Removing carbonyl sulfide with metal-modified activated carbon

A Cu-Co-K/activated carbon (AC) adsorbent has been developed for the removal of carbonyl sulfide (COS). The effects of COS concentration, reaction temperature and relative humidity were closely examined. A breakthrough of 33.23 mg COS·g⁻¹ adsorbent at 60°C, under 30% relative humidity and in presence of 1.0% oxygen was exhibited in the Cu-Co-K/AC adsorbent prepared. Competitive adsorption studies for COS in the presence of CS₂, and H₂S were also conducted. TPD analysis was used to identify sulfur-containing products on the carbon surface, and the results indicated that H₂S, COS and SO₂ were all evident in the effluent gas generated from the exhausted Cu-Co-K/AC. Structure of the activated carbon samples has been characterized using nitrogen adsorption, and their surface chemical structures were also determined with X-ray photoelectron spectroscopy (XPS). It turns out that the modification with Cu(OH)₂CO₃-CoPcS-KOH can significantly improve the COS removal capacity, forming SO42− species simultaneously. Regeneration of the spent activated carbon sorbents by thermal desorption has also been explored.     

A Cu-modified active carbon fiber significantly promoted H2S and PH3 simultaneous removal at a low reaction temperature

• Cu_0.15-ACF performs the best for H₂S and PH₃ simultaneous removal. • 550°C and 90°C are separately calcination and reaction temperatures. • The reason why Cu_0.15/ACF shows better performance was found. • The accumulation of H₂PO₄⁻ and SO₄²⁻(H₂O)₆ is the deactivation cause of Cu_0.15/ACF. Poisonous gases, such as H₂S and PH₃, produced by industrial production harm humans and damage the environment. In this study, H₂S and PH₃ were simultaneously removed at low temperature by modified activated carbon fiber (ACF) catalysts. We have considered the active metal type, content, precursor, calcination, and reaction temperature. Experimental results exhibited that ACF could best perform by loading 15% Cu from nitrate. The optimized calcination temperature and reaction temperature separately were 550°C and 90°C. Under these conditions, the most removal capacity could reach 69.7 mg/g and 132.1 mg/g, respectively. Characterization results showed that moderate calcination temperature (550°C) is suitable for the formation of the copper element on the surface of ACF, lower or higher temperature will generate more cuprous oxide. Although both can exhibit catalytic activity, the role of the copper element is significantly greater. Due to the exceptional dispersibility of copper (oxide), the ACF can still maintain the advantages of larger specific surface area and pore volume after loading copper, which is the main reason for better performance of related catalysts. Finally, increasing the copper loading amount can significantly increase the crystallinity and particle size of copper (oxide) on the ACF, thereby improving its catalytic performance. In situ IR found that the reason for the deactivation of the catalyst should be the accumulation of generated H₂PO₄⁻ and SO₄²⁻(H₂O)₆ which could poison the catalyst.     

Enhanced dewatering characteristics of waste activated sludge with Fenton pretreatment: effectiveness and statistical optimization

In this work, the enhanced dewaterabing characteristics of waste activated sludge using Fenton pretreatment was investigated in terms of effectiveness and statistical optimization. Response surface method （RSM） and central composite design （CCD） were applied to evaluate and optimize the effectiveness of important operational parameters, i.e., H202 concentrations, Fe2＋ concentrations and initial pH values. A significant quadratic polynomial model was obtained （R2= 0.9189） with capillary suction time （CST） reduction efficiency as the response. Numerical optimization based on desirability function was carried out. The optimum values for H202, Fe2, and initial pH were found to be 178 mg-g-1 VSS （volatile suspended solids）, 211mg.gI VSS and 3.8, respectively, at which CST reduction efficiency of 98.25% could be achieved. This complied well with those predicted by the established polynomial model. The results indicate that Fenton pretreatment is an effective technique for advanced waste activated sludge dewatering. The enhancement of sludge dewaterability by Fenton＇s reagent lies in the migration of sludge bound water due to the disintegration of sludge flocs and microbial cells lysis.     

