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1.
Environ Sci Technol ; 54(8): 4963-4973, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32167297

RESUMO

Household drinking water storage is commonly practiced in rural India. Fecal contamination may be introduced at the water source, during collection, storage, or access. Within a trial of a community-level water supply intervention, we conducted five quarterly household-level surveys to collect information about water, sanitation, and hygiene practices in rural India. In a random subsample of households, we tested stored drinking water samples for Escherichia coli, concurrently observing storage and access practices. We conducted 9961 surveys and collected 3296 stored water samples. Stored water samples were frequently contaminated with E. coli (69%), and E. coli levels were the highest during the wet season. Most households contributing two or more drinking water samples had detectable E. coli in some (47%) or all (44%) samples. Predictors of stored water contamination with E. coli included consumption of river water and open defecation; consumption of reverse osmosis-treated water and safe water access practices appeared to be protective. Until households can be reached with on-premises continuous safe water supplies, suboptimal household water storage practices are likely to continue. Improvements to source water quality alone are unlikely to prevent exposure to contaminated drinking water unless attention is also given to improving household water storage, access, and sanitation practices.


Assuntos
Água Potável , Escherichia coli , Humanos , Higiene , Índia , Microbiologia da Água , Qualidade da Água , Abastecimento de Água
2.
Environ Sci Technol ; 51(9): 5127-5136, 2017 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-28391685

RESUMO

The effects of an in situ chemical oxidation (ISCO) treatment aimed predominantly at remediation of chlorinated volatile organic compounds (cVOCs) and perfluoroalkyl acids (PFAAs) co-contaminants were investigated. Soil and groundwater samples were collected before and after an ISCO pilot-scale field test of a peroxone activated persulfate (OxyZone) technology. Statistically significant decreases in PFAA groundwater concentrations were observed in post-treatment samples. Reductions in PFAA aqueous phase concentrations were also supported by decreases in soil concentrations. Importantly, there was no evidence for increased aqueous PFAA concentrations due to mobilization from soil or conversion of precursors into PFAAs. As indicated by chloride data from inside and outside the treatment zone, displacement and/or dilution could not explain the observed decrease in PFAA concentration. Also, relatively constant pH values, due to using a buffered oxidant solution, did not support increased PFAA removal via soil sorption. Overall, the use of peroxone activated persulfate to treat cVOCs had no discernible negative impacts on PFAA co-contaminants at the Site. Rather, the data suggest that PFAA concentrations decreased due to ISCO treatment.


Assuntos
Água Subterrânea/química , Poluentes Químicos da Água , Oxidantes/química , Solo/química , Poluentes do Solo
3.
Environ Sci Technol ; 49(24): 14383-91, 2015 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-26562065

RESUMO

Nonpoint source pollution (NPS) such as stormwater runoff may introduce high loads of bacteria, impairing surface water bodies. The existing filter materials in stormwater best management practices (BMP) are typically not designed to inactivate bacteria. Herein, novel filtration media were extensively tested for microbial load reduction in stormwater runoff. Red cedar wood chips (RC) were amended with different loadings of either 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA) or silver nanoparticles (AgNP). Under batch conditions at 25 °C, log10 removal values (LRV) up to 3.71 ± 0.38 (mean ± standard error) for TPA-RC and 2.25 ± 1.00 for AgNP-RC were achieved for Escherichia coli (E. coli), whereas unmodified RC achieved less than 0.5 LRV. Similar trends were observed at 17.5 °C, however at low temperature (10 °C) no statistically significant difference in E. coli inactivation between modified and unmodified RC was detected. Inactivation kinetic studies show that TPA-RC has higher inactivation rate constants compared to AgNP-RC. Under dynamic flow conditions a mass balance approach indicates that even after remobilization up to 99.8% of E. coli removal using 9 mg/g TPA-RC compared to 64.8% for unmodified RC. This study demonstrates that RC wood chips amended with antimicrobial compounds show promising applications as filtration material for the reduction of microbiological contamination load in stormwater runoff.


