Permeable reactive barrier（PRB） filled with zero valent iron（ZVI, Fe0） can be an effective option to remove nitrate from contaminated groundwater. The long-term performance of such PRBs, however, might be compromi...Permeable reactive barrier（PRB） filled with zero valent iron（ZVI, Fe0） can be an effective option to remove nitrate from contaminated groundwater. The long-term performance of such PRBs, however, might be compromised by the problem of declining reactivity and permeability, which could cause a decrease in the nitrate removal efficiency. In this study we explored suitable model formulations that allow for a process-based quantification of the passivation effect on denitrification rates and tested the model for a 40 years long operation scenario. The conceptual model underlying our selected formulation assumes the declining reactivity of the ZVI material through the progressing passivation caused by the precipitation of secondary minerals and the successive depletion of the ZVI material. Two model scenarios, i.e., the base model scenario which neglects the explicit consideration of the passivation effect and one performed with the model in which the impact of the passivation effect on denitrification was considered, were compared. The modeling results illustrate that nitrate removal in the model of considered passivation started to be incomplete after 10 years, and the effluent nitrate concentration of PRB rose up to 86% of the injected water concentration after 40 years, in contrast to the base scenario, corresponding well with the field observations of successively declining nitrate removal efficiencies. The model results also showed that the porosity of the PRB increased in both models. In order to improve and recover the reactivity of ZVI, pyrite was added to the PRB, resulting in completely nitrate removal and lower consumption of ZVI.展开更多
Metal and acid ions contamination of soil in China is serious. To find an efficient solution for remediating the combined pollution,electrokinetics( EK) coupled with chitosan( CTS)permeable reactive barrier( EK/CPRB) ...Metal and acid ions contamination of soil in China is serious. To find an efficient solution for remediating the combined pollution,electrokinetics( EK) coupled with chitosan( CTS)permeable reactive barrier( EK/CPRB) was used to investigate the performances of metal and acid ions remediation. Adsorption characteristics of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- onto CTS were also conducted. The results showed the sorption of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- on CTS could be well described by Freundlich model. When the CTS dosage is 8 g,the total removal efficiency for Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- is 86. 8%,90. 2%,92. 4%,90. 0% and 82. 5%,respectively. CTS enhanced ions remediation efficiencies significantly compared with the single EK system,especially for SO_4^(2-) and NO_3^-. The results indicate EK/CPRB system is suitable for the remediation of soil contaminated by both metal ions and acid ions.展开更多
This work reports on applying iron oxide coated sand (IOCS) media in an experimental permeable reactive barrier to remove uranium (U) species from uranium containing water. A field study was conducted at the legacy Gu...This work reports on applying iron oxide coated sand (IOCS) media in an experimental permeable reactive barrier to remove uranium (U) species from uranium containing water. A field study was conducted at the legacy Gunnar uranium mine & mill site that was abandoned in the 1960s with limited to no decommissioning. The flooded Gunnar mine pit presently contains about 3.2 million m<sup>3</sup> of water contaminated by dissolved U (1.2 mg/L), Ra-226 (0.4 Bq/L), and minor concentrations of other contaminants (As, Se, etc.). The water is seeping over the pit rim into Lake Athabasca, posing potential environmental and health concerns. IOCS media can be used to immobilize uranium species through an adsorption process. Herein, the preparation of hydrous ferric oxide sorbents and their supported forms onto silica sands is described. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (pXRD) were used for structural characterization. The adsorption properties of the IOCS sorbent media were modeled by the Langmuir adsorption isotherm, where a maximum uranium uptake capacity was estimated. Bench-scale adsorption kinetic experiments were also performed before moving to a field trial. Based on these lab results and input on field-scale parameters, a pilot permeable reactive barrier was fabricated and a field test conducted near the Gunnar pit in June 2019. This pilot test provided technical data and information needed for designing a full-scale permeable barrier that employs the IOCS media. This approach can be applied for in-situ water treatment at Gunnar and other legacy uranium sites.展开更多
This study employed a modified biochar material to construct a permeable reactive barrier(PRB)for the treatment of water bodies polluted with mercury and arsenic.The experimental results demonstrated that the addition...This study employed a modified biochar material to construct a permeable reactive barrier(PRB)for the treatment of water bodies polluted with mercury and arsenic.The experimental results demonstrated that the addition of goethite-modified biochar significantly enhanced the remediation efficiency of As(III),achieving a maximum removal rate of 100%.Conversely,pure biochar exhibited high efficiency in the removal of Hg(II),with a maximum removal rate approaching 100%.Furthermore,the pH level of the water significantly influenced the adsorption efficiency of heavy metal ions,with the optimal removal performance observed at a pH of 6.0.The PRB system demonstrated excellent removal rates under low concentrations of heavy metals.However,as the concentration increased,the remediation efficiency exhibited a slight decrease.In summary,the findings of this study provide compelling evidence for the use of modified biochar in the construction of PRBs for the remediation of mercury and arsenic-polluted water bodies.Furthermore,the study reveals the mechanism by which pH and heavy metal concentration influence remediation efficiency.展开更多
A novel permeable reactive barrier(PRB)configuration,the so-called passive convergence-permeable reactive barrier(PC-PRB),is proposed to overcome several shortcomings of traditional PRB configurations,such as high dep...A novel permeable reactive barrier(PRB)configuration,the so-called passive convergence-permeable reactive barrier(PC-PRB),is proposed to overcome several shortcomings of traditional PRB configurations,such as high dependency to site hydrogeological characteristics and plume size.The PC-PRB is designed to make the plume converge towards the PRB due to the passive hydraulic decompression-convergent flow effect.The corresponding passive groundwater convergence(PC)system is deployed upstream of the PRB system,which consists of passive wells,water pipes,and a buffer layer.A two-dimensional(2D)finite-difference hydrodynamic code,entitled PRB-Flow,is developed to examine the hydraulic performance parameters(i.e.,capture width(W)and residence time(t))of PC-PRB.It is proved that the horizontal 2D capture width(Wh)and vertical 2D capture depth(Wv)of the PC-PRB remarkably increase compared to that of the continuous reactive barrier(C-PRB).The aforementioned relative growth values in order are greater than 50%and 25%in this case study.Therefore,the PRB geometric dimensions as well as the materials cost required for the same plume treatment lessens.The sensitivity analysis reveals that the dominant factors influencing the hydraulic performance of the PC-PRB are the water pipe length(Lp),PRB length(LPRB),passive well height(Hw),and PRB height(HPRB).The discrepancy between the Wh of PC-PRB and that of the C-PRB(i.e.,∆Wh)has a low correlation with PRB parameters and mainly depends on Lp,which could dramatically simplify the PC-PRB design procedure.Generally,the proposed PC-PRB exhibits an effective PRB configuration to enhance hydraulic performance.展开更多
