HOC process. Compared with the ME-HOC process, the BE-HOC configuration and dual-coagulant mode further facilitated polymeric hydrolyzed coagulant species formation, thereby improving ozone catalytic and coagulation performance. According to trapping experiments and EPR analysis, •OH formation was enhanced in the BE-HOC process and dual-coagulant mode. In addition, more active reaction sites of generated hydrolyzed coagulant species were observed with bipolar connection and in the dual-coagulant generation mode based on X-ray photoelectron spectroscopy (XPS) analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we compared dissolved organic carbon (DOC) and UV 254 removal efficiencies of the hybrid ozonation-coagulation (HOC) and pre-ozonation-coagulation (POC) processes for humic acid (HA) at pH 5 with AlCl 3 •6H 2 O as the coagulant. The DOC and UV 254 removal efficiencies of the HOC process were higher than those of the POC process at ozone dosages less than 2.0 mg O 3 (mg DOC)−1. The ozone dosage was optimized at 0.3 and 0.1 mg O 3 (mg DOC)−1 for the HOC and POC processes, respectively, implying a more rigorous ozone dosage for the POC process. During the POC process, pre-ozonation was observed to increase the binding sites of HA (e.g., hydroxyl and carboxyl groups), improving the complexation of dissolved organic matter. For the HOC process, in addition to its role in the oxidation of organic matter, ozone also reacted with coagulants. The reaction between ozone and coagulants can facilitate the formation of Al 13. Moreover, the oxidation of •OH and ozone can increase the charge density of the HA binding sites, homogenizing the binding sites of HA and enhancing the complexation with Al 13. [Display omitted] • HOC process has a wider ozone dosage range than pre-ozonation-coagulation process. • Ozone can react with hydrolysed Al species besides HA in the HOC process. • Ozone homogenizes the protonated groups of HA and hydrolysed coagulant species. • Simultaneous homogenization facilitates the binding between HA and coagulants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microscopic Fe-graphitic carbon galvanic cell array was created for PMS activation process. • Carbon assisted galvanic corrosion significantly facilitated the Fe2+/H* generation from Fe0. • Radicals, FeIV = O, and electron-shuttle were proved to be involved in reaction. Zero-valent iron (ZVI) usually activates peroxymonosulfate (PMS) through the generation of Fe2+ from the self-corrosion of ZVI in a Fenton-like reaction. However, the generation rate of Fe2+ forms the reaction rate-limiting step. Against this, a microscopic Fe-graphitic carbon galvanic cell array (GCA) was created to intensify the PMS activation process. The synergistic effect between a ZVI anode and a graphitic carbon cathode accelerated the generation of Fe2+ via ZVI galvanic corrosion to significantly increase the PMS activation performance. Distinctive short-circuiting of the anode and cathode in GCA effectively enhanced the galvanic corrosion. The electrochemical behavior of GCA was characterized in detail to elucidate the PMS activation mechanism. The microscopic Fe-graphitic carbon galvanic cell array provided a promising pathway for pollutant remediation. [ABSTRACT FROM AUTHOR]