Assuntos
Anti-Infecciosos/farmacologia , Poluição Ambiental/análise , Escherichia coli/efeitos dos fármacos , Cupressaceae/química , Cupressaceae/ultraestrutura , Filtração , Cinética , Viabilidade Microbiana/efeitos dos fármacos , Porosidade , Prata , Temperatura
4.
J Environ Qual ; 44(5): 1459-72, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26436263

RESUMO

Bacteria removal efficiencies in a conventional soil-based wastewater treatment system (OWTS) have been modeled to elucidate the fate and transport of bacteria under environmental and operational conditions that might be expected under changing climatic conditions. The HYDRUS 2D/3D software was used to model the impact of changing precipitation patterns, bacteria concentrations, hydraulic loading rates (HLRs), and higher subsurface temperatures at different depths and soil textures. Modeled effects of bacteria concentration shows that greater depth of treatment was required in coarser soils than in fine-textured ones to remove . The initial removal percentage was higher when HLR was lower, but it was greater when HLR was higher. When a biomat layer was included in the transport model, the performance of the system improved by up to 12.0%. Lower bacteria removal (<5%) was observed at all depths under the influence of precipitation rates ranging from 5 to 35 cm, and 35-cm rainfall combined with a 70% increase in HLR. Increased subsurface temperature (23°C) increased bacteria removal relative to a lower temperature range (5-20°C). Our results show that the model is able to effectively simulate bacteria removal and the effect of precipitation and temperature in different soil textures. It appears that the performance of OWTS may be impacted by changing climate.

5.
Ground Water ; 62(4): 513-526, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38131444

RESUMO

The coastal zone, which is the interface between land and sea, is hydrodynamically very active due to the complex interactions of various hydrological controls and variable-density fluids. These forces vary over time, resulting in a state of dynamic equilibrium in the system. The major hydrological processes in coastal aquifer systems are salt water intrusion and submarine groundwater discharge, which are interdependent. Monitoring these complex processes is crucial for sustainable coastal zone management but poses a significant research challenge. In this study, we demonstrate the effectiveness of non-invasive geophysical techniques, specifically the time-lapse electrical resistivity imaging method, in conjunction with groundwater monitoring, for monitoring coastal groundwater dynamics in an unconfined aquifer at varying time scales and hydrogeological settings present at formerly glaciated sites worldwide. We generated two-dimensional baseline salt water intrusion maps for the test site, located on the coast of Rhode Island, USA. The time-lapse electrical resistivity survey method enables the rapid estimation of fresh groundwater discharge. Our approach offers insight into the mechanisms and seasonably variable salt water-freshwater interactions in unconfined heterogeneous aquifers. Although the results are site-specific, their implications are broad and may stimulate other studies related to sea to land pollution (sea water intrusion) and land to sea pollution (groundwater discharge) in heterogeneous coastal aquifer settings.


Assuntos
Monitoramento Ambiental , Água Subterrânea , Movimentos da Água , Monitoramento Ambiental/métodos , Hidrologia/métodos
6.
Water (Basel) ; 15(3): 1-31, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36959915

RESUMO

Recalcitrant groundwater contamination is a common problem at hazardous waste sites worldwide. Groundwater contamination persists despite decades of remediation efforts at many sites because contaminants sorbed or dissolved within low-conductivity zones can back diffuse into high-conductivity zones, and therefore act as a continuing source of contamination to flowing groundwater. A review of the available literature on remediation of plume persistence due to back diffusion was conducted, and four sites were selected as case studies. Remediation at the sites included pump and treat, enhanced bioremediation, and thermal treatment. Our review highlights that a relatively small number of sites have been studied in sufficient detail to fully evaluate remediation of back diffusion; however, three general conclusions can be made based on the review. First, it is difficult to assess the significance of back diffusion without sufficient data to distinguish between multiple factors contributing to contaminant rebound and plume persistence. Second, high-resolution vertical samples are decidedly valuable for back diffusion assessment but are generally lacking in post-treatment assessments. Third, complete contaminant mass removal from back diffusion sources may not always be possible. Partial contaminant mass removal may nonetheless have potential benefits, similar to partial mass removal from primary DNAPL source zones.