Groundwater vanadium(V)(V(V))contamination is ubiquitous in vanadium mining/smelting region and development of novel strategy for its remediation is of particular significance.Herein woodchip-sulfur packed biological ...Groundwater vanadium(V)(V(V))contamination is ubiquitous in vanadium mining/smelting region and development of novel strategy for its remediation is of particular significance.Herein woodchip-sulfur packed biological permeable reactive barrier(bio-PRB)is established towards successful V(V)bio-detoxification.V(V)removal was accelerated under such mixotrophic condition,compared with heterotrophic and autotrophic V(V)reductions.The performance of bio-PRB was relatively steady with V(V)removal efficiency of 68.5%–98.2%under fluctuant geochemical and hydrodynamic conditions.Microbial community analysis indicated that heterotrophic Geobacter was the main reducer to convert V(V)to insoluble V(IV),by consumption of organic source attributed to woodchip hydrolysis and sulfur anabolism of autotrophs(e.g.,Sulfuricurvum and Thiobacillus).V(V)reduction and elemental sulfur oxidation were regulated by genes as omcA,omcB and mtrC and soxB,respectively.The elevated contents of cytochrome c and nicotinamide adenine dinucleotide implied that improved electron transfer facilitated V(V)reduction.This study provides a cost-effective,robust and sustainable route for V(V)-polluted aquifer remediation.展开更多
Permeable reactive barriers(PRBs)are used for groundwater remediation at contaminated sites worldwide.This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-...Permeable reactive barriers(PRBs)are used for groundwater remediation at contaminated sites worldwide.This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron(ZVI)as a reductant and as a reactive material.Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking.Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants.Additionally,there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time.In this review paper,we describe the underlying mechanisms of PRB performance and remove isolated misconceptions.We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products.We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs.Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI.Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity,which negatively impacts hydraulic conductivity,allowing contaminants to potentially bypass the treatment zone.Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.展开更多
A laboratory-scale study with a sand column was designed to simulate trichloroethylene（TCE） pollution in the aquifer environment with three-section controlled-release potassium permanganate（CRP） barriers.The main ...A laboratory-scale study with a sand column was designed to simulate trichloroethylene（TCE） pollution in the aquifer environment with three-section controlled-release potassium permanganate（CRP） barriers.The main objective of this study was to evaluate the feasibility of CRP barriers in remediation of TCE in aquifers in a long-term and controlled manner.CRP particles with a 1：3 molar ratio of KMnO 4 to stearic acid showed the best controlled-release properties in pure water,and the theoretical release time was 138.5 days.The results of TCE removal in the test column indicated that complete removal efficiency of TCE in a sand column by three-section CRP barriers could be reached within 15 days.The molar ratio of KMnO 4 to TCE in the three-section CRP barriers was 16：1,which was much lower than 82：1 as required when KMnO 4 solution is used directly to achieve complete destruction of TCE.This result revealed that the efficiency of CRP for remediation of TCE was highly improved after encapsulation.展开更多
This study attempted to construct a three series barrier system to treat high concentrations of trichloroethylene （TCE; 500 mg/L） in synthetic groundwater. The system consisted of three reactive barriers using iron ...This study attempted to construct a three series barrier system to treat high concentrations of trichloroethylene （TCE; 500 mg/L） in synthetic groundwater. The system consisted of three reactive barriers using iron fillings as an iron-based barrier in the first column, sugarcane bagasse mixed with anaerobic sludge as an anaerobic barrier in the second column, and a biofilm coated on oxygen carbon inducer releasing material as an aerobic barrier in the third column. In order to evaluate the extent of removal of TCE and its metabolites in the aquifer down gradient of the barrier system, a fourth column filled with sand was applied. Residence time of the system was investigated by a bromide tracer test. The results showed that residence time in the column system of the control set and experimental set were 23.62 and 29.99 days, respectively. The efficiency of the three series barrier system in removing TCE was approximately 84% in which the removal efficiency of TCE by the iron filling barrier, anaerobic barrier and aerobic barrier were 42%, 16% and 25%, respectively. cis-Dichloroethylene （cis-DCE）, vinyl chloride （VC）, ethylene and chloride ions were observed as metabolites following TCE degradation. The presence of chloride ions in the effluent from the column system indicated the degradation of TCE. However, cis-DCE and VC were not fully degraded by the proposed barrier system which suggested that another remediation technology after the barrier treatment such as air sparging and adsorption by activated carbon should be conducted.展开更多
To recognize properties of a mixture of Vistula sand （medium sand acc. to USCS） with Slovak zeolite as reactive materials suitable for permeable reactive barriers proposed for protection of groundwater environment i...To recognize properties of a mixture of Vistula sand （medium sand acc. to USCS） with Slovak zeolite as reactive materials suitable for permeable reactive barriers proposed for protection of groundwater environment in vicinity of old landfills comprehensive laboratory investigations were performed. The present study investigates the removal of contaminants specific for landfill leachates onto zeolite-sand mixtures containing 20%, 50% and 80% of zeolite （ZS20, ZS50 and ZS80）. Taking into account the results of batch tests it was concluded that the Langmuir isotherm best fitted the data. It was observed that the presence of ammonium, calcium and magnesium decreases the removal efficiency of copper by 32%. Column tests of contaminant migration through the attenuation zone of the reactive materials were interpreted using the software package CXTFIT, which solves a one-dimensional advection-dispersion equation. Column test results also indicate the strong influence of the presence of interfering substances on copper immobilisation; dynamic sorption capacities decrees twofold. Throughout the landfill leachate flow through ZS80 sample, a constant reduction of NH＋4 （at 100%）, K＋ （at 93%） and Fe total （at an average of 86%） were observed. There was no reduction in chemical oxygen demand and biochemical oxygen demand.展开更多