Mechanism insight into the formation of H2S from thiophene pyrolysis: A theoretical study

• Possible formation pathways of H₂S were revealed in thiophene pyrolysis. • The influence of hydrogen radicals on thiophene pyrolysis was examined. • Thiophene decomposition starts with hydrogen transfer between adjacent C atoms. • The presence of hydrogen radicals significantly promotes the formation of H₂S. Pyrolysis is an efficient and economical method for the utilization of waste rubber, but the high sulfur content limits its industrial application. Currently, the migration and transformation of the element S during pyrolysis of waste rubber is far from well known. In this work, a density functional theory (DFT) method was employed to explore the possible formation pathways of H₂S and its precursors (radicals HS· and S·) during the pyrolysis of thiophene, which is an important primary pyrolytic product of rubber. In particular, the influence of reactive hydrogen radicals was carefully investigated in the thiophene pyrolysis process. The calculation results indicate that the decomposition of thiophene tends to be initiated by hydrogen transfer between adjacent carbon atoms, which needs to overcome an energy barrier of 312.4 kJ/mol. The optimal pathway to generate H₂S in thiophene pyrolysis involves initial H migration and S-C bond cleavage, with an overall energy barrier of 525.8 kJ/mol. In addition, a thiol intermediate that bears unsaturated C-C bonds is essential for thiophene pyrolysis to generate H₂S, which exists in multiple critical reaction pathways. Moreover, the presence of hydrogen radicals significantly changes the decomposition patterns and reduces the energy barriers for thiophene decomposition, thus promoting the formation of H₂S. The current work on H₂S formation from thiophene can provide some theoretical support to explore clean utilization technologies for waste rubber.     

Simultaneous removal of hydrogen sulfide and volatile organic sulfur compounds in off-gas mixture from a wastewater treatment plant using a two-stage bio-trickling filter system

A two-stage BTF system was established treating odorous off-gas mixture from a WWTP. The two-stage BTF system showed resistance for the lifting load of H₂S and VOSC. Miseq Illumina sequencing showed separated functional microbial community in BTFs. Avoiding H₂S inhibition and enhancement of VOSC degradation was achieved. Key control point was discussed to help industrial application of the system. Simultaneous removal of hydrogen sulfide (H₂S) and volatile organic sulfur compounds (VOSCs) in off-gas mixture from a wastewater treatment plant (WWTP) is difficult due to the occasional inhibitory effects of H₂S on VOSC degradation. In this study, a two-stage bio-trickling filter (BTF) system was developed to treat off-gas mixture from a real WWTP facility. At an empty bed retention time of 40 s, removal efficiencies of H₂S, methanethiol, dimethyl sulfide, and dimethyl disulfide were 90.1, 88.4, 85.8, and 61.8%, respectively. Furthermore, the effect of lifting load shock on system performance was investigated and results indicated that removal of both H₂S and VOSCs was slightly affected. Illumina Miseq sequencing revealed that the microbial community of first-stage BTF contained high abundance of H₂S-affinity genera including Acidithiobacillus (51.43%), Metallibacterium (25.35%), and Thionomas (8.08%). Analysis of mechanism demonstrated that first stage of BTF removed 86.1% of H₂S, mitigating the suppression on VOSC degradation in second stage of BTF. Overall, the two-stage BTF system, an innovative bioprocess, can simultaneously remove H₂S and VOSC.     

Efficient production of hydrogen peroxide in microbial reverse-electrodialysis cells coupled with thermolytic solutions

● Appreciable H₂O₂ production rate was achieved in MRCs utilizing NH₄HCO₃ solutions. ● Carbon black outperformed activated carbon as the catalyst for H₂O₂ production. ● The optimum carbon black loading for H₂O₂ production on air-cathode was 10 mg/cm². ● The optimum number of cell pairs was determined to be three. ● A maximum power density of 980 mW/m² was produced by MRCs with 5 cell pairs. H₂O₂ was produced at an appreciable rate in microbial reverse-electrodialysis cells (MRCs) coupled with thermolytic solutions, which can simultaneously capture waste heat as electrical energy. To determine the optimal cathode and membrane stack configurations for H₂O₂ production, different catalysts, catalyst loadings and numbers of membrane cell pairs were tested. Carbon black (CB) outperformed activated carbon (AC) for H₂O₂ production, although AC showed higher catalytic activity for oxygen reduction. The optimum CB loading was 10 mg/cm² in terms of both the H₂O₂ production rate and power production. The optimum number of cell pairs was determined to be three based on a tradeoff between H₂O₂ production and capital costs. A H₂O₂ production rate as high as 0.99 ± 0.10 mmol/(L·h) was achieved with 10 mg/cm² CB loading and 3 cell pairs, where the H₂O₂ recovery efficiency was 52 ± 2% and the maximum power density was 780 ± 37 mW/m². Increasing the number of cell pairs to five resulted in an increase in maximum power density (980 ± 21 mW/m²) but showed limited effects on H₂O₂ production. These results indicated that MRCs can be an efficient method for sustainable H₂O₂ production.     

