Search

Context: Dissolved oxygen (DO) transfer is an important matter for water quality. Several devices have been designed to supply the required DO in some bodies of water during their treatment and restoration. However, these entail a high energy consumption, thus requiring the optimization of use parameters. Method: This work studies the effect of the power and number of paddles used in a horizontal axis aerator. Measurements were made on anoxic water samples using three mechanical aerating devices made up of 6, 12, and 24 paddles while varying the rotation speed from the supplied voltage. Results: The highest values obtained for the transfer coefficient KLa are reported by devices with a greater number of blades. Nevertheless, the Standard Aeration Efficiency (SAE) and the Standard Oxygen Transfer Rate (SOTR) efficiency reveal that the 6-paddle wheels are more energy-efficient. Conclusions: It is shown that DO transfer does not depend solely on the impacts associated with the number of paddles, and that the maximum transfer efficiency is obtained with a lower number of paddles. These results contribute to improving the understanding of the operation of these mechanical systems in terms of DO transfer., Contexto: La transferencia del oxígeno disuelto (OD) es un tema de importancia para la calidad del agua. Diversos dispositivos se han diseñado para suministrar el OD requerido en algunos cuerpos de agua durante su tratamiento y restauración; sin embargo, estos conllevan un alto consumo de energía, requiriendo optimizar los parámetros de uso. Método: Este trabajo estudió el efecto de la potencia y número de aspas utilizadas en un aireador de eje horizontal. Las mediciones se realizaron en muestras de agua anóxica, utilizando tres dispositivos aireadores conformados por 6, 12 y 24 aspas, variando la velocidad de rotación a partir del voltaje suministrado. Resultados: Los mayores valores obtenidos del coeficiente de transferencia KLa se presentan en dispositivos con mayor cantidad de aspas. Sin embargo, la eficiencia estándar de aireación (SAE) y la eficiencia de transferencia de oxígeno estándar (SOTR) revelaron que el dispositivo con 6 aspas presenta una mayor eficiencia energética. Conclusiones: Se demostró que la transferencia de OD no depende únicamente de los impactos asociados al número de aspas, y que la máxima eficiencia en la transferencia se obtiene con un menor número de aspas. Estos resultados pueden contribuir en mejorar el entendimiento del funcionamiento de estos sistemas mecánicos en términos de transferencia de OD.

Context: Dissolved oxygen (DO) transfer is an important matter for water quality. Several devices have been designed to supply the required DO in some bodies of water during their treatment and restoration. However, these entail a high energy consumption, thus requiring the optimization of use parameters. Method: This work studies the effect of the power and number of paddles used in a horizontal axis aerator. Measurements were made on anoxic water samples using three mechanical aerating devices made up of 6, 12, and 24 paddles while varying the rotation speed from the supplied voltage. Results: The highest values obtained for the transfer coefficient KLa are reported by devices with a greater number of blades. Nevertheless, the Standard Aeration Efficiency (SAE) and the Standard Oxygen Transfer Rate (SOTR) efficiency reveal that the 6-paddle wheels are more energy-efficient. Conclusions: It is shown that DO transfer does not depend solely on the impacts associated with the number of paddles, and that the maximum transfer efficiency is obtained with a lower number of paddles. These results contribute to improving the understanding of the operation of these mechanical systems in terms of DO transfer., Contexto: La transferencia del oxígeno disuelto (OD) es un tema de importancia para la calidad del agua. Diversos dispositivos se han diseñado para suministrar el OD requerido en algunos cuerpos de agua durante su tratamiento y restauración; sin embargo, estos conllevan un alto consumo de energía, requiriendo optimizar los parámetros de uso. Método: Este trabajo estudió el efecto de la potencia y número de aspas utilizadas en un aireador de eje horizontal. Las mediciones se realizaron en muestras de agua anóxica, utilizando tres dispositivos aireadores conformados por 6, 12 y 24 aspas, variando la velocidad de rotación a partir del voltaje suministrado. Resultados: Los mayores valores obtenidos del coeficiente de transferencia KLa se presentan en dispositivos con mayor cantidad de aspas. Sin embargo, la eficiencia estándar de aireación (SAE) y la eficiencia de transferencia de oxígeno estándar (SOTR) revelaron que el dispositivo con 6 aspas presenta una mayor eficiencia energética. Conclusiones: Se demostró que la transferencia de OD no depende únicamente de los impactos asociados al número de aspas, y que la máxima eficiencia en la transferencia se obtiene con un menor número de aspas. Estos resultados pueden contribuir en mejorar el entendimiento del funcionamiento de estos sistemas mecánicos en términos de transferencia de OD.

