Effects of Potassium Ferrate and Low-Temperature Thermal Hydrolysis Co-Pretreatment on the Hydrolysis and Anaerobic Digestion Process of Waste Activated Sludge

This study evaluated the effect of potassium ferrate(PF)and low-temperature thermal hydrolysis co-pretreatment on the promotion of sludge hydrolysis process and the impact on acid production in the subsequent anaerobic digestion process.The analytical investigations showed that co-pretreatment significantly facilitated the hydrolysis process of the sludge and contributed to the accumulation of short-chain fatty acids(SCFAs).The pretreatment conditions under the optimal leaching of organic matter from sludge were hydrothermal temperature of 75℃,hydrothermal treatment time of 12 h,and PF dosage of 0.25 g g^(−1)TSS(total suspended solids),according to the results of orthogonal experiments.By pretreatment under proper conditions,the removal rate of soluble chemical oxygen demand(SCOD)achieved 71.8%at the end of fermentation and the removal rate of total phosphorus(TP)was 69.1%.The maximum yield of SCFAs was 750.3 mg L^(−1),7.45 times greater than that of the blank group.Based on the analysis of the anaerobic digestion mechanism,it was indicated that the co-pretreatment could destroy the floc structure on the sludge surface and improve organic matter dissolving,resulting in more soluble organic substances for the acidification process.Furthermore,microbial community research revealed that the main cause of enhanced SCFAs generation was an increase in acidogenic bacteria and a reduction of methanogenic bacteria.

Low-Temperature Carbonized Nitrogen-Doped Hard Carbon Nanofiber Toward High-Performance Sodium-Ion Capacitors

Carbon nanofiber(CNF)was widely utilized in the field of electrochemical energy storage due to its superiority of conductivity and mechanics.However,CNF was generally prepared at relatively high temperature.Herein,nitrogen-doped hard carbon nanofibers(NHCNFs)were prepared by a lowtemperature carbonization treatment assisted with electrospinning technology.Density functional theory analysis elucidates the incorporation of nitrogen heteroatoms with various chemical states into carbon matrix would significantly alter the total electronic configurations,leading to the robust adsorption and efficient diffusion of Na atoms on electrode interface.The obtained material carbonized at 600°C(NHCNF-600)presented a reversible specific capacity of 191.0 mAh g^(−1)and no capacity decay after 200 cycles at 1 A g^(−1).It was found that the sodium-intercalated degree had a correlation with the electrochemical impedance.A sodium-intercalated potential of 0.2 V was adopted to lower the electrochemical impedance.The constructed sodium-ion capacitor with activated carbon cathode and presodiated NHCNF-600 anode can present an energy power density of 82.1 Wh kg^(−1)and a power density of 7.0 kW kg^(−1).

Twice-split phosphorus application alleviates low-temperature impacts on wheat by improved spikelet development and setting

Extreme low-temperature incidents have become more frequent and severe as climate change intensifies.In HuangHuai-Hai wheat growing area of China,the late spring coldness occurring at the jointing-booting stage(the anther interval stage)has resulted in significant yield losses of winter wheat.This study attempts to develop an economical,feasible,and efficient cultivation technique for improving the low-temperature(LT)resistance of wheat by exploring the effects of twice-split phosphorus application(TSPA)on wheat antioxidant characteristics and carbon and nitrogen metabolism physiology under LT treatment at the anther interval stage using Yannong 19 as the experimental material.The treatments consisted of traditional phosphorus application and TSPA,followed by a-4℃ LT treatment and natural temperature(NT)control at the anther interval stage.Our analyses showed that,compared with the traditional application,the TSPA increased the net photosynthetic rate(P_(n)),stomatal conductance(Gs),and transpiration rate(T_(r))of leaves and reduced the intercellular carbon dioxide concentration(C_(i)).The activity of carbon and nitrogen metabolism enzymes in the young wheat spikes was also increased by the TSPA,which promoted the accumulation of soluble sugar(SS),sucrose(SUC),soluble protein(SP),and proline(Pro)in young wheat spike and reduced the toxicity of malondialdehyde(MDA).Due to the improved organic nutrition for reproductive development,the young wheat spikes exhibited enhanced LT resistance,which reduced the sterile spikelet number(SSN)per spike by 11.8%and increased the spikelet setting rate(SSR)and final yield by 6.0 and 8.4%,respectively,compared to the traditional application.The positive effects of split phosphorus application became more pronounced when the LT treatment was prolonged.

