Multilevel investigation of the ecotoxicological effects of sewage sludge biochar on the earthworm Eisenia fetida.

The ecological risks of sewage sludge biochar (SSB) after land use is still not truly reflected. Herein, the ecological risks of SSB prepared at different temperature were investigated using the earthworm E. fetida as a model organism from the perspectives of organismal, tissue, cellular, and molecular level. The findings revealed that the ecological risk associated with low-temperature SSB (SSB300) was more pronounced compared to medium- and high-temperature SSB (SSB500 and SSB700), and the ecological risk intensified with increasing SSB addition rates, as revealed by an increase in the integrated biomarker response v2 (IBRv2) value by 2.59-25.41 compared to those of SSB500 and SSB700. Among them, 10% SSB300 application caused significant oxidative stress and neurotoxicity in earthworms compared to CK (p < 0.001). The weight growth rate and cocoon production rate of earthworms were observed to decrease by 25.06% and 69.29%, respectively, while the mortality rate exhibited a significant increase of 33.34% following a 10% SSB300 application, as compared to the CK. Moreover, 10% SSB300 application also resulted in extensive stratum corneum injury and significant longitudinal muscle damage in earthworms, while also inducing severe collapse of intestinal epithelial cells and disruption of intestinal integrity. In addition, 10% SSB300 caused abnormal expression of earthworm detoxification and cocoon production genes (p < 0.001). These results may improve our understanding of the ecotoxicity of biochar, especially in the long term application, and contribute to providing the guidelines for applying biochar as a soil amendment.

Catalytic pyrolysis of liquor-industry waste: Product and mechanism analysis.

The effects of three catalysts, namely Ni/γ-Al2O3, Fe/γ-Al2O3, and Mg/γ-Al2O3, on the three-phase products of liquor-industry waste pyrolysis were investigated in this study. Results indicated that the catalytic performance of Ni/γ-Al2O3 outperformed those of Fe/γ-Al2O3 and Mg/γ-Al2O3 significantly. The application of Ni/γ-Al2O3 facilitated the reformation of pyrolysis volatiles, leading to increased yields of H2 (174.1 mL/g), CH4 (80.7 mL/g), and CO (88.2 mL/g) by 980.00 %, 133.24 %, and 83.37 %, respectively. compared to catalyst-free conditions. The Ni/γ-Al2O3 also increased the low-level calorific value of biogas by 109.3 % compared to that under non-catalyst conditions. Moreover, Ni/γ-Al2O3 enhanced the relative concentrations of hydrocarbons in tar by 23.15 % while reducing the relative concentrations of O-species by 15.73 % compared to catalyst-free conditions through induced deoxygenation, decarboxylation, decarbonylation reactions as well as efficient steam reforming processes for tar and syngas upgrading purposes. Thus, incorporating Ni/γ-Al2O3 into the pyrolysis process represents a renewable approach for waste-to-energy conversion.

A novel magnetic sludge biochar was prepared by making full use of internal iron in sludge combining KMnO4-NaOH modification to enhance the adsorption of Pb (â ¡), Cu (â ¡) and Cd (â ¡).

This study synthesized novel magnetic biochar (PCMN600) by KMnO4-NaOH combined modification using iron-containing pharmaceutical sludge to remove toxic metals from wastewater effectively. Various characterization experiments of engineered biochar showed that the modification process introduced ultrafine MnOx particles on the carbon surface and resulted in higher BET surface area and porosity along with more oxygen-containing surface functional groups. Batch adsorption studies indicated that the maximum adsorption capacities of PCMN600 for Pb2+, Cu2+ and Cd2+ were 181.82 mg/g, 30.03 mg/g and 27.47 mg/g, respectively, at a temperature of 25 °C and pH of 5.0, which were much higher than that of pristine biochar (26.46 mg/g, 6.56 mg/g and 6.40 mg/g). The adsorption datums of three toxic metal ions fitted well to the pseudo-second-order model and Langmuir isotherm, and the sorption mechanisms were identified as electrostatic attraction, ion exchange, surface complexation, cation-π interaction and precipitation. The strong magnetic properties of the engineered biochar endowed the adsorbent with remarkable reusability, and after five cycles of recycling, PCMN600 still retained nearly 80% of its initial adsorption capacities.

