The capacity of a calcareous desert soil, Thiokol silt loam, to retain natural , as well as added , orthophosphate-P was measured by equilibrium adsorption employing a batch technique and evaluated using the two-slope Langmuir adsorption isotherm. From these data, corrected to account for indigenous soil P, a hypothesis was formulated as to the nature of retention of P by the soil, including the identification of two interfacial reactions involving P, and a value calculated for the adsorption maximum as defined by the Langmuir isotherm equation f o r P with soil at each of two soil depths and t h ree constant temperatures within the range of biological activity . The initial reaction was considered to be surface adsorption , where phosphate ions interact with the clayand lime mineral surfaces at definite sites. The activity of the second mechanism was identified as adsorption, and in addition, the heterogeneous nucleation of metal phosphates on the lime mineral surfaces. In addition to these quantitative studies, the flux of P in the soil was also investigated for the same soil and temperatures by means of kinetic experiments conducted to identify the nature (mechanisms) and measure the rates and release maxima of indigenous P release from the soil. These experiments were carried out using an anion-exchange resin as an infinite sink for P, again applying a batch technique. Ultimately, the release of indigenous P from the soil under saturated conditions was attributed to three simultaneous first-order reactions. 'll1e rate constants of the three reactions were found to be of orders of 10-4, 10-5, and 10-6 (1/sec), and did not vary significantly with soil depth or ternperature. The three reactions above were identified as dissolution of poorly crystalline or amorphous calcium phosphates, the desorption of surface site adsorbed or labile P, and the slow dissolution of calcium hydroxyapatite, respectively.

Orientador: Ademércio Antonio Paccola / Banca: Wolmar Apparecida Carvalho / Banca: Sandra Maria Barbalho / Banca: Silas Macedo Silva / Banca: Rosana Cavalcante dos Santos / Resumo: O processo de solubilização, dissolução de minerais do solo e suas interações com os processos de adsorção e dessorção de fosfato são de alta importância devido às possibilidades de otimização no processo de adubação do solo para o plantio. Alguns autores sugerem que a dissolução de ferro nos solos ocorre por redução microbiana e complexação, interferindo diretamente no processo de adsorção e dessorção do fosfato. O objetivo deste trabalho foi investigar a relação existente entre liberação de ferro, a neoformação de óxidos de ferro e adsorção e dessorção de fosfato em um Latossolo Vermelho distrófico de região Tropical Úmida. A relação foi estudada em solos sob diferentes tipos de ocupação: cana de açúcar, café, milho, reflorestamento de eucalipto e floresta natural. Amostras de solo foram coletadas nos horizontes A e B, tratadas com solução de sacarose a 3% e mantidas em repouso. O processo redox ocorreu em todas as amostras tratadas o que foi comprovado pela análise de pH onde se obteve uma acidificação do meio e posterior aumento do pH, indicando o estabelecimento de um equilíbrio químico do processo, mantendo assim o pH estável. Análises quantitativas de ferro, zinco, cobre, manganês e fósforo foram realizadas no solo natural, no solo sob tratamento e na fase líquida das amostras. A estes solos foram adicionadas duas concentrações de fosfato: 200 mg.dm3 e 400 mg.dm3 e calculadas as adsorções. A comparação dos resultados destas análises mostrou que a fixação de fósforo foi maior nos solos submetidos ao tratamento. Isto pode ser explicado pela decomposição microbiana dos compostos orgânicos, na interface com a atmosfera oxidante, que provocou a precipitação dos óxidos e hidróxidos dos metais onde os íons fosfato foram fixados pelos óxidos e hidróxidos reprecipitados. / Abstract: The solubilization process, minerals dissolution and its interactions with the phosphate adsorption/desorption processes are of high importance due to the possibilities of improvement in the process of the soil manuring in the plant crops.Some authors suggest that the iron dissolution in the soils occurs by microbial reduction and complexation, interfering directly in the phosphate adsorption /desorption process.The purpose of this work was to investigate the existent connection between the iron liberation, the neoformation of iron oxides and the phosphate adsorption/ desorption in a "Latossolo Vermelho Distrófico"of humid tropical region.This connection was studied in soils by different crops: sugar cane, coffee, corn, reforestation with eucalyptus and natural forest. Soil's samples were collected in A and B horizon, treated with sucrose 3% solution and maintained in repose.Redox process occurred in all the treated samples, what was proved by the pH analysis, in where were obtained some acidification of the environment and subsequent pH increase, indicating the establishment of a chemical balance of the process, maintaining like this the pH stable. Quantitative analyses of iron, zinc, copper, manganese and match were accomplished in the natural soil, in the soil under treatment and in the liquid phase of the samples.Two phosphate concentrations: 200 mg.dm3 and 400 mg.dm3 were added to these soils and the adsorptions were calculated. The comparison of these analyses results shows that the phosphorous fixation was higher in the soils submitted to the treatment. This can be explained by the microbial decomposition of the organic compounds, in the interface with the oxidant atmosphere, which nettled the precipitation of the oxides and hydroxides of the metals in where the phosphate ions were fixated by oxides and hydroxides reprecipitated. / Doutor

No description available.