Effect of inorganic carbon on anaerobic ammonium oxidation enriched in sequencing batch reactor

The present lab-scale research reveals the enrichment of anaerobic ammonium oxidation microorganism from methanogenic anaerobic granular sludge and the effect of inorganic carbon(sodium bicarbonate)on anaerobic ammonium oxidation.The enrichment of anammox bacteria was carried out in a 7.0-L sequencing batch reactor(SBR)and the effect of bicarbonate on anammox was conducted in a 3.0-L SBR.Research results,especially the biomass,showed first signs of anammox activity after 54 d cultivation with synthetic wast...

Mechanisms of granular activated carbon anaerobic fluidized-bed process for treating phenols wastewater

Granular activated carbon (GAC) anaerobic fluidized bed reactor was applied to treating phenols wastewater. When influent phenol concentration was 1000 mg/L, volume loadings of phenol and COD Cr were 0 39 kg/(m 3·d) and 0 98 kg/(m 3·d), their removal rates were 99 9% and 96 4% respectively. From analyzing above results, the main mechanisms of the process are that through fluidizing GAC, its adsorption is combined with biodegradation, both activities are brought into full play, and phenol in wastewater is effectively decomposed. Meanwhile problems concerning gas liquid separation and medium plugging are well solved.

Boosting energy-storage capability in carbon-based supercapacitors using low-temperature water-in-salt electrolytes

Supercapacitors(SCs) are high-power energy storage devices with ultra-fast charge/discharge properties.SCs using concentrated aqueous-based electrolytes can work at low temperatures due to their intrinsic properties, such as higher freezing point depression(FPD) and robustness. Besides the traditional organic-and aqueous-based(salt-in-water) electrolytes used in SCs, water-in-salt(WISE) sodium perchlorate electrolytes offer high FPD, non-flammability, and low-toxicity conditions, allowing the fabrication of safer, environmentally friendly, and more robust devices. For the first time, this work reports a comprehensive study regarding WISE system’s charge-storage capabilities and physicochemical properties under low-temperature conditions(T < 0 ℃) using mesoporous carbon-based electrodes. The effect of temperature reduction on the electrolyte viscosity and electrical properties was investigated using different techniques and the in-situ(or operando) Raman spectroscopy under dynamic polarization conditions.The cell voltage, equivalent series resistance, and specific capacitance were investigated as a function of the temperature. The cell voltage(U) increased ~ 50%, while the specific capacitance decreased ~20%when the temperature was reduced from 25 ℃ to -10 ℃. As a result, the maximum specific energy(E = CU^(2)/2) increased ~ 100%. Therefore, low-temperature WISEs are promising candidates to improve the energy-storage characteristics in SCs.