Synthesis of two nitrogen-doped carbon quantum dots to construct fluorescence probes for sensitive Hg2+ detection with dual signal output.

The rapid and sensitive detection of heavy metal ions is of great importance in food safety and for the environment. Therefore, two novel probes, M-CQDs and P-CQDs, based on carbon quantum dots were utilized to detect Hg2+ based on fluorescence resonance energy transfer and photoinduced electron transfer mechanisms. The M-CQDs were prepared from folic acid and m-phenylenediamine (mPDA) using a hydrothermal method. Similarly, the novel P-CQDs were obtained according to the same synthetic procedure used to create M-CQDs except the mPDA was replaced with p-phenylenediamine (pPDA). Upon the addition of Hg2+ to the M-CQDs probe, the fluorescence intensity reduced significantly with a linear concentration range between 5 and 200 nM. The limit of detection (LOD) was calculated to be 2.15 nM. On the contrary, the fluorescence intensity of the P-CQDs was enhanced greatly after the addition of Hg2+. The Hg2+ detection was realized with a wide linear range from 100 to 5000 nM and the LOD was calculated to be as low as 52.5 nM. The fluorescence "quenching" and "enhancing" effect exhibited by the M-CQDs and P-CQDs, respectively, is due to the different distribution of -NH2 in the mPDA and pPDA precursors. Notably, paper-based chips modified with M/P-CQDs were established for visual Hg2+ sensing, demonstrating the possibility for real-time detection of Hg2+. Moreover, the practicality of this system was confirmed through the successful measurement of Hg2+ in tap water and river water samples.

Spectroscopic fingerprints profiling the polysaccharide/protein/humic architecture of stratified extracellular polymeric substances (EPS) in activated sludge.

Extracellular polymeric substances (EPS), with a stratified structure including tightly-bound EPS (TB-EPS), loosely-bound EPS (LB-EPS), and soluble EPS (S-EPS) surrounding the microbial cells, are known to vitally affect the physicochemical and biological functions of activated sludge in wastewater treatment. Polysaccharides (PS), proteins (PN), and humic acids (HA) are key components of EPS but their roles in constructing the multi-layer architecture are still unclear. This study explored the EPS characteristics in relation to the components using spectroscopic fingerprinting techniques. Ultraviolet-visible (UV-vis) spectra demonstrated stark difference between TB-EPS and other EPS. Fluorescence excitation-emission matrix (FEEM) and apparent quantum yield revealed further detailed differences. Fluorescence quotient analysis highlighted the dominance of TB-EPS, LB-EPS, and S-EPS in the excitation/emission wavelength (Ex/Em) region of Em = 350-400 nm, Em > 400 nm, and low-Stokes shift band (Em - Ex < 25 nm), respectively. Wavelength-wise prediction of the FEEM intensity was achieved through multiple linear regression against the chemical composition and variance partitioning analysis witnessed binary interactions of PS×HA and PS×PN in S-EPS, PN×HA and PS×PN in LB-EPS, and ternary interaction of PS×PN×HA in TB-EPS as well as the wavelength-specific fluorescence responses of these interactions. Further, X-ray photoelectron spectroscopy, infrared spectra, and circular dichroism spectra corroborated the differences in primary, secondary, and tertiary structures across the EPS layers. Ultrahigh-performance liquid chromatography-mass spectrometry detected molecular fragments confirming the multi-component hybridization among PS, PN, and HA. This study demonstrates a spectroscopic approach to sensitively fingerprint the fine structure of EPS, which has the potential for rapid monitoring of EPS and related sludge properties in wastewater treatment systems.

Kill two birds with one stone: The management of hazardous waste and the preparation of efficient adsorbents for Pb(II) were realized by the pyrolysis of penicillin mycelial dreg.