Influence of H2S and NH3 on biogas dry reforming using Ni catalyst: a study on single and synergetic effect

● NH₃ in biogas had a slight inhibitory effect on dry reforming. ● Coexistence of H₂S and NH₃ led to faster decline of biogas conversion. ● Regeneration was effective for catalysts deactivated under synergetic effect. Biogas is a renewable biomass energy source mainly composed of CH₄ and CO₂. Dry reforming is a promising technology for the high-value utilization of biogas. Some impurity gases in biogas can not be completely removed after pretreatment, which may affect the performance of dry reforming. In this study, the influence of typical impurities H₂S and NH₃ on dry reforming was studied using Ni/MgO catalyst. The results showed that low concentration of H₂S in biogas could cause serious deactivation of catalyst. Characterization results including EDS, XPS and TOF-SIMS confirmed the adsorption of sulfur on the catalyst surface, which was the cause of catalyst poisoning. We used air calcination method to regenerate the sulfur-poisoned catalysts and found that the regeneration temperature higher than 500 °C could help catalyst recover the original activity. NH₃ in the concentration range of 50–10000 ppm showed a slight inhibitory effect on biogas dry reforming. The decline rate of biogas conversion efficiency increased with the increase of NH₃ concentration. This was related to the reduction of oxygen activity on catalyst surface caused by NH₃. The synergetic effect of H₂S and NH₃ in biogas was investigated. The results showed that biogas conversion decreased faster under the coexistence of H₂S and NH₃ than under the effect of H₂S alone, so as the surface oxygen activity of catalyst. Air calcination regeneration could also recover the activity of the deactivated catalyst under the synergetic effect of H₂S and NH₃.     

低碳氮比废水好氧颗粒污泥系统稳定性及微生物种群多样性研究

低碳氮比(C/N)废水处理是含氮废水处理中的难题之一.本实验在C/N为4:1和2:1(COD和NH₄⁺-N浓度分别为400 mg·L^-1和100 mg·L^-1,400 mg·L^-1和200 mg·L^-1)条件下,考察好氧颗粒污泥系统对低碳氮比废水的处理效果、长期运行稳定性,研究C/N对好氧颗粒微生物结构变化的影响.研究结果表明,在C/N为4:1的废水中接种活性污泥培养好氧颗粒污泥,形成的颗粒沉降性能良好,MLSS为4.94 g·L^-1,SVI30为40 mL·g^-1,COD去除率90%以上,氨氮去除率接近100%.降低碳氮比,即C/N为2:1后,好氧颗粒的物理及硝化性能无明显变化,MLSS为11.38 g·L^-1,SVI₃₀/SVI₅维持在1左右,COD去除率大于85%,氨氮去除率98%.碳氮比降低使颗粒微生物多样性减少,其中陶厄氏菌受影响较小,而硝化功能菌出现更替:噬氢菌、食酸菌、里德拜特氏菌消失,鞘氨醇单胞菌、束缚杆菌等成为优势菌种.实验表明,该低碳氮比条件下好氧颗粒污泥系统能够稳定运行,且具有优良的处理性能.     

