An autotrophic nitrogen removal process:Short-cut nitrification combined with ANAMMOX for treating diluted effluent from an UASB reactor fed by landfill leachate

A combined process consisting of a short-cut nitrification （SN） reactor and an anaerobic ammonium oxidation upflow anaerobic sludge bed （ANAMMOX） reactor was developed to treat the diluted effluent from an upflow anaerobic sludge bed （UASB） reactor treating high ammonium municipal landfill leachate.The SN process was performed in an aerated upflow sludge bed （AUSB） reactor （working volume 3.05 L）,treating about 50% of the diluted raw wastewater.The ammonium removal efficiency and the ratio of NO 2 N to NOx-N in the effluent were both higher than 80%,at a maximum nitrogen loading rate of 1.47 kg/（m 3 ·day）.The ANAMMOX process was performed in an UASB reactor （working volume 8.5 L）,using the mix of SN reactor effluent and diluted raw wastewater at a ratio of 1：1.The ammonium and nitrite removal efficiency reached over 93% and 95%,respectively,after 70-day continuous operation,at a maximum total nitrogen loading rate of 0.91 kg/（m 3 ·day）,suggesting a successful operation of the combined process.The average nitrogen loading rate of the combined system was 0.56 kg/（m 3 ·day）,with an average total inorganic nitrogen removal efficiency 87%.The nitrogen in the effluent was mostly nitrate.The results provided important evidence for the possibility of applying SN-ANAMMOX after UASB reactor to treat municipal landfill leachate.

Effects of exposure to 1.8 GHz radiofrequency field on the expression of Hsps and phosphorylation of MAPKs in human lens epithelial cells

The growing public concerns about the possible health effects of exposure to radio frequency （RF） fields from mobile telephones have arisen in many countries because of the increased use of mobile telecommunication devices. This in turn has led to an increase in cognate epidemiological and experimental investigations. However, the results of these studies are conflicting.

Biofuel Recovery from Plantain and Banana Plant Wastes:Integration of Biochemical and Thermochemical Approach

Globally,fossil fuel dependence has created several environmental challenges and climate change.Hence,creating other alternative renewable and ecologically friendly bio-energy sources is necessary.Lignocellulosic biomass has gained significant attention recently as a renewable material for biofuel production.The large amounts of plantain and banana plant parts wasted after harvesting,as well as the peels generated daily by the fruit market and industries,demonstrate the potential of bioenergy resources.This review briefly assesses plantain and banana plant biomass(PBB)generated in the developing,developed,and underdeveloped countries,the consumable parts,and feasible products yield.It emphasized the advantages and disadvantages of the commonly adopted treatment technologies of composting,incineration,and landfilling.Further,the utilization of PBB as catalysts in biodiesel synthesis was briefly highlighted.To optimize recovery of biofuel,different integration routes of pyrolysis,anaerobic digestion,fermentation,hydrothermal carbonization,hydrothermal liquefaction,and hydrothermal gasification for the valorization of the PBB were proposed.The complex compounds present in the PBB(hemicellulose,cellulose,and lignin)can be converted into valuable bio-products such as methane gas and bio-ethanol for bioenergy,and nutrients to promote bioactive ingredients.The investigation of the viability and innovation potential of the integrated routes’technology is necessary to improve the circular bio-economy and the recovery of biofuels from biomass waste,particularly PBB.

Municipal wastewater treatment in China:Development history and future perspectives

China has the world's largest and still growing wastewater sector and water market,thus its future development will have profound influence on the world.The high-speed development of China's wastewater sector over the past 40 years has forged its global leading treatment capacity and innovation ability.However,many problems were left behind,including underdeveloped sewers and sludge disposal facilities,low sustainability of the treatment processes,questionable wastewater treatment plant(WWTP)effluent discharge standards,and lacking global thinking on harmonious development between wastewater management,human society and the nature.Addressing these challenges calls for fundamental changes in target design,policy and technologies.In this mini-review,we revisit the development history of China's municipal wastewater management and identify the remaining challenges.Also,we highlight the future needs of sustainable development and exploring China's own wastewater management path,and outlook the future from several aspects including targets of wastewater management,policies and technologies,especially the new concept WWTP.Furthermore,we envisage the establishment of new-generation WWTPs with the vision of turning WWTP from a site of pollutant removal into a plant of energy,water and fertilizer recovery and an integrated part urban ecology in China.