Made available in DSpace on 2014-06-11T19:31:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-04-22Bitstream added on 2014-06-13T21:02:54Z : No. of bitstreams: 1 mendonca_cctn_dr_botfca.pdf: 609115 bytes, checksum: 61293a5052971a6e02dc4478d68dbc4f (MD5) / Universidade Estadual Paulista (UNESP) / O processo de solubilização, dissolução de minerais do solo e suas interações com os processos de adsorção e dessorção de fosfato são de alta importância devido às possibilidades de otimização no processo de adubação do solo para o plantio. Alguns autores sugerem que a dissolução de ferro nos solos ocorre por redução microbiana e complexação, interferindo diretamente no processo de adsorção e dessorção do fosfato. O objetivo deste trabalho foi investigar a relação existente entre liberação de ferro, a neoformação de óxidos de ferro e adsorção e dessorção de fosfato em um Latossolo Vermelho distrófico de região Tropical Úmida. A relação foi estudada em solos sob diferentes tipos de ocupação: cana de açúcar, café, milho, reflorestamento de eucalipto e floresta natural. Amostras de solo foram coletadas nos horizontes A e B, tratadas com solução de sacarose a 3% e mantidas em repouso. O processo redox ocorreu em todas as amostras tratadas o que foi comprovado pela análise de pH onde se obteve uma acidificação do meio e posterior aumento do pH, indicando o estabelecimento de um equilíbrio químico do processo, mantendo assim o pH estável. Análises quantitativas de ferro, zinco, cobre, manganês e fósforo foram realizadas no solo natural, no solo sob tratamento e na fase líquida das amostras. A estes solos foram adicionadas duas concentrações de fosfato: 200 mg.dm3 e 400 mg.dm3 e calculadas as adsorções. A comparação dos resultados destas análises mostrou que a fixação de fósforo foi maior nos solos submetidos ao tratamento. Isto pode ser explicado pela decomposição microbiana dos compostos orgânicos, na interface com a atmosfera oxidante, que provocou a precipitação dos óxidos e hidróxidos dos metais onde os íons fosfato foram fixados pelos óxidos e hidróxidos reprecipitados. / The solubilization process, minerals dissolution and its interactions with the phosphate adsorption/desorption processes are of high importance due to the possibilities of improvement in the process of the soil manuring in the plant crops.Some authors suggest that the iron dissolution in the soils occurs by microbial reduction and complexation, interfering directly in the phosphate adsorption /desorption process.The purpose of this work was to investigate the existent connection between the iron liberation, the neoformation of iron oxides and the phosphate adsorption/ desorption in a Latossolo Vermelho Distróficoof humid tropical region.This connection was studied in soils by different crops: sugar cane, coffee, corn, reforestation with eucalyptus and natural forest. Soil's samples were collected in A and B horizon, treated with sucrose 3% solution and maintained in repose.Redox process occurred in all the treated samples, what was proved by the pH analysis, in where were obtained some acidification of the environment and subsequent pH increase, indicating the establishment of a chemical balance of the process, maintaining like this the pH stable. Quantitative analyses of iron, zinc, copper, manganese and match were accomplished in the natural soil, in the soil under treatment and in the liquid phase of the samples.Two phosphate concentrations: 200 mg.dm3 and 400 mg.dm3 were added to these soils and the adsorptions were calculated. The comparison of these analyses results shows that the phosphorous fixation was higher in the soils submitted to the treatment. This can be explained by the microbial decomposition of the organic compounds, in the interface with the oxidant atmosphere, which nettled the precipitation of the oxides and hydroxides of the metals in where the phosphate ions were fixated by oxides and hydroxides reprecipitated.

