Emerging Views on the Overall Process Treatment of Municipal Domestic Waste for the Sustainable Use of Landfills in China

1.Introduction With the continuous improvement of living standards and the rapid development of urbanization,the annual production of municipal domestic waste in China has reached over 2108 t and is expected to increase in the future.Landfill technology,which is the main method for the traditional treatment of domestic waste,accounts for more than 60%of the total treatment in China.However,current single-landfill technologies have a series of problems(Fig.1(a)).First,recyclable resources within the vast amount of domestic waste often cannot be recycled and utilized,thereby causing resources to be wasted and deviated from sustainable cycles.Second,the amount of domestic waste that is decomposed and disposed of by landfill technology is considerably less than the amount entering landfill sites each year.Accordingly,a large area of valuable land must be developed for the construction of new landfill sites.

Effects of persulfate-assisted hydrothermal treatment of municipal sludge on aqueous phase characteristics and phytotoxicity

Hydrothermal technology (HT) has received much attention in recent years as a process to convert wet organic waste into hydrochar.The aqueous phase (HTAP) produced by this process is still a burden and has become a bottleneck issue for HT process development.In this study,we provide the?rst investigation of the HTAP characteristics,phytotoxicity,and their correlation with persulfate (PS)(PS,2.0 mmol/g TS)-assisted municipal sludge HT.The results showed that PS accelerated the hydrolysis of protein substances and increased the concentration of NH_(4)^(+)by 13.4%to 190.5%and that of PO_(4)^(3-)by 24.2%to 1103.7%in HTAP at hydrothermal temperatures of 120 to 240℃.PS can reduce the phytotoxicity of HTAP by reducing aldehydes,ketones,N heterocyclic compounds,and particle size and by increasing its humi?cation index.The maximum values of the root length and biomass of pakchoi(Brassica chinensis L.) seedlings occurred when electrical conductivity was 0.2 mS/cm of HTAP.This work provided a new strategy for the selection and design of HTAP management strategies.

Exogenous-organic-matter-driven mobilization of groundwater arsenic

The potential release capacity of arsenic(As)from sediment was evaluated under a high level of exogenous organic matter(EOM)with both bioreactive and chemically reactive organic matters(OMs).The OMs were characterized by FI,HIX,BIX,and SUVA254 fluorescence indices showing the biological activities were kept at a high level during the experimental period.At the genus level,Fe/Mn/As-reducing bacteria(Geobacter,Pseudomonas,Bacillus,and Clostridium)and bacteria(Paenibacillus,Acidovorax,Delftia,and Sphingomonas)that can participate in metabolic transformation using EOM were identified.The reducing condition occurs which promoted As,Fe,and Mn releases at very high concentrations of OM.However,As release increased during the first 15-20 days,followed by a decline contributed by secondary iron precipitation.The degree of As release may be limited by the reactivity of Fe(hydro)oxides.The EOM infiltration enhances As and Mn releases in aqueous conditions causing the risk of groundwater pollution,which could occur in specific sites such as landfills,petrochemical sites,and managed aquifer recharge projects.

Influence of surface properties and antecedent environmental conditions on particulate-associated metals in surface runoff

Particulate-associated trace metals have been regarded as an important pollution source for urban surface runoff.Cd,Pb,Cu,Zn and total solids(TS)washed off two different surfaces(low-elevated facade and road surfaces)under two kinds of antecedent environmental conditions(dry and snow-melting)were determined in this study.Wet-vacuuming sweeping(WVS)and surface washing(SW)methods,representing the maximum pollution potential and common rainfall-induced wash-off condition respectively,were used to collect the particulate matters.The result shows that the wash-off concentrations of trace metals were found in the order of Cd(2.28±2.08 mg/l)<Pb(435.85±412.61 mg/l)<Cu(0.93±0.61 mg/l)<Zn(2.52±2.30 mg/l).The snow-melting process had a considerable influence on the wash-off concentrations of the trace metals on both road and facade surfaces.It reduced >38% and >79% of metals and TS concentrations in the facade surface and road surface runoff respectively.The wash-off concentrations of Cd,Cu,and Zn on the road surface 45e780% higher than those on the facade surfaces.The sensitivity analysis based on the Bayesian network indicates that the wash-off concentrations of metals were mainly dependent on the antecedent environmental conditions or the surface properties while the sampling methods had a minor influence.Therefore,to accurately model the pollutant migration in the surface runoff requires an improving method considering different surfaces and antecedent environment conditions.