• Excellent As removal efficiency of 98.9% was achieved by doping Cu oxides into Fe-Mn binary oxide. • Cu-ion-doping can promote the reactivity of Mn oxides to improve As(III) oxidation. • The Fe-Mn-Cu ternary oxide can activate adsorbed oxygen to form superoxide radicals. • Multiple pathways for As(III) oxidation were proposed for the enhanced removal of As(III). Mn-oxide-containing adsorbents have shown outstanding performances for the removal of As(III) through an "oxidation-adsorption" process. In this study, a new adsorbent of Fe-Mn-Cu ternary oxide (FMCTO) was fabricated to improve the redox reaction rate and to enhance the recovery of oxidative ability. FMCTO exhibited a stronger ability for As(III) removal than most of other adsorbents, because it has better oxidative capability for As(III) oxidation. The state of dynamic equilibrium for As(III) removal by FMCTO could be basically achieved within 3 h, and the As removal efficiency reached 98.9% at time = 24 h. The Langmuir As adsorption capacity of FMCTO was determined to be 204.8 mg/g. The As(III) removal efficiency of FMCTO was further boosted by 7% through oxygen gas aeration and decreased by 19% with nitrogen gas in the ambient during the first 3 h, indicating the positive effect of oxygen on As(III) oxidation. EPR and UV spectra methods were used to confirm the generation of superoxide radical (O 2 −) and the enhanced production of Mn(III) soluble species on FMCTO surfaces, thus achieving a better As(III) oxidation performance. The XPS analysis results showed that the electron transfer from Cu(I) to Mn(IV) could improve the stability of Mn(III) within FMCTO. Meanwhile, Mn(II) ions could be oxidized to Mn(III) by O 2 −. Hence, the formation of a redox cycle between Mn(II) and Mn(III) along with the production of O 2 − plays a vital role in the upgraded As(III) removal mechanisms. This study provides new insights into the promotion of the capability of Mn-containing adsorbents for achieving the improved removal of As from As(III)-contaminated water. [ABSTRACT FROM AUTHOR]

• Kilogram-scale N-CoFeO can be synthesized through a facile solid-state procedure. • γ-Fe 2 O 3 containing nanocage was successfully created on the surface of N-CoFeO. • The created nanocage is very effective in minimizing cobalt leaching from catalyst. • The mechanism of cobalt leaching minimization was carefully elucidated. We report a solid-state synthesis procedure for the facile fabrication of N-doped cobalt ferrite (N-CoFeO). A surface ferric coagulation-thermal treatment process was then developed to minimize cobalt leaching by creating a γ-Fe 2 O 3 -containing nanocage on the surface of the N-CoFeO. A remarkable decrease in the concentration of leached Co from 182.2 μg L−1 to 2.7 μg L−1 evidenced the promising potential of the cobalt leaching inhibition method. Further study confirmed that the minimization of cobalt leaching was achieved via cation vacancies in the γ-Fe 2 O 3 -containing nanocage. This cation vacancies could bind metal ions and facilitate the generation of surface hydroxyl groups, rendering negligible Co leaching during reaction process. Furthermore, the nanocage covered N-CoFeO (N-CoFeO@Fe x) exhibited superior performance for bisphenol A degradation within a wide pH range. Higher dosages of both the catalyst and peroxymonosulfate jointly intensified the degradation performance. Both radical and non-radical pathways were involved in the degradation process. It also should be noted that HO exhibited negligible contributions to BPA degradation during the catalytic process. Furthermore, BPA degradation pathway was proposed by chromatography-mass analysis assisted with density functional theory (DFT) calculation, and the mechanism were proposed comprehensively. [ABSTRACT FROM AUTHOR]

• A comprehensive study on the transportation characteristics of PPCPs in sewers. • Mass balance analysis reveals degradation pathway of PPCPs in sewers. • Six transformation products were identified by used UHPLC-Q Exactive MS. • The environmental risk of PPCPs in sewers were evaluated for the first time. The release of pharmaceuticals and personal care products (PPCPs) is one of the most concern issues which affect the stability of environment. In this study, the transformation, typical metabolites and risk evaluation of five dominating PPCPs (acetaminophen, triclosan, caffeine, N,N-diethyl-m-toluamide and sulfamethoxazole) were investigated in a pilot sewer. Firstly, the mass balance analysis indicated, although the PPCPs have the peculiarity of degradation-resistant, the biodegradation of PPCPs still plays a more important role in sewers, and then, liquid chromatography coupled to mass spectrometry (UHPLC-Q Exactive MS) methods were utilized to reveal their fate during pipeline transportation. In total, six transformation products (TPs) were detected and identified. The transformation occurring in sewers involved rearrangement of the aminobenzene moiety, ether bond breaking, hydrolysis of hydroxy compounds and dealkylation. Finally, risk(s) were estimated by calculating risk quotients (RQs). TCS is "high risk" (RQ > 200), SMX is "minimal risk" (RQ < 0.3), and the other compounds examined are "low or medium risk" and vary widely (RQ ≈ 3.75–98.19). Thus, based on this investigation, insights into PPCPs bioconversions in sewers were revealed, which could improve the understanding of subsequent treatment process of the wastewater treatment plant (WWTP) and reduced environmental risks caused by micropollutants. [ABSTRACT FROM AUTHOR]