Context: The lack of dissolved oxygen (DO) in water bodies has become a serious problem for several ecosystems due to drastic changes in their climatic, biological, and physical conditions. The presence of microorganisms, organic matter, and clays, which are carried by landslides and rainwater, affect the process of restoration and transfer of DO in water, thus making it necessary to study how these factors affect the process of DO transfer in water bodies. Method: This work is focused on studying the influence of clays during the DO transfer process in water bodies. To this effect, samples of clays from the region of Paipa, Boyacá, were added in 1, 3 and 5% by weight into the samples of clean water. The aeration process was performed using a constant flow diffusion system. The tests were carried out until the saturation of dissolved oxygen in each of the water samples was obtained. Results: The results show that the presence of clays during the transfer of DO have little influence on bodies of water. However, variations were observed in time intervals of <5 min in which the increase in the percentage of clays favored the transfer of DO. Conclusions: With these results, it is concluded that the presence of clays can generate a beneficial effect during the transfer of DO in bodies of water with a high oxygen deficiency, whereas, for water samples with a relatively high percentage of DO, clays can hinder the DO restoration process., Contexto: La carencia de oxígeno disuelto (OD) en cuerpos de agua se ha convertido en un problema ambiental para varios ecosistemas debido a cambios drásticos en sus condiciones climáticas, bilógicas y físicas. La presencia de microorganismos, materia orgánica y arcillas, transportados por deslizamientos y aguas lluvias, afectan los procesos de restauración y transferencia de OD en el agua, lo que hace necesario estudiar cómo dichos factores afectan el proceso de transferencia de OD. Método: Este trabajo se centra en estudiar la influencia de las arcillas durante el proceso de transferencia de OD en cuerpos de agua. Para esto, se utilizaron muestras de arcillas de la región de Paipa-Boyacá, adicionadas en 1, 3 y 5% en peso a muestras de agua limpia. El proceso de aireación se llevó a cabo utilizando un sistema de difusión de flujo constante. Los ensayos se realizaron hasta obtener la saturación de oxígeno disuelto en cada una de las muestras de agua trabajadas. Resultados: Los resultados muestran que la presencia de arcillas durante la transferencia de OD tienen poca influencia en los cuerpos de agua. Sin embargo, se observaron variaciones en intervalos de tiempo <5 min en los que el incremento del porcentaje de arcillas favorecía la transferencia de OD. Conclusiones: Con estos resultados se concluye que la presencia de arcillas puede generar un efecto benéfico durante la transferencia de OD en cuerpos de agua con una alta carencia de oxígeno, mientras que, para muestras de agua con un porcentaje relativamente alto de OD, las arcillas perjudican el proceso de restauración de OD.

In this work, the implementation of two types of blades in a prototype of horizontal axis mechanical aeration was analyzed, starting from the dissolved oxygen (DO) transfer analysis. Measurements were made in anoxic water samples, using two types of paddle-wheelswith the same area and impact angle, but with a different curvature. The data obtained show that the two types of paddle-wheelshave the same standard aeration efficiency (SAE) in both devices, obtaining a value of 0.50 kgO2/kWh. However, the standard oxygen transfer rate (SOTR) for the flat paddle-wheelaerator was 34.9% higher than that obtained with curved paddle-wheels. The KLa values obtained wereof 2.61 h-1for the flat paddle-wheelsaerator and 1.94 h-1for the curved paddle-wheel, reflecting a lower oxygen transfer rate for the latter. However, energy consumption is lower by implementing the curved blades within the aeration system. This demonstrates the importance of design parameters during construction of the device. The results of this study contribute to the improvement of mechanical aerators, reducing the energy consumption associated with oxygenation processes., En este trabajo se analizó la implementación de dos tipos de aspas en un prototipo de aireación mecánica de eje horizontal, partiendo del análisis de transferencia de oxígeno disuelto (OD). Las mediciones se realizaron en muestras de agua anóxica, utilizando dos tipos de aspas con una misma área y ángulo de impacto, pero con una diferente curvatura. Los datos obtenidos muestran que los dos tipos de aspas presentan la misma eficiencia estándar de aireación (SAE) en ambos dispositivos, obteniendo un valor de 0.50 kgO2/kWh. Sin embargo, la tasa de transferencia estándar de oxígeno (SOTR) para el aireador de aspas rectas fue un 34.9% mayor que el obtenido con aspas curvas. Los valores de KLa presentaron valores de 2.61 h-1 para el aireador de aspas rectas y de 1.94 h-1 para el de aspas curvas, reflejando una menor tasa de transferencia de oxígeno para este último. Sin embargo, el consumo energético es menor cuando se implementan las aspas curvas, demostrando la importancia de estos parámetros durante el diseño de sistemas aireadores. Los resultados de este estudio contribuyen en la mejora de aireadores mecánicos, disminuyendo el consumo de energía asociado a los procesos de oxigenación.