The penicillin industry produces a large amount of penicillin mycelial dreg (PMD), potentially causing severe environmental problems without proper treatment and disposal. To achieve the goals of PMD management, the present work explored the potential of PMD as a novel feedstock to produce biochar with very high adsorption performance. PMD was pyrolyzed at 400-800 °C to prepare biochars (PMD-BCs), and the physical and chemical properties were characterized using various methods. The adsorption capacities of Pb2+ on PMD-BC400, PMD-BC600, and PMD-BC800 were 37.04, 62.89, and 107.53 mg/g, respectively, at a temperature of 25 °C and pH of 5.0. The adsorption process of Pb2+ on PMD-BCs can be well described by the Langmuir model and pseudo-second-order model. Mineral precipitation, ion exchange, functional group complexation and Pb2+-π interaction were involved in the adsorption of Pb2+ on PMD-BCs. Moreover, mineral precipitation and ion exchange dominated Pb2+ sorption on PMD-BCs (84.71-92.73%). This study indicates the transition of PMD to biochar for Pb2+ adsorption is a promising method for PMD utilization.

Revisiting the Surface Energy Parameters of Standard Test Liquids with a Corrected Contact Angle Method over Rough Surfaces.

Interfacial free energy is a quantitative basis for explaining and predicting interfacial behavior that is ubiquitous in nature. The contact angle (CA) method can determine the surface free energy (γ) as well as Lifshitz-van der Waals (γLW) and Lewis acid/base (γ+/γ-) components of a solid material from its CAs with a set of known test liquids according to the extended Young-Dupré equation. However, the reliability of the "known" parameters of the test liquids is questioned due to the long-neglected surface roughness effect during calibration of the liquids. This study proposed a simple and practicable two-step approach to correct the energy parameters of several test liquids by incorporating Wenzel's surface roughness relationship into CA measurement. Step 1: water and two apolar liquids (diiodomethane and α-bromonaphthalene) were used as benchmarks to calibrate the surface roughness and energy parameters of two reference solids [apolar poly(tetrafluoroethylene) and monopolar poly(methyl methacrylate)], and step 2: the reference solids were used to calibrate any other test liquids by solving the energy parameters from their CAs in the extended Young-Dupré-Wenzel model. Monte Carlo simulation was used to evaluate error transmission and robustness of the model solutions. The obtained energy parameters (γLW/γ+/γ-) of four test liquids (dimethyl sulfoxide, formamide, ethylene glycol, and glycerol) are 28.01/13.68/4.67, 34.95/3.53/37.62, 26.26/7.51/15.74, and 32.99/9.24/26.02 mJ/m2, respectively, and different from the literature values. The liquids were applied to characterize an example solid surface with true γLW/γ+/γ- values of 28.00/1.00/8.00 mJ/m2 and a roughness index (r) of 1.60. Without correction of the liquid parameters, the calculated surface energy, hydration energy, and hydrophobic attraction energy of the solid sample can deviate by 50, 13, and 27%, respectively. This proves the necessity of correcting parameters of the test liquids before they can be used in CA and interfacial energy studies in the presence of surface roughness.

Transformation and stabilization of heavy metals during pyrolysis of organic and inorganic-dominated sewage sludges and their mechanisms.

Improperdisposal of sludge will release heavy metals contained in sludge into soils or waters which could further move through the food chain, posing a risk to human health. Understanding the transformation and stabilization of heavy metals (HMs) during pyrolysis is of great value for safe disposal of sludge. Herein, municipal sewage sludge (MSS, organic-dominated) and pharmacy sludge (PS, inorganic-dominated) were pyrolyzed to investigate the effects of organic and inorganic components and temperature on the stabilization of HMs in sludges. The results showed that pyrolysis can promote the transition of HMs from mobile fractions to stable fractions. Compared to MSS and PS, the potential ecological risk index of biochar derived from MSS and PS decreased by 95.51% and 85.05%, respectively, after pyrolysis at 800 °C. The stabilization of HMs in MSS was mainly due to the complexation reactions between metals and amide functional groups (-CO-NH-) during pyrolysis. Moreover, the mechanism of HMs stabilization in PS lied in the formation of a stable crystal-structure such as copper iron oxide (Cu6Fe3O7) and copper iron phosphate (Cu2Fe5(PO4)6, Cu3Fe4(PO4)6) with iron-containing minerals after high-temperature pyrolysis. The results of this study indicated that the organic and inorganic components of sludge play different roles in the stabilization and transformation of HMs during pyrolysis, which provided a scientific basis for the ecotoxicity reduction of HMs and safe disposal of sludge.