Magnetic mesoporous carbon composites are promising adsorbents for water purification. However, the sustainable synthesis of such mesoporous carbon nanospheres with controllable structures and compositions using renewable biomass as a carbon source is still a great challenge. Herein, mesoporous carbon nanospheres have been successfully synthesized via direct pyrolysis of iron-phenolic coordination polymers. Such coordination polymers are fabricated using plant phenol as a renewable carbon source and iron ions as a metal source. The resultant magnetic mesoporous carbon nanospheres show large pore size (6.7 nm), high specific surface area (512.3 m2/g), excellent performance for Cr(VI) removal with a high adsorption capacity (336.7 mg/g), fast adsorption rate (1.60 × 10−3 mg g−1 min−1) and easy magnetic separation property. In the adsorption process, Cr(VI) is first trapped on the surface of magnetic mesoporous carbon nanospheres via electrostatic interaction. Then part of the adsorbed Cr(VI) is reduced to low-toxic Cr(III) by α-Fe/Fe 3 C nanoparticles dispersed in carbon nanospheres. This work provides an efficient synthesis strategy for magnetic mesoporous carbon nanospheres using plant polyphenol as a carbon source, which could be used in environmental science, energy storage and catalysis. Image 1 • Magnetic mesoporous carbon nanospheres have been prepared from plant phenol. • Magnetic mesoporous carbon nanospheres show high uptake capacity to Cr(VI). • The uptake of Cr(VI) involves electrostatic interaction and reduction to less toxic Cr(III). [ABSTRACT FROM AUTHOR]

• Fe-N-C was prepared and utilized to activate PMS to degrade organic pollutants. • Fe-N-C showed 37.07 and 6.04-fold higher activity to biochar and N-biochar. • Synergistic effects between Fe and N species facilitated the production of ROS. • SO 4 •−, •OH and 1O 2 were identified under the Fe-N-C/PMS treatment. • Fe-N-C showed great separation performance and reusability. This study shows that the simple pyrolysis of mixed sawdust, FeCl 3 and dicyandiamide can produce Fe/N co-doped biochar (Fe-N-C) with great catalytic and separation performances. Fe-N-C had a larger specific surface area (215.25 m2/g), higher defective degree (I D / I G = 0.98) and more active species for PMS activation because of the synergy between Fe and N doping. Furthermore, graphitic N, pyridinic N, Fe-N x , Fe 2 O 3 and Fe0 were identified as the dominant reactive species contributing to the activation of PMS. As a result, the production of reactive oxidizing species (ROS), including both sulfate radical (SO 4 •−), hydroxyl radical (•OH) and singlet oxygen (1O 2), in the Fe-N-C/PMS system was significantly promoted. As a result, Fe-N-C exhibited 37.07 and 6.04-fold higher reaction rates for activating peroxymonosulfate (PMS) to degrade bisphenol A (BPA) relative to the rates achieved by pristine biochar and nitrogen doped biochar, respectively. Moreover, the mineralization rate of BPA by the Fe-N-C/PMS system was 68.9%, which was much higher than that achieved by the pristine biochar/PMS and N-biochar/PMS systems. Chemical-quenching tests further suggested that SO 4 •− and •OH played dominant roles in the degradation of BPA under acidic and neutral conditions, while 1O 2 played a dominant role under alkaline conditions. Furthermore, the potential of Fe-N-C to be used in practical applications was systematically evaluated in terms of its stability, separability and selectivity to organics; the effect of operating parameters was also studied. Generally, our study highlighted the great potential of Fe/N co-doped biochar and provided valuable insight into the synthesis of highly efficient carbon-based catalysts for environmental applications. [ABSTRACT FROM AUTHOR]