No description available.

The treatment and control of superfluous aqueous phosphate is a critical task in environmental management. Magnetic bio-activated carbon is a good adsorbent for physical adsorption methods with several environmental and economic advantages. A streamlined and new method for production of magnetic bio-activated carbon from lignin is finished and presented by Tong Han. To enhance the phosphate adsorption and find the optimization process for mac production from lignin, it’s necessary to investigate influence of process parameters on the quality of the final products systematically. In this work, four different modification of process are used to investigate the influence of process parameters on the quality of the final products systematically, which shows how the proportion of iron oxides, the dispersion of iron oxides and the degree of activation influence the capacities. And the maximum capacity is around 50mg/g, which is a relatively high improvement. / Behandling och kontroll av överflödigt vattenhaltigt fosfat är en kritisk uppgift i miljöhantering. Magnetiskt bioaktiverat kol är ett bra adsorbent för fysiska adsorptionsmetoder med flera miljömässiga och ekonomiska fördelar. En strömlinjeformad och ny metod för produktion av magnetiskt bioaktiverat kol från lignin är färdig och presenteras av Tong Han. För att förbättra fosfatadsorptionen och hitta optimeringsprocessen för mac-produktion från lignin är det nödvändigt att systematiskt undersöka påverkan av processparametrar på kvaliteten på de slutliga produkterna. I detta arbete används fyra olika modifieringar av processen för att systematiskt undersöka påverkan av processparametrar på slutprodukternas kvalitet, vilket visar hur andelen järnoxider, spridningen av järnoxider och graden av aktivering påverkar kapaciteten. Och den maximala kapaciteten är cirka 50 mg / g, vilket är en relativt hög förbättring.

Eutrophication due to excess loading of phosphorus (P) is a leading cause of water quality degradation within the United States. The aim of this study was to investigate P removal and recovery with 12 materials (four calcite varieties, wollastonite, dolomite, hydroxylapatite, eggshells, coral sands, biochar, and activated carbon. This was accomplished through a series of batch experiments with synthetic wastewater solutions ranging from 10-100 mg PO₄-P/ L. The results of this study were used to establish large-scale, calcite-based column filter experiments located in the Rubenstein School of Environment and Natural Resources' Eco-Machine. Influent and effluent wastewater samples were routinely collected for 64 days. Measures of filter performance included changes in pH, percent reduction and mass adsorbed of P. After the columns reached saturation, filter media was analyzed for the mineralogical content by X-ray powder diffraction (XRD). In the batch experiments, P removal and recovery varied among the media and across treatments. The best performing minerals were calcite, wollastonite, and hydroxylapatite. Eggshells, activated carbon, and coral sands also reduced and adsorbed P. The remaining materials had the lowest reductions and adsorption of P. Results from batch experiments informed the design of large column filters within the Rubenstein School of the Environment and Natural Resources' Eco-Machine. Removal and adsorption rates of P by the three column filters were similar. The columns achieved an average P reduction of 12.53% (se = 0.98) and an average P adsorption of 0.649 mg PO₄-P/ kg media (se = 0.03) over a 4-h hydraulic retention time. Paired T-tests showed that P reductions were statistically significant (p-value < 0.05) on the majority of sampling dates until the columns reached saturation. Saturation was reached after 31 days for two of the columns and 36 days for the third column. The filter media consistently buffered the pH of the wastewater to approximately 6.0-7.0 with no indication of diminishing buffer capacity after saturation. XRD analysis was not able to detect any P species within the crystalline structure of the filter media. This research contributes to the understanding of how the selected media perform during P removal and recovery programs, while providing information on the performance of large column filters operating within advanced, ecologically engineered wastewater treatment systems.