The Sabodala mine uses laterite in the tailings and water dams as the main material for the dikes of the hydraulic structures and as a sealing layer(phys-ical barrier)to limit the seepage of discharge water and protec...The Sabodala mine uses laterite in the tailings and water dams as the main material for the dikes of the hydraulic structures and as a sealing layer(phys-ical barrier)to limit the seepage of discharge water and protect groundwater from contamination,arsenic in particular.For the permanent storage of arse-nic in mining environments and the protection of environmental matrices(soil,water and air),it is processed in the form of scorodite(FeAsO_(4)∙2H_(2)O)or arsenic-adsorbed ferrihydrite.Both minerals are ecologically stable under a wide range of physicochemical conditions.This study aims to investigate the geochemical behaviour of laterite and its use in a Reactive Permeable Barrier(RPB)for the responsible management of arsenic mine tailings in a sustainable development context.The methodology begins with a physico-chemical and mineralogical characterization of laterite and mine tailings.After characteri-zation,two kinetic tests were carried out in a control Mini-Cell Alteration(MCA)and a laterite beneficiation test in a Reactive Permeable Barrier(RPB).Electrochemical parameters(pH,electrical conductivities),sulphates,calcium ions and metalloids(As and Sb)in the leachates were measured.The results of physico-chemical and mineralogical characterizations of laterite and mine tailings showed that:(i)laterites are composed of quartz(SiO_(2)),kaolinite(Al_(2)Si_(2)O_(5)(OH)_(4)),hematite(Fe_(2)O_(3)),goethite(FeO(OH))and anatase(TiO_(2));(ii)tailings contain high levels of arsenic and antimony;(iii)they also include calcite,ferrodolomite,quartz albite,muscovite and chlorite.Kinetic tests in MCA geochemical studies have shown that mine tailings are non-acid-gener-ating,with low metalloid mobility(0.90%for arsenic and 0.86%for anti-mony).The study of laterite recovery in an RPB in MCA showed a high reten-tion of metalloids(55.26%for arsenic and 57.14%for antimony)and sulphate and calcium ions by the laterite layer.This reactive property of laterite helps protect groundwater from pollutants leached from mine tailings and should enable the mine to develop an appropriate management approach as part of a sustainable development strategy.展开更多
Activities at a former Chemistry Triangle in Bitterfeld, Germany, resulted in contamination of groundwater with a mixture of trichloroethylene(TCE) and monochlorobenzene(MCB). The objective of this study was to develo...Activities at a former Chemistry Triangle in Bitterfeld, Germany, resulted in contamination of groundwater with a mixture of trichloroethylene(TCE) and monochlorobenzene(MCB). The objective of this study was to develop a barrier system, which includes an ORC(oxygen release compounds) and GAC(granular activated carbon) layer for adsorption of MCB and bioregeneration of GAC, a Fe 0 layer for chemical reductive dechlorination of TCE and other chlorinated hydrocarbon in situ . A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system. This experiment was performed using a series of continuous flow Teflon columns including an ORC column, a GAC column, and a Fe 0 column. Simulated MCB and TCE contaminated groundwater was pumped upflow into this system at a flow rate of 1.1 ml/min. Results showed that 17%—50% of TCE and 28%—50% of MCB were dissipated in ORC column. Chloride ion, however, was not released, which suggest the dechlorination do not happen in ORC column. In GAC column, the adsorption of contaminants on activated carbon and their induced degradation by adapted microorganisms attached to the carbon surface were observed. Due to competitive exchange processes, TCE can be desorbed by MCB in GAC column and further degraded in iron column. The completely dechlorination rate of TCE was 0.16—0.18 cm -1 , 1—4 magnitudes more than the formation rate of three dichloroethene isomers. Cis-DCE is the main chlorinated product, which can be cumulated in the system, not only depending on the formation rate and its decaying rate, but also the initial concentration of TCE.展开更多
The co-contamination of metals and organic pollutants,such as Pb and methyl tert-butyl ether(MTBE),in groundwater,has become a common and major phenomenon in many contaminated sites.This study evaluated the feasibilit...The co-contamination of metals and organic pollutants,such as Pb and methyl tert-butyl ether(MTBE),in groundwater,has become a common and major phenomenon in many contaminated sites.This study evaluated the feasibility of their simultaneous removal with permeable reactive barrier(PRB)packed with mixed zeolites(clinoptilolite and ZSM-5)using fixed-bed column tests and breakthrough curve modeling.The effect of grain size on the permeability of PRB and removal efficacy was also assessed by granular and power clinoptilolite.The replacement of granular clinoptilolite by powder clinoptilolite largely reduced the breakthrough time but increased the saturation time nearly fourfold.The column adsorption capacity of clinoptilolite powders almost tripled that of clinoptilolite granules(130.6mg/g versus 45.3 mg/g)due to higher specific surface areas.The minimum thickness and corresponding longevity of PRB were calculated as 7.12 cm and 321.5 min when 5%of granular clinoptilolite was mixed with 5%ZSM-5 and 90%sand as mixed PRB reactive media compared with 10.86 cm and 1230.2 min for the application of powder clinoptilolite.This study is expected to provide theoretical support and guidance for the practical application of mixed adsorbents in PRBs.展开更多
Identification of chemical oxygen demand(COD)in municipal solid waste(MSW)landfill leachates is a challenging problem.This paper investigated the feasibility of using sodium persulfate(PS),a strong oxidant,as a permea...Identification of chemical oxygen demand(COD)in municipal solid waste(MSW)landfill leachates is a challenging problem.This paper investigated the feasibility of using sodium persulfate(PS),a strong oxidant,as a permeable reactive barrier(PRB)filling material.Firstly,sustained-release persulfate balls were manufactured to adjust the release rate of persulfate,the oxidation agent.In addition,Fe(II)-loaded activated carbon(Fe-AC)was used to help with an even distribution of Fe(II)in the porous medium(PRB in this case).Then,the oxidation efficiency and kinetic rate of COD removal by the sustained-release balls were subjected to batch tests.A mass ratio of 1:1.4:0.24:0.7 for PS:cement:sand:water was the most efficient for COD removal(95%).The breakthrough curve for a 5 mm sustained-release ball revealed that the retardation factor was 1.27 and that the hydrodynamic dispersion coefficient was 15.6 cm^(2)/d.The corresponding half-life of COD oxidation was 0.43 d,which was comparable with the half-life of PS release from sustained-release balls(0.56 d).The sustained-release persulfate balls were shown to be an economical material with a simple recipe and production method when catalyzed by Fe-AC.Compared with cutting-edge methods,sustained-release balls used in PRBs offer significant advantages in terms of both effectiveness and economy for the preparation of sustained-release and catalytic materials.These results verified the feasibility of using sustained-release persulfate balls as a PRB material for COD removal.展开更多