• SRB metabolism provides a key medium (Methyl-CoM) for rapid generation of MA. • MA metabolism involves in H 2 S consuming process via L-Cysteine from sulfide metabolism. • The H 2 S consuming guarantees the suitable pH and S2- conditions for SRB and MA. • The heavily intertwined symbiosis leads to harmonious H 2 S and CH 4 generation in sewer. Sulfide and methane emissions always simultaneously exist in natural environment and constitute a major topic of societal concern. However, the metabolic environments between sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) exist a great difference, which seems to be opposite to the coexisting phenomenon. To explore this issue, the comprehensive biofilm structures, substrate consuming and metabolism pathways of SRB and MA were investigated in a case study of urban sewers. The results showed that, due to the stricter environmental requirements of MA than SRB, SRB became the preponderant microorganism which promoted the rapid generation of sulfide in the initial period of biofilm formation. According to a metagenomic analysis, the SRB appeared to be more preferential than MA in sewers, and the preponderant SRB could provide a key medium (Methyl-coenzyme M) for methane metabolism. Therefore, the diversity of MA gradually increased, and the symbiosis system formed preliminarily. In addition, via L-cysteine, methane metabolism also participated in sulfide consumption which was involved in cysteine and methionine metabolism. This phenomenon of sulfide consumption led to the forward reaction of sulfide metabolism, which could promote sulfide generation while stabilizing the pH value (H+ concentration) and S2- concentrations which should have inhibited SRB and MA production. Therefore, the heavily intertwined interactions between sulfide and methane metabolism provided environmental security for SRB and MA, and completely formed the symbiosis between SRB and MA. Based on these findings, an ecological model involving synergistic mechanism between sulfide and methane generation is proposed and this model can also improve understanding on the symbiosis of SRB and MA in the natural environment. [ABSTRACT FROM AUTHOR]

In order to improve the dissolved organic matter removal efficiency, an electro-hybrid ozonation-coagulation (E-HOC) system was developed in this study, in which the electro-coagulation (EC) and ozonation occurred simultaneously in one integrated unit. Higher removal efficiency was observed for the E-HOC process compared with those of EC, ozonation and pre-ozonation-EC process for the treatment of wastewater treatment plant (WWTP) effluent and ibuprofen (IBP). 58.6% dissolved organic carbon (DOC) removal efficiency was achieved in the E-HOC process for the treatment of WWTP effluent at optimal operational condition (current density 15 mA/cm2, initial pH 5 and ozone dosage 1.5 mg O 3 /mg DOC). Based on the reactive oxygen species (ROS) detection and reactions on the electrodes, the synergistic effects between ozone and coagulants (SOC) were found to be involved in the E-HOC process. According to pseudo-first-order rate constant analyses, the contribution of five possible organic removal pathways was quantified. It was revealed that the peroxone and SOC effects exhibited almost equal contribution to IBP removal at initial pH 5 under different current densities, both of which played the dominant role in the E-HOC process. However, the contribution of the SOC effects decreased significantly when the initial pH increased to 7 and 9. As an important pathway for organic removal in the E-HOC process at initial pH 5, the mechanism of the SOC effects was analysed at initial pH 5. It was revealed the SOC effects can further improve hydroxyl radicals (•OH) generation, and the surface hydroxyl groups of the hydrolysed Al species generated from anode electrolysis were determined to be the active sites to generate ROS in the SOC effects. Image 1 • The E-HOC showed higher organic removal than EC, ozonation and pre-ozonation-EC. • Synergistic effects between ozone and coagulants (SOC) are involved in the E-HOC. • The peroxone and SOC effects played almost equal major role in the E-HOC at pH 5. • The SOC effects can further improve the ROS generation in the E-HOC process. [ABSTRACT FROM AUTHOR]