Low-temperature Denitration Mechanism of NH_(3)-SCR over Fe/AC Catalyst

To study the modification mechanism of activated carbon(AC)by Fe and the low-temperature NH_(3)-selective catalytic reduction(SCR)denitration mechanism of Fe/AC catalysts,Fe/AC catalysts were prepared using coconut shell AC activated by nitric acid as the support and iron oxide as the active component.The crystal structure,surface morphology,pore structure,functional groups and valence states of the active components of Fe/AC catalysts were characterised by X-ray diffraction,scanning electron microscopy,nitrogen adsorption and desorption,Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy,respectively.The effect of Fe loading and calcination temperature on the low-temperature denitration of NH_(3)-SCR over Fe/AC catalysts was studied using NH_(3)as the reducing gas at low temperature(150℃).The results show that the iron oxide on the Fe/AC catalyst is spherical and uniformly dispersed on the surface of AC,thereby improving the crystallisation performance and increasing the number of active sites and specific surface area on AC in contact with the reaction gas.Hence,a rapid NH_(3)-SCR reaction was realised.When the roasting temperature remains constant,the iron oxide crystals formed by increasing the amount of loading can enter the AC pore structure and accumulate to form more micropores.When the roasting temperature is raised from 400 to 500℃,the iron oxide is mainly transformed fromα-Fe_(2)O_(3)toγ-Fe_(2)O_(3),which improves the iron oxide dispersion and increases its denitration active site,allowing gas adsorption.When the Fe loading amount is 10%,and the roasting temperature is 500℃,the NO removal rate of the Fe/AC catalyst can reach 95%.According to the study,the low-temperature NH_(3)-SCR mechanism of Fe/AC catalyst is proposed,in which the redox reaction between Fe~(2+)and Fe~(3+)will facilitate the formation of reactive oxygen vacancies,which increases the amount of oxygen adsorption on the surface,especially the increase in surface acid sites,and promotes and adsorbs more reaction gases(NH_(3),O_(2),NO).The transformation from the standard SCR reaction to the fast SCR reaction is accelerated.

Hybrid hard carbon framework derived from polystyrene bearing distinct molecular crosslinking for enhanced sodium storage

Exploiting high-performance yet low-cost hard carbon anodes is crucial to advancing the state-of-the-art sodium-ion batteries.However,the achievement of superior initial Coulombic efficiency(ICE)and high Na-storage capacity via low-temperature carbonization remains challenging due to the presence of tremendous defects with few closed pores.Here,a facile hybrid carbon framework design is proposed from the polystyrene precursor bearing distinct molecular bridges at a low pyrolysis temperature of 800℃ via in situ fusion and embedding strategy.This is realized by integrating triazine-and carbonylcrosslinked polystyrene nanospheres during carbonization.The triazine crosslinking allows in situ fusion of spheres into layered carbon with low defects and abundant closed pores,which serves as a matrix for embedding the well-retained carbon spheres with nanopores/defects derived from carbonyl crosslinking.Therefore,the hybrid hard carbon with intimate interface showcases synergistic Na ions storage behavior,showing an ICE of 70.2%,a high capacity of 279.3 mAh g^(-1),and long-term 500 cycles,superior to carbons from the respective precursor and other reported carbons fabricated under the low carbonization temperature.The present protocol opens new avenues toward low-cost hard carbon anode materials for high-performance sodiumion batteries.

Low-temperature phase transformation from nanotube to sp^3 superhard carbon phase

Numerous new carbon allotropes have been uncovered by compressing carbon nanotubes based on our computational investigation. The volume compression calculations suggest that these new phases have a very high anti-compressibility with a large bulk modulus （B0）. The predicted B0 of new phases is larger than that of c-BN （373 GPa） and smaller than that of diamond （453 GPa）. All of the predicted structures are superhard transparent materials with a larger band gap and possess the covalent characteristics with sp3-hybridized electronic states. The simulated results will help us better understand the structural phase transition of cold-compressed carbon nanotubes.

