Bended probe diagnostics of the plasma characteristics within an ECR ion source with a rectangular waveguide

To reveal the argon plasma characteristics within the entire region of an electron cyclotron resonance（ECR） ion source, the plasma parameters were diagnosed using a bended Langmuir probe with the filament axis perpendicular to the diagnosing plane. Experiments indicate that,with a gas volume flow rate and incident microwave power of 4 sccm and 8.8 W, respectively,the gas was ionized to form plasma with a luminous ring. When the incident microwave power was above 27 W, the luminous ring was converted to a bright column, the dark area near its axis was narrowed, and the microwave power absorbing efficiency was increased. This indicates that there was a mode transition phenomenon in this ECR ion source when the microwave power increased. The diagnosis shows that, at an incident microwave power of 17.4 W, the diagnosed electron temperature and ion density were below 8 eV and 3×10^17 m^-3, respectively, while at incident microwave power levels of 30 W and 40 W, the maximum electron temperature and ion density were above 11 eV and 6.8×10^17 m^-3, respectively. Confined by magnetic mirrors, the higher density plasma region had a bow shape, which coincided with the magnetic field lines but deviated from the ECR layer.

Effects of different biochars on antibiotic resistance genes during swine manure thermophilic composting

Elimination of antibiotic resistance genes(ARGs)in animal manure from concentrated animal feeding operations by thermophilic composting has drawn increasing attention.This study investigated the effects of sawdust biochar,corn stover biochar and peanut hull biochar with three spiked levels on ARGs in swine manure during thermophilic composting.Thirteen ARGs corresponding to four classes of antibiotics(tetracyclines,sulfonamides,macrolides and quinolones)were determined in the composting piles.Results indicated that the ten tested composting groups became fully mature after 30-day thermophilic composting process.tetM,tetO and ermB were reduced in all tested groups;tetC and tetG,tetX,sul1,sul2,ermF,qnrD and aac(6’)-Ib were mostly reduced under low level biochar addition but increased under higher level biochar addition;gyrA increased under medium biochar addition and reduced in other groups;oqxB remained comparatively stable throughout the composting process.The addition levels of spiked biochar are more important than types of spiked biochar on the removal of ARGs in the composting pile.The average removal rates of ARGs in the control group,low,medium and high level biochar addition groups were 0.24 logs,0.52-0.72 logs,-0.52-0.18 logs and-0.19-0.21 logs,respectively.In summary,low level biochar addition could enhance the elimination of studied ARGs in swine manure during the composting process,while medium level biochar addition to the composting piles would increase the risk of ARGs’propagation.

Investigation and analysis of the linkage mechanism and whole process cost of livestock manure organic fertilizer

In recent years,the utilization of manure resources for livestock and poultry farming has attracted a widespread attention,and manure resources utilization models suitable for different regional characteristics have formed gradually.Among them,the production of organic fertilizer from animal manure is a vital utilization method.However,there are still some problems such as high production costs,difficult sales,and the unwillingness of farmers to use organic fertilizers which have affected the breeding cycle and the sustainability of manure treatment in livestock and poultry breeding.This article selected 371 organic fertilizer plants,related farms and farmers in China,focusing on the main links of the entire process of livestock manure-organic fertilizer-farm application,and studied the mode of animal manure collection by organic fertilizer plants.The costs of organic fertilizer production and farmland application were discussed.Moreover,suggestions were made for the promotion and implementation of large-scale organic fertilizers to make good utilization of manure resources in livestock and poultry farming.

Metagenome analysis reveals potential microbial functions in topsoil of wheat-maize rotation system with five-year application of fertilizers

Fertilization mode affects soil quality and ecological health.The effects of four fertilization regimens on lignocellulose content,readily degradable carbohydrate decomposition,and potential microbial functions in the topsoil of a wheat-maize rotation system between 2012 and 2017 were investigated.The fertilization regimens of control(control NFNB),high chemical fertilizer(HCF),high biochar plus low chemical fertilizer(HBLCF),and biochar-based fertilizer(BBF)were compared on soil fundamental properties,microbial structure,and potential function in soil carbohydrate degradation based on metagenome analysis.The diversity of carbohydrate-active enzyme genes in the topsoil microbial consortia in the four trials was primarily distributed within the ten ecologically most dominant phyla.Application of BBF was associated with the lowest decline in total nitrogen and P2O5(2012-2017:6.5%and 28.1%,respectively)and the most effective carbohydrate decomposition(2015-2017:67.0%for cellulose and 59.9%for readily degradable carbohydrate).Carbohydrate transport and metabolism accounted for 6.0%of reads assigned functional classification under the BBF regimen.These findings reveal the ecologically functional diversity of topsoil microorganisms and suggest BBF application as a promising strategy for sustainable agriculture and beneficial to soil health.