Morphological changes within the porous architecture of laboratory scale zero valent iron （ZVI） permeable reactive barriers （PRBs）, after exposure to different groundwater conditions, have been quantified experime...Morphological changes within the porous architecture of laboratory scale zero valent iron （ZVI） permeable reactive barriers （PRBs）, after exposure to different groundwater conditions, have been quantified experimentally for different ZVI/sand ratios （10%, 50% and 100%, W/W） with the aim of inferring porosity changes in field barriers. Column studies were conducted to simulate interaction with different water chemistries, a synthetic groundwater, acidic drainage and deionised （DI） water as control. Morphological changes, in terms of pore size and distribution, were measured using X-ray computed tomography （CT）. CT image analysis revealed significant morphological changes in columns treated with different water chemistries. For example, 100% ZVI （W/W） columns had a higher frequency of small pores （0.6 mm） was observed in ZVI grains reacted with typical groundwater, resulting in a porosity of 27%, compared to 32% when exposed to DI water. In comparison, ZVI grains treated with the acidic drainage had higher porosity （44%） and larger average pore size （2.8 mm）. 10% ZVI PRB barrier material had the highest mean porosity （56%） after exposure to any water chemistry whilst 100% ZVI （W/W） columns always had the lowest （34%） with the 50% ZVI （W/W） in between （40%）. These results agree with previously published PRB field data and simultaneously conducted geochemical monitoring and mass balance calculation, indicating that both the geochemical and hydraulic environment of the PRB play an important role in determining barrier lifespan. This study suggests that X-ray CT image analysis is a powerful tool for studying the detailed inter pores between ZVI grains within PRBs.展开更多
Dealing with groundwater impacted by persistent,low-concentration chlorinated solvents is a major challenge for site remediation,as technologies designed for fast contaminant removal or destruction often are not cost-...Dealing with groundwater impacted by persistent,low-concentration chlorinated solvents is a major challenge for site remediation,as technologies designed for fast contaminant removal or destruction often are not cost-effective.For long-term plume management,in situ contaminant sequestration using carbonaceous materials is a more viable strategy.Here,we prove the concept that the effectiveness of this approach can be improved by modulating the compositional and surface properties of carbonaceous materials to maximize the synergy between contaminant binding and abiotic transformation.We found that two pine wood biochars pyrolyzed at 600 and 700℃exhibit not only faster adsorption kinetics for 1,1,2,2-tetrachloroethane than those prepared at lower temperatures(500℃and below),but also greater efficacy in enhancing the dehydrochlorination of the contaminant.The higher catalytic efficiency is counterintuitive,as it is commonly accepted that surface carboxyl and phenolic groups are the catalytic sites.With supplementary experiments carried out using modified materials and at varied pH values,we found that the surprisingly higher catalytic activities of these two samples are due to their higher carbonate contents.Interestingly,trichloroethylene,the hydrolysis product,is more adsorptive to the biochars than the parent compound.Thus,by promoting the abiotic transformation,these two biochars enable much more effective plume interception than the less-reactive materials.The findings have important implications for dealing with long-term,persistent groundwater contamination,particularly,the“rebounding”problem often occurring post active site remediation.展开更多
The purpose of this study is to estimate the removal efficiency of As and Cr(VI)by one kind of industrial waste–iron chips,as well as to estimate the effects of typical inorganic anions(sulfate,phosphate,and nitrate)...The purpose of this study is to estimate the removal efficiency of As and Cr(VI)by one kind of industrial waste–iron chips,as well as to estimate the effects of typical inorganic anions(sulfate,phosphate,and nitrate),and typical organic anions(citrate,oxalate,and humate)on As or Cr(VI)removal.The results showed that 98%of As(V)and 92%of As(III)could be removed from aqueous phase by the iron chips within 60 min.Compared with As species,Cr(VI)was removed much more rapidly and efficiently with 97%of Cr(VI)being removed within 25 min.The removal efficiency for arsenic was in the order:As(III)(sulfate),As(III)(nitrate)or As(III),As(III)(humate),As(III)(oxalate),As(III)(citrate),As(III)(phosphate),and for chromate was in the order:Cr(VI)(sulfate),Cr(VI)(phosphate)or Cr(VI)(nitrate)or Cr(VI)(oxalate),Cr(VI),Cr(VI)(citrate),Cr(VI)(humate).In all the treatments,pH level increased with time except for As(III),the removal of which was either without anions or in the presence of humate or nitrate.展开更多
This paper presents an approach described as“non-traditional”for restoring water quality and ecosystem services that have been degraded as a result of excess nitrogen.It focuses on emerging technologies often referr...This paper presents an approach described as“non-traditional”for restoring water quality and ecosystem services that have been degraded as a result of excess nitrogen.It focuses on emerging technologies often referred to as green infrastructure.These technologies may provide cost effective alternatives to traditional,gray infrastructure such as sewering and is likely to provide significant co-benefits including the creation of local jobs,the preservation of real estate values,and habitat enhancement.The paper focuses on the Three Bays estuary on Cape Cod to illustrate the benefits and potential of green infrastructure technologies.The Three Bays estuary is presented as a case study and as a representative example of implementation of the broader Cape Cod Water Quality Management Plan Update(208 Plan Update)-a nationally-recognized watershed planning project designed to provide a pathway for the fifteen towns of Cape Cod to achieve compliance with Section 208 of the Clean Water Act.The Three Bays estuary and embayment system is a scenic Cape Cod bay that hosts sailing,kayaking,swimming and shellfishing and is located in the Town of Barnstable.It is comprised of three primary segments that include West Bay,North Bay and Cotuit Bay.Sub-systems include Prince Cove that flows into North Bay,the Narrows that flows between North Bay and Cotuit Bay and Eel Pond that flows into East Bay(see Figure 1).The Massachusetts Estuaries Project(MEP)is a state-sanctioned watershedmodeling project that assesses the conditions of the state’s estuaries and required restoration goals.Its technical report(2006)indicates that the water quality of the Three Bays system has resulted in seriously degraded to moderately degraded habitat.The system is listed as an impaired water body on the US Environmental Protection Agency(EPA)303d list of impaired waters.An approved Total Maximum Daily Load(TMDL)for nitrogen has been established for the embayment.This assessment is supported by more recent empirical water quality data collected within the embayment.The more current data documents a continuing decline in water quality with more common algae blooms(see Figure 2).展开更多