Context: The lack of dissolved oxygen (DO) in water bodies has become a serious problem for several ecosystems due to drastic changes in their climatic, biological, and physical conditions. The presence of microorganisms, organic matter, and clays, which are carried by landslides and rainwater, affect the process of restoration and transfer of DO in water, thus making it necessary to study how these factors affect the process of DO transfer in water bodies. Method: This work is focused on studying the influence of clays during the DO transfer process in water bodies. To this effect, samples of clays from the region of Paipa, Boyacá, were added in 1, 3 and 5% by weight into the samples of clean water. The aeration process was performed using a constant flow diffusion system. The tests were carried out until the saturation of dissolved oxygen in each of the water samples was obtained. Results: The results show that the presence of clays during the transfer of DO have little influence on bodies of water. However, variations were observed in time intervals of <5 min in which the increase in the percentage of clays favored the transfer of DO. Conclusions: With these results, it is concluded that the presence of clays can generate a beneficial effect during the transfer of DO in bodies of water with a high oxygen deficiency, whereas, for water samples with a relatively high percentage of DO, clays can hinder the DO restoration process., Contexto: La carencia de oxígeno disuelto (OD) en cuerpos de agua se ha convertido en un problema ambiental para varios ecosistemas debido a cambios drásticos en sus condiciones climáticas, bilógicas y físicas. La presencia de microorganismos, materia orgánica y arcillas, transportados por deslizamientos y aguas lluvias, afectan los procesos de restauración y transferencia de OD en el agua, lo que hace necesario estudiar cómo dichos factores afectan el proceso de transferencia de OD. Método: Este trabajo se centra en estudiar la influencia de las arcillas durante el proceso de transferencia de OD en cuerpos de agua. Para esto, se utilizaron muestras de arcillas de la región de Paipa-Boyacá, adicionadas en 1, 3 y 5% en peso a muestras de agua limpia. El proceso de aireación se llevó a cabo utilizando un sistema de difusión de flujo constante. Los ensayos se realizaron hasta obtener la saturación de oxígeno disuelto en cada una de las muestras de agua trabajadas. Resultados: Los resultados muestran que la presencia de arcillas durante la transferencia de OD tienen poca influencia en los cuerpos de agua. Sin embargo, se observaron variaciones en intervalos de tiempo <5 min en los que el incremento del porcentaje de arcillas favorecía la transferencia de OD. Conclusiones: Con estos resultados se concluye que la presencia de arcillas puede generar un efecto benéfico durante la transferencia de OD en cuerpos de agua con una alta carencia de oxígeno, mientras que, para muestras de agua con un porcentaje relativamente alto de OD, las arcillas perjudican el proceso de restauración de OD.