Treatment of recalcitrant wastewater and hydrogen production via microbial electrolysis cells

A large amount of real complex wastewaters are generated every year,which leads to a great environmental burden.Various treatment technologies were deployed to remove the contaminants in the wastewaters.However,these actual wastewaters have not been sufficiently treated due to their complex properties,high-concentration organics,incomplete utilization of hard-biodegradable substrates,the high energy input required,etc.Recently,microbial electrolysis cells(MECs),a great potential technology,has emerged for various wastewater treatment,because not only do they demonstrate satisfactory performance during wastewater treatment,but they also generate renewable H2 as a clean energy carrier.Unlike previous reviews,this review introduced the characteristics of every complicated wastewater,and focused on analyzing and summarizing MEC development for wastewater treatment.The performances of MECs were systematically reviewed in terms of organics removal,H2 production,Columbic efficiency,and energy efficiency.MEC performances for treating actual complex wastewaters and producing H2 can be optimized through operation parameters,electrode materials,catalyst materials,etc.In addition,the challenges and opportunities including complexity of wastewaters,instability of H2 production,robust microorganisms,effect of membrane on two-chamber MEC,and integration of MEC with other treatment processes were deeply discussed.Except for the technical feasibility,both environmental feasibility and economic feasibility also need to meet social requirements.This review can indeed provide a basis for high-efficiency treatment and practical commercial applications of recalcitrant wastewaters via MECs in the future.

Heavy metals and community structure of microorganism changes during livestock manure composting with inoculation of effective microorganisms

Effective microorganisms(EM)is usually used in composting to improve the composting process.However,the effect of EM on heavy metals evolution was still unclear.This study was performed to illustrate the microbial community changes that occur during composting with the addition of EM and to determine the evolution of heavy metal speciation during this process.The requirement of harmlessness for pig manure was met after the addition of EM at a dosage of 0.5%,with a germination index of 96.42%.The bacterial and fungal diversity were both found to decrease during the composting process.Additionally,the bioavailability of Cu and Pb decreased significantly during composting.Significant correlations were observed between the microbial composition and the percentage of different heavy metals fractions;however,the mechanism responsible for this correlation requires further investigation.This study has the potential to contribute to control of heavy metal contamination during the process of recycling pig manure through the controlled addition of EM.

Anaerobic co-digestion of sodium hydroxide pretreated sugarcane leaves with pig manure and dairy manure

Sugarcane leaves(SL)pretreated by alkali was used as substrate to enhance biogas production via mesophilic anaerobic digestion(AD)in this study.Effectiveness of different concentrations of NaOH pretreatment on AD performance was investigated.Results showed that compared to untreated sample of SL,the lignocellulose(LCH)content of NaOH pretreated group was decreased by 5.79%-16.85%.However,the cumulative biogas production of the pretreated samples increased in the range of 34.54%-82.67%;moreover,T90 was shorten by 5-7 d.The highest anaerobic digestibility of SL was achieved at 6%NaOH pretreatment,which produced 287.30 mL/g TS of biogas.A significant interactive effect of the three parameters(temperature,SL/manure mixing ratio and C/N ratio)was found on the biogasification of anaerobic co-digestion,and a maximum biogas production was achieved at 36.2oC,mixing ratio of 1.6 and C/N ratio of 29.2.These show that the verification experiment confirmed the optimization results.This study provides meaningful insight for exploring efficient pretreatment strategy and optimal condition to stabilize and enhance AD performance for practical application.

Study on dynamic sorption characteristics of modified biochars for ammonium in biogas slurry

The objective of this study was to investigate the relationship between ammonium(NH^(+)_(4)-N)dynamic sorption capacity and physicochemical properties of modified biochars.Biochars,producing from three species of agricultural wastes of cornstalk(A),corncob(B)and sawdust(C)at 550°C,600°C and 650°C,were modified by four methods of NaOH plus microwave(NaM),KOH(K),FeCl 3(Fe)and HNO 3(H).The static and dynamic adsorption experiments were conducted to investigate sorption characteristics of modified biochars on NH^(+)_(4)-N in slurry of piggery manure anaerobic digestate.Four modified biochars with better NH^(+)_(4)-N adsorption rates were selected through static kinetics adsorption tests,which showed that chemical reactions might have occurred during the NH^(+)_(4)-N sorption process and the maximum NH^(+)_(4)-N removal rates of B-550-Fe,A-550-NaM,A-550-K and C-600-NaM were 66.64%,57.50%,52.39%and 45.20%,respectively.The dynamic adsorption column experiment was conducted in a three-stage adsorption column packed with the selected three modified biochars.NH^(+)_(4)-N dynamic adsorption depended on the slurry inflow flow rate,the type of biochar and the depth of packed biochar.The optimal adsorption process was elected by the method of orthogonal experiment.The data showed that using deeper packed biochar and applying lower flow rates could be a better strategy to increase NH^(+)_(4)-N adsorption.The maximum NH^(+)_(4)-N removal rate in the slurry could reach 85.60%in the three-stage adsorption process.It concluded that NH^(+)_(4)-N adsorption in three-stage adsorption process could be an effective method to recover nitrogen from piggery manure anaerobic digestate.

