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1.
Br J Clin Pharmacol ; 90(2): 378-387, 2024 02.
Artigo em Inglês | MEDLINE | ID: mdl-37879905

RESUMO

The prevalence of undocumented medical treatments among children is a significant issue, as well as many EU countries lack access to newly developed children-friendly medicines. Consequently, there is a pressing need for supplementary resources that can facilitate informed decision-making regarding children's medication. We therefore aim to describe the process of establishing a children's Drug and Therapeutics Committee (cDTC), as well as the preparing and implementation of recommendations for children in the capital region of Denmark. Following the guidelines outlined by the World Health Organization, we established a cDTC, and recommendations for paediatric medication practice were constructed from assessments of medication use patterns among children in the capital region between 2019 and 2021. The recommendations were meticulously crafted based on evaluation of the current marketing authorization landscape and existing best available evidence. In 2019, the capital region established the first cDTC supported by expert councils and an editorial board. A total of 2429 purchase item numbers covering 1 222 846 defined daily doses and 592 088 purchased packages covering 10 200 000 defined daily doses were identified in the secondary and primary sectors, respectively. Three comprehensive lists covering recommendations for newborns and children were published between 2021 and 2020 totaling 331 recommended pharmaceutical products. The recommendations primarily intended for use in the secondary healthcare sector were implemented through the revision of 38 paediatric- and six neonatal product ranges throughout capital region. In conclusion, recommendation lists for children governed by a cDTC provide a rational auxiliary tool that can be immediately implemented in the clinic.


Assuntos
Comitê de Farmácia e Terapêutica , Criança , Recém-Nascido , Humanos , Análise Custo-Benefício
2.
Water Environ Res ; 88(8): 747-55, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27456145

RESUMO

The present study focuses on anaerobic organic matter transformation processes in force mains for the purpose of improving existing sewer process models. Wastewater samples were obtained at 100 m intervals from a 1 km long pilot scale force main and measured for several wastewater parameters. Transformation rates for selected parameters were calculated and their spatial variability analyzed. In terms of electron transfer, fermentation was the most significant process, resulting in a net volatile fatty acid formation of 0.83 mmol/L. Sulfate reduction resulted in a production of 0.73 mmol/L of inorganic sulfide. Methanogenesis was negligable in all experiments despite an anaerobic residence time of more than 30 hours. As a result of the anaerobic processes, the wastewater pH decreased by approximately one pH unit, resulting in a corresponding increase in the fraction of molecular hydrogen sulfide. A significant spatial variablilty was observed for the average transformation rates of all parameters.


Assuntos
Bactérias Anaeróbias/metabolismo , Fermentação , Águas Residuárias/microbiologia , Biotransformação , Carbono/metabolismo , Concentração de Íons de Hidrogênio , Metano/metabolismo , Compostos Orgânicos/metabolismo , Esgotos , Sulfatos/metabolismo , Águas Residuárias/análise
3.
Water Environ Res ; 87(11): 1980-9, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26564586

RESUMO

An extensive measuring campaign targeted on sewer odor problems was undertaken in San Francisco. It was assessed whether a conceptual sewer process model could reproduce the measured concentrations of total sulfide in the wastewater and H2S gas in the sewer atmosphere, and to which degree such simulations have potential for further improving odor and sulfide management. The campaign covered measurement of wastewater sulfide by grab sampling and diurnal sampling, and H2S gas in the sewer atmosphere was logged. The tested model was based on the Wastewater Aerobic/Anaerobic Transformations in Sewers (WATS) sewer process concept, which never had been calibrated to such an extensive dataset. The study showed that the model was capable of reproducing the general levels of wastewater sulfide, wastewater pH, and sewer H2S gas. It could also reproduce the general variability of these parameters, albeit with some uncertainty. It was concluded that the model could be applied for the purpose in mind.