In this work, the implementation of two types of blades in a prototype of horizontal axis mechanical aeration was analyzed, starting from the dissolved oxygen (DO) transfer analysis. Measurements were made in anoxic water samples, using two types of paddle-wheelswith the same area and impact angle, but with a different curvature. The data obtained show that the two types of paddle-wheelshave the same standard aeration efficiency (SAE) in both devices, obtaining a value of 0.50 kgO2/kWh. However, the standard oxygen transfer rate (SOTR) for the flat paddle-wheelaerator was 34.9% higher than that obtained with curved paddle-wheels. The KLa values obtained wereof 2.61 h-1for the flat paddle-wheelsaerator and 1.94 h-1for the curved paddle-wheel, reflecting a lower oxygen transfer rate for the latter. However, energy consumption is lower by implementing the curved blades within the aeration system. This demonstrates the importance of design parameters during construction of the device. The results of this study contribute to the improvement of mechanical aerators, reducing the energy consumption associated with oxygenation processes., En este trabajo se analizó la implementación de dos tipos de aspas en un prototipo de aireación mecánica de eje horizontal, partiendo del análisis de transferencia de oxígeno disuelto (OD). Las mediciones se realizaron en muestras de agua anóxica, utilizando dos tipos de aspas con una misma área y ángulo de impacto, pero con una diferente curvatura. Los datos obtenidos muestran que los dos tipos de aspas presentan la misma eficiencia estándar de aireación (SAE) en ambos dispositivos, obteniendo un valor de 0.50 kgO2/kWh. Sin embargo, la tasa de transferencia estándar de oxígeno (SOTR) para el aireador de aspas rectas fue un 34.9% mayor que el obtenido con aspas curvas. Los valores de KLa presentaron valores de 2.61 h-1 para el aireador de aspas rectas y de 1.94 h-1 para el de aspas curvas, reflejando una menor tasa de transferencia de oxígeno para este último. Sin embargo, el consumo energético es menor cuando se implementan las aspas curvas, demostrando la importancia de estos parámetros durante el diseño de sistemas aireadores. Los resultados de este estudio contribuyen en la mejora de aireadores mecánicos, disminuyendo el consumo de energía asociado a los procesos de oxigenación.

The Pattern Of Chemical Pollution In Riam Kanan River, Kabupaten Banjar. Riam Kanan river is utilized by the community for various needs, such as for households, cultivation of fish in keramba, mining of sand and coral. This research aimed to know the pattern of chemical pollution in Riam Kanan river, which was related to flow direction, pollutant source especially keramba of fish, and flow rate, with the parameters of pH, dissolved oxygen (DO) and biochemical oxygen demand (BOD). The research was conducted by observation, field measurement and laboratory examination. Water sampling was done at 8 location : The reservoir of Riam Kanan, PLTA Ir. P. M. Noor, Tambela Sari Village, Tambela Village, Awang Bangkal Village, Mandikapau Village, The Dam of Irigation Karang Intan, and Sungai Asam village with length of rivers 13.41 km. The results showed that the flow of river ranged from 15.53 to 147.72 m3/sec,. The pH of water ranged 6.13 - 6.70. DO levels ranged 2.34 - 6.95 mg/L while BOD levels ranged 1.16 - 2.91 mg/L. The utilization of river flow for keramba of fish, households activities and sand and coral excavations had affected the quality of water, especially the level of dissolved oxygen along the river flow.

The Pattern Of Chemical Pollution In Riam Kanan River, Kabupaten Banjar. Riam Kanan river is utilized by the community for various needs, such as for households, cultivation of fish in keramba, mining of sand and coral. This research aimed to know the pattern of chemical pollution in Riam Kanan river, which was related to flow direction, pollutant source especially keramba of fish, and flow rate, with the parameters of pH, dissolved oxygen (DO) and biochemical oxygen demand (BOD). The research was conducted by observation, field measurement and laboratory examination. Water sampling was done at 8 location : The reservoir of Riam Kanan, PLTA Ir. P. M. Noor, Tambela Sari Village, Tambela Village, Awang Bangkal Village, Mandikapau Village, The Dam of Irigation Karang Intan, and Sungai Asam village with length of rivers 13.41 km. The results showed that the flow of river ranged from 15.53 to 147.72 m3/sec,. The pH of water ranged 6.13 - 6.70. DO levels ranged 2.34 - 6.95 mg/L while BOD levels ranged 1.16 - 2.91 mg/L. The utilization of river flow for keramba of fish, households activities and sand and coral excavations had affected the quality of water, especially the level of dissolved oxygen along the river flow.