基金supported by the National Natural Science Foundation of China(Nos.41402213 and 51279016)the Open Fund of Three Gorges Research Center for Geo-hazard,Ministry of Education,China University of Geosciences(No.TGRC201403)+2 种基金the Open Fund of the Key Laboratory of Groundwater Contamination and Remediation,China Geological Survey(CGS)and Hebei Province(No.KF201508)the Foundation of Central Public Welfare Scientific Institute Basic Scientific Research(No.CKSF2016021/YT)the Technology Foundation for Selected Overseas Chinese Scholar,Ministry of Personnel of China(2014)
文摘Permeable reactive barrier（PRB） filled with zero valent iron（ZVI, Fe0） can be an effective option to remove nitrate from contaminated groundwater. The long-term performance of such PRBs, however, might be compromised by the problem of declining reactivity and permeability, which could cause a decrease in the nitrate removal efficiency. In this study we explored suitable model formulations that allow for a process-based quantification of the passivation effect on denitrification rates and tested the model for a 40 years long operation scenario. The conceptual model underlying our selected formulation assumes the declining reactivity of the ZVI material through the progressing passivation caused by the precipitation of secondary minerals and the successive depletion of the ZVI material. Two model scenarios, i.e., the base model scenario which neglects the explicit consideration of the passivation effect and one performed with the model in which the impact of the passivation effect on denitrification was considered, were compared. The modeling results illustrate that nitrate removal in the model of considered passivation started to be incomplete after 10 years, and the effluent nitrate concentration of PRB rose up to 86% of the injected water concentration after 40 years, in contrast to the base scenario, corresponding well with the field observations of successively declining nitrate removal efficiencies. The model results also showed that the porosity of the PRB increased in both models. In order to improve and recover the reactivity of ZVI, pyrite was added to the PRB, resulting in completely nitrate removal and lower consumption of ZVI.
基金National Natural Science Foundations of China(Nos.21477018,21007010)the Fundamental Research Funds for the Central Universities,China(No.15D111323)+1 种基金Hunan Province Ministry of Transportation Scientific Research Projects,China(Nos.200908,201105)Ministry of Transport Science and Technology Program,China(No.2010353343290)
文摘Metal and acid ions contamination of soil in China is serious. To find an efficient solution for remediating the combined pollution,electrokinetics( EK) coupled with chitosan( CTS)permeable reactive barrier( EK/CPRB) was used to investigate the performances of metal and acid ions remediation. Adsorption characteristics of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- onto CTS were also conducted. The results showed the sorption of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- on CTS could be well described by Freundlich model. When the CTS dosage is 8 g,the total removal efficiency for Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- is 86. 8%,90. 2%,92. 4%,90. 0% and 82. 5%,respectively. CTS enhanced ions remediation efficiencies significantly compared with the single EK system,especially for SO_4^(2-) and NO_3^-. The results indicate EK/CPRB system is suitable for the remediation of soil contaminated by both metal ions and acid ions.
文摘This work reports on applying iron oxide coated sand (IOCS) media in an experimental permeable reactive barrier to remove uranium (U) species from uranium containing water. A field study was conducted at the legacy Gunnar uranium mine & mill site that was abandoned in the 1960s with limited to no decommissioning. The flooded Gunnar mine pit presently contains about 3.2 million m<sup>3</sup> of water contaminated by dissolved U (1.2 mg/L), Ra-226 (0.4 Bq/L), and minor concentrations of other contaminants (As, Se, etc.). The water is seeping over the pit rim into Lake Athabasca, posing potential environmental and health concerns. IOCS media can be used to immobilize uranium species through an adsorption process. Herein, the preparation of hydrous ferric oxide sorbents and their supported forms onto silica sands is described. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (pXRD) were used for structural characterization. The adsorption properties of the IOCS sorbent media were modeled by the Langmuir adsorption isotherm, where a maximum uranium uptake capacity was estimated. Bench-scale adsorption kinetic experiments were also performed before moving to a field trial. Based on these lab results and input on field-scale parameters, a pilot permeable reactive barrier was fabricated and a field test conducted near the Gunnar pit in June 2019. This pilot test provided technical data and information needed for designing a full-scale permeable barrier that employs the IOCS media. This approach can be applied for in-situ water treatment at Gunnar and other legacy uranium sites.
文摘This study employed a modified biochar material to construct a permeable reactive barrier(PRB)for the treatment of water bodies polluted with mercury and arsenic.The experimental results demonstrated that the addition of goethite-modified biochar significantly enhanced the remediation efficiency of As(III),achieving a maximum removal rate of 100%.Conversely,pure biochar exhibited high efficiency in the removal of Hg(II),with a maximum removal rate approaching 100%.Furthermore,the pH level of the water significantly influenced the adsorption efficiency of heavy metal ions,with the optimal removal performance observed at a pH of 6.0.The PRB system demonstrated excellent removal rates under low concentrations of heavy metals.However,as the concentration increased,the remediation efficiency exhibited a slight decrease.In summary,the findings of this study provide compelling evidence for the use of modified biochar in the construction of PRBs for the remediation of mercury and arsenic-polluted water bodies.Furthermore,the study reveals the mechanism by which pH and heavy metal concentration influence remediation efficiency.
基金supported by the National Key R&D Program of China(No.2018YFC1802306)the National Natural Science Foundation of China(No.42177177).