Effects of mixture ratio on anaerobic co-digestion with fruit and vegetable waste and food waste of China

The biochemical methane potentials for typical fruit and vegetable waste （FVW） and food waste （FW） from a northern China city were investigated, which were 0.30, 0.56 m3 CH4/kgVS （volatile solids） with biodegradabilities of 59.3% and 83.6%, respectively. Individual anaerobic digestion testes of FVW and FW were conducted at the organic loading rate （OLR） of 3 kg VS/（m3-day） using a lab-scale continuous stirred-tank reactor at 35°C. FVW could be digested stably with the biogas production rate of 2.17 ma/（m3-day） and methane production yield of 0.42 m3 CH4/kg VS. However, anaerobic digestion process for FW was failed due to acids accumulation. The effects of FVW： FW ratio on co-digestion stability and performance were further investigated at the same OLR. At FVW and FW mixing ratios of 2：1 and 1：1, the performance and operation of the digester were maintained stable, with no accumulation of volatile fatty acids （VFA） and ammonia. Changing the feed to a higher FW content in a ratio of FVW to FW 1：2, resulted in an increase in VFAs concentration to 1100-1200 rag/L, and the methanogenesis was slightly inhibited. At the optimum mixture ratio 1：1 for co-digestion of FVW with FW, the methane production yield was 0.49 m3 CH4/kg VS, and the volatile solids and soluble chemical oxygen demand （sCOD） removal efficiencies were 74.9% and 96.1%, respectively.

Strategies to improve aerobic granular sludge stability and nitrogen removal based on feeding mode and substrate

A systemic strategy was proposed to improve aerobic granular sludge(AGS)stability and nitrogen(N)removal efficiency by optimizing feeding mode and substrate aiming at complicated wastewater characteristics.Key functional groups at the genus level identified by high-throughput sequencing were evaluated as well.The results showed that anaerobic feeding mode and acetate promoted the compact AGS formation with excellent total nitrogen(TN)removal efficiency(averaging 91.7%±4.1%)at various dissolved oxygen conditions.While the aerobic feeding mode led to a loose AGS structure with a vulnerable anaerobic core and poor TN removal efficiency(averaging58.8%±7.4%).Simultaneous nitrification and denitrification process played the dominant role in N removal in compact AGS over the alternating nitrification and denitrification process.High-concentration glucose undermined feast-famine condition with filamentous bacteria growth out of granule and decreased TN removal efficiency to 67.3%±15.2%.Lower food to microorganism ratio may result in a lower N removal rate attributed to the sharply increased biomass concentration fed by glucose.Ammonia-oxidizing bacteria,nitrite-oxidizing bacteria,denitrifying bacteria,and denitrifying phosphorus accumulation organisms enriched during AGS granulation also contributed to the efficient N removal.The proposed strategy provided insights into the relationship between various factors and stable AGS formation,and systemic operation methods for various complicated wastewater treatment.

Starch/polyvinyl alcohol blended materials used as solid carbon source for tertiary denitrification of secondary efuent

Starch/polyvinyl alcohol （PVA） blended materials for using as a solid carbon source （SCS） were prepared by blending PVA and gelatinized starch in an aqueous solution system, in which PVA served as framework material and starch as carbon source. The optimization of starch content and temperature effects were investigated. It was indicated that higher denitrification efficiency could be achieved with more starch in the materials. The average specific denitrification rates were 0.93, 0.66, 0.37 and 0.36 mg/（g·day） corresponding to starch content of 70%, 60%, 40% and 30% respectively at 37℃. The denitrification rates increased when operating temperature was raised from 23℃ to 30℃ and then 37℃. The mechanism of carbon release was analyzed incorporating the experimental results of abiotic release in deionized water. The organic carbon was mainly hydrolyzed by microbes, and the biological release efficiencies were at the range of 89.2% to 96.0%. A long-term experiment with a continuous flow reactor with SCS material containing 70% starch was conducted to gain some experience for practical application. When the influent nitrate concentration was in the range of 35.2 to 39.1 mg/L, hydraulic retention time of 4 hr, and operating temperature of 30℃, a nitrogen removal efficiency up to 94.6% and denitrification rate of 0.217 kg/（m3.day） was achieved. The starch-based materials developed in this study can be used as a solid carbon source for tertiary nitrogen removal from secondary effluent.