The River Ganga (2,525 km long) is the largest River basin in India, covering 26.2 percent of India's total geographical area and recently granted living entity status by the court. It is the holiest River and also among the dirtiest in the world. That’s why it is mandatory to maintain its water quality (WQ). Though, monitoring and assessment of WQ of a River is a very challenging task. In this research work, Soft Computing (SC) based popular and commononly used Artificial Neural Network (ANN) technique has been used for modelling the WQ of the Ganga River by developing a prediction model based on six different training functions. Five sampling stations along this River stretch were selected from DEVPRAYAG to ROORKEE in the Uttarakhand state of India. The monthly data sets of five water quality parameters temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD) and total coliform (TC) for the time period from 2001 to 2015 have been taken. The feed forward error back propagation neural network method has been used to develop the WQ-prediction model by conducting various experiments following a neural network structure of 5-10-1, 0.1 as a training goal and various training functions. Using the Mean square error (MSE) statistical method the prediction performance of the developed model was evaluated. The model developed with traincgp (Conjugate Gradient with Polak-Ribiere Restarts) comes out to be the worst one (MSE=0.786) while the other model with trainlm (Levenberg-Marquardt backpropagation) rule proved to be the best one (MSE=0.163) among others. Consequently, it is found that ANNs are capable of predicting WQ of the River Ganga with acceptable results.

The River Ganga (2,525 km long) is the largest River basin in India, covering 26.2 percent of India's total geographical area and recently granted living entity status by the court. It is the holiest River and also among the dirtiest in the world. That’s why it is mandatory to maintain its water quality (WQ). Though, monitoring and assessment of WQ of a River is a very challenging task. In this research work, Soft Computing (SC) based popular and commononly used Artificial Neural Network (ANN) technique has been used for modelling the WQ of the Ganga River by developing a prediction model based on six different training functions. Five sampling stations along this River stretch were selected from DEVPRAYAG to ROORKEE in the Uttarakhand state of India. The monthly data sets of five water quality parameters temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD) and total coliform (TC) for the time period from 2001 to 2015 have been taken. The feed forward error back propagation neural network method has been used to develop the WQ-prediction model by conducting various experiments following a neural network structure of 5-10-1, 0.1 as a training goal and various training functions. Using the Mean square error (MSE) statistical method the prediction performance of the developed model was evaluated. The model developed with traincgp (Conjugate Gradient with Polak-Ribiere Restarts) comes out to be the worst one (MSE=0.786) while the other model with trainlm (Levenberg-Marquardt backpropagation) rule proved to be the best one (MSE=0.163) among others. Consequently, it is found that ANNs are capable of predicting WQ of the River Ganga with acceptable results.

The River Ganga (2,525 km long) is the largest River basin in India, covering 26.2 percent of India's total geographical area and recently granted living entity status by the court. It is the holiest River and also among the dirtiest in the world. That’s why it is mandatory to maintain its water quality (WQ). Though, monitoring and assessment of WQ of a River is a very challenging task. In this research work, Soft Computing (SC) based popular and commononly used Artificial Neural Network (ANN) technique has been used for modelling the WQ of the Ganga River by developing a prediction model based on six different training functions. Five sampling stations along this River stretch were selected from DEVPRAYAG to ROORKEE in the Uttarakhand state of India. The monthly data sets of five water quality parameters temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD) and total coliform (TC) for the time period from 2001 to 2015 have been taken. The feed forward error back propagation neural network method has been used to develop the WQ-prediction model by conducting various experiments following a neural network structure of 5-10-1, 0.1 as a training goal and various training functions. Using the Mean square error (MSE) statistical method the prediction performance of the developed model was evaluated. The model developed with traincgp (Conjugate Gradient with Polak-Ribiere Restarts) comes out to be the worst one (MSE=0.786) while the other model with trainlm (Levenberg-Marquardt backpropagation) rule proved to be the best one (MSE=0.163) among others. Consequently, it is found that ANNs are capable of predicting WQ of the River Ganga with acceptable results.