7.
Sci Total Environ ; 836: 155641, 2022 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-35513146

RESUMO

Saltwater intrusion (SWI) into coastal aquifers is a growing problem for the drinking water supply of coastal communities worldwide, including for the sustainability of coastal ecosystems depending on freshwater inflow. The interface between freshwater and seawater in coastal aquifers is highly dynamic and is sensitive to changes in the hydraulic gradient between the sea- and groundwater levels. Sea level rise, storm surges, and drought are natural drivers changing the hydrostatic equilibrium between fresh- and saltwater. Coastal aquifers are further stressed by groundwater over-pumping because of the increasing needs of coastal populations. A systematic literature review and analysis of the current state of understanding the SWI drivers is presented, focusing on recent (1980 to 2020) investigations in the contiguous United States (CONUS). Results confirm that SWI is an active research area in CONUS. The drivers of SWI are increasingly better understood and quantified; however, the need for increased monitoring is also recognized. Our study shows that the number of monitoring sites have not increased significantly over the review period. Additionally, geophysical, and geochemical investigation techniques and numerical modeling tools are not utilized to their full potential, and data on SWI is not readily available from some sources. We conclude that there is a need for more SWI monitoring networks and closer multi-disciplinary collaboration, particularly between practitioners in the field and emerging modeling technique experts. Though we focus primarily on CONUS, our insights may be of value to the broader SWI research community and coastal water quality managers around the globe.


Assuntos
Ecossistema , Água Subterrânea , Monitoramento Ambiental , Água Doce , Água Subterrânea/análise , Elevação do Nível do Mar , Água do Mar/análise , Estados Unidos
8.
Mar Pollut Bull ; 174: 113254, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34923404

RESUMO

Microplastics are small plastic particles found ubiquitously in marine environments. In this study, a hybridized method was developed for the extraction of microplastics (45-1000 µm) from sediments using sodium bromide solution for density separation. Method development was tested using spiked microplastics as internal standards. The method was then used to extract microplastics from sediments in Narragansett Bay, Rhode Island, USA. Suspect microplastics were analyzed with Raman spectroscopy. Microplastic abundance ranged from 40 particles/100 g sediment to 4.6 million particles/100 g sediment (wet weight). Cellulose acetate fibers were the most abundant microplastic. These results are some of the first data for microplastics in Rhode Island sediments.


Assuntos
Microplásticos , Poluentes Químicos da Água , Baías , Monitoramento Ambiental , Sedimentos Geológicos , Plásticos , Rhode Island , Poluentes Químicos da Água/análise
9.
Front Chem ; 8: 641, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32850657

RESUMO

The use of chlorine dioxide to disinfect drinking water and ameliorate toxic components of wastewater has significant advantages in terms of providing safe water. Nonetheless, significant drawbacks toward such usage remain. These drawbacks include the fact that toxic byproducts of the disinfection agents are often formed, and the complete removal of such agents can be challenging. Reported herein is one approach to solving this problem: the use of α-cyclodextrin to affect the product distribution in chlorine dioxide-mediated decomposition of organic pollutants. The presence of α-cyclodextrin leads to markedly more oxidation and less aromatic chlorination, in a manner that is highly dependent on analyte structure and other reaction conditions. Mechanistic hypotheses are advanced to explain the cyclodextrin effect, and the potential for use of α-cyclodextrin for practical wastewater treatment is also discussed.

10.
Mar Pollut Bull ; 159: 111507, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32763561

RESUMO

Microplastics (MPs) are small (<5 mm) plastic particles which pose a threat to marine ecosystems. Identifying MPs is crucial for understanding their fate and effects. Many MP extraction methods exist, but procedural differences prevent meaningful comparisons across datasets. This method comparison examines the efficiency of five methods for extracting MPs (40-710 µm) from marine sediments. Known quantities of MPs were spiked into sediments. The MPs were extracted and enumerated to demonstrate percent recovery. Findings determined that sediment matrix, MP properties, and extraction method affect the percent recovery of MPs from sediments. Average recoveries of spiked microplastics were between 0 and 87.4% and varied greatly by sediment type, microplastic, and method of extraction. In general, larger particle and lower density MPs were more effectively recovered. Marine sediments low in organic matter and with larger grain size also had higher percent recoveries of MPs. These findings support the need for method optimization and unified procedures.