Removal of toxic chromium(VI) from aqueous solution by activated carbon using Casuarina equisetifolia

Highly activated carbon from the seed husk of Casuarina Casuarinas equisetifolia, a worldwide famous plant, have been prepared and tested for the removal of toxic Cr(VI) from its aqueous solution. The adsorbent was investigated for influences of initial chromium concentration (75, 100, 125, and 150 mg l^-1), pH, contact time, and quantity of carbon on removal of Cr(VI) from aqueous solution at room temperature (25±2 °C). The adsorption kinetic of Cr(VI) was studied, and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R²≥0.99). The Langmuir and Freundlich models fit the isotherm data well. Furthermore, the Gibbs free energy was obtained for each system and was found to be-5.29 kJ mol^-1 for removal of Cr(IV). The negative value of Δ G° indicates the feasibility and spontaneous nature of adsorption. The results indicate that acidic pH (1.05) supported the adsorption of Cr(IV) on activated carbon. The maximum adsorption capacity of Cr(VI) on activated carbon was about 172.4 mg g^-1 at pH 1.05.     

Modification of the activated sludge model for chemical dosage

Full-scale experiments have been carried out to adapt the activated sludge model ASM2d to include the influence of metal dosage (Fe³⁺ and Al³⁺) for phosphorus removal. Phosphorus removal rates, nitrification rates, as well as pH and sludge settling performance, were evaluated as functions of the metal dosages. Furthermore, models relating certain parameters to the dosage of chemicals have been derived. Corresponding parameters in the ASM2d and the secondary settler models, included in the Benchmark Simulation Model No 1 (BSM1), have been modified to take the metal influence into consideration. Based on the effluent limits and penalty policy of China, an equivalent evaluation method was derived for the total cost assessment. A large number of 300-day steady-state and 14-day open-loop dynamic simulations were performed to demonstrate the difference in behavior between the original and the modified BSM1. The results show that 1) both in low and high mole concentrations, Fe³⁺ addition results in a higher phosphorus removal rate than Al³⁺; 2) the sludge settling velocity will increase due to the metal addition; 3) the respiration rate of the activated sludge is decreased more by the dosage of Al³⁺ than Fe³⁺; 4) the inhibition of Al³⁺ on the nitrification rate is stronger than that of Fe³⁺; 5) the total operating cost will reach the minimum point for smaller dosages of Fe³⁺, but always increase with Al³⁺ addition.     

Fabrication,characterization and evaluation of mesoporous activated carbons from agricultural waste: Jerusalem artichoke stalk as an example

This work explores the feasibility of Jerusalem artichoke stem (JAS), an agricultural waste, as an alternative precursor for fabrication of mesoporous activated carbon (MAC) via conventional ZnCl₂ activation. The as-prepared JAS-MACs were characterized by thermogravimetric, nitrogen gas adsorption isotherm and high resolution scanning electron microscopy analysis. The interacting effects of chemical dosage, activation temperature and time on the mesoporosity, mesopore volume and carbon yield were investigated, and further optimized by response surface methodology (RSM). The Brunauer-Emmett-Teller surface area, mesoporosity and mesopore volume of the JAS-MAC prepared under optimum condition were identified to be 1631 m²·g^-1, 90.16% and 1.11 cm³·g^-1, respectively. Compared with commercial activated carbons, this carbon exhibited a comparable monolayer adsorption capacity of 374.5 mg·g^-1 for Methylene Blue dye. The findings suggest that RSM could be an effective approach for optimizing the pore structure of fabricated activated carbons.     

硝酸钙投加频次对污泥生物调理效果的影响

在接种了反硝化菌的剩余污泥中投加硝酸钙药剂,利用反硝化菌消耗NO3-进行反硝化作用去除污泥中易生物降解的有机物,利用Ca2＋的中和、架桥作用,改善污泥的脱水性能.固定NO;总投加浓度为100 mg?g-1 TS,在6d的时间内,按1次、2次、3次、6次的投加频次向污泥中投加硝酸钙.结果表明,1次投加对污泥脱水性能的提升...     