Three-dimensional graphene/amino-functionalized metal-organic framework for simultaneous electrochemical detection of Cd(II), Pb(II), Cu(II), and Hg(II).

Trace detection of multiple toxic heavy metals is a very important and difficult problem, conveniently, sensitively, and reliably. In this work, we developed an innovative electrochemical sensor for simultaneously detected heavy metal ions (Cd2+, Hg2+, Cu2+, and Pb2+). In order to detect trace amounts of Cd(II), Pb(II), Cu(II), and Hg(II) in food quickly, accurately, and at low cost, this study used electrochemical reduction to prepare a screen-printed electrode (3DGO) modified with 3DGO and UiO-66-NH2 composite nanomaterials (UiO-66-NH2/SPCE). The sensing platform is composed of three-dimensional graphene (3DGO), aminated UiO-66 metal-organic framework, named 3DGO/UiO-66-NH2. It is worth noting that the porous structure, amino functional groups on the surface, and large specific surface area of UiO-66-NH2 can enrich and promote the absorption of heavy metal ions. 3DGO was introduced to improve the electrochemical activity and conductivity of UiO-66-NH2 material. The construction of this new sensing platform, which can synchronously, reliably, and sensitively simultaneously detect Cd2+, Pb2+, Cu2+, and Hg2+ only in 150 s in the linear range of 0.01-0.35 pM with the detection limitations, is 10.90 fM, 5.98 fM, 2.89 fM, and 3.1 fM, respectively. This method provides a new strategy that uses MOF materials for electrochemical detection of a variety of heavy metal ions in food.

Rapid biodegradation of atrazine by a novel Paenarthrobacter ureafaciens ZY and its effects on soil native microbial community dynamic.

An atrazine-utilizing bacterium, designated as ZY, was isolated from agricultural soil and identified as Paenarthrobacter ureafaciens. The P. ureafaciens ZY demonstrated a significant degradation capacity of atrazine, with the degradation efficiency of 12.5 mg L-1 h-1 in liquid media (at pH 7, 30°C, and the atrazine level of 100 mg L-1). The P. ureafaciens ZY contained three atrazine-degrading genes (i.e., trzN, atzB, and atzC) could metabolize atrazine to form cyanuric acid, which showed lower biotoxicity than the parent atrazine as predicted by Ecological Structure Activity Relationships model. A laboratory-scale pot experiment was performed to examine the degradation of atrazine by P. ureafaciens ZY inoculation and investigate its effects on the native microbial communities. The results exhibited that the P. ureafaciens ZY was conductive to the degradation of atrazine, increased the total soil phospholipid fatty acids at the atrazine level of 50, 70, and 100 mg kg-1. By using high-throughput sequencing analysis, Frateuria, Dyella, Burkholderia-Caballeronia-Paraburkholderia were considered as the most important indigenous atrazine-degrading microorganisms due to their relative abundances were positively correlated with the atrazine degradation rate. In addition, P. ureafaciens ZY also increased the abundance of atrazine-degrading genus Streptomyces and Bacillus, indicating that there may be a synergic relationship between them in the process of atrazine degradation. Our work provides a new insight between inoculums and native microorganisms on the degradation of atrazine.

Magnetic porous biochar with nanostructure surface derived from penicillin fermentation dregs pyrolysis with K2FeO4 activation: Characterization and application in penicillin adsorption.