• Nitrogen-doped biochar was prepared from sawdust and different nitrogen precursors. • The catalytic activity of N-biochar relies heavily on the preparation conditions. • The optimal catalyst exhibited excellent performance on the activation of PMS. • The catalytic system can work effectively at a wide pH range and real water matrix. • SO 4 −, OH and 1O 2 were responsible for the degradation of the organic species. The fabrication of low-cost, high-performance and environmentally friendly carbon-based catalysts capable of activating peroxymonosulfate (PMS) for wastewater treatment applications is still a challenge. In this work, a novel nitrogen-doped biochar (N-biochar) was prepared through a facile one-step calcination method using sawdust and different organic nitrogen-containing compounds as starting materials. It was found that the catalytic activity of the N-biochar relies heavily on the type of nitrogen precursor, the relative amount of sawdust to nitrogen precursor, and the calcination temperature. Different types and amounts of the nitrogen precursor mainly affect the content of total nitrogen and pyridinic nitrogen, and the calcination temperature mainly affects the content of graphitic nitrogen in the N-biochar. Based on a systematic comparison, an optimized N-biochar (N-C-d-4-800) with a higher content of graphitic and pyridinic N, rich defects, larger SSA and porous structure was obtained, and exhibited a superior catalytic activity for activating PMS to oxidize various organic pollutants, such as bisphenol A (BPA), phenol, acetaminophen (AAP) and sulfamethoxazole (SMX). Moreover, the N-C-d-4-800/PMS system can work effectively at a wide pH range and high salinity conditions, despite the background of the real water matrix. The present study highlights the enormous potential of the novel N-biochar prepared from sawdust for wastewater remediation applications. [ABSTRACT FROM AUTHOR]

As the initial stage of the sewage treatment system, the degradation of pollutants inevitably involves an entropy change process. Microorganisms play a vital role, where they interact with pollutants and constantly adjust own ecosystem. However, there is a lack of research on the entropy change and external dissipation processes within the sewer system. In this study, considering the characteristics of microbial population changes in the biofilm within the urban sewage pipe network, entropy theory is applied to characterize the attributes of different microorganisms. Through revealing the entropy change of the microbial population and chemical composition, a coupling relationship between the functional bacteria diversity, organic substances composition, and external dissipation in the pipeline network is proposed. The results show that the changes of nutrient availability, microbial community structure, and environmental conditions all affect the changes of information entropy in the sewer network. This study is critical for assessing the understanding of ecological dynamics and energy flows within these systems and can help researchers and operation managers develop strategies to optimize wastewater treatment processes, mitigate environmental impacts, and promote sustainable management practices., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

With high organics and ammonia, leachate from waste transfer stations (WTSs) is among the most complex wastewater that cannot be easily disposed by signal biological processes. In this study, an electro-dissolved ozone flotation (E-DOF) was established, in which dissolved ozone flotation (DOF) and electro-coagulation (EC) occurred concurrently in one unit and integrated with anoxic/oxic membrane bioreactor (A/O-MBR) to dispose leachate from a WTS. In the integrated reactor, E-DOF acted as pretreatment and advanced treatment unit. A/O-MBR acted as secondary treatment unit. The E-DOF pretreatment achieved 34.48% COD and 16.96% NH 3 -N removal efficiency through synergistic effect between EC and DOF. BOD 5 /COD of leachate was increased from 0.32 to 0.51 after E-DOF pretreatment, indicating the enhancement of biodegradability. Molecular weight distribution (MWD) and three-dimensional excitation-emission matrix (3D-EEM) analysis demonstrate that the reduction of molecular weight and elimination of refractory organics through EC, ozone, and their interacted product (•OH) are attributed to biodegradability enhancement in lechate. Microbial community analysis proved that chemoheterotrophy and oxic chemoheterotrophy functions, mainly provided by Truepera, Aquamicrobium, Saprospiraceae, and Lentimicrobiaceae, ensured the efficient degradation of organic in the secondary processes. E-DOF advanced treatment effectively disposed residual contaminant in MBR effluent. The E-DOF advanced treatment mainly disposed residual contaminant in MBR effluent. High removal efficiency of COD (98.59 ± 0.27%), NH 3 -N (95.59 ± 0.50%), TN (95.37 ± 0.73%), and TP (96.75 ± 1.66%) were observed in the integrated reactor, and final effluent met the discharge standards for inclusion in the sewage pipe network in China., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)