Decolorization of Methyl Orange by a new clay-supported nanoscale zero-valent iron:Synergetic effect,efficiency optimization and mechanism

In this study, a novel nanoscale zero-valent iron（n ZVI） composite material was successfully synthesized using a low-cost natural clay, ＂Hangjin 2~#clay＂（HJ clay） as the support and tested for the decolorization of the azo dye Methyl Orange（MO） in aqueous solution by n ZVI particles. According to the characterization and MO decolorization experiments, the sample with 5：1 HJ clay-supported n ZVI（HJ/n ZVI） mass ratio（HJ-n ZVI5） showed the best dispersion and reactivity and the highest MO decolorization efficiency. With the same equivalent Fe0 dosage, the HJ-n ZVI1 and HJ-n ZVI5 samples demonstrated a synergetic effect for the decolorization of MO： their decolorization efficiencies were much higher than that achieved by physical mixing of HJ clay and n ZVIs, or the sum of HJ clay and n ZVIs alone. The synergetic effect was primarily due to the improved dispersion and more effective utilization of the n ZVI particles on/in the composite materials. Higher decolorization efficiency of MO was obtained at larger HJ-n ZVI dosage, higher temperature and under N2 atmosphere, while the MO initial concentration and p H were negatively correlated to the efficiency. HJ clay not only works as a carrier for n ZVI nanoparticles, but also contributes to the decolorization through an ＂adsorption-enhanced reduction＂ mechanism. The high efficiency of HJ-n ZVI for decontamination gives it great potential for use in a variety of remediation applications.

Chemodiversity of soil dissolved organic matter affected by contrasting microplastics from different types of polymers

Chemodiversity of dissolved organic matter(DOM)is a crucial factor controlling soil nutrient availability,greenhouse gas emissions,and pollutant migration.Microplastics(MPs)are widespread pollutants in terrestrial ecosystems in many regions.However,the effects of MPs on DOM chemodiversity are not sufficiently understood,particularly under different types of polymers.Using UV-Vis spectroscopy,3D fluorescence spectroscopy,and Fourier-transform ion cyclotron resonance mass spectrometry,the effects of three prevalent MPs[polyethylene,polystyrene,and polyvinyl chloride(PVC)]on the chemical properties and composition of soil DOM were investigated via a 310-d soil incubation experiment.The results showed that MPs reduced the aromatic and hydrophobic soil DOM components by more than 20%,with PVC MPs having the greatest effect.Furthermore,as MP contents increase,the humification level of soil DOM significantly decreases.MPs increased DOM molecules with no heteroatom by 8.3%-14.0%,but decreased DOM molecules with nitrogen content by 17.0%-47.8%.This may be because MPs cause positive“priming effect,”resulting in the breakdown of bioavailable components in soil DOM.This is also related to MPs changing microbial richness and diversity and enriching microbial communities involved in lignin compositions degradation.In the presence of MPs,soil DOM chemodiversity depended on soil pH,electrical conductivity,dissolved organic carbon,soil organic matter,bacterial Shannon,and fungal Chao index.Specifically,DOM in MP-contaminated soils featured more lipids and less condensed aromatics and proteins/amino sugars,thereby conferring a lower DOM aromaticity and higher lability.