Influence of extracellular polymeric substances from activated sludge on the aggregation kinetics of silver and silver sulfide nanoparticles

• The NPs aggregation in the electrolyte solution is consistent with the DLVO theory. • In NaNO₃ and low Ca(NO₃)₂, EPS alleviates the NPs aggregation by steric repulsion. • In high Ca(NO₃)₂, EPS accelerates the NPs aggregation by exopolysaccharide bridging. • Ag₂S NPs have stronger stability compared with Cit-Ag NPs in aqueous systems. Extracellular polymeric substances (EPS) in activated sludge from wastewater treatment plants (WWTPs) could affect interactions between nanoparticles and alter their migration behavior. The influence mechanisms of silver nanoparticles (Ag NPs) and silver sulfide nanoparticles (Ag₂S NPs) aggregated by active EPS sludge were studied in monovalent or divalent cation solutions. The aggregation behaviors of the NPs without EPS followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The counterions aggravated the aggregation of both NPs, and the divalent cation had a strong neutralizing effect due to the decrease in electrostatic repulsive force. Through extended DLVO (EDLVO) model analysis, in NaNO₃ and low-concentration Ca(NO₃)₂ (<10 mmol/L) solutions, EPS could alleviate the aggregation behaviors of Cit-Ag NPs and Ag₂S NPs due to the enhancement of steric repulsive forces. At high concentrations of Ca(NO₃)₂ (10‒100 mmol/L), exopolysaccharide macromolecules could promote the aggregation of Cit-Ag NPs and Ag₂S NPs by interparticle bridging. As the final transformation form of Ag NPs in water environments, Ag₂S NPs had better stability, possibly due to their small van der Waals forces and their strong steric repulsive forces. It is essential to elucidate the surface mechanisms between EPS and NPs to understand the different fates of metal-based and metal-sulfide NPs in WWTP systems.     

Oxidation and biotoxicity assessment of microcystin-LR using different AOPs based on UV,O3 and H2O2

MC-LR removal performances under different AOPs were compared systematically. Higher removal efficiency and synergistic effects were obtained by combined process. The acute biotoxicity raised in different degrees after oxidation. Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H₂O₂ and O₃/H₂O₂ advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H₂O₂ process and O₃/H₂O₂ were effective methods to remove MC-LR from water, and they two performed better than UV-, O₃-, H₂O₂-alone processes under the same conditions. The effects of UV intensity, H₂O₂ concentration and O₃ concentration on the removal performance were explored. The synergistic effects between UV and H₂O₂, O₃ and H₂O₂ were observed. UV dosage of 1800 mJ·cm⁻² was required to remove 90% of 100 mg·L⁻¹ MC-LR, which amount significantly decreased to 500 mJ·cm⁻² when 1.7 mg·L⁻¹ H₂O₂ was added. 0.25 mg·L⁻¹ O₃, or 0.125 mg·L⁻¹ O₃ with 1.7 mg·L⁻¹ H₂O₂ was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H₂O₂, O₃/H₂O₂ and O₃-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg·L⁻¹ Zn²⁺, raised to 0.05 mg·L⁻¹ Zn²⁺ after UV/H₂O₂ or O₃/H₂O₂ reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided.     

Evaluation of the technoeconomic feasibility of electrochemical hydrogen peroxide production for decentralized water treatment

• Gas diffusion electrode (GDE) is a suitable setup for practical water treatment. • Electrochemical H₂O₂ production is an economically competitive technology. • High current efficiency of H₂O₂ production was obtained with GDE at 5–400 mA/cm². • GDE maintained high stability for H₂O₂ production for ~1000 h. • Electro-generation of H₂O₂ enhances ibuprofen removal in an E-peroxone process. This study evaluated the feasibility of electrochemical hydrogen peroxide (H₂O₂) production with gas diffusion electrode (GDE) for decentralized water treatment. Carbon black-polytetrafluoroethylene GDEs were prepared and tested in a continuous flow electrochemical cell for H₂O₂ production from oxygen reduction. Results showed that because of the effective oxygen transfer in GDEs, the electrode maintained high apparent current efficiencies (ACEs,>80%) for H₂O₂ production over a wide current density range of 5–400 mA/cm², and H₂O₂ production rates as high as ~202 mg/h/cm² could be obtained. Long-term stability test showed that the GDE maintained high ACEs (>85%) and low energy consumption (<10 kWh/kg H₂O₂) for H₂O₂ production for 42 d (~1000 h). However, the ACEs then decreased to ~70% in the following 4 days because water flooding of GDE pores considerably impeded oxygen transport at the late stage of the trial. Based on an electrode lifetime of 46 days, the overall cost for H₂O₂ production was estimated to be ~0.88 $/kg H₂O₂, including an electricity cost of 0.61 $/kg and an electrode capital cost of 0.27 $/kg. With a 9 cm² GDE and 40 mA/cm² current density, ~2–4 mg/L of H₂O₂ could be produced on site for the electro-peroxone treatment of a 1.2 m³/d groundwater flow, which considerably enhanced ibuprofen abatement compared with ozonation alone (~43%–59% vs. 7%). These findings suggest that electrochemical H₂O₂ production with GDEs holds great promise for the development of compact treatment technologies for decentralized water treatment at a household and community level.     