Assuntos
Modelos Teóricos , Esgotos/análise , Sulfetos/análise , Drenagem Sanitária , Concentração de Íons de Hidrogênio , Odorantes , São Francisco
4.
Pharmacol Res Perspect ; 11(1): e01037, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36545691

RESUMO

There is currently insufficient knowledge of gestational age dependent medicine disposition in neonates. Accordingly, the use of off-label medication, i.e., use of medicines outside its approved marketing authorization, is high in the neonatal departments. By using data from the Danish National Pharmaceutical Hospital Purchase Database, we identified the most commonly occurring medications and calculated the on/off-label ratios for premature and term neonates. Data was extracted on ATC level 5 and based on defined daily doses as per WHO. Data covered the 4 high-level NICUs and 10 of 13 of the intermediate/standard level Danish neonatal departments. Of the identified medication, 87% and 70% did not have approved marketing authorization for use in premature and full-term neonates, respectively. Furthermore, one-fifth of the top 100 medicines did not have a (Danish) marketing license. Overall, off-label medication was widespread covering virtually all ATC groups and no ATC group had an off-label level lower than 50% (range 50%-100%). Finally, in 21% of medications, additives from 8 different chemical groups with potential deleterious effects for neonates were identified. In conclusion, off-label medication in the Danish neonatal departments is widespread. The pharmaceutical industry is unlikely to solve this problem, and we may for a very long time be occasionally forced to use off-label medication. Practical solution must therefore come from multidisciplinary clinical and academic collaboration. Use of formulation list as guidance for prescriptions and NICU-friendly galenic formulations may mitigate the problem temporarily while waiting for definitive studies.


Assuntos
Uso Off-Label , Nascimento Prematuro , Recém-Nascido , Feminino , Humanos , Hospitais , Padrões de Prática Médica , Dinamarca
5.
Water Environ Res ; 84(3): 265-73, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22755494

RESUMO

Hydrogen sulfide adsorption and oxidation by corroding concrete surfaces at different air-flows were quantified using a pilot-scale sewer reactor. The setup was installed in an underground sewer research station with direct access to wastewater. Hydrogen sulfide gas was injected into the headspace of the sewer reactor once per hour in peak concentrations of approximately 500 ppmv. The investigated range of sewer air-flows was representative for natural ventilated sewer systems, and covered both laminar and turbulent conditions. The experiments demonstrated a significant effect of sewer air-flow on the kinetics of hydrogen sulfide removal from the sewer headspace. From the lowest to the highest air-flow investigated, the rate of adsorption and oxidation increased more than threefold. At all air-flows, the reaction kinetics followed a simple n-th order rate equation with a reaction order of 0.8. The effect of air-flow on hydrogen sulfide adsorption and oxidation kinetics was quantified by a simple empirical equation.


Assuntos
Sulfeto de Hidrogênio/isolamento & purificação , Esgotos , Eliminação de Resíduos Líquidos , Adsorção , Reatores Biológicos , Cinética , Temperatura
6.
Water Environ Res ; 84(7): 605-16, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22876483

RESUMO

Five sorption materials were studied with a focus on polishing pretreated stormwater: crushed limestone, shell-sand, zeolite, and two granulates of olivine. These materials are commercially available at comparatively low cost and have been subjected to a minimum of modification from their natural states. The sorbents were tested for phosphorus, arsenic, cadmium, chromium, copper, nickel, lead, and zinc at concentration and conditions relevant for typical stormwater. The materials were tested for sorption capacity and kinetics. Desorption was tested under neutral and alkaline conditions and in the presence of chloride. For most sorbent/sorbate combinations, significant sorption occurred within the first minutes of contact between sorbent and sorbate. Treatment to the low microgram per liter range could be achieved by contact times of less than 1 hour. The study indicated that sorption filters can be designed for long life expectancy at comparatively low cost by applying the materials tested.


Assuntos
Metais/química , Fósforo/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Purificação da Água/instrumentação , Adsorção , Chuva , Purificação da Água/métodos
7.
Water Sci Technol ; 66(8): 1728-34, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22907458

RESUMO

A conceptual model to simulate transformations of organic matter and sulfur compounds in the wastewater phase of sewer networks under anaerobic conditions was developed. For calibration and validation of the model, a series of laboratory experiments on generation of readily biodegradable organic matter and sulfide under anaerobic conditions in samples of wastewater was conducted. Compared with previous studies, the proposed model includes sulfate reduction in the bulk water as well as a revised description of fermentation processes. Substrate affinity for fermentative bacteria was found to be significantly higher than what has been proposed in the activated sludge model, resulting in higher fermentation rates at low substrate concentrations. The findings of the study are important to understand formation of volatile organic compounds and odorous substances in sewers.