The “neighbor avoidance effect” of microplastics on bacterial and fungal diversity and communities in different soil horizons

Microplastics are a new type of environmental pollutant,and pose a serious threat to soil ecosystems.It is important to study microplastics effects on soil microorganisms to better understand their effects on terrestrial ecosystems.Therefore,we collected soil and microplastic samples from corn,pepper,peanut and cucumber fields in Shunyi District,Beijing,China,and used Illumina MiSeq high-throughput sequencing technology to analyze bacterial and fungal community composition and diversity.We focused on microplastic surface and its surrounding“rhizosphere-like”soil in the 0e10 cm(humus)and 10e20 cm(eluvial)deep horizons.Microbial richness and diversity on microplastic surface were significantly lower than those in surrounding“rhizosphere-like”soil,and microbial richness and diversity were reduced to a greater extent in the humus horizon than in the eluvial horizon.Microplastics likely enriched the microbes involved in their biodegradation.The relative abundance levels of Cyanobacteria and Basidiomycota on microplastic surfaces were significantly higher than those in surrounding“rhizosphere-like”soil,while the relative abundance levels of Acidobacteria,Chloreflexi,and Mortierellomycota were higher in“rhizosphere-like”soil.Furthermore,the relative abundance levels of pathways related to human diseases,animal pathogen,and fungal parasites were significantly higher on microplastic surfaces than in“rhizosphere-like”soil.These results show that the microbial diversity,richness,community structure and function between microplastic surfaces and surrounding“rhizosphere-like”soil are significantly different,leading to a“rhizosphere-like neighbor avoidance effect”between microplastic surfaces and the surrounding soil.

Bioreduction of hexavalent chromium:Effect of compost-derived humic acids and hematite

Composting can enhance the nutrie nt ele ments cycling and reduce carbon dioxide production.However,little information is available regarding the application of compost for the remediation of the contaminated soil.In this study,we assess the response of the redox capacities(electron accepting capacities(EAC)and electron donating capacities(EDC))of compost-derived humic acids(HAs)to the bioreduction of hexavalent chromium(Cr(Ⅵ)),especially in presence of hematite.The result showed that the compost-derived HAs played an important role in the bioreduction of Cr(Ⅵ)in presence and absence of hematite under the anoxic,neutral(pH 7)and motionless conditions.Based on the pseudo-first order kinetic model,the rate constants of Cr(Ⅵ)reduction increased by 1.36-2.0 times when compost-derived HAs was added.The redox capacity originating from the polysaccharide structure of compost-derived HAs made them effective in the direct Cr(Ⅵ)reduction(without MR-1)at pH 7.Meanwhile,the reduction rates were inversely proportional to the composting treatment time.When iron mineral(Fe_(2)O_(3))and compost-derived HAs were both present,the rate constants of Cr(Ⅵ)reduction increased by 2.35-5.09,which were higher than the rate of Cr(Ⅵ)reduction in HA-only systems,indicating that the hematite played a crucial role in the bioreduction process of Cr(Ⅵ).EAC and quinonoid structures played a major role in enhancing the bioreduction of Cr(Ⅵ)when iron mineral and compost-derived HAs coexisted in the system.The results can extend the application fields of compost and will provide a new insight for the remediation of Cr(Ⅵ)-contaminated soil.

Mineralization of phenol by ozone combined with activated carbon:Performance and mechanism under different pH levels

The degradation of phenol using ozone with activated carbon(O_(3)/AC system)was investigated in this study.The O_(3)/AC system was also compared with the single O_(3) and AC systems.The total organic carbon(TOC)removal efficiency in the O_(3)/AC system was roughly 26%and 30%higher than the single AC and O_(3) systems,respectively.It was demonstrated that the phenol degradation rate and TOC removal efficiency were significantly affected by the ozone concentration,AC dosage,and solution pH.The pseudo-first-order and pseudo-second-order kinetic models were fitted to identify the mechanisms of the phenol removal process.The results of Scanning Electron Microscopy,Brunauer-Emmett-Teller,and Fourier-transform infrared spectroscopy of raw and used AC indicated that the surface morphology,microstructure,and functional group properties had been changed during the reaction process.The possible O_(3)/AC system mineralization mechanism for phenol removal was tentatively proposed using scavenging active species such as·OH,O_(2)^(·-),and H_(2)O_(2).The transformation byproducts generated during the application of the O_(3)/AC system were identified by High Performance Liquid Chromatography and Gas Chromatography-Mass Spectrometry analyses.Therefore,the mineralization pathway of phenol in detail was proposed in acidic(pH 3.0)and alkaline(pH 11.0)conditions.This study provided a more systematic explanation of the mineralization mechanism for phenol in the O_(3)/AC system.