Bei der Aufbereitung von Rohwässern zu Trinkwasser fallen in der Regel unvermeidbare Rückstände an, die den gesetzlichen Bestimmungen entsprechend entsorgt werden müssen. Schlammhaltige Wässer, die den größten Anteil an Wasserwerksrückständen einnehmen, entstehen bei der Spülung von Filtern und enthalten nahezu alle aus dem Rohwasser entfernten Stoffe und nicht im Trinkwasser verbleibende Aufbereitungschemikalien. Während früher in vielen Wasserwerken Teile des schlammhaltigen Filterspülwassers nach einem Sedimentationsvorgang wieder in den Aufbereitungsprozess zurückgeführt wurden, ist dies in Deutschland auf Grund einer möglichen Beeinträchtigung der Trinkwasserqualität bei mikrobiologisch belasteten Wässern (z. B. Oberflächenwasser) ohne eine adäquate Behandlung (z. B. Ultrafiltration) nicht mehr erlaubt. Somit müssen schlammhaltige Filterspülwässer anderweitig entsorgt werden, z. B. durch eine Einleitung in die Kanalisation. Die dabei auftretenden Auswirkungen auf Abwasserbehandlungsanlagen sind noch nicht ausreichend bekannt. In der vorliegenden Arbeit werden unterschiedliche Ultrafiltrationsmodule (Kapillarmembranmodul und getauchtes Modul) hinsichtlich ihrer Eignung zur Aufbereitung aluminiumhaltiger schlammhaltiger Filterspülwässer und damit zur Rückführung des entstehenden Filtrates in den Aufbereitungsprozess untersucht. Die grundsätzliche Eignung beider Modulsysteme wird nachgewiesen. Bei Verwendung von getauchten Modulen kann auf eine vorangehende Sedimentationsanlage verzichtet werden. Als kritisch muss unabhängig vom gewählten Modulkonzept die Entsorgung des anfallenden Retentates angesehen werden, da die gesetzlich vorgeschriebenen Grenzwerte der Indirekteinleitung für mehrere Parameter nicht eingehalten werden. Bilanzierungen der relevanten Schadstoffe ergeben, dass der Schadstoffeintrag überwiegend diffus mit dem Rohwasser in das Wasserwerk erfolgt. Zur Untersuchung von Auswirkungen der Einleitung aluminiumhaltiger schlammhaltiger Filterspülwässer aus der Oberflächenwasseraufbereitung auf die Abwasserbehandlung wurden labortechnische Versuche zur Ermittlung des Phosphatadsorptionspotenzials durchgeführt. Neben der Abhängigkeit der Phosphatadsorptionskapazität vom pH-Wert wurde der Einfluss der Feststoffkonzentration des schlammhaltigen Filterspülwassers in Versuchen mit Modellwasser nachgewiesen. Eine Erhöhung der Feststoffkonzentration wirkt einer möglichst hohen Ausnutzung des Adsorptionspotenzials entgegen. Während für die Ultrafiltrationsbehandlung gegenüber der Indirekteinleitung ein Kostenvorteil ermittelt wird, ist die für die Nutzung des Phosphatadsorptionsanteils verfügbare Schlammmenge für einen alleinigen Einsatz in der Kläranlage bei gleichen Einzugsgebieten nicht ausreichend. / In most water treatment plants (WTPs), during the water purification process, residuals are generated that have to be disposed according to current regulations. Most of the residuals are derived from filter backwash processes (i. e. spent filter backwash water, SFBW) and contain substances that are removed from the raw water. In addition, in the spent filter backwash water, chemicals can be found that are required for the operation of the water treatment process and do not remain in the drinking water. Over recent decades, SFBW has been returned to the beginning of the water treatment plant (WTP) after a sedimentation process in order to reduce the amount of water being discharged. Concerns over the recycling of microorganisms, of heavy metals or precursors for disinfection by-products, have led to a significant reduction of the number of WTPs that directly return filter backwash water to the water treatment process. According to German technical standards, the reuse of SFBW might only be possible after the application of groundwater infiltration or an equivalent technique. Because of an almost complete recovery of particles and microorganisms, ultrafiltration treatment is a proven alternative to groundwater recharge of SFBW. In this work, different ultrafiltration modules for the treatment and reuse of SFBW are compared. Capillary as well as submerged membrane modules are suitable for the treatment of SFBW. If submerged membrane modules are used, no sedimentation period prior to ultrafiltration treatment is necessary. As a consequence of the accumulation of particulate matter including heavy metals and other compounds in the retentate during ultrafiltration treatment, threshold values of several regulations cannot be met, and either the discharge of retentate into the sewer will be charged or alternative disposal options must be considered. Mass balances for an entire WTP showed most of these contaminants