The River Ganga (2,525 km long) is the largest River basin in India, covering 26.2 percent of India's total geographical area and recently granted living entity status by the court. It is the holiest River and also among the dirtiest in the world. That’s why it is mandatory to maintain its water quality (WQ). Though, monitoring and assessment of WQ of a River is a very challenging task. In this research work, Soft Computing (SC) based popular and commononly used Artificial Neural Network (ANN) technique has been used for modelling the WQ of the Ganga River by developing a prediction model based on six different training functions. Five sampling stations along this River stretch were selected from DEVPRAYAG to ROORKEE in the Uttarakhand state of India. The monthly data sets of five water quality parameters temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD) and total coliform (TC) for the time period from 2001 to 2015 have been taken. The feed forward error back propagation neural network method has been used to develop the WQ-prediction model by conducting various experiments following a neural network structure of 5-10-1, 0.1 as a training goal and various training functions. Using the Mean square error (MSE) statistical method the prediction performance of the developed model was evaluated. The model developed with traincgp (Conjugate Gradient with Polak-Ribiere Restarts) comes out to be the worst one (MSE=0.786) while the other model with trainlm (Levenberg-Marquardt backpropagation) rule proved to be the best one (MSE=0.163) among others. Consequently, it is found that ANNs are capable of predicting WQ of the River Ganga with acceptable results.

To evaluate the hypothesis that plant-mediated oxygen supplies decrease methane (CH4) production and total global warming potential (GWP) in a tropical peatland, the authors compared the fluxes and dissolved concentrations of greenhouse gases [GHGs; CH4, carbon dioxide (CO2) and nitrous oxide (N2O)] and dissolved oxygen (DO) at multiple peatland ecosystems in Central Kalimantan, Indonesia. Study ecosystems included tropical peat swamp forest and degraded peatland areas that were burned and/or drained during the rainy season. CH4 fluxes were significantly influenced by land use and drainage, which were highest in the flooded burnt sites (5.75 +/- 6.66 mg C m(-2) h(-1)) followed by the flooded forest sites (1.37 +/- 2.03 mg C m(-2) h(-1)), the drained burnt site (0.220 +/- 0.143 mg C m(-2) h(-1)), and the drained forest site (0.0084 +/- 0.0321 mg C m(-2) h(-1)). Dissolved CH4 concentrations were also significantly affected by land use and drainage, which were highest in the flooded burnt sites (124 +/- 84 mu mol L-1) followed by the drained burnt site (45.2 +/- 29.8 mu mol L-1), the flooded forest sites (1.15 +/- 1.38 mu mol L-1) and the drained forest site (0.860 +/- 0.819 mu mol L-1). DO concentrations were influenced by land use only, which were significantly higher in the forest sites (6.9 +/- 5.6 mu mol L-1) compared to the burnt sites (4.0 +/- 2.9 mu mol L-1). These results suggest that CH4 produced in the peat might be oxidized by plant-mediated oxygen supply in the forest sites. CO2 fluxes were significantly higher in the drained forest site (340 +/- 250 mg C m(-2) h(-1) with a water table level of -20 to -60 cm) than in the drained burnt site (108 +/- 115 mg C m(-2) h(-1) with a water table level of -15 to +10 cm). Dissolved CO2 concentrations were 0.6-3.5 mmol L-1, also highest in the drained forest site. These results suggested enhanced CO2 emission by aerobic peat decomposition and plant respiration in the drained forest site. N2O fluxes ranged from -2.4 t

To evaluate the hypothesis that plant-mediated oxygen supplies decrease methane (CH4) production and total global warming potential (GWP) in a tropical peatland, the authors compared the fluxes and dissolved concentrations of greenhouse gases [GHGs; CH4, carbon dioxide (CO2) and nitrous oxide (N2O)] and dissolved oxygen (DO) at multiple peatland ecosystems in Central Kalimantan, Indonesia. Study ecosystems included tropical peat swamp forest and degraded peatland areas that were burned and/or drained during the rainy season. CH4 fluxes were significantly influenced by land use and drainage, which were highest in the flooded burnt sites (5.75 +/- 6.66 mg C m(-2) h(-1)) followed by the flooded forest sites (1.37 +/- 2.03 mg C m(-2) h(-1)), the drained burnt site (0.220 +/- 0.143 mg C m(-2) h(-1)), and the drained forest site (0.0084 +/- 0.0321 mg C m(-2) h(-1)). Dissolved CH4 concentrations were also significantly affected by land use and drainage, which were highest in the flooded burnt sites (124 +/- 84 mu mol L-1) followed by the drained burnt site (45.2 +/- 29.8 mu mol L-1), the flooded forest sites (1.15 +/- 1.38 mu mol L-1) and the drained forest site (0.860 +/- 0.819 mu mol L-1). DO concentrations were influenced by land use only, which were significantly higher in the forest sites (6.9 +/- 5.6 mu mol L-1) compared to the burnt sites (4.0 +/- 2.9 mu mol L-1). These results suggest that CH4 produced in the peat might be oxidized by plant-mediated oxygen supply in the forest sites. CO2 fluxes were significantly higher in the drained forest site (340 +/- 250 mg C m(-2) h(-1) with a water table level of -20 to -60 cm) than in the drained burnt site (108 +/- 115 mg C m(-2) h(-1) with a water table level of -15 to +10 cm). Dissolved CO2 concentrations were 0.6-3.5 mmol L-1, also highest in the drained forest site. These results suggested enhanced CO2 emission by aerobic peat decomposition and plant respiration in the drained forest site. N2O fluxes ranged from -2.4 t