Assuntos
Plásticos , Poluentes Químicos da Água/análise , Ecossistema , Monitoramento Ambiental , Sedimentos Geológicos , Microplásticos
11.
Am J Trop Med Hyg ; 102(3): 497-506, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31264565

RESUMO

Sustainable and low-cost methods for delivery of safe drinking water in resource-limited settings remain suboptimal, which contributes to global diarrhea morbidity. We aimed to assess whether delivery of riverbank filtration-treated water to newly installed water storage tanks (improved quality and access, intervention condition) reduced reported diarrhea in comparison to delivery of unfiltered river water (improved access alone, control condition) in rural Indian villages. We used a stepped wedge cluster-randomized trial (SW-CRT) design involving four clusters (villages). Selection criteria included village size, proximity to a river, and lack of existing or planned community-level safe water sources. All adults and children were eligible for enrollment. All villages started in the control condition and were sequentially randomized to receive the intervention at 3-month intervals. Our primary outcome was 7-day-period prevalence of self- or caregiver-reported diarrhea, measured at 3-month intervals (five time points). Analysis was by intention to treat. Because blinding was not possible, we incorporated questions about symptoms unrelated to water consumption to check response validity (negative control symptoms). We measured outcomes in 2,222 households (9,836 participants). We did not find a measurable reduction in diarrhea post-intervention (RR: 0.98 [95% CI: 0.24-4.09]); possible explanations include low intervention uptake, availability of other safe water sources, low baseline diarrheal prevalence, and reporting fatigue. Our study highlights both the difficulties in evaluating the impact of real-world interventions and the potential for an optimized SW-CRT design to address budgetary, funding, and logistical constraints inherent in such evaluations.


Assuntos
Diarreia/epidemiologia , Diarreia/prevenção & controle , Filtração/métodos , População Rural , Abastecimento de Água/normas , Adolescente , Adulto , Criança , Pré-Escolar , Análise por Conglomerados , Feminino , Humanos , Índia/epidemiologia , Masculino , Rios , Purificação da Água , Adulto Jovem
12.
J Hazard Mater ; 380: 120875, 2019 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-31336268

RESUMO

This research investigates the formation of free radical intermediates in an advanced oxidation processes (AOP) capable of destroying recalcitrant contaminants. The AOP studied is marketed as OxyZone® and relies on the premise of successful persulfate activation by peroxone (hydrogen peroxide plus ozone) and the formation of free radicals. The goal of this research was to determine which radicals are involved in the treatment of the model contaminant, 1,4-dioxane, which is a ubiquitous, recalcitrant organic groundwater pollutant difficult to destroy by conventional oxidants. In a parallel study, the peroxone activation persulfate (PAP) solution investigated herein rapidly degraded 1,4-dioxane. The degradation rates of 1,4-dioxane were measured as a function the oxidant:contaminant ratio. Its degradation products or mechanism were not investigated, however. Electron paramagnetic resonance (EPR) spectroscopy spin trapping was used to identify radicals produced in the oxidant solution, its active ingredients, and their possible interplay. The data presented herein indicate that the combination of hydrogen peroxide and dissolved ozone in the presence of persulfate results in the co-occurrence hydroxyl and sulfate radicals and possibly superoxide/hydroperoxyl radicals. These findings progress our understanding of the chemical radicals formed during PAP treatment of aqueous phase contaminants, such as 1,4-dioxane.

13.
J Contam Hydrol ; 208: 68-78, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29289350

RESUMO

In a field study, aqueous cyclodextrin (CD) was investigated for its ability to extract chlorinated volatile organic compounds (cVOC), such as trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), and dichloroethene (DCE) through in-situ flushing of a sandy aquifer. After cessation of aquifer flushing, a plume of CD was left. Changes in CD, cVOC, and inorganic terminal electron acceptors (TEAs) (DO, nitrate, sulfate, iron) were monitored in four rounds of wellwater sampling (20, 210, 342, and 425days after cessation of active pumping). Post-CD flushing VOC levels rebounded (850% for TCE, 190% for TCA, and 53% for DCE) between the first two sampling rounds, apparently due to rate-limited desorption from aquifer media and dissolution from remaining NAPL. However, substantial reduction in the mass of TCE (6.3 to 0.11mol: 98%) and TCA (2.8 to 0.73mol: 74%) in groundwater was observed between 210 and 425days. DCE should primarily be produced from the degradation of TCE and is expected to subsequently degrade to chloroethene. Since DCE levels decreased only slightly (0.23 to 0.17mol: 26%), its degradation rate should be similar to that produced from the decaying TCE. Cyclodextrin was monitored starting from day 210. The mass of residual CD (as measured by Total Organic Carbon) decreased from 150mol (day 210) to 66 (day 425) (56% decrease). The naturally anaerobic zone within the aquifer where residual CD mass decreased coincided with a loss of other major potential TEAs: nitrate (97% loss), sulfate (31%) and iron (31%). In other studies, TCE and 1,1,1-TCA have been found to be more energetically favorable TEAs than sulfate and iron and their degradation via reductive dechlorination has been found to be enhanced by the fermentation of carbohydrates. Such processes can explain these observations, but more investigation is needed to evaluate whether residual levels of CD can facilitate the anaerobic degradation of chlorinated VOCs.