Study on Low-Temperature Properties of the Asphalt Modified by Carbon Nanotubes(CNTs)and Crumb Rubber(CR)

The effect of adding crumb rubber(CR)and carbon nanotubes(CNTs)on the low-temperature properties of virgin asphalt was studied.Using the force-ductility test and the bending beam rheometer(BBR)test,the deformation resistance and rheological properties of asphalt samples at low temperatures were evaluated,respectively.Based on the result of BBR test,the creep functions of the Burgers model and the Zener model were used to fit the low-temperature creep characteristics of the asphalt samples.Furthermore,the differential scanning calorimetry(DSC)test and the attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR)test were utilized to appraise the low-temperature stability and chemical properties of asphalt samples,respectively.The results showed that CR significantly improved the low-temperature properties of virgin asphalt,while CNTs had little effect.Moreover,during the degradation of CR,aromatic and aliphatic components were released.In particular,the aliphatic components of CR-modified asphalt were much higher than those of virgin asphalt,which had a significant effect on improving the low-temperature properties of the asphalt.The DSC test results showed that CR enhanced the low-temperature stability of the asphalt,while the addition of CNTs presented a slightly negative effect.

Anaerobic tapered fluidized bed reactor for starch wastewater treatment and modeling using multilayer perceptron neural network

treatability of synthetic sago wastewater was investigated in a laboratory anaerobic tapered fluidized bed reactor （ATFBR） with a mesoporous granular activated carbon （GAC） as a support material. The experimental protocol was defined to examine the effect of the maximum organic loading rate （OLR）, hydraulic retention time （HRT）, the efficiency of the reactor and to report on its steady- state performance. The reactor was subjected to a steady-state operation over a range of OLR up to 85.44 kg COD/（m^3·d）. The COD removal efficiency was found to be 92% in the reactor while the biogas produced in the digester reached 25.38 m^3/（m^3·d） of the reactor. With the increase of OLR from 83.7 kg COD/（m^3·d）, the COD removal efficiency decreased. Also an artificial neural network （ANN） model using multilayer perceptron （MLP） has been developed for a system of two input variable and five output dependent variables. For the training of the input-output data, the experimental values obtained have been used. The output parameters predicted have been found to be much closer to the corresponding experimental ones and the model was validated for 30% of the untrained data. The mean square error （MSE） was found to be only 0.0146.

The Preparation of Mn-Fe/CNTs Catalyst at the Low-Temperature Selective Catalytic Reduction of NO with NH₃

The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH3 was investigated. The results showed that the active components were loaded suc-cessfully and easily on the carriers by impregnation. The Mn-Fe/CNTs catalyst was chose 10% Fe(NO3)3 solution to impregnate Mn-Fe/CNTs. The species of active components loaded on the catalyst were Fe2O3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.

Effect of Acetylene Concentration on Denitriflcation and Related Microbial Processes in Anaerobically incubated Soil Slnrries

In order to study the influence of difference in C2H2 concentration on the production of CO2, N2O,NH4-N and volatile fatty acids （VFA）, soil slurries with a gradient in C2H2 concentration were anaerobicallyincubated at 25°C for 2 weeks. Acetate, butyrate and CO2 production and NH4-N accumulation wereinhibited in the slurries in the presence of C2H2; and the inhibition effect increased with increasing C2H2from 0 to 20 kpa in the headspace gas of the incubation bottle. However, N2O, isobutyrate and propionateproduction was not obviously different among the slurries amended with C2H2 from 2.5 to 20 kpa. Therefore,the results implied that the C2H2 did not promote the inhibition but only increased the side effect onother microbial processes. The C2H2 of 2.5 kpa was suggested to be the optimum choice for the presentdenitrification study.