Evaluation of different clean heat supply modes based on crop straws in the rural area of Northern China

This study evaluated eight different types of heat supply modes based on crop residues utilization in the rural area of Northern China,including straw densified solid fuel combustion,pyrolysis char combustion,biogas combustion,and pyrolysis gas combustion for single household heating;straw densified solid fuel combustion,baling straw combustion,biogas combustion,and pyrolysis gas combustion for centralized heating;centralized gas supply and centralized pyrolysis gas supply modes.Comprehensively evaluation was the cost of these different eight heat supply modes.The results showed that the cost of straw densified solid fuel combustion,pyrolysis char combustion for single household heating were 2346 RMB/household and 2390 RMB/household.With the heating scale of 200-500 households,the pipe network distance was 8 m/household,and the total annual heating cost was predicted at 2201-2992 RMB/household.Among them,the cost of straw baling combustion for centralized heating was the lowest,the cost of densified solid fuel,biogas,and pyrolysis for centralized heating was the second,and the cost of biogas and pyrolysis gas for centralized gas supply was the highest.For the increase in every 1 m of the pipeline distance,the investment cost will increase by about 645 RMB for each household.This study provides a basis for the implementation of clean heat supply technologies in less-developed areas and guidance of village heat-supply subsidy policies.

Airflow field simulation model building and application for aerobic compost using CFD

Composting is a suitable low-cost strategy to transform animal waste into a stabilized end product,and the airflow field in the pile affects the fermentation states.For piles in the aeration weak zone,anaerobic fermentation may happen as the lack of oxygen.While in practice,due to the extremely low speed and harsh condition,the airflow field was scarcely researched.This study adopted Computational Fluid Dynamics(CFD)to investigate the airflow field in the compost pile.A three-dimensional CFD model was built;the compost pile in this model was simplified as porous media;unstructured mesh was adopted to discretize the geometric model;standard k-εmodel and SIMPLE scheme were employed for numerical methods.The CFD model was validated with the field experiment in the cooling period.Then the model was applied to research the airflow field in the pile with increased pipe diameter.Results showed that it was feasible to investigate the airflow field in the pile with CFD.For boundary conditions in the CFD model,treating the compost pile as a homogeneous porous media is reasonable.The CFD model was successfully validated by the field measurement(the average relative difference between the simulated and measured air speed was within 10%).Airflow in the existing compost pile showed nonuniform distribution with stagnation and vortex zones;the turbulence intensities were 3.57 and 1.43 for the airflow in the pile and the reactor,respectively.When pipe diameter increased,the airflow distribution uniformity in the pile was improved significantly.With diameter raising to 0.04 m,the turbulence intensity decreased to 1.54 and 0.42 for the airflow in the pile and the reactor,respectively.The CFD model developed in this research can provide qualitative and quantitative analyses of the airflow field in compost piles,and can be a theoretical basis for the aeration system design.

Survey on heavy metal concentrations and maturity indices of organic fertilizer in China

A nationwide survey of organic fertilizer was carried out in China,and 263 samples were collected to be analyzed for maturity indices(moisture content(MC),pH,electrical conductivity(EC),E4/E6,and germination index(GI))and 7 heavy metals(Cu,Zn,Cd,Pb,Cr,As and Ni).The MC,pH,EC,E4/E6 and GI showed large variations among the organic fertilizer samples with ranges of 6.9%-66.68%,4.40-9.19,0.76-13.38 mS/cm,1.07-9.40,and 10%-150%,respectively.The concentrations of 7 heavy metals(Cu,Zn,Cd,Pb,As,Cr,Ni)were also with large variations at 7.53-580.4,0-2818,0.02-149.3,0(not detected)-1321,0.14-26.9,3.70-1237,and 0(not detected)-214.6 mg/kg dry weight.Compared with the limit values of the Chinese standard for organic fertilizers(NY525-2012),9.51%,73.4%,3.19%,and 3.04%of the samples exceeded the limit values of Cd,Pb,As and Cr,respectively.No limits have been set for Cu,Zn and Ni in China,and 35.0%,13.3%and 16.7%of the samples exceeded the Cu,Zn and Ni limits for composts in Germany,respectively.Monte Carlo simulations indicated that with the continuous application of organic fertilizer,Cu,Zn,Cd,Pb and Cr would accumulate to the risk control standard for soil contamination of agricultural land(GB15618-2018)within a relatively short period.It is urgent to establish suitable limits of heavy metals in organic fertilizer in China to control the risk of heavy metal pollution in agricultural land.