Methanogenic community dynamics in anaerobic co-digestion of fruit and vegetable waste and food waste

A lab-scale continuously-stirred tank reactor （CSTR）, used for anaerobic co-digestion of fruit and vegetable waste （FVW） and food waste （FW） at different mixture ratios, was operated for 178 days at the organic loading rate of 3 kg VS （volatile solids）/（m3.day）. The dynamics of the Archaeal community and the correlations between environmental variables and methanogenic community structure were analyzed by polymerase chain reactions - denaturing gradient gel electrophoresis （PCR-DGGE） and redundancy analysis （RDA）, respectively. PCR-DGGE results demonstrated that the mixture ratio of FVW to FW altered the community composition of Archaea. As the FVW]FW ratio increased, Methanoculleus, Methanosaeta and Methanosarcina became the predominant methanogens in the community. Redundancy analysis results indicated that the shift of the methanogenic community was significantly correlated with the composition of acidogenic products and methane production yield. Different mixture ratios of substrates led to different compositions of intermediate metabolites, which may affect the methanogenic community. These results suggested that the analysis of microbial communities could be used to diagnose anaerobic processes.

Revealing the effect of preparation parameters on zeolite adsorption performance for low and medium concentrations of ammonium

The effect of preparation parameters on the performance of zeolite for ammonium (20-300 mg N/L) adsorption from simulated wastewater is reported.It was found that the ratios of Na2O/SiO2 and Si/Al had a more important influence than crystallization time on zeolite adsorption properties.Relatively low Na2O/SiO2 ratios were beneficial for fabrication of zeolites with high proportions of micropore area and volume,which led to the surface adsorption mechanism being dominated by surface free energy and pore effects.However,with decreasing Si/Al ratios,the effect of ion-exchange was more prominent due to the high negative surface potential of zeolite.In addition,the concentration of weak acid sites on the zeolites was increased with lower ratios of Na2O/SiO2 and Si/Al,which may promote ammonium removal.Therefore,the most effective zeolite for ammonium removal,which was fabricated at Na2O/SiO2 =1.375,Si/Al =4 and crystallization time of 48 hr,exhibited the cooperative effects of adsorption,ion-exchange and a large amount of weak acid sites.The maximum ammonium adsorption capacity (35.06 t 0.98 mg/g) and the removal efficiency (94.44%± 4.00%) were obtained at the dosage of 4.0 g/L zeolite NaX at ammonium concentrations of 300 mg N/L and 20 mg N/L,respectively.The Freundlich isotherm and pseudo-first-order kinetics models provided excellent fitting for the ammonium adsorption process.In addition,zeolite NaX showed about 1.23-3.2 times the ammonium adsorption capacity of clinoptilolite.The stable and efficient reusability of zeolite NaX after five regeneration cycles demonstrated that this adsorbent has considerable potential for practical industrial applications.

Waste activated sludge treatment based on temperature staged and biologically phased anaerobic digestion system

The concept of temperature staged and biological phased （TSBP） was proposed to enhance the performance of waste-activated sludge anaerobic digestion. Semi-continuous experiments were used to investigate the effect of temperature （35 to 70℃） as well as the hydraulic retention time （HRT） （2, 4 and 6 days） on the acidogenic phase. The results showed that the solubilization degree of waste- activated sludge increased from 14.7% to 30.1% with temperature increasing from 35 to 70℃, while the acidification degree was highest at 45℃ （17.6%）, and this was quite different from the temperature impact on hydrolysis. Compared with HRT of 2 and 6 days, 4 days was chosen as the appropriate HRT because of its relatively high solubilization degree （24.6%） and acidification degree （20.1%） at 45℃. The TSBP system combined the acidogenic reactor （45℃, 4 days） with the methanogenic reactor （35℃, 16 days） and the results showed 84.8% and 11.4% higher methane yield and volatile solid reduction, respectively, compared with that of the single-stage anaerobic digestion system with HRT of 20 days at 35℃. Moreover, different microbial morphologies were observed in the acidogenic- and methanogenic-phase reactors, which resulted from the temperature control and HRT adjustment. All the above results indicated that 45℃ was the optimum temperature to inhibit the activity of methanogenic bacteria in the acidogenic phase, and temperature staging and phase separation was thus accomplished. The advantages of the TSBP process were also confirmed by a full-scale waste-activated sludge anaerobic digestion project which was an energy self-sufficient system.