延时厌氧调控DPAOs内碳源转化实现反硝化除磷

采用SBR反应器,以模拟市政污水为进水基质,在富集PAOs后采用厌氧/缺氧/好氧运行方式富集DPAOs,探讨延长厌氧时间过程中DPAOs内碳源利用、脱氮除磷效果及富集程度.结果表明:厌氧时间由50min延长至70和90min,DPAOs内碳源的储量及利用率增加,延时厌氧条件的改进使DPAOs富集程度增加.厌氧90min COD和TP的平均去除率分别为91.54%和94.6%,DPAOs/PAOs及DPAOs对内碳源贡献率达69.4%和60.1%,继续延长厌氧时间至110和130min后,DPAOs内碳源的储量降低系统除磷效率下降,厌氧130min TP平均去除率、DPAOs/PAOs及DPAOs对内碳源贡献率分别降至84.6%、50.2%和36.4%.延时厌氧运行过程中,LB-EPS含量变化较小,内碳源储量的改变对TB-EPS影响较大.微生物群落结构分析表明,系统内优势菌门为拟杆菌门(Bacteroidetes)、变形菌门(Proteobacteria)和绿弯菌门(Chloroflexi).厌氧90min时以Dechloromonas、Candidatus_Accumulibacter为代表的DPAOs是系统内优势微生物(相对丰度由接种污泥1.44%、2.12%增至15.58%、5.86%);厌氧130min时DPAOs丰度减少,以Candidatus_Competibacter为代表的DGAOs明显增多(相对丰度由厌氧90min的3.29%增至16.16%),导致系统除磷性能下降.

铁碳材料促进有机固体废弃物厌氧消化作用的研究进展

有机固体废弃物的厌氧消化在实现废物资源化利用中有重要意义。近年来,通过使用不同类型的添加剂提高厌氧消化的效率成为研究热点,其中铁基和碳基材料因为具有良好的导电性被广泛使用。着重归纳了铁基和碳基材料促进有机固体废弃物厌氧消化的研究进展,总结了两种添加剂在厌氧消化中的作用机制。铁基材料主要通过降低氧化还原电位为微生物创造生存条件、加强直接种间电子转移(DIET)、通过刺激关键酶促进水解和酸化过程的作用。碳基材料除可加强DIET外,还通过吸附抑制性化合物和富集功能性微生物及支持微生物定殖来发挥作用。同时,铁碳材料可协同促进厌氧消化。最后,深入分析了这两种材料在有机固体废弃物的厌氧消化过程中存在问题,并展望了其发展前景。

污水生物脱氮外加碳源的开发与应用

外加碳源在污水生物脱氮过程中发挥着重要作用。根据外加碳源参与生物反硝化反应的作用机制及利用速率的差异性,可将其分为速效碳源、缓释碳源和迟效类碳源,其中后两者合称为复合型碳源。文章第一部分总结了速效碳源的不同种类对反硝化性能和污泥性状的影响。第二部分阐述了以天然植物基质浸出液和可生物降解聚合物为代表的缓释碳源。第三部分介绍了以餐厨垃圾发酵液、污水厂污泥水解液及高浓度有机废水发酵液为代表的迟效碳源。基于降低脱氮成本和废物资源化利用等目的,概述这两类复合碳源的制备过程、生物脱氮性能以及实际应用的可行性等方面内容,提出其质量和性能提升的潜在路径。最后指出建立新型复合碳源的综合性能评价体系是开发利用生物脱氮用新型外加碳源的前提和保障。

厨余垃圾湿式与干式厌氧消化处理全链条碳排放比较分析

目前厌氧消化技术是我国应用最普遍的厨余垃圾处理技术,可分为干式与湿式2大类。厨余垃圾厌氧消化处理碳排放核算方法尚未建立。本研究基于沼液回流的“预处理制浆液+湿式厌氧消化”和“预处理除杂+干式厌氧消化”分别分析干式、湿式厨余垃圾厌氧消化工艺全链条的碳排放,通过确定厌氧消化的碳排放源与碳排放边界,测算直接碳排放量、间接碳排放量和可避免碳排放量,最后综合这3类排放量得出厌氧消化的净碳排放量。研究发现,采用沼液回流方式的干式厌氧消化工艺全链条碳减排量较高,达到了-84.43 kg/t,其中,干式处理直接碳排放主要来源为杂质焚烧,湿式处理直接碳排放主要来源为污水处理与杂质焚烧;两者的间接碳排放主要来源均为电力消耗。沼气发电与余热利用产生的碳减排效应是厨余垃圾厌氧消化处理全流程中最大的碳减排子项,以沼气产率为产出目标比以肥料为目标可产生更优的碳减排效应。本研究可为厨余垃圾厌氧消化碳排放方法学的建立提供参考。