Continuous biohydrogen production from diluted molasses in an anaerobic contact reactor

An anaerobic contact reactor (ACR) system comprising a continuous flow stirred tank reactor (CSTR) with settler to decouple the hydraulic retention time (HRT) from solids retention time (SRT) was developed for fermentative hydrogen production from diluted molasses by mixed microbial cultures. The ACR was operated at various volumetric loading rates (VLRs) of 20–44 kgCOD·m^-3·d^-1 with constant HRT of 6 h under mesophilic conditions of 35°C. The SRT was maintained at about 46–50 h in the system. At the initial VLR of 20 kgCOD·m^-3·d^-1, the hydrogen production rate dropped from 22.6 to 1.58 L·d^-1 as the hydrogen was consumed by the hydrogentrophic methanogen. After increasing the VLR to 28 kgCOD·m^-3·d^-1 and discharging the sludge for 6 consecutive times, the hydrogentrophic methanogens were eliminated, and the hydrogen content reached 36.4%. As the VLR was increased to 44 kgCOD·m^-3·d^-1, the hydrogen production rate and hydrogen yield increased to 42.1 L·d^-1 and 1.40 mol H₂·molglucose-consumed^-1, respectively. The results showed that a stable ethanol-type fermentation that favored hydrogen production in the reactor was thus established with the sludge loading rate (SLR) of 2.0–2.5 kgCOD·kgMLVSS^-1·d^-1. It was found that the ethanol increased more than other liquid fermentation products, and the ethanol/acetic acid (mol/mol) ratio increased from 1.27 to 2.45 when the VLR increased from 28 to 44 kgCOD·m^-3·d^-1, whereas the hydrogen composition decreased from 40.4% to 36.4%. The results suggested that the anaerobic contact reactor was a promising bioprocess for fermentative hydrogen production.     

Cultivation of aerobic granular sludge in a conventional,continuous flow,completely mixed activated sludge system

Aerobic granules were formed in a conventional, continuous flow, completely mixed activated sludge system (CMAS). The reactor was inoculated with seed sludge containing few filaments and fed with synthetic municipal wastewater. The settling time of the sludge and the average dissolved oxygen (DO) of the reactor were 2 h and 4.2 mg·L^-1, respectively. The reactor was agitated by a stirrer, with a speed of 250 r·min^-1, to ensure good mixing．The granular sludge had good settleability, and the sludge volume index (SVI) was between 50 and 90 mL·g^-1. The laser particle analyzer showed the diameter of the granules to be between 0.18 and 1.25 mm. A scanning electron microscope (SEM) investigation revealed the predominance of sphere-like and rod-like bacteria, and only few filaments grew in the granules. The microbial community structure of the granules was also analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Sequencing analysis indicated the dominant species were α, β, and γ-Proteobacteria, Bacteroidetes, and Firmicutes. The data from the study suggested that aerobic granules could form, if provided with sufficient number of filaments and high shear force. It was also observed that a high height-to-diameter ratio of the reactor and short settling time were not essential for the formation of aerobic granular sludge.     