Magnetic porous biochars (MCHCl, MCHAc) with nanostructure on surfaces were prepared from penicillin fermentation dregs by pyrolysis with K2FeO4 activation and used in penicillin adsorption. MCHCl and MCHAc had high BET surface areas of 672 and 735 m2/g, respectively; mainly be attributed to the activation of K2FeO4 as well as acid pickling. Saturation magnetizations of MCHCl and MCHAc were 75.29 and 42.45 emu/g, respectively; the magnetism was mainly derived from the Fe3O4 and Fe3C in magnetic biochars. MCHCl had nano sticks of ~ 80 nm and MCHAc had petal-like slice of ~ 30 nm on surfaces. The maximum adsorption capacities of penicillin on MCHCl and MCHAc were 196 and 322 mg/g at 308 K, respectively. The adsorptions of penicillin on MCHCl and MCHAc were consistent with pseudo primary kinetics and the Langmuir adsorption isotherm model, and thermodynamic analysis indicated that the adsorption mechanism included physical and chemical adsorption.

Pyrolysis of penicillin fermentation residue and sludge to produce biochar: Antibiotic resistance genes destruction and biochar application in the adsorption of penicillin in water.

A process of antibiotic fermentation residue and sludge pyrolysis to produce biochar was proposed, with antibiotic resistance genes destruction and biochar application in the adsorption of penicillin in water. The results showed that the ß-lactam resistance genes were completely destroyed during pyrolysis. The prepared biochar from antibiotic fermentation residues (AFRB) and sludge (AFSB) at 800 °C and 600 °C had a good adsorption effect on the low concentration penicillin in water, with removal efficiencies of 93.32% and 98.50% for penicillin in aqueous solution and maximum adsorption capacities of 44.05 mg/g and 23.26 mg/g, respectively. Characterization of AFRB revealed that its surface was predominantly aromatic carbon, AFSB contained significant amounts of Fe3O4. Weak interactions (H‧‧‧π, H‧‧‧OË­C, π-π interactions) and active sites (aromatic ring, H and -CË­O groups) of penicillin with aromatic structures on AFRB and the chemisorption (-CË­O-Fe-, -CË­OO-Fe-), and active sites (-CË­O, -COO- groups) of penicillin on the (110) surface of Fe3O4 on AFSB were revealed by quantum chemical methods. This work provides a novel pathway for the risk reduction of antibiotic production residue and sludge associated with the generation of biochar for antibiotic removal from the environment.

Role of shear stress in biological aerated filter with nanobubble aeration: Performance, biofilm structure and microbial community.

This study comprehensively investigated the role of shear stress in a biological aerated filter under nanobubble aeration with the operation of an internal reflux and mechanical bubbling, where nanobubbles provide an opportunity to separately assess the effect of the hydraulic shear stress and aeration on the properties of the biofilms. Shear stress optimized the oxygen distribution, which improved the dissolved oxygen of the effluent three- and four-fold through reflux and mechanical bubbling, respectively. Proper shear stress enhanced the spatial development of the biofilms and promoted the activity and stability of nanobubble-aerated biofilms, achieving a sufficient contaminant removal efficiency that meets the local standard. Shear stress and aeration individually regulated the functional pathways and improved the development of the biofilm structure and the performance. The results indicate that nanobubble is a promising aeration technology when accompanied by a shearing strategy.

Comparison of pyrolysis process, various fractions and potential soil applications between sewage sludge-based biochars and lignocellulose-based biochars.

To deeply assess the feasibility of sewage sludge-based biochars for use in soil applications, this review compared sewage sludge-based biochars (SSBBs) with lignocellulose-based biochars (LCBBs) in terms of their pyrolysis processes, various fractions and potential soil applications. Based on the reviewed literature, significant differences between the components of SSBB and LCBB result in different pyrolysis behavior. In terms of the fractions of biochars, obvious differences were confirmed to exist in the carbon content, surface functional groups, types of ash fractions and contents of potential toxic elements (PTEs). However, a clear influence of the feedstock on labile carbon and polycyclic aromatic hydrocarbons (PAHs) was not observed in the current research. These differences determined subsequent discrepancies in the soil application potential and corresponding mechanisms. The major challenges facing biochar application in soils and corresponding recommendations for future research were also addressed. LCBBs promote carbon sequestration, heavy metal retention and organic matter immobilization. The application of SSBBs is a promising approach to improve soil phosphorus fertility, immobilize heavy metals and provide available carbon sources for soil microbes to stimulate microbial biomass. The present review provides guidance information for selecting appropriate types of biochars to address targeted soil issues.