一种三回路式淡水循环养殖系统的构建及应用

为满足人们对优质鱼类蛋白日益增长的需求和环保要求,在海南琼海构建了三回路式高密度循环水养殖系统,以微滤机反冲洗水作为反硝化碳源,建立了水循环处理、鱼粪污泥厌氧消化对鱼类生长和污染物控制的运行方式。在121 d的吉富罗非鱼(Oreochromis mossambicus)养殖实验中,养殖密度达到107.7kg·m^(-3),存活率100%,饲料转化率(FCR)1.74;鱼缸中总氨氮(TAN)、亚硝酸盐氮(NO_(2)^(-)-N)和硝酸盐氮(NO_(3)^(-)-N)的平均浓度分别为0.95、0.15和43.01 mg·L^(-1)。每日外排水量为系统总水量的2.66%、养殖水量的6.67%;试验期间,厌氧消化单元内仅有少量污泥残留而无外排。微生物群落分析表明,共21个菌属参与了氮代谢,包括红细菌属(Rhodobacte)、黄杆菌属(Flavobacterium)和固氮螺旋菌属(Azospira)等。结果表明,该循环水养殖系统为罗非鱼等淡水鱼类养殖提供了一种潜在的生态可持续循环养殖模式。

改性剂添加量对改性微米铁-微生物耦合体系去除三氯乙烯效能的影响

基于球磨法的硫化与碳改性是提高微米零价铁(Micron zero-valent iron,mZVI)对三氯乙烯(Trichloroethylene,TCE)还原选择性的有效手段,但其改性效果常受改性剂添加量的影响,且其对改性mZVI和微生物耦合体系修复效能的影响尚未明确。本文通过构建多个硫化mZVI-微生物体系(S-mZVI bm/AB)和碳改性mZVI-微生物体系(C-mZVI bm/AB),系统研究改性剂添加量对改性mZVI-微生物耦合体系去除TCE和代表性共存电子受体NO_(3)^(-)的影响。实验结果表明:不同改性剂添加量的S-mZVI bm/AB和C-mZVI bm/AB体系均可显著促进TCE的去除,且促进程度随改性剂添加量的增加呈现先上升后下降的趋势;S-mZVI bm/AB体系可抑制NO_(3)^(-)的去除,且抑制程度随S/Fe摩尔比的增加呈现上升趋势,而C/Fe质量比不会影响C-mZVI bm/AB体系中NO_(3)^(-)的去除;S-mZVI bm/AB和C-mZVI bm/AB体系均可调控TCE及NO-3的产物构成,并均促进了饱和碳烃化合物及N_(2)生成,且该促进作用与改性剂添加量成正比。通过分析微生物群落结构探究了耦合体系脱氯及其脱氮的影响机制,发现在S-mZVI bm/AB和C-mZVI bm/AB体系中均存在大量参与脱氯和反硝化的细菌,反硝化菌的丰度高于脱氯菌,是NO_(3)^(-)快速去除和较高浓度N 2产生的原因。

载铁颗粒活性炭对染料废水厌氧生物降解性能的影响研究

染料废水成分复杂、色度高、可生化性差、处理难度大。厌氧生物处理技术是处理染料废水的有效手段之一。但是,厌氧生物处理过程复杂,涉及多种微生物协同代谢,存在降解速率缓慢的缺点。为此,本研究制备了载铁颗粒活性炭复合材料,并应用于模拟染料废水的厌氧生物处理中,以改善该废水的厌氧生物降解性能。材料的SEM-EDS和XRD分析结果表明,制备的改性颗粒活性炭表面已成功负载了铁;模拟染料废水COD和色度去除结果显示,以Fe3+与Fe2+比例为2∶1制备获得的载铁颗粒活性炭可显著强化染料废水的厌氧生物处理性能。