Assuntos
Esgotos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Anaerobiose
8.
Artigo em Inglês | MEDLINE | ID: mdl-22571535

RESUMO

Dissolved and colloidal bound pollutants are generally poorly removed from stormwater in wet detention ponds. These fractions are, however, the most bio-available, and therefore three wet detention ponds were amended with planted sand filters, sorption filters and addition of precipitation chemicals to enhance the removal of dissolved pollutants and pollutants associated with fine particles and colloids. The three systems treated runoff from industrial, residential and combined (residential and highway) catchments and had permanent volumes of 1,990, 6,900 and 2,680 m(3), respectively. The treatment performance of the ponds for elimination of total suspended solids (TSS), total nitrogen (Tot-N), total phosphorous (Tot-P), PO(4)-P, Pb, Zn, Cd, Ni, Cr, Cu, Hg were within the range typically reported for wet detention ponds, but the concentrations of most of the pollutants were efficiently reduced by the planted sand filters at the outlets. The sorption filters contributed to further decrease the concentration of PO(4)-P from 0.04 ± 0.05 to 0.01 ± 0.01 mg L(-1) and were also efficient in removing heavy metals. Dosing of iron sulphate to enrich the bottom sediment with iron and dosing of aluminium salts to the inlet water resulted in less growth of phytoplankton, but treatment performance was not significantly affected. Heavy metals (Pb, Zn, Cd, Ni, Cr and Cu) accumulated in the sediment of the ponds. The concentrations of Zn, Ni, Cu and Pb in the roots of the wetland plants were generally correlated to the concentrations in the sediments. Among 13 plant species investigated, Rumex hydrolapathum accumulated the highest concentrations of heavy metals in the roots (Concentration Factor (CF) of 4.5 and 5.9 for Zn and Ni, respectively) and Iris pseudacorus the lowest (CF < 1). The translocation of heavy metals from roots to the aboveground tissues of plants was low. Therefore the potential transfer of heavy metals from the metal-enriched sediment to the surrounding ecosystem via plant uptake and translocation is negligible.


Assuntos
Cidades , Monitoramento Ambiental/estatística & dados numéricos , Água Doce/análise , Sedimentos Geológicos/análise , Chuva , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Absorção , Coloides/análise , Dinamarca , Monitoramento Ambiental/métodos , Metais Pesados/análise , Metais Pesados/farmacocinética , Nitrogênio/análise , Fósforo/análise , Rumex/metabolismo , Análise Espectral
9.
Water Environ Res ; 83(6): 532-40, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21751712

RESUMO

Anaerobic transformations of wastewater organic matter in the bulk water phase of collection system networks were investigated in laboratory-scale experiments. The wastewater was collected from three locations, which provided samples with different characteristics, ranging from young to mature. Hydrolysis, fermentation, and sulfate reduction were identified as the most important anaerobic processes. Significant quantities of readily biodegradable substrate were produced by hydrolysis of complex organic substrates. The readily biodegradable substrate was further fermented into volatile fatty acids (VFA). The rate of fermentation was found to be limited by the hydrolysis process. The readily biodegradable substrate generated was almost entirely composed of VFA, primarily acetic and propionic acids. A production of sulfide was observed in all experiments, demonstrating that part of the readily biodegradable substrate was consumed by sulfate respiration. The sulfide production was most pronounced in mature wastewater that had previously undergone extended anaerobic transport.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Anaerobiose , Reatores Biológicos , Fatores de Tempo , Água/química , Poluentes Químicos da Água , Purificação da Água
10.
Sci Total Environ ; 407(8): 2989-95, 2009 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-19193392

RESUMO

The high pollution load in wastewater at the beginning of a rain event is commonly known to originate from the erosion of sewer sediments due to the increased flow rate under storm weather conditions. It is essential to characterize the biodegradability of organic matter during a storm event in order to quantify the effect it can have further downstream to the receiving water via discharges from Combined Sewer Overflow (CSO). The approach is to characterize the pollutograph during first flush. The pollutograph shows the variation in COD and TSS during a first flush event. These parameters measure the quantity of organic matter present. However these parameters do not indicate detailed information on the biodegradability of the organic matter. Such detailed knowledge can be obtained by dividing the total COD into fractions with different microbial properties. To do so oxygen uptake rate (OUR) measurements on batches of wastewater have shown itself to be a versatile technique. Together with a conceptual understanding of the microbial transformation taking place, OUR measurements lead to the desired fractionation of the COD. OUR results indicated that the highest biodegradability is associated with the initial part of a storm event. The information on physical and biological processes in the sewer can be used to better manage sediment in sewers which can otherwise result in depletion of dissolved oxygen in receiving waters via discharges from CSOs.