文摘A novel permeable reactive barrier(PRB)configuration,the so-called passive convergence-permeable reactive barrier(PC-PRB),is proposed to overcome several shortcomings of traditional PRB configurations,such as high dependency to site hydrogeological characteristics and plume size.The PC-PRB is designed to make the plume converge towards the PRB due to the passive hydraulic decompression-convergent flow effect.The corresponding passive groundwater convergence(PC)system is deployed upstream of the PRB system,which consists of passive wells,water pipes,and a buffer layer.A two-dimensional(2D)finite-difference hydrodynamic code,entitled PRB-Flow,is developed to examine the hydraulic performance parameters(i.e.,capture width(W)and residence time(t))of PC-PRB.It is proved that the horizontal 2D capture width(Wh)and vertical 2D capture depth(Wv)of the PC-PRB remarkably increase compared to that of the continuous reactive barrier(C-PRB).The aforementioned relative growth values in order are greater than 50%and 25%in this case study.Therefore,the PRB geometric dimensions as well as the materials cost required for the same plume treatment lessens.The sensitivity analysis reveals that the dominant factors influencing the hydraulic performance of the PC-PRB are the water pipe length(Lp),PRB length(LPRB),passive well height(Hw),and PRB height(HPRB).The discrepancy between the Wh of PC-PRB and that of the C-PRB(i.e.,∆Wh)has a low correlation with PRB parameters and mainly depends on Lp,which could dramatically simplify the PC-PRB design procedure.Generally,the proposed PC-PRB exhibits an effective PRB configuration to enhance hydraulic performance.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.41672237)the Beijing Natural Science Foundation(Grant No.8192040).
文摘Groundwater vanadium(V)(V(V))contamination is ubiquitous in vanadium mining/smelting region and development of novel strategy for its remediation is of particular significance.Herein woodchip-sulfur packed biological permeable reactive barrier(bio-PRB)is established towards successful V(V)bio-detoxification.V(V)removal was accelerated under such mixotrophic condition,compared with heterotrophic and autotrophic V(V)reductions.The performance of bio-PRB was relatively steady with V(V)removal efficiency of 68.5%–98.2%under fluctuant geochemical and hydrodynamic conditions.Microbial community analysis indicated that heterotrophic Geobacter was the main reducer to convert V(V)to insoluble V(IV),by consumption of organic source attributed to woodchip hydrolysis and sulfur anabolism of autotrophs(e.g.,Sulfuricurvum and Thiobacillus).V(V)reduction and elemental sulfur oxidation were regulated by genes as omcA,omcB and mtrC and soxB,respectively.The elevated contents of cytochrome c and nicotinamide adenine dinucleotide implied that improved electron transfer facilitated V(V)reduction.This study provides a cost-effective,robust and sustainable route for V(V)-polluted aquifer remediation.
文摘Permeable reactive barriers(PRBs)are used for groundwater remediation at contaminated sites worldwide.This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron(ZVI)as a reductant and as a reactive material.Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking.Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants.Additionally,there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time.In this review paper,we describe the underlying mechanisms of PRB performance and remove isolated misconceptions.We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products.We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs.Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI.Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity,which negatively impacts hydraulic conductivity,allowing contaminants to potentially bypass the treatment zone.Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.
基金supported by the National Natural Science Foundation of China (No. 50978059,51178117)the Program for New Century Excellent Talents in University(No. NCET-11-0853)
文摘A laboratory-scale study with a sand column was designed to simulate trichloroethylene（TCE） pollution in the aquifer environment with three-section controlled-release potassium permanganate（CRP） barriers.The main objective of this study was to evaluate the feasibility of CRP barriers in remediation of TCE in aquifers in a long-term and controlled manner.CRP particles with a 1：3 molar ratio of KMnO 4 to stearic acid showed the best controlled-release properties in pure water,and the theoretical release time was 138.5 days.The results of TCE removal in the test column indicated that complete removal efficiency of TCE in a sand column by three-section CRP barriers could be reached within 15 days.The molar ratio of KMnO 4 to TCE in the three-section CRP barriers was 16：1,which was much lower than 82：1 as required when KMnO 4 solution is used directly to achieve complete destruction of TCE.This result revealed that the efficiency of CRP for remediation of TCE was highly improved after encapsulation.
基金the travel funds from Rajamangala University of Technology-Isan-Kalasin Campus and the GraduateSchool,Khon Kaen University
文摘This study attempted to construct a three series barrier system to treat high concentrations of trichloroethylene （TCE; 500 mg/L） in synthetic groundwater. The system consisted of three reactive barriers using iron fillings as an iron-based barrier in the first column, sugarcane bagasse mixed with anaerobic sludge as an anaerobic barrier in the second column, and a biofilm coated on oxygen carbon inducer releasing material as an aerobic barrier in the third column. In order to evaluate the extent of removal of TCE and its metabolites in the aquifer down gradient of the barrier system, a fourth column filled with sand was applied. Residence time of the system was investigated by a bromide tracer test. The results showed that residence time in the column system of the control set and experimental set were 23.62 and 29.99 days, respectively. The efficiency of the three series barrier system in removing TCE was approximately 84% in which the removal efficiency of TCE by the iron filling barrier, anaerobic barrier and aerobic barrier were 42%, 16% and 25%, respectively. cis-Dichloroethylene （cis-DCE）, vinyl chloride （VC）, ethylene and chloride ions were observed as metabolites following TCE degradation. The presence of chloride ions in the effluent from the column system indicated the degradation of TCE. However, cis-DCE and VC were not fully degraded by the proposed barrier system which suggested that another remediation technology after the barrier treatment such as air sparging and adsorption by activated carbon should be conducted.
基金supported by Grants no. 2P04G 088 29 and N N523 561638 from the Ministry of Science and Higher Education, Warsaw, Poland
文摘To recognize properties of a mixture of Vistula sand （medium sand acc. to USCS） with Slovak zeolite as reactive materials suitable for permeable reactive barriers proposed for protection of groundwater environment in vicinity of old landfills comprehensive laboratory investigations were performed. The present study investigates the removal of contaminants specific for landfill leachates onto zeolite-sand mixtures containing 20%, 50% and 80% of zeolite （ZS20, ZS50 and ZS80）. Taking into account the results of batch tests it was concluded that the Langmuir isotherm best fitted the data. It was observed that the presence of ammonium, calcium and magnesium decreases the removal efficiency of copper by 32%. Column tests of contaminant migration through the attenuation zone of the reactive materials were interpreted using the software package CXTFIT, which solves a one-dimensional advection-dispersion equation. Column test results also indicate the strong influence of the presence of interfering substances on copper immobilisation; dynamic sorption capacities decrees twofold. Throughout the landfill leachate flow through ZS80 sample, a constant reduction of NH＋4 （at 100%）, K＋ （at 93%） and Fe total （at an average of 86%） were observed. There was no reduction in chemical oxygen demand and biochemical oxygen demand.