to originate from non-point sources in the watershed. Lab-scale experiments are performed for the examination of the phosphate adsorption potential of SFBW derived from surface water treatment using aluminum-based coagulants. Besides a strong influence of the pH-value present in the SFBW, an influence of the TSS-concentration of SFBW on phosphate adsorption capacity could be demonstrated. Elevated TSS-concentrations resulted in a lower phosphate adsorption capacity of the investigated SFBW. While ultrafiltration treatment with subsequent reuse of SFBW might be cheaper than the discharge to the sewer system, the amount of SFBW required for a complete phosphate removal in the wastewater treatment plant is to large and therefore, no economic advantage of phosphate adsorption could be demonstrated

[Truncated abstract] Relationships between the persistence of organic matter added to soil, the dynamics of soil organic carbon (C) and phosphorus (P) were examined in four experiments on lateritic soils of Western Australia. The main objective was to quantify the release of P following organic matter application in soils which have high P adsorbing capacity. Another objective was to confirm that due to its recalcitrant materials, the effect of peat lasted longer in soil than other sources of organic matter in terms of increasing plant-available P fractions. Three experiments were conducted under glasshouse conditions for various lengths of time, with nine- to twelve-month incubations to investigate these hypotheses. As expected, organic matter with lower C:N ratios than peat (lucerne hay) decomposed more rapidly compared with peat, and the most active mineralisation took place within the first three months of incubation. Soil organic-C (extracted by 0.5 M K2SO4) had a significant positive correlation with P extracted with 0.5 M NaHCO pH 8.53. For a higher application rate (120 ton ha-1), peat was better than wheat straw and lucerne hay in increasing extractable bicarbonate-P concentrations in soil, especially at incubation times up to 12 months. Throughout the experiment, peat was associated with a steady increase in all parameters measured. In contrast to peat, nutrient release from lucerne hay and wheat straw was rapid and diminished over time. There was a tendency for organic-C (either in the form of total extractable organic-C or microbial biomass-C) to steadily increase in soil with added peat throughout the experiment. Unlike wheat straw and lucerne hay, extractable organic-C from peat remained in soil and there was less C loss in the form of respiration. Therefore, peat persisted and sequestered C to the soil system for a longer time than the other source of organic matter. Freshly added organic matter was expected to have a greater influence on P transformation from adsorbed forms in lateritic soils than existing soil organic matter. By removing the existing soil organic matter, the effect of freshly applied organic matter can be determine separately from that of the existing soil organic matter for a similar organic-C content. In order to do this, some soil samples were combusted up to 450° C to eliminate inherent soil organic matter. The release of P was greater when organic-C from fresh organic matter was applied to combusted soils than in uncombusted soils that contained the existing soil organic matter. The exception only applied for parameters related to soil micro-organisms such as biomass-C and phosphatase. For such parameters, new soil organic matter did not create conditions favourable for organisms to increase in activity despite the abundance of organic matter available. More non-extractable-P was formed in combusted soils compared to bicarbonate-P and it contributed to more than 50% of total-P. As for the first experiment, peat also showed a constant effect in increasing bicarbonate extractable-P in the soil

Bei der Aufbereitung von Rohwässern zu Trinkwasser fallen in der Regel unvermeidbare Rückstände an, die den gesetzlichen Bestimmungen entsprechend entsorgt werden müssen. Schlammhaltige Wässer, die den größten Anteil an Wasserwerksrückständen einnehmen, entstehen bei der Spülung von Filtern und enthalten nahezu alle aus dem Rohwasser entfernten Stoffe und nicht im Trinkwasser verbleibende Aufbereitungschemikalien. Während früher in vielen Wasserwerken Teile des schlammhaltigen Filterspülwassers nach einem Sedimentationsvorgang wieder in den Aufbereitungsprozess zurückgeführt wurden, ist dies in Deutschland auf Grund einer möglichen Beeinträchtigung der Trinkwasserqualität bei mikrobiologisch belasteten Wässern (z. B. Oberflächenwasser) ohne eine adäquate Behandlung (z. B. Ultrafiltration) nicht