Aerobic granular sludge formation based on substrate availability:Effects of flow pattern and fermentation pretreatment

The influences of flow patterns(mixed-flow and plug-flow)and fermentation pretreatment on aerobic granular sludge(AGS)formation with various substrate availability levels were investigated by running four identical laboratory-scale sequencing batch reactors(R1-R4),comparing two anaerobic feeding strategies and three kinds of substrates.R1 achieved faster granulation with a fast influent fill step followed by a modified anaerobic mixed-flow phase,but the AGS showed poorer stability with a cracked structure and a high suspended solids concentration in the effluent.The anaerobic plug-flow feeding mode(with influent fed slowly from the bottom)in R2 provided deeper penetration depth for the substance to reach the core of A G S and accordingly strengthen A G S stability.An acidogenic upflow sludge bed reactor was introduced as a pretreatment to improve the AGS performance by enhancing glucose pre-fermentation(R4).AGS fed with mixed volatile fatty acids(VFA)after glucose fermentation showed similar performance compared with the reactor fed with acetate in the aspects of stability,structure,size distribution and nitrogen removal efficiency,and 74%similarity in the microbial community.For actual wastewater with low VFA concentrations,fermentation treatment was suggested as a promising pretreatment for stable AGS granulation and operation.

Ammonia removal from low-strength municipal wastewater by powdered resin combined with simultaneous recovery as struvite

Low-strength municipal wastewater is considered to be a recoverable nutrient resource with economic and environmental benefits.Thus,various technologies for nutrient removal and recovery have been developed.In this paper,powdered ion exchange resin was employed for ammonia removal and recovery from imitated low-strength municipal wastewater.The effects of various working conditions(powdered resin dosage,initial concentration,and pH value)were studied in batch experiments to investigate the feasibility of the approach and to achieve performance optimization.The maximum adsorption capacity determined by the Langmuir model was 44.39 mg/g,which is comparable to traditional ion exchange resin.Further,the effects of co-existing cations(Ca^(2+),Mg^(2+),K^(+))were studied.Based on the above experiments,recovery of ammonia as struvite was successfully achieved by a proposed two-stage crystallization process coupled with a powdered resin ion exchange process.Scanning electron microscopy(SEM)and X-ray diffractometry(XRD)results revealed that struvite crystals were successfully gained in alkaline conditions(pH=10).This research demonstrates that a powdered resin and two-stage crystallization process provide an innovative and promising means for highly efficient and easy recovery from low-strength municipal wastewater.

Membrane fouling controlled by coagulation/adsorption during direct sewage membrane filtration(DSMF) for organic matter concentration

Unlike the role of the membrane in a membrane bioreactor, which is designed to replace a sediment tank, direct sewage membrane filtration（DSMF）, with the goal of concentrating organic matters, is proposed as a pretreatment process in a novel sewage treatment concept. The concept of membrane-based pretreatment is proposed to divide raw sewage into a concentrated part retaining most organics and a filtered part with less pollutant remaining, so that energy recovery and water reuse, respectively, could be realized by post-treatment. A pilot-scale experiment was carried out to verify the feasibility of coagulant/adsorbent addition for membrane fouling control, which has been the main issue during this DSMF process. The results showed that continuous coagulant addition successfully slowed down the increase in filtration resistance, with the resistance maintained below 1.0 × 1013m^（-1） in the first 70 hr before a jump occurred. Furthermore,the adsorbent addition contributed to retarding the occurrence of the filtration resistance jump, achieving simultaneous fouling control and chemical oxygen demand（COD）concentration improvement. The final concentrated COD amounted to 7500 mg/L after 6 days of operation.