Assuntos
Sedimentos Geológicos/química , Esgotos/química , Poluentes da Água/metabolismo , Poluição da Água/análise , Biodegradação Ambiental , Sedimentos Geológicos/microbiologia , Oxigênio/química , Chuva , Esgotos/microbiologia , Eliminação de Resíduos Líquidos
11.
Water Environ Res ; 81(4): 365-73, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19445325

RESUMO

Abiotic and biotic oxidation of hydrogen sulfide related to concrete corrosion was studied in corrosion products originating from a sewer manhole. The concrete corrosion products were suspended in an acidic solution, mimicking the conditions in the pore water of corroded concrete. The removal of hydrogen sulfide and dissolved oxygen was measured in parallel in the suspension, upon which the suspension was sterilized and the measurement repeated. The results revealed the biotic oxidation to be fast compared with the abiotic oxidation. The stoichiometry of the hydrogen sulfide oxidation was evaluated using the ratio between oxygen and hydrogen sulfide uptake. The ratio for the biotic oxidation pointed in the direction of elemental sulfur being formed as an intermediate in the oxidation of hydrogen sulfide to sulfuric acid. The experimental results were applied to suggest a hypothesis and a mathematical model describing the hydrogen sulfide oxidation pathway in a matrix of corroded concrete.


Assuntos
Materiais de Construção , Corrosão , Sulfeto de Hidrogênio/química , Modelos Teóricos , Oxirredução
12.
Water Res ; 42(15): 4206-14, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18723203

RESUMO

Hydrogen sulfide oxidation on sewer pipe surfaces was investigated in a pilot scale experimental setup. The experiments were aimed at replicating conditions in a gravity sewer located immediately downstream of a force main where sulfide related concrete corrosion and odor is often observed. During the experiments, hydrogen sulfide gas was injected intermittently into the headspace of partially filled concrete and plastic (PVC and HDPE) sewer pipes in concentrations of approximately 1,000 ppm(v). Between each injection, the hydrogen sulfide concentration was monitored while it decreased because of adsorption and subsequent oxidation on the pipe surfaces. The experiments showed that the rate of hydrogen sulfide oxidation was approximately two orders of magnitude faster on the concrete pipe surfaces than on the plastic pipe surfaces. Removal of the layer of reaction (corrosion) products from the concrete pipes was found to reduce the rate of hydrogen sulfide oxidation significantly. However, the rate of sulfide oxidation was restored to its background level within 10-20 days. A similar treatment had no observable effect on hydrogen sulfide removal in the plastic pipe reactors. The experimental results were used to model hydrogen sulfide oxidation under field conditions. This showed that the gas-phase hydrogen sulfide concentration in concrete sewers would typically amount to a few percent of the equilibrium concentration calculated from Henry's law. In the plastic pipe sewers, significantly higher concentrations were predicted because of the slower adsorption and oxidation kinetics on such surfaces.


Assuntos
Sulfeto de Hidrogênio/química , Odorantes , Esgotos/química , Materiais de Construção , Corrosão , Oxirredução , Projetos Piloto , Plásticos/química , Eliminação de Resíduos Líquidos/instrumentação
13.
Sci Total Environ ; 394(1): 162-70, 2008 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-18281080

RESUMO

Hydrogen sulfide absorption and oxidation by corroding concrete surfaces was quantified in a test rig consisting of 6 concrete pipes operated under sewer conditions. The test rig was placed in an underground sewer monitoring station with access to fresh wastewater. Hydrogen sulfide gas was injected into the pipe every 2nd hour to peak concentrations around 1000 ppm. After some months of operation, the hydrogen sulfide became rapidly oxidized by the corroding concrete surfaces. At hydrogen sulfide concentrations of 1000 ppm, oxidation rates as high as 1 mg S m(-2) s(-1) were observed. The oxidation process followed simple nth order kinetics with a process order of 0.45-0.75. Extrapolating the results to gravity sewer systems showed that hydrogen sulfide oxidation by corroding concrete is a fast process compared to the release of hydrogen sulfide from the bulk water, resulting in low gas concentrations compared with equilibrium. Balancing hydrogen sulfide release with hydrogen sulfide oxidation at steady state conditions demonstrated that significant corrosion rates--several millimeters of concrete per year--can potentially occur at hydrogen sulfide gas phase concentrations well below 5-10 ppm. The results obtained in the study advances the knowledge on prediction of sewer concrete corrosion and the extent of odor problems.