Assuntos
Ciclodextrinas/química , Água Subterrânea/química , Solventes/química , Poluentes Químicos da Água/química , Biodegradação Ambiental , Ciclodextrinas/metabolismo , Dicloroetilenos/química , Dicloroetilenos/metabolismo , Fermentação , Água Subterrânea/análise , Halogenação , Ferro , Solventes/análise , Tricloroetanos/química , Tricloroetanos/metabolismo , Tricloroetileno/química , Tricloroetileno/metabolismo , Virginia , Poluentes Químicos da Água/metabolismo
15.
J Contam Hydrol ; 91(1-2): 43-57, 2007 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-17125885

RESUMO

A significant amount of contamination enters water bodies via stormwater runoff and, to reduce the amount of pollution, retention ponds are installed at many locations. While effective for treating suspended solids, retention ponds do not effectively remove dissolved constituents, such as polycyclic aromatic hydrocarbons (PAH). Previous laboratory studies demonstrates that aspen wood cuttings can be utilized to enhance the removal of dissolved contaminants. The objective of this pilot-scale field test was to determine if wood filters could effectively remove dissolved PAH from the runoff under field conditions. Four wood filter tests were conducted, lasting from 1 to 9 weeks, to determine the degree of PAH attenuation from the aqueous phase as a function of wood mass, residence times, and seasonable changes. The prototype wood filters removed on average between 18.5% and 35.6% (up to 66.5%) of the dissolved PAH contaminants. The PAH removal effectiveness of the wood was not affected by changes in water temperature or pH. The filter effectiveness increased with filter size and was highest in continuously submerged parts of the filter system. Also, heavier molecular weight PAH compounds (e.g. chrysene) were more effectively removed than lighter molecular weight compounds. Disassociation of weakly particle-bound PAH from the filter was identified as the most likely cause for a temporary drop of the wood filter's PAH load during intense storms. Simple filter design changes are likely to double the filter effectiveness and alleviate the disassociation problem.


Assuntos
Cidades , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Chuva , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Filtração , Concentração de Íons de Hidrogênio , Tamanho da Partícula , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Temperatura , Fatores de Tempo , Poluentes Químicos da Água/toxicidade , Purificação da Água/instrumentação , Madeira
16.
J Contam Hydrol ; 196: 1-9, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27993469

RESUMO

Recalcitrant organic groundwater contaminants, such as 1,4-dioxane, may require strong oxidants for complete mineralization. However, their efficacy for in-situ chemical oxidation (ISCO) is limited by oxidant decay and reactivity. Hydroxypropyl-ß-cyclodextrin (HPßCD) was examined for its ability to stabilize aqueous-phase ozone (O3) and prolong oxidation potential through inclusion complex formation. Partial transformation of HPßCD by O3 was observed. However, HPßCD proved to be sufficiently recalcitrant, because it was only partially degraded in the presence of O3. The formation of a HPßCD:O3 clathrate complex was observed, which stabilized decay of O3. The presence of HPßCD increased the O3 half-life linearly with increasing HPßCD:O3 molar ratio. The O3 half-life in solutions increased by as much as 40-fold relative to HPßCD-free O3 solutions. Observed O3 release from HPßCD and indigo oxidation confirmed that the formation of the inclusion complex is reversible. This proof-of-concept study demonstrates that HPßCD can complex O3 while preserving its reactivity. These results suggest that the use of clathrate stabilizers, such as HPßCD, can support the development of a facilitated-transport enabled ISCO for the O3 treatment of groundwater contaminated with recalcitrant compounds.