Recovery of Cu(Ⅱ) from aqueous solution by induced crystallization in a long-term operation

The feasibility of copper recovery by induced crystallization in a long period（174 days） was investigated in a seeded fluidized bed reactor（FBR）. The process was divided into 3 periods according to different influent conditions, and the period Ⅲ was separated into Ⅲ-a and Ⅲb due to the adjustment of the molar ratio of CO3^2- concentration to copper concentration（[CT]/[Cu^2＋]）. The removal efficiency could exceed 95% and the average effluent copper concentration decreased to 3.0 mg/L. The mean particle size of seed grains with copper crystals coating on, raised to 0.36 mm from initial 0.18 mm. During period Ⅲ-a, the supersaturation exceeded 2.88 × 104, the removal efficiency decreased to 60%–80% and the particle size dropped to 0.30 mm, due to the generation of fines by homogeneous crystallization and seeds breaking. And the morphology of the crystals on the seed grains changed from rod-like to spherical which lead to the particle size decreasing. In period Ⅲ-b,the supersaturation was modified by adjusting the molar ratio of [CT]/[Cu^2＋] to 1.2 from 2.The efficiency was back to 95% and the mean particle size grew to 0.36 mm at the end of Ⅲb, the crystals coating on the seeds turned back to rod-like products of good stability. This study illustrated that the copper salt crystal could keep on growing on the seed grains for over 150 days, the feasibility and controllability of copper recovery by induced crystallization process in FBR were satisfactory, even under the dramatic changes in influent conditions.

Enhanced triallyl isocyanurate(TAIC)degradation through application of an 03/UV process:Performance optimization and degradation pathways

Triallyl isocyanurate(TAIC,C12H15N3O3)has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact.TAIC degradation was enhanced when an ozone(O3)/ultraviolet(UV)process was applied compared with the application of an independent O3 process.Although 99%of TAIC could be degraded in 5 min during both processes,the O3/UV process had a 70%mineralization rate that was much higher than that of the independent O3 process(9%)in 30 min.Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent 03 and O3/UV processes.pH impacted both the direct and indirect oxidation processes.Acidic and alkaline conditions preferred direct and indirect reactions respectively,with a pH of 9 achieving maximum Total Organic Carbon(TOC)removal.Both CO32-and HCO3-decreased TOC removal,however only CO32-negatively impacted TAIC degradation.Effects of Cl-as a radical scavenger became more marked only at high concentrations(over 500 mg/L Cl-).Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO·accordingly.

Oxygen tolerance capacity of upflow anaerobic solid-state(UASS) with anaerobic filter(AF) system

In order to investigate the oxygen tolerance capacity of upflow anaerobic solid-state（UASS）with anaerobic filter（AF） system, the effect of microaeration on thermophilic anaerobic digestion of maize straw was investigated under batch conditions and in the UASS with AF system. Aeration intensities of 0–431 m L O2/gvswere conducted as pretreatment under batch conditions. Aeration pretreatment obviously enhanced anaerobic digestion and an aeration intensity of 431 m L O2/gvsincreased the methane yield by 82.2%. Aeration intensities of 0–355 m L O2/gvswere conducted in the process liquor circulation of the UASS with AF system. Dissolved oxygen（DO） of UASS and AF reactors kept around 1.39 ±0.27 and 0.99 ± 0.38 mg/L, respectively. p H was relatively stable around 7.11 ± 0.04. Volatile fatty acids and soluble chemical oxygen demand concentration in UASS reactor were higher than those in AF reactor. Methane yield of the whole system was almost stable at 85 ± 7 m L/gvs as aeration intensity increased step by step. The UASS with AF system showed good oxygen tolerance capacity.

Lewis acid-oxygen vacancy interfacial synergistic catalysis over SO4^2-/Ce0.84Zr0.16O2-WO3-ZrO2 for N,N-diethylation of aniline with ethanol

Herein,a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis fo r aniline N,N-diethylation with ethanol was proposed,and the SO4^2-/Ce0.84Zr0.16O2-WO3-ZrO2 catalyst(SCWZ)with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method,which shows better catalytic activity than the reported solid acidic catalysts.Besides,the SO4^2-/ZrO2(SZ)and SO4^2-/WO3-ZrO2(SWZ)catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component.The SO4^2-and WO3 mainly generate Lewis acid by bonding with ZrO2,which is beneficial for the fracture of the N-H bond in aniline.The Ce0.84Zr0.16O2 solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species,which can participate in stripping-OH from ethanol,then the carbocation will also be released,which only needs1.3805 kcal/mol energy,calculated by density functional theory(DFT),to be input.In comparison,the traditional reaction mechanism needs the Br■nsted acidic sites to promote the protonation of ethanol,then dehydration and subsequent formation of carbocation followed,and 108.6846 kcal/mol energy needs to be input,which is far higher than that of the new mechanism.The apparent activation energy(Ea)over SCWZ was measured by experiment to be 34.09 kJ/mol,which is much lower than that of SWZ(47.10 kJ/mol)and SZ(54.37 kJ/mol),illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ.Besides,the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100%and 73%,respectively,The SCWZ can be renewed for 4 times without rapid deactivation,and the longevity of SCWZ is longer than that of SWZ and SZ,as the loaded SO4^2-and tetragonal ZrO2 are stabilized by Ce0.84Zr0.16O2 and WO3,respectively.