To evaluate the hypothesis that plant-mediated oxygen supplies decrease methane (CH4) production and total global warming potential (GWP) in a tropical peatland, the authors compared the fluxes and dissolved concentrations of greenhouse gases [GHGs; CH4, carbon dioxide (CO2) and nitrous oxide (N2O)] and dissolved oxygen (DO) at multiple peatland ecosystems in Central Kalimantan, Indonesia. Study ecosystems included tropical peat swamp forest and degraded peatland areas that were burned and/or drained during the rainy season. CH4 fluxes were significantly influenced by land use and drainage, which were highest in the flooded burnt sites (5.75 +/- 6.66 mg C m(-2) h(-1)) followed by the flooded forest sites (1.37 +/- 2.03 mg C m(-2) h(-1)), the drained burnt site (0.220 +/- 0.143 mg C m(-2) h(-1)), and the drained forest site (0.0084 +/- 0.0321 mg C m(-2) h(-1)). Dissolved CH4 concentrations were also significantly affected by land use and drainage, which were highest in the flooded burnt sites (124 +/- 84 mu mol L-1) followed by the drained burnt site (45.2 +/- 29.8 mu mol L-1), the flooded forest sites (1.15 +/- 1.38 mu mol L-1) and the drained forest site (0.860 +/- 0.819 mu mol L-1). DO concentrations were influenced by land use only, which were significantly higher in the forest sites (6.9 +/- 5.6 mu mol L-1) compared to the burnt sites (4.0 +/- 2.9 mu mol L-1). These results suggest that CH4 produced in the peat might be oxidized by plant-mediated oxygen supply in the forest sites. CO2 fluxes were significantly higher in the drained forest site (340 +/- 250 mg C m(-2) h(-1) with a water table level of -20 to -60 cm) than in the drained burnt site (108 +/- 115 mg C m(-2) h(-1) with a water table level of -15 to +10 cm). Dissolved CO2 concentrations were 0.6-3.5 mmol L-1, also highest in the drained forest site. These results suggested enhanced CO2 emission by aerobic peat decomposition and plant respiration in the drained forest site. N2O fluxes ranged from -2.4 t

In a partial nitrification/anammox process applied in the moving bed biofilm reactor (MBBR), oxygen is an important parameter for the process performance and efficiency. The objective of this study was to investigate different aeration strategies, characterized by the ratio between non - aerated and aerated phase duration (R) and dissolved oxygen concentration (DO). Experiments were carried out in a MBBR of 200 L filled with 40% of AnoxKaldnes biocarriers. Moreover activities of different groups of bacteria under each investigated aeration strategies were studied by SAA (Specific Anammox Activity), OUR (Oxygen Uptake Rate) and NUR (Nitrate Utilization Rate) tests. Four different aeration strategies were introduced in the system with DO 3 mg/l and R=0, DO 3.5 mg/l and R = 1/3, DO 3 mg/l and R = 1/3, and DO 3.5 mg/l and R = 1; air supply was decreased gradually. The obtained results showed that with the same level of DO concentration (3 mg/l) but different R (0, 1/3), nitrogen removal efficiencies were similar, which meant that with R = 1/3, energy could be saved without any loss of the process efficiency. The highest nitrogen removal efficiency of 88 % and nitrogen removal rate of 3.11 g N /m2·d were obtained at R = 1/3 and DO = 3.5 mg/l. A proper duration of non-aerated phase could improve anaerobic conditions in the biofilm and decrease possible inhibition effects of oxygen on anammox bacteria., QC 20120214