Region-gridding recycling of bulk organic waste: Emerging views based on coordinated urban and rural development

Bulk organic waste(BOW)has a large outputin China.The improper disposal of BOW will not onlybring serious environmental pollution,but also cause wasteof biomass resources.The viewpoint proposes a region-gridding recycling management system of BOW thathighlights the coordinated development of environmental,agricultural and energy elements in urban and rural areas.The viewpoint aims to drive the upstream and downstreamindustrial chains of BOW treatments,avoid the repeatedconstruction of resource facilities,guide the upgrading ofresource-based technologies,promote the professionaliza-tion of farmers,and thus built the high-quality modernagricultural recycling industrial park based on systemmanagement.

Enhanced activation of peroxydisulfate by strontium modified BiFeO3 perovskite for ciprofloxacin degradation

A series of Sr-doped BiFeO3 perovskites(Bi1-xSrxFeO3,BSFO)fabricated via sol-gel method was applied as peroxydisulfate(PDS)activator for ciprofloxacin(CIP)degradation.Various technologies were used to characterize the morphology and physicochemical features of prepared BSFO samples and the results indicated that Sr was successfully inserted into the perovskites lattice.The catalytic performance of BiFeO3 was significantly boosted by strontium doping.Specifically,Bi0.9Sr0.1FeO3(0.1 BSFO)exhibited the highest catalytic performance for PDS activation to remove CIP,where 95%of CIP(10 mg/L)could be degraded with the addition of 1 g/L 0.1 BSFO and 1 mmol/L PDS within 60 min.Moreover,0.1 BSFO displayed high reusability and stability with lower metal leaching.Weak acidic condition was preferred to neutral and alkaline conditions in 0.1 BSFO/PDS system.The boosted catalytic performance can be interpreted as the lower oxidation state of Fe and the existence of affluent oxygen vacancies generated by Sr doping,that induced the formation of singlet oxygen(^1O_(2))which was confirmed as the dominant reactive species by radical scavenging studies and electron spin resonance(ESR)tests.The catalytic oxidation mechanism related to major ^1O_(2) and minor free radicals was proposed.Current study opens a new avenue to develop effective A-site modified perovskite and expands their application for PDS activation in wastewater remediation.

Advances in Fe(Ⅲ)bioreduction and its application prospect for groundwater remediation:A review

Microbial Fe(Ⅲ)reduction is a significant driving force for the biogeochemical cycles of C,O,P,S,N,and dominates the natural bio-purification of contaminants in groundwater(e.g.,petroleum hydrocarbons,chlorinated ethane,and chromium).In this review,the mechanisms and environmental significance of Fe(Ⅲ)(hydro)oxides bioreduction are summarized.Compared with crystalline Fe(Ⅲ)(hydro)oxides,amorphous Fe(m)(hydro)oxides are more bioavailable.Ligand and electron shuttle both play an important role in microbial Fe(Ⅲ)reduction.The restrictive factors of Fe(Ⅲ)(hydro)oxides bioreduction should be further investigated to reveal the characteristics and mechanisms of the process.It will improve the bioavailability of crystalline Fe(Ⅲ)(hydro)oxides and accelerate the anaerobic oxidation efficiency of the reduction state pollutants.Furthermore,the approach to extract,culture,and incubate the functional Fe(Ⅲ)reducing bacteria from actual complicated environment,and applying it to the bioremediation of organic,ammonia,and heavy metals contaminated groundwater will become a research topic in the future.There are a broad application prospects of Fe(Ⅲ)(hydro)oxides bioreduction to groundwater bioremediation,which includes the in situ injection and permeable reactive barriers and the innovative Kariz wells system.The study provides an important reference for the treatment of reduced pollutants in contaminated groundwater.