mehr erlaubt. Somit müssen schlammhaltige Filterspülwässer anderweitig entsorgt werden, z. B. durch eine Einleitung in die Kanalisation. Die dabei auftretenden Auswirkungen auf Abwasserbehandlungsanlagen sind noch nicht ausreichend bekannt. In der vorliegenden Arbeit werden unterschiedliche Ultrafiltrationsmodule (Kapillarmembranmodul und getauchtes Modul) hinsichtlich ihrer Eignung zur Aufbereitung aluminiumhaltiger schlammhaltiger Filterspülwässer und damit zur Rückführung des entstehenden Filtrates in den Aufbereitungsprozess untersucht. Die grundsätzliche Eignung beider Modulsysteme wird nachgewiesen. Bei Verwendung von getauchten Modulen kann auf eine vorangehende Sedimentationsanlage verzichtet werden. Als kritisch muss unabhängig vom gewählten Modulkonzept die Entsorgung des anfallenden Retentates angesehen werden, da die gesetzlich vorgeschriebenen Grenzwerte der Indirekteinleitung für mehrere Parameter nicht eingehalten werden. Bilanzierungen der relevanten Schadstoffe ergeben, dass der Schadstoffeintrag überwiegend diffus mit dem Rohwasser in das Wasserwerk erfolgt. Zur Untersuchung von Auswirkungen der Einleitung aluminiumhaltiger schlammhaltiger Filterspülwässer aus der Oberflächenwasseraufbereitung auf die Abwasserbehandlung wurden labortechnische Versuche zur Ermittlung des Phosphatadsorptionspotenzials durchgeführt. Neben der Abhängigkeit der Phosphatadsorptionskapazität vom pH-Wert wurde der Einfluss der Feststoffkonzentration des schlammhaltigen Filterspülwassers in Versuchen mit Modellwasser nachgewiesen. Eine Erhöhung der Feststoffkonzentration wirkt einer möglichst hohen Ausnutzung des Adsorptionspotenzials entgegen. Während für die Ultrafiltrationsbehandlung gegenüber der Indirekteinleitung ein Kostenvorteil ermittelt wird, ist die für die Nutzung des Phosphatadsorptionsanteils verfügbare Schlammmenge für einen alleinigen Einsatz in der Kläranlage bei gleichen Einzugsgebieten nicht ausreichend. / In most water treatment plants (WTPs), during the water purification process, residuals are generated that have to be disposed according to current regulations. Most of the residuals are derived from filter backwash processes (i. e. spent filter backwash water, SFBW) and contain substances that are removed from the raw water. In addition, in the spent filter backwash water, chemicals can be found that are required for the operation of the water treatment process and do not remain in the drinking water. Over recent decades, SFBW has been returned to the beginning of the water treatment plant (WTP) after a sedimentation process in order to reduce the amount of water being discharged. Concerns over the recycling of microorganisms, of heavy metals or precursors for disinfection by-products, have led to a significant reduction of the number of WTPs that directly return filter backwash water to the water treatment process. According to German technical standards, the reuse of SFBW might only be possible after the application of groundwater infiltration or an equivalent technique. Because of an almost complete recovery of particles and microorganisms, ultrafiltration treatment is a proven alternative to groundwater recharge of SFBW. In this work, different ultrafiltration modules for the treatment and reuse of SFBW are compared. Capillary as well as submerged membrane modules are suitable for the treatment of SFBW. If submerged membrane modules are used, no sedimentation period prior to ultrafiltration treatment is necessary. As a consequence of the accumulation of particulate matter including heavy metals and other compounds in the retentate during ultrafiltration treatment, threshold values of several regulations cannot be met, and either the discharge of retentate into the sewer will be charged or alternative disposal options must be considered. Mass balances for an entire WTP showed most of these contaminants to originate from non-point sources in the watershed. Lab-scale experiments are performed for the examination of the phosphate adsorption potential of SFBW derived from surface water treatment using aluminum-based coagulants. Besides a strong influence of the pH-value present in the SFBW, an influence of the TSS-concentration of SFBW on phosphate adsorption capacity could be demonstrated. Elevated TSS-concentrations resulted in a lower phosphate adsorption capacity of the investigated SFBW. While ultrafiltration treatment with subsequent reuse of SFBW might be cheaper than the discharge to the sewer system, the amount of SFBW required for a complete phosphate removal in the wastewater treatment plant is to large and therefore, no economic advantage of phosphate adsorption could be demonstrated