Preparation of porous biochar based on pharmaceutical sludge activated by NaOH and its application in the adsorption of tetracycline.

In this study, two different kinds of pharmaceutical sludge activated by NaOH were used to prepare biochar. The characteristics of biochar prepared by impregnation method and dry mixing method were analyzed, including N2 adsorption-desorption isotherms, surface functional group analysis and micromorphological observation. The results showed that the biochar prepared by impregnation method had more micropores, while that prepared by dry mixing activation method had more mesopores. The adsorption reaction of tetracycline on the two different kind of biochar was investigated. Several important factors such as solution initial pH, tetracycline concentration and reaction time on adsorption reaction were investigated. The results show that both kinds of biochar have high tetracycline adsorption efficiency and excellent pH adaptability. The biochar manufactured by dry mixing activation method had better adsorption performance (379.78 mg/g, 25 °C). Regeneration experiments showed that the adsorbent had stable performance in absorbing tetracycline. Direct dry mixing activation method is a simple and effective method used to prepare porous biochar, which can be used for the resourceful utilization of pharmaceutical sludge. This work provides extensive information on the use of biochar derived from pharmaceutical sludge for the removal of TC from hospital and pharmaceutical production wastewater.

Effect of nanobubble application on performance and structural characteristics of microbial aggregates.

Herein an investigation on the performance and structural properties with aspects of stability, composition, functional group, and three-dimensional distribution were approached to evaluate the influence of nanobubble aeration to the two most common microbial aggregates, activated sludge and biofilm. This study found that applying nanobubble effectively provided extra oxygen for microbial aggregates and achieved a 10.58% improvement in total nitrogen removal. The structure of microbial aggregates was enhanced, where extracellular protein and polysaccharides respectively increased as maximum as 3.40 and 1.70 times in biofilm and activated sludge, accompanied by the development of activated sludge floc size and the thickness of biofilm. Further investigation on extracellular polymeric substance and surface of microbial aggregates showed the composition of functional substances of microbial aggregates were shifted by the application of nanobubble, especially the oxygen-sensitive ones. Confocal laser scanning microscopy imaging visualized that the nanobubble changed the morphology of biofilm to a more evenly one. However, an adaptive process was more needed for activated sludge rather than biofilm, it suggested application of NB optimized the distribution of functional microorganisms in-depth and the metabolism pathway of them by accelerating the structure development of microbial aggregates, especially for biofilm.

The characteristics of pharmaceutical sludge-derived biochar and its application for the adsorption of tetracycline.

In this study, the specific surface area, pore structure, surface functional groups and microstructure of the biochar derived from the pyrolysis of pharmaceutical sludge are analyzed. The results showed that the pyrolysis temperature had a great influence on the properties of sludge-based biochar (SBB), and the specific surface area of the SBB first increased and then decreased with an increase in the pyrolysis temperature. The maximum specific surface area was 214.97 m2/g at 600 °C, while the pore volume increased with an increase in the pyrolysis temperature. The pickling process removed impurities in the SBB and increased the specific surface area of the material (319.80 m2/g). The effects of pyrolysis temperature, pH, adsorption time, and initial pollutant concentration on the adsorption process were also studied. The results showed that the adsorbents had good pH adaptability, and biochar produced at 600 °C had the best adsorption capacity (94.69 mg/g). Pickling increased the adsorption capacity to 157.38 mg/g. The results showed that pharmaceutical sludge has great potential as a raw material for the preparation of adsorbent. These benefits can compensate for the cost of sludge pyrolysis treatment.

Analysis of the complexation behaviors of Cu(II) with DOM from sludge-based biochars and agricultural soil: Effect of pyrolysis temperature.