文摘The Sabodala mine uses laterite in the tailings and water dams as the main material for the dikes of the hydraulic structures and as a sealing layer(phys-ical barrier)to limit the seepage of discharge water and protect groundwater from contamination,arsenic in particular.For the permanent storage of arse-nic in mining environments and the protection of environmental matrices(soil,water and air),it is processed in the form of scorodite(FeAsO_(4)∙2H_(2)O)or arsenic-adsorbed ferrihydrite.Both minerals are ecologically stable under a wide range of physicochemical conditions.This study aims to investigate the geochemical behaviour of laterite and its use in a Reactive Permeable Barrier(RPB)for the responsible management of arsenic mine tailings in a sustainable development context.The methodology begins with a physico-chemical and mineralogical characterization of laterite and mine tailings.After characteri-zation,two kinetic tests were carried out in a control Mini-Cell Alteration(MCA)and a laterite beneficiation test in a Reactive Permeable Barrier(RPB).Electrochemical parameters(pH,electrical conductivities),sulphates,calcium ions and metalloids(As and Sb)in the leachates were measured.The results of physico-chemical and mineralogical characterizations of laterite and mine tailings showed that:(i)laterites are composed of quartz(SiO_(2)),kaolinite(Al_(2)Si_(2)O_(5)(OH)_(4)),hematite(Fe_(2)O_(3)),goethite(FeO(OH))and anatase(TiO_(2));(ii)tailings contain high levels of arsenic and antimony;(iii)they also include calcite,ferrodolomite,quartz albite,muscovite and chlorite.Kinetic tests in MCA geochemical studies have shown that mine tailings are non-acid-gener-ating,with low metalloid mobility(0.90%for arsenic and 0.86%for anti-mony).The study of laterite recovery in an RPB in MCA showed a high reten-tion of metalloids(55.26%for arsenic and 57.14%for antimony)and sulphate and calcium ions by the laterite layer.This reactive property of laterite helps protect groundwater from pollutants leached from mine tailings and should enable the mine to develop an appropriate management approach as part of a sustainable development strategy.
文摘Activities at a former Chemistry Triangle in Bitterfeld, Germany, resulted in contamination of groundwater with a mixture of trichloroethylene(TCE) and monochlorobenzene(MCB). The objective of this study was to develop a barrier system, which includes an ORC(oxygen release compounds) and GAC(granular activated carbon) layer for adsorption of MCB and bioregeneration of GAC, a Fe 0 layer for chemical reductive dechlorination of TCE and other chlorinated hydrocarbon in situ . A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system. This experiment was performed using a series of continuous flow Teflon columns including an ORC column, a GAC column, and a Fe 0 column. Simulated MCB and TCE contaminated groundwater was pumped upflow into this system at a flow rate of 1.1 ml/min. Results showed that 17%—50% of TCE and 28%—50% of MCB were dissipated in ORC column. Chloride ion, however, was not released, which suggest the dechlorination do not happen in ORC column. In GAC column, the adsorption of contaminants on activated carbon and their induced degradation by adapted microorganisms attached to the carbon surface were observed. Due to competitive exchange processes, TCE can be desorbed by MCB in GAC column and further degraded in iron column. The completely dechlorination rate of TCE was 0.16—0.18 cm -1 , 1—4 magnitudes more than the formation rate of three dichloroethene isomers. Cis-DCE is the main chlorinated product, which can be cumulated in the system, not only depending on the formation rate and its decaying rate, but also the initial concentration of TCE.
基金supported by a China Scholarship Council(CSC)Ph.D.studentship and the National Key R&D Program of China(No.2020YFC1808201)。
文摘The co-contamination of metals and organic pollutants,such as Pb and methyl tert-butyl ether(MTBE),in groundwater,has become a common and major phenomenon in many contaminated sites.This study evaluated the feasibility of their simultaneous removal with permeable reactive barrier(PRB)packed with mixed zeolites(clinoptilolite and ZSM-5)using fixed-bed column tests and breakthrough curve modeling.The effect of grain size on the permeability of PRB and removal efficacy was also assessed by granular and power clinoptilolite.The replacement of granular clinoptilolite by powder clinoptilolite largely reduced the breakthrough time but increased the saturation time nearly fourfold.The column adsorption capacity of clinoptilolite powders almost tripled that of clinoptilolite granules(130.6mg/g versus 45.3 mg/g)due to higher specific surface areas.The minimum thickness and corresponding longevity of PRB were calculated as 7.12 cm and 321.5 min when 5%of granular clinoptilolite was mixed with 5%ZSM-5 and 90%sand as mixed PRB reactive media compared with 10.86 cm and 1230.2 min for the application of powder clinoptilolite.This study is expected to provide theoretical support and guidance for the practical application of mixed adsorbents in PRBs.
基金Ministry of Science and Technology of China(Nos.2019YFC1805002 and 2018YFC1802300)National Natural Science Foundation of China(Nos.42177118 and 51779219)+1 种基金Basic Science Center Program for Multiphase Evolution in Hypergravity of the National Natural Science Foundation of China(No.51988101)Overseas Expertise Introduction Center for Discipline Innovation(No.B18047),China.
文摘Identification of chemical oxygen demand(COD)in municipal solid waste(MSW)landfill leachates is a challenging problem.This paper investigated the feasibility of using sodium persulfate(PS),a strong oxidant,as a permeable reactive barrier(PRB)filling material.Firstly,sustained-release persulfate balls were manufactured to adjust the release rate of persulfate,the oxidation agent.In addition,Fe(II)-loaded activated carbon(Fe-AC)was used to help with an even distribution of Fe(II)in the porous medium(PRB in this case).Then,the oxidation efficiency and kinetic rate of COD removal by the sustained-release balls were subjected to batch tests.A mass ratio of 1:1.4:0.24:0.7 for PS:cement:sand:water was the most efficient for COD removal(95%).The breakthrough curve for a 5 mm sustained-release ball revealed that the retardation factor was 1.27 and that the hydrodynamic dispersion coefficient was 15.6 cm^(2)/d.The corresponding half-life of COD oxidation was 0.43 d,which was comparable with the half-life of PS release from sustained-release balls(0.56 d).The sustained-release persulfate balls were shown to be an economical material with a simple recipe and production method when catalyzed by Fe-AC.Compared with cutting-edge methods,sustained-release balls used in PRBs offer significant advantages in terms of both effectiveness and economy for the preparation of sustained-release and catalytic materials.These results verified the feasibility of using sustained-release persulfate balls as a PRB material for COD removal.