A laboratory study was carried out to investigate the influence of the biomass content in the sediment on the rate of diagenesis of particulate organic materials (POM) and the consequent sediment oxygen demand (SOD) and nutrient fluxes. Fish food pellets were loaded into the sediment to simulate a sudden POM input. Three types of sediments with different biomass contents were tested, including a raw marine sediment, the marine sediment after one month of cultivation and an artificial sediment of sand and clay without any biomass. There was little difference in organic flux from the three different sediments. However, compared to the artificial sediment, the marine sediments had much higher SOD and ammonia flux. A mathematical model also has been developed for the SOD dynamics and nutrient fluxes. Both the experimental and simulation results indicate the important role of the biomass in the sediment in POM diagenesis, SOD and nutrient fluxes. © 2008 Elsevier Ltd. All rights reserved.

A laboratory study was carried out to investigate the influence of the biomass content in the sediment on the rate of diagenesis of particulate organic materials (POM) and the consequent sediment oxygen demand (SOD) and nutrient fluxes. Fish food pellets were loaded into the sediment to simulate a sudden POM input. Three types of sediments with different biomass contents were tested, including a raw marine sediment, the marine sediment after one month of cultivation and an artificial sediment of sand and clay without any biomass. There was little difference in organic flux from the three different sediments. However, compared to the artificial sediment, the marine sediments had much higher SOD and ammonia flux. A mathematical model also has been developed for the SOD dynamics and nutrient fluxes. Both the experimental and simulation results indicate the important role of the biomass in the sediment in POM diagenesis, SOD and nutrient fluxes. © 2008 Elsevier Ltd. All rights reserved.

A laboratory study was carried out to investigate the influence of the biomass content in the sediment on the rate of diagenesis of particulate organic materials (POM) and the consequent sediment oxygen demand (SOD) and nutrient fluxes. Fish food pellets were loaded into the sediment to simulate a sudden POM input. Three types of sediments with different biomass contents were tested, including a raw marine sediment, the marine sediment after one month of cultivation and an artificial sediment of sand and clay without any biomass. There was little difference in organic flux from the three different sediments. However, compared to the artificial sediment, the marine sediments had much higher SOD and ammonia flux. A mathematical model also has been developed for the SOD dynamics and nutrient fluxes. Both the experimental and simulation results indicate the important role of the biomass in the sediment in POM diagenesis, SOD and nutrient fluxes. © 2008 Elsevier Ltd. All rights reserved.

The effects of oxygenation and aeration on water quality, rainbow trout (Oncorhynchus mykiss) production, and economics were compared at the Wytheville State Fish Hatchery (WSFH) for 270 days. Mean dissolved oxygen (DO) concentrations and delta DO were significantly higher (P < 0.001) in the oxygenated raceways (9.5 and 2.75 mg/L, respectively) compared to aerated raceways (7.4 and 0.57 mg/L). Total settleable solids loads were significantly greater (P < 0.001) in aerated raceways (10.3 g/L/day) than in oxygenated raceways (8.8 g/L/day). Dissolved nitrogen (%), total gas pressure, and other water quality parameters (CO2, nitrite nitrogen, alkalinity, pH, and TAN) did not differ significantly between the treatments (P > 0.05). Raceway trout production (kg/day), trout growth rates (grams), feed conversion rate (FCR), and fish survival were not significantly different between treatments (P > 0.05). Blood hematocrit (Hct) and percent visceral mass were significantly elevated (P < 0.001) in oxygenated raceways compared to aerated raceways at 46 and 14.4% and 44 and 13%, respectively. Carrying capacity estimates derived from fish loading trials were significantly different (P < 0.001) at 3,355 and 2,217 kg/raceway in oxygenated and aerated raceways, respectively. Estimates of carrying capacity calculated using a fish loading (Ld) equation were also significantly different (P < 0.001) at 1,530 and 990 kg for oxygenated and aerated raceways, respectively. Oxygen injection increased the cost of production by $0.20/kg, however, net present value analysis (NPV) of oxygenated and aerated raceways over 5 years at a 10% discount rate yielded estimates of $50,666.51 and $32,742.15, respectively. Oxygen injection is an effective means of increasing DO concentrations, reducing effluent solids loading, and increasing raceway carrying capacity.