Assuntos
Dioxanos/análise , Água Subterrânea/química , Ozônio/química , Poluentes Químicos da Água/análise , beta-Ciclodextrinas/química , 2-Hidroxipropil-beta-Ciclodextrina , Dioxanos/química , Recuperação e Remediação Ambiental , Meia-Vida , Modelos Teóricos , Oxirredução , Ozônio/análise , Soluções , Espectrometria de Massas por Ionização por Electrospray , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/química , beta-Ciclodextrinas/análise
17.
BMJ Open ; 7(3): e015036, 2017 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-28314746

RESUMO

INTRODUCTION: Diarrhoea is a leading cause of death globally, mostly occurring as a result of insufficient or unsafe water supplies, inadequate sanitation and poor hygiene. Our study aims to investigate the impact of a community-level hygiene education program and a water quality intervention using riverbank filtration (RBF) technology on diarrhoeal prevalence. METHODS AND ANALYSIS: We have designed a stepped wedge cluster randomised trial to estimate the health impacts of our intervention in 4 rural villages in Karnataka, India. At baseline, surveys will be conducted in all villages, and householders will receive hygiene education. New pipelines, water storage tanks and taps will then be installed at accessible locations in each village and untreated piped river water will be supplied. A subsequent survey will evaluate the impact of hygiene education combined with improved access to greater water volumes for hygiene and drinking purposes (improved water quantity). Villages will then be randomly ordered and RBF-treated water (improved water quality) will be sequentially introduced into the 4 villages in a stepwise manner, with administration of surveys at each time point. The primary outcome is a 7-day period prevalence of self-reported diarrhoea. Secondary outcomes include self-reported respiratory and skin infections, and reported changes in hygiene practices, household water usage and water supply preference. River, tank and tap water from each village, and stored water from a subset of households, will be sampled to assess microbial and chemical quality. ETHICS AND DISSEMINATION: Ethics approval was obtained from the Monash University Human Research Ethics Committee in Australia and The Energy and Resources Institute Institutional Ethics Committee in India. The results of the trial will be presented at conferences, published in peer-reviewed journals and disseminated to relevant stakeholders. This study is funded by an Australian National Health and Medical Research Council (NHMRC) project grant. TRIAL REGISTRATION NUMBER: ACTRN12616001286437; pre-results.


Assuntos
Diarreia/prevenção & controle , Filtração , Educação em Saúde , Higiene , Engenharia Sanitária , Qualidade da Água , Abastecimento de Água , Água Potável , Características da Família , Humanos , Índia , Prevalência , Características de Residência , Rios , População Rural , Inquéritos e Questionários , Tecnologia , Água
18.
Chemosphere ; 144: 728-35, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26408980

RESUMO

1,4-dioxane is often found as a co-contaminant with chlorinated volatile organic compounds (VOCs) at solvent release sites such as landfills, solvent recycling facilities, or fire training areas. Historically, soil and groundwater samples were not routinely analyzed for 1,4-dioxane and therefore the number of known 1,4-dioxane sites is still increasing. Due to its co-occurrence with chlorinated compounds, remediation strategies are needed that simultaneously treat both 1,4-dioxane as well as chlorinated VOC co-contaminants. In this proof of concept laboratory study, the fate of 1,4-dioxane was examined during the targeted destruction of aqueous phase VOC, using a peroxone activated persulfate (PAP) chemical oxidation method. Bench-scale experiments were carried out to evaluate the treatability of 1,4-dioxane as both a single-contaminant and in the presence of trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1-TCA). Possible dependencies on oxidant concentration and reaction kinetics were studied. The oxidative destruction of 1,4-dioxane, TCE and 1,1,1-TCA in single-contaminant batch systems followed pseudo-first-order reaction kinetics and even at the most dilute oxidant concentration lasted for at least 13 days. The rate of oxidation for each contaminant increased linearly with increasing persulfate concentration over the range of oxidant concentrations tested. The rate of oxidative destruction, from most easily degraded to least, was: TCE > 1,4-dioxane > 1,1,1-TCA. Oxidation rates were up to 87% slower in a mixture of these three compounds. Although additional tests are necessary, our data suggest that PAP oxidation of 1,4-dioxane might aid in the cleanup of VOC contaminated sites.