14.
Water Environ Res ; 80(4): 380-4, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18536490

RESUMO

Sulfide precipitation by addition of iron salts is a widely used strategy for sulfide control in wastewater collection systems. Several parameters, such as pH, oxidation-reduction conditions, and reactant concentrations, are known to affect the feasibility of the method. However, their combined effects are difficult to predict for complex media, such as wastewater. This study investigates the effect of pH and reactant concentrations on the efficiency of iron sulfide precipitation in anaerobic municipal wastewater. Laboratory experiments showed that, when the pH was below 7, typically less than 40% of the added ferrous iron reacted by sulfide precipitation, although sulfide was in excess. However, when the pH was above 8, almost complete precipitation of all the added ferrous iron was observed. Varying the ferric-iron-to-ferrous-iron ratio demonstrated that improved efficiency could be achieved when using a 1:1 mixture of ferric chloride and ferrous sulfate.


Assuntos
Ferro/química , Esgotos/química , Sulfetos/química , Eliminação de Resíduos Líquidos/métodos , Precipitação Química , Concentração de Íons de Hidrogênio , Odorantes
15.
Water Environ Res ; 80(2): 118-26, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18330221

RESUMO

A conceptual model that simulates the formation and fate of odorous substances in branched collection systems is presented. The model predicts the activity of the relevant biomass phenotypes under aerobic, anoxic, and anaerobic conditions in force mains and gravity sewers. The formation and fate of individual, malodorous substances in the bulk water, biofilms, and sediments are modeled. The release of odorous compounds from the bulk water to the sewer gas phase, their fate in the gas phase, and their subsequent release into the urban atmosphere is simulated. Examples of model application include the prediction of hydrogen sulfide and malodorous fermentation products from force mains and gravity sewers.


Assuntos
Sulfeto de Hidrogênio/análise , Modelos Biológicos , Odorantes/análise , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Anaerobiose , Biofilmes , Biomassa , Simulação por Computador , Sedimentos Geológicos/análise , Sulfeto de Hidrogênio/metabolismo , Matemática , Oxirredução , Oxigênio/metabolismo , Água/análise
16.
Water Environ Res ; 80(1): 16-25, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18254394

RESUMO

The formation and fate of sulfide in a force main and a downstream-located gravity sewer were investigated in an extensive field study. Sulfide formation in the force main was significant. However, during 14 minutes of transport in the gravity sewer, the sulfide concentration decreased 30%, on average. An application of a conceptual sewer process model for simulating the formation and fate of sulfide was demonstrated. Overall, the model predicted that approximately 90% of the decrease of the sulfide concentration in the gravity sewer was the result of sulfide oxidation and that only a small fraction entered the sewer atmosphere, causing odor and corrosion. Even so, the model predicted concrete corrosion rates of up to 1.2 mm/y in the gravity sewer section.


Assuntos
Aerobiose , Anaerobiose , Sulfetos/metabolismo , Eliminação de Resíduos Líquidos , Simulação por Computador , Corrosão , Dinamarca , Modelos Biológicos , Oxigênio/análise , Movimentos da Água
17.
Water Environ Res ; 78(3): 275-83, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16629268

RESUMO

Kinetics and stoichiometry of aerobic chemical and biological sulfide oxidation in wastewater from sewer networks were studied. In this respect, the effects of temperature and pH were investigated in the ranges 10 to 20 degrees C and 5 to 9, respectively. The temperature dependency of sulfide oxidation kinetics was described using an Arrhenius relationship. The effect of pH on the rate of chemical sulfide oxidation is related to the dissociation of hydrogen sulfide (H2S) to hydrogen sulfide ion (HS(-)), with HS(-) being more readily oxidized than H2S. Biological sulfide oxidation exhibited the highest rates at ambient wastewater pH, and the reaction was inhibited at both low and high pH values. Chemical sulfide oxidation was found to produce thiosulfate and sulfate, while elemental sulfur was the main product of biological sulfide oxidation. Based on the investigations, general rate equations and stoichiometric constants were determined, enabling the processes to be incorporated to conceptual sewer process models.