Contribution of redox-active properties of compost-derived humic substances in hematite bioreduction

The compost-derived humic substances(HS)can function as electron mediators for promoting hematite bioreduction because of its redox capacity.Humification process can affect redox capacities of compost-derived HS by changing its intrinsic structure.However,the redox properties of compost-derived HS link-ing with hematite bioreduction during composting still remain unclear.Herein,we investigated the redox capacities of compost-derived HS,and assessed the responses of the redox capacities to the hematite bioreduction.The result showed that compost-derived HS(i.e.,humic acids(HA)and fulvic acids(FA))were able to accept electrons from Shewanella oneidensis MR-1,and the electron accepting capacity was increased during composting.Furthermore,it could be functioned as electron mediators for promoting the hematite bioreduction,achieving 1.19-2.15 times compared with the control experience.Not only the aromatic structures(quinone)but also the non-quinone structures such as nitrogen-and sulfur-containing functional moieties were served as the redox-active functional groups of compost-derived HS.Our work proved that the aromatic functional groups and the heteroatom structures(especially N)were important to the hematite bioreduction.This study highlights the redox-active properties of compost-derived HS and its impact on the microbial reduction of iron mineral.Redox capacity of compost-derived HS might mitigate the environmental risk of contaminants when the composting production was added into the contaminated soils as low-cost repair materials.

Lignin-phenol monomers govern the pyrolytic conversion of natural biomass from lignocellulose to products

The effect of the interaction between lignin-phenol monomers and holocellulose in natural biomass on the distribution of pyrolysis products remains unknown.The results of this study showed that the interaction between lignin and holocellulose during the pyrolysis of natural biomass became more pronounced as the pyrolysis temperature increased.The interaction between lignin and holocellulose in the natural crosslinked structure promoted the generation of CO and inhibited the generation of CO2 at 750
C.Lignin inhibited the decarboxylic reaction of hemicellulose during pyrolysis but was important for the generation of levoglucosan during cellulose pyrolysis.Holocellulose slowed the demethoxyreaction of lignin guaiacol but promoted the removal of aliphatic hydrocarbon substituents from the aromatic ring.The cinnamyl phenol monomers of lignin increased the rates of change of biomass pyrolysis products with the lignin mass fraction at 400
C.However,when the pyrolysis temperature increased to 750
C,all types of lignin phenol monomers increased the rates of change of the biomass pyrolysis products.Our results provide new insights that have implications for the development of pyrolysis techniques for the resource recycling of various types of biomass for the preparation of high-grade gaseous and liquid fuels.

On the applicability of the‘humic acids’nomenclature from natural ecosystems to engineering sciences

‘Humic acids(HA)’are the major constituents of natural organic matter(NOM)derived from the plant or biological residues by decomposition and synthesis in natural ecosystems.They have been defined as relatively high molecular weight aggregates of macromolecules associations with series of highly reactive functional compounds,and considered to be as irreplaceable roles(such as the impact on global carbon and nitrogen dynamics,atmosphere,living plants,chemically reactive and NOM structure stabilization)in natural ecosystems[1].

Competition between toxic and nontoxic Microcystis (Cyanophyceae) under different light and temperature conditions

Dear Editor,In aquatic environments,cyanobacteria usually proliferate faster than other phytoplankton assemblages during warm seasons,particularly in eutrophic waters(Ma et al.,2015).Microcystis,a common cyanobacterial genus that potentially produces microcystins(MCs)and nontoxic strains,dominates in eutrophic freshwater bodies,and its biomass increases quickly during the warm period;these changes result in increased water turbidity and changes in light quality and quantity in the water column(Li and Li,2012).Additionally,

Moving policy and regulation forward for single-use plastic alternatives

Single-use plastics are often used once or cannot be reused for extended periods.They are widely consumed with the rapid development of social economy.The waste generated by single-use plastics threatens ecosystem health by entering the environment and ultimately restricts sustainable human development.The innovation of sustainable and environmentally friendly single-use plastic alternative materials and the joint participation of governments,enterprises and the public are promising technologies and management approaches that can solve the problem of single-use plastics wastes.The development of single-use plastic alternative products can be promoted fundamentally only by improving relevant legislation and standards,providing differentiated industrial policies,encouraging scientific and technological innovation and expanding public participation.