Pyrolysis temperature is one of the important factors that affect the structure and composition of biochar-derived dissolved organic matter (DOM), which may impact interaction between biochar-derived DOM and Cu(II). Moreover, soil application of biochars pyrolyzed at different temperatures is supposed to cause different complexation behaviors between soils-derived DOM and Cu(II). However, little is known about these aspects. Here, incubation experiments and quenching titration experiments were conducted to explore such pyrolysis temperatures-dependent changes in sludge and sludge-based biochars (SSBA). Two-dimension correlation spectroscopy (2D-COS) indicated humic-like fraction had stronger affinities with Cu(II) in DOM from both sewage sludge (SS) and 500 °C sludge-based biochars (SSB5) while protein-like fraction showed the fastest response to Cu(II) binding in DOM from 300 °C sludge-based biochars (SSB3). One protein-like substance (Component 1) and two humic-like substances (Component 2 and 3) were identified in the DOM derived from SSBA through excitation-emission matrix-parallel factor (EEM-PARAFAC) analysis. Moreover, the Cu(II) complexation affinities of component 1, 2 and 3 decreased from 4.43, 4.53 and 4.86 to 3.26, 3.50 and 3.39 with increasing pyrolysis temperatures, respectively. The addition of 10% SS evidently increased the complexation affinities of humic-like substances in soil-derived DOM from 4.43 to 4.68 to 4.60-6.86, while the complexation affinities of humic-like substances decreased from 4.52 to 4.78 to 3.82-4.50 at a 10% amendment of sludge-based biochars. Compared with sewage sludge, agricultural soil amended with 10% sludge-based biochars had better performance in the aspect of Cu(II) mobility, but had weaker detoxication effect on Cu(II).

Mass transfer of nanobubble aeration and its effect on biofilm growth: Microbial activity and structural properties.

It is necessary to improve the performance and reduce the aeration cost is of wastewater treatment by aerobic biofilm systems. Nanobubble aeration is supposed to be a promising method to achieve these goals. Compared with coarse bubbles, dissolved oxygen profiling showed that the nanobubbles provided more oxygen to biofilms, offering superior oxygen supply capacity and 1.5 times higher oxygen transfer efficiency. Nanobubble aeration accelerated the growth of the biofilm and achieved better removal efficiencies of chemical oxygen demand and ammonia, with as maximum as six times higher dehydrogenase activity, and more extracellular polymeric substance content than when using the traditional aeration mode. This is attributed to the enhancement of metabolism and the proliferation of microorganisms. Confocal laser-scanning microscopy imaging confirmed that nanobubble aeration affected the components of biofilm by shifting the microbial community and changing its metabolic pathways of biofilms, such as carbohydrate synthesis. Nanobubble aeration resulted in an energy saving of approximately 80%. The assessment of nanobubble aerated biofilm growth suggests that this technique can offer a rapid-initiation, high efficiency, and low-cost strategy for aerobic biofilm systems in wastewater treatment.

Biofilm characteristics, microbial community structure and function of an up-flow anaerobic filter-biological aerated filter (UAF-BAF) driven by COD/N ratio.

The biofilm characteristics, microbial community structure and function in a lab-scale up-flow anaerobic filter-biological aerated filter (UAF-BAF) driven by COD/N ratio were investigated. Results showed that the TN removal rate of system reduced from 68.7% to 50.6% with COD/N ratio ranging from 10 to 3. Biofilm characteristics analysis indicated that the biomass, biofilm thickness, polysaccharide and protein contents in extracellular polymeric substance and dehydrogenase activity from biofilm in the UAF-BAF declined with the decrease of COD/N ratio. The biofilm structure visualized by confocal laser scanning microscopy displayed that the total cells and EPS content decreased as the COD/N ratio downshifted. 16S rRNA sequencing illustrated that Zoogloea and Pleomorphomonas were the major contributors to TN removal in the UAF, with dramatically decreasing abundance. Functional prediction indicated that the genes involved in nitrogen metabolism and nitrate reductase (EC 1.7.99.4) also decreased, which was responsible for the decrease of TN removal. This study provided insights into understanding of the biofilm structure and underlying ecological function in the UAF-BAF, which would help to regulate wastewater biofilm and improve process performance.