Assuntos
Esgotos/microbiologia , Sulfetos/metabolismo , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Sulfeto de Hidrogênio/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Modelos Biológicos , Oxirredução , Esgotos/química , Sulfatos/metabolismo , Enxofre/metabolismo , Temperatura , Tiossulfatos/metabolismo
18.
Sci Total Environ ; 566-567: 1579-1587, 2016 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-27302374

RESUMO

The invertebrate diversity in nine stormwater wet detention ponds (SWDP) was compared with the diversity in eleven small shallow lakes in the western part of Denmark. The SWDPs and lakes were chosen to reflect as large a gradient of pollutant loads and urbanization as possible. The invertebrates as well as the bottom sediments of the ponds and shallow lakes were analyzed for copper, iron, zinc, cadmium, chromium, lead, aluminum, nickel, arsenic and the potentially limiting nutrient, phosphorus. The Principal Component Analysis showed that invertebrates in SWDPs and lakes differed with respect to bioaccumulation of these elements, as did the sediments, albeit to a lesser degree. However, the Detrended Correspondence Analysis and the TWINSPAN showed that the invertebrate populations of the ponds and lakes could not be distinguished, with the possible exception of highway ponds presenting a distinct sub-group of wet detention ponds. The SWDPs and shallow lakes studied seemed to constitute aquatic ecosystems of similar taxon richness and composition as did the 11 small and shallow lakes. This indicates that SWDPs, originally constructed for treatment and flood protection purposes, become aquatic environments which play a local role for biodiversity similar to that of natural small and shallow lakes.


Assuntos
Biodiversidade , Sedimentos Geológicos/análise , Invertebrados , Metais Pesados/análise , Poluentes Químicos da Água/análise , Animais , Dinamarca , Monitoramento Ambiental , Lagos/análise , Lagoas/análise
19.
Water Res ; 39(17): 4119-25, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16135381

RESUMO

Oxidation of sulfide under aerobic conditions by biofilms grown on municipal wastewater in 6 identical pipe reactors was investigated. The biofilms were grown at pH 7.6 and temperatures of 20 and 25 degrees C under aerobic-anaerobic transient conditions with pulse dosing of sulfide in the bulk water. The pulse dosing of sulfide served to simulate conditions in a gravity sewer located downstream of a pressure main. During growth of the biofilms, sulfide was pulse dosed in concentrations of 0, 0.5, 2.0 and 5.0 g Sm(-3) with a frequency of 1h(-1). Based on a series of batch experiments, kinetics and stoichiometry of sulfide oxidation by the sewer biofilms was investigated and a rate equation and a stoichiometric constant proposed. Sulfide oxidation kinetics was significantly faster for biofilms grown at sulfide loadings of 0.5, 2.0 and 5.0 g Sm(-3)h(-1) than for biofilms grown in the absence of sulfide. However, the kinetics of sulfide oxidation was relatively constant for biofilms grown at sulfide loadings above 0.5 g Sm(-3)h(-1). Mass balance calculations of dissolved oxygen and sulfur compounds suggested the oxidation product to be elemental sulfur. Further oxidation of elemental sulfur could not be documented.


Assuntos
Biofilmes , Sulfetos/química , Cinética , Oxirredução
20.
Water Res ; 39(12): 2747-55, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15978649

RESUMO

Interactions between iron and sulfide in domestic wastewater from a gravity sewer were investigated with particular emphasis on redox cycling of iron and iron sulfide formation. The concentration ranges of iron and total sulfide in the experiments were 0.4-5.4mgFeL(-1) and 0-5.1mgSL(-1), respectively. During anaerobic conditions, iron reduction kinetics were investigated and reduction rates amounted on average to 1.32mgFeL(-1)d(-1). Despite the very low solubility of iron sulfide, the reduced iron reacted only partly with sulfide to produce iron sulfide, even when dissolved sulfide was in excess. When a ferric chloride solution was added to sulfide containing anaerobic wastewater, the ferric iron was quickly reduced to ferrous forms by oxidation of dissolved sulfide and the ferrous iron precipitated almost completely as iron sulfide. During aerobic conditions, iron sulfide was oxidized with a half-life period of 11.7h. The oxidation rate of iron sulfide was significantly lower than that reported for the oxidation of dissolved sulfide.


Assuntos
Reatores Biológicos , Ferro/química , Esgotos/química , Sulfetos/química , Eliminação de Resíduos Líquidos/métodos , Precipitação Química , Concentração de Íons de Hidrogênio , Metais/química , Oxirredução , Esgotos/microbiologia , Solubilidade , Fatores de Tempo
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