文摘Morphological changes within the porous architecture of laboratory scale zero valent iron （ZVI） permeable reactive barriers （PRBs）, after exposure to different groundwater conditions, have been quantified experimentally for different ZVI/sand ratios （10%, 50% and 100%, W/W） with the aim of inferring porosity changes in field barriers. Column studies were conducted to simulate interaction with different water chemistries, a synthetic groundwater, acidic drainage and deionised （DI） water as control. Morphological changes, in terms of pore size and distribution, were measured using X-ray computed tomography （CT）. CT image analysis revealed significant morphological changes in columns treated with different water chemistries. For example, 100% ZVI （W/W） columns had a higher frequency of small pores （0.6 mm） was observed in ZVI grains reacted with typical groundwater, resulting in a porosity of 27%, compared to 32% when exposed to DI water. In comparison, ZVI grains treated with the acidic drainage had higher porosity （44%） and larger average pore size （2.8 mm）. 10% ZVI PRB barrier material had the highest mean porosity （56%） after exposure to any water chemistry whilst 100% ZVI （W/W） columns always had the lowest （34%） with the 50% ZVI （W/W） in between （40%）. These results agree with previously published PRB field data and simultaneously conducted geochemical monitoring and mass balance calculation, indicating that both the geochemical and hydraulic environment of the PRB play an important role in determining barrier lifespan. This study suggests that X-ray CT image analysis is a powerful tool for studying the detailed inter pores between ZVI grains within PRBs.
基金supported by the National Natural Science Foundation of China(22125603 and 22020102004)Tianjin Municipal Science and Technology Bureau(23 JCYBJC01650,23 JCQNJC01340 and 21 JCJQJC00060)the Fundamental Research Funds for the Central Universities and the Ministry of Education of China(T2017002).
文摘Dealing with groundwater impacted by persistent,low-concentration chlorinated solvents is a major challenge for site remediation,as technologies designed for fast contaminant removal or destruction often are not cost-effective.For long-term plume management,in situ contaminant sequestration using carbonaceous materials is a more viable strategy.Here,we prove the concept that the effectiveness of this approach can be improved by modulating the compositional and surface properties of carbonaceous materials to maximize the synergy between contaminant binding and abiotic transformation.We found that two pine wood biochars pyrolyzed at 600 and 700℃exhibit not only faster adsorption kinetics for 1,1,2,2-tetrachloroethane than those prepared at lower temperatures(500℃and below),but also greater efficacy in enhancing the dehydrochlorination of the contaminant.The higher catalytic efficiency is counterintuitive,as it is commonly accepted that surface carboxyl and phenolic groups are the catalytic sites.With supplementary experiments carried out using modified materials and at varied pH values,we found that the surprisingly higher catalytic activities of these two samples are due to their higher carbonate contents.Interestingly,trichloroethylene,the hydrolysis product,is more adsorptive to the biochars than the parent compound.Thus,by promoting the abiotic transformation,these two biochars enable much more effective plume interception than the less-reactive materials.The findings have important implications for dealing with long-term,persistent groundwater contamination,particularly,the“rebounding”problem often occurring post active site remediation.
基金This paper was supported by Asian Institute at Nankai University,Tianjin,China.
文摘The purpose of this study is to estimate the removal efficiency of As and Cr(VI)by one kind of industrial waste–iron chips,as well as to estimate the effects of typical inorganic anions(sulfate,phosphate,and nitrate),and typical organic anions(citrate,oxalate,and humate)on As or Cr(VI)removal.The results showed that 98%of As(V)and 92%of As(III)could be removed from aqueous phase by the iron chips within 60 min.Compared with As species,Cr(VI)was removed much more rapidly and efficiently with 97%of Cr(VI)being removed within 25 min.The removal efficiency for arsenic was in the order:As(III)(sulfate),As(III)(nitrate)or As(III),As(III)(humate),As(III)(oxalate),As(III)(citrate),As(III)(phosphate),and for chromate was in the order:Cr(VI)(sulfate),Cr(VI)(phosphate)or Cr(VI)(nitrate)or Cr(VI)(oxalate),Cr(VI),Cr(VI)(citrate),Cr(VI)(humate).In all the treatments,pH level increased with time except for As(III),the removal of which was either without anions or in the presence of humate or nitrate.
文摘This paper presents an approach described as“non-traditional”for restoring water quality and ecosystem services that have been degraded as a result of excess nitrogen.It focuses on emerging technologies often referred to as green infrastructure.These technologies may provide cost effective alternatives to traditional,gray infrastructure such as sewering and is likely to provide significant co-benefits including the creation of local jobs,the preservation of real estate values,and habitat enhancement.The paper focuses on the Three Bays estuary on Cape Cod to illustrate the benefits and potential of green infrastructure technologies.The Three Bays estuary is presented as a case study and as a representative example of implementation of the broader Cape Cod Water Quality Management Plan Update(208 Plan Update)-a nationally-recognized watershed planning project designed to provide a pathway for the fifteen towns of Cape Cod to achieve compliance with Section 208 of the Clean Water Act.The Three Bays estuary and embayment system is a scenic Cape Cod bay that hosts sailing,kayaking,swimming and shellfishing and is located in the Town of Barnstable.It is comprised of three primary segments that include West Bay,North Bay and Cotuit Bay.Sub-systems include Prince Cove that flows into North Bay,the Narrows that flows between North Bay and Cotuit Bay and Eel Pond that flows into East Bay(see Figure 1).The Massachusetts Estuaries Project(MEP)is a state-sanctioned watershedmodeling project that assesses the conditions of the state’s estuaries and required restoration goals.Its technical report(2006)indicates that the water quality of the Three Bays system has resulted in seriously degraded to moderately degraded habitat.The system is listed as an impaired water body on the US Environmental Protection Agency(EPA)303d list of impaired waters.An approved Total Maximum Daily Load(TMDL)for nitrogen has been established for the embayment.This assessment is supported by more recent empirical water quality data collected within the embayment.The more current data documents a continuing decline in water quality with more common algae blooms(see Figure 2).