Concept and application of anaerobic suspended granular sludge bed （SGSB） reactor for wastewater treatment

Bed expansion serves an important function in the design and operation of an upflow anaerobic reactor. An analysis of the flow pattern of expanded granular sludge bed （EGSB） reactors shows that most EGSB reactors do not behave as expanded bed reactors, as is widely perceived. Rather, these reactors behave as fluidized bed reactors based on the classic chemical reactor theory. In this paper, four bed expansion modes, divided as static bed, expanded bed, suspended bed, and fluidized bed, for bioreactors are proposed. A high-rate anaerobic suspended granular sludge bed （SGSB） reactor was then developed. The SGSB reactor is an upflow anaerobic reactor, and its expansion degree can be easily controlled within a range to maintain the suspended status of the sludge bed by controlling upfiow velocity. The results of the full-scale reactor confirmed that the use of SGSB reactors is advantageous. The full-scale SGSB reactor runs stably and achieves high COD removal efficiency （about 90%） at high loading rates （average 40 kg-COD·m^-3·d^-1, maximum to 52 kg·COD·m^-3 ·d^-1） based on the SGSB theory, and its expansion degree is between 22% and 37%.

Development and material characteristics of glaucoma surgical implants

Background:Glaucoma is the leading cause of irreversible blindness worldwide.The reduction of intraocular pressure has proved to be the only factor which can be modified in the treatment,and surgical management is one of the important methods for the treatment of glaucoma patients.Main text:In order to increase aqueous humor outflow and further reduce intraocular pressure,various drainage implants have been designed and applied in clinical practice.From initial Molteno,Baerveldt and Ahmed glaucoma implants to the Ahmed ClearPath device,Paul glaucoma implant,EX-PRESS and the eyeWatch implant,to iStent,Hydrus,XEN,PreserFlo,Cypass,SOLX Gold Shunt,etc.,glaucoma surgical implants are currently undergoing a massive transformation on their structures and performances.Multitudinous materials have been used to produce these implants,from original silicone and porous polyethylene,to gelatin,stainless steel,SIBS,titanium,nitinol and even 24-carat gold.Moreover,the material geometry,size,rigidity,biocompatibility and mechanism(valved versus nonvalved)among these implants are markedly different.In this review,we discussed the development and material characteristics of both conventional glaucoma drainage devices and more recent implants,such as the eyeWatch and the new minimally invasive glaucoma surgery(MIGS)devices.Conclusions:Although different in design and materials,these delicate glaucoma surgical implants have widely expanded the glaucoma surgical methods,and improved the success rate and safety of glaucoma surgery significantly.However,all of these glaucoma surgical implants have various limitations and should be used for different glaucoma patients at different conditions.

National Natural Science Foundation(No.81870641 and 82070939);Zhejiang Province Key Research and Development Program(No.2020C03035);Medical Health Science and technology Project of Zhejiang Provincial Health Commission(No.2022RC031).

Background:Normal tension glaucoma(NTG)is a multifactorial disease in the pathogenesis of which intraocular pressure(IOP)-independent factors play a key role.Main text:There is considerable evidence that impairment of the ocular blood flow(OBF)is involved both in the onset and progression of this disease.With the development of the hypothesis of OBF in NTG,various imaging techniques have been developed to evaluate the OBF and blood vessels.Moreover,vascular dysregulation,which is a main factor in Flammer syndrome,was frequently observed in NTG patients.Disturbed OBF leads to increased oxidative stress,which plays an important role in the pathogenesis of glaucomatous optic neuropathy.These results suggested that IOP-independent management may provide alternative treatment options for NTG patients.Conclusions:In this review,we mainly focus on the mechanisms of the abnormal OBF in NTG.