Assuntos
Dioxanos/química , Halogenação , Peróxido de Hidrogênio/química , Ozônio/química , Solventes/química , Sulfatos/química , Poluentes Químicos da Água/química , Água Subterrânea/química , Cinética , Oxirredução , Tricloroetanos/química , Tricloroetileno/química
19.
PLoS One ; 11(6): e0158292, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27355369

RESUMO

Most of the non-point source nitrogen (N) load in rural areas is attributed to onsite wastewater treatment systems (OWTS). Nitrogen compounds cause eutrophication, depleting the oxygen in marine ecosystems. OWTS rely on physical, chemical and biological soil processes to treat wastewater and these processes may be affected by climate change. We simulated the fate and transport of N in different types of OWTS drainfields, or soil treatment areas (STA) under current and changing climate scenarios, using 2D/3D HYDRUS software. Experimental data from a mesocosm-scale study, including soil moisture content, and total N, ammonium (NH4+) and nitrate (NO3-) concentrations, were used to calibrate the model. A water content-dependent function was used to compute the nitrification and denitrification rates. Three types of drainfields were simulated: (1) a pipe-and-stone (P&S), (2) advanced soil drainfields, pressurized shallow narrow drainfield (PSND) and (3) Geomat (GEO), a variation of SND. The model was calibrated with acceptable goodness-of-fit between the observed and measured values. Average root mean square error (RSME) ranged from 0.18 and 2.88 mg L-1 for NH4+ and 4.45 mg L-1 to 9.65 mg L-1 for NO3- in all drainfield types. The calibrated model was used to estimate N fluxes for both conventional and advanced STAs under current and changing climate conditions, i.e. increased soil temperature and higher water table. The model computed N losses from nitrification and denitrification differed little from measured losses in all STAs. The modeled N losses occurred mostly as NO3- in water outputs, accounting for more than 82% of N inputs in all drainfields. Losses as N2 were estimated to be 10.4% and 9.7% of total N input concentration for SND and Geo, respectively. The highest N2 losses, 17.6%, were estimated for P&S. Losses as N2 increased to 22%, 37% and 21% under changing climate conditions for Geo, PSND and P&S, respectively. These findings can provide practitioners with guidelines to estimate N removal efficiencies for traditional and advanced OWTS, and predict N loads and spatial distribution for identifying non-point sources. Our results show that N losses on OWTS can be modeled successfully using HYDRUS. Furthermore, the results suggest that climate change may increase the removal of N as N2 in the drainfield, with the magnitude of the effect depending on a drainfield type.


Assuntos
Nitrogênio/análise , Solo/química , Águas Residuárias/análise , Purificação da Água/métodos , Compostos de Amônio/química , Calibragem , Clima , Mudança Climática , Simulação por Computador , Desnitrificação , Condutividade Elétrica , Monitoramento Ambiental , Eutrofização , Água Subterrânea/química , Concentração de Íons de Hidrogênio , Nitratos/química , Nitrogênio/química , Oxigênio/química , Software , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise
20.
Chemosphere ; 54(7): 831-9, 2004 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-14637340

RESUMO

Roadway runoff derived polynuclear aromatic hydrocarbons (PAHs) impact the quality of surface and ground water. Inexpensive aspen wood fibers have been investigated as a means to remove dissolved PAH under laboratory conditions. Our isotherm experiments demonstrated that the uptake of naphthalene, fluorene, anthracene, and pyrene required up to 12.5 days to reach equilibrium. Aspen wood-water sorption coefficients, Kww, were linearly correlated to octanol-water partition coefficients and the molecular weight of the studied PAH compounds. The correlation between Kww and molecular weight was the most significant. Column experiments were carried out to study the sorption and desorption of fluorene, anthracene, and pyrene under dynamic conditions. The results indicate linear sorption, but non-linear desorption behavior. The degree of desorption was inversely correlated to a compound's hydrophobicity. Flow interruption experiments showed that sorption and desorption was rate limited. A mass balance of the sorption and desorption tests indicated that sorptive uptake exceeded desorptive release over a given number of pore volumes. Further, absolute mass-removal efficiency increased with the molecular weight and hydrophobicity of the PAH compound. Batch and column studies demonstrated that aspen wood has the potential to become an effective remedial agent for PAH in stormwater runoff or other PAH contaminated waters.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos/química , Purificação da Água/métodos , Adsorção , Interações Hidrofóbicas e Hidrofílicas , Cinética , Peso Molecular , Populus/química , Madeira
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