Occurrence and removal of selected polycyclic musks in two sewage treatment plants in Xi’an, China

Polycyclic musks are widely used for cosmetics and other personal care and household cleaning products. The occurrence and removal of two representative polycyclic musks, galaxolide (HHCB) and tonalide (AHTN) were investigated in three different processes of two sewage treatment plants (STPs) in Xi’an, China. The samples were preconcentrated by solid phase extraction procedure and analyzed using a gas chromatography mass spectrometry (GC/MS) by a modified procedure. The HHCB was in the range of 82.8 to 182.5 ng·L^-1 in the influents and 22.6 to 103.9 ng·L^-1 in the effluents. The AHTN ranged from 11.0 to 19.3 ng·L^-1 in the influents and 2.2 to 8.8 ng·L^-1 in the effluents. The removal efficiency of the two musks varied in the ranges of 43.1%–70.4% for HHCB and 54.2%–84.4% for AHTN. Concentrations of the two musks in aqueous phase of three processes slightly increased along the primary process, and significantly removed during the biologic treatment processes, revealing that the selected musks could be remarkably removed in varied activated sludge processes. Advanced processes of activated sludge did not show a significant superiority on selected musk removal compared to the conventional process. The selected musk removal mainly resulted from the adsorption function of activated sludge. There was no significant change of HHCB/AHTN ratios along the treatment flow, indicating that each sewage treatment structure had a similar removal efficiency for the two musks.     

A “Seawater-in-Sludge” approach for capacitive biochar production via the alkaline and alkaline earth metals activation

• Capacitive biochar was produced from sewage sludge. • Seawater was proved to be an alternative activation agent. • Minerals vaporization increased the surface area of biochar. • Molten salts acted as natural templates for the development of porous structure. Sewage sludge is a potential precursor for biochar production, but its effective utilization involves costly activation steps. To modify biochar properties while ensuring cost-effectiveness, we examined the feasibility of using seawater as an agent to activate biochar produced from sewage sludge. In our proof-of-concept study, seawater was proven to be an effective activation agent for biochar production, achieving a surface area of 480.3 m²/g with hierarchical porosity distribution. Benefited from our design, the catalytic effect of seawater increased not only the surface area but also the graphitization degree of biochar when comparing the pyrolysis of sewage sludge without seawater. This leads to seawater activated biochar electrodes with lower resistance, higher capacitance of 113.9 F/g comparing with control groups without seawater. Leveraging the global increase in the salinity of groundwater, especially in coastal areas, these findings provide an opportunity for recovering a valuable carbon resource from sludge.     

Effects of Al3+ on pollutant removal and extracellular polymeric substances (EPS) under anaerobic,anoxic and oxic conditions

The highest removal efficiencies of COD and TN were achieved under 10 mg/L of Al³⁺. The highest TP removal efficiency occurred under 30 mg/L of Al³⁺. EPS, PS and PN concentrations increased with the addition of Al³⁺. Sludge properties significantly changed with the addition of Al³⁺. Aluminum ions produced by aluminum mining, electrolytic industry and aluminum-based coagulants can enter wastewater treatment plants and interact with activated sludge. They can subsequently contribute to the removal of suspended solids and affect activated sludge flocculation, as well as nitrogen and phosphorus removal. In this study, the effects of Al³⁺ on pollutant removal, sludge flocculation and the composition and structure of extracellular polymeric substances (EPS) were investigated under anaerobic, anoxic and oxic conditions. Results demonstrated that the highest chemical oxygen demand (COD) and total nitrogen (TN) removal efficiencies were detected for an Al³⁺ concentration of 10 mg/L. In addition, the maximal dehydrogenase activity and sludge flocculation were also observed at this level of Al³⁺. The highest removal efficiency of total phosphorus (TP) was achieved at an Al³⁺ concentration of 30 mg/L. The flocculability of sludge in the anoxic zone was consistently higher than that in the anaerobic and oxic zones. The addition of Al³⁺ promoted the secretion of EPS. Tryptophan-like fluorescence peaks were detected in each EPS layer in the absence of Al³⁺. At the Al³⁺ concentration of 10 mg/L, fulvic acid and tryptophan fluorescence peaks began to appear, while the majority of protein species and the highest microbial activity were also detected. Low Al³⁺ concentrations (<10 mg/L) could promote the removal efficiencies of COD and TN, yet excessive Al³⁺ levels (>10 mg/L) weakened microbial activity. Higher Al³⁺ concentrations (>30 mg/L) also inhibited the release of phosphorus in the anaerobic zone by reacting with PO₄^3-.