RESUMEN
This paper presents a comparative analysis among four control strategies for the control of a combined anaerobic-aerobic wastewater treatment configuration. The anaerobic stage is an Upflow Anaerobic Sludge Blanket (UASB) reactor, whereas the aerobic stage consists of the Activated Sludge (AS) process. The control variables are solids concentration in the effluent and sludge wastage rate. The proposed control strategy is considered the most reliable among them. It is based on two cascaded PI-controllers for the solids concentration in the effluent and a look-up table for the sludge wastage rate control. Experimental and simulated results are presented.
Asunto(s)
Aerobiosis , Anaerobiosis , Reactores Biológicos , Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos/métodos , Aguas del Alcantarillado/química , Factores de TiempoRESUMEN
This paper presents a combined wastewater treatment configuration composed by an Upflow Anaerobic Sludge Blanket (UASB) reactor followed by an Activated Sludge (AS) system. A control strategy has been developed for this innovative (especially for domestic sewage) treatment configuration and tested in a real pilot-scale system called STEPAA-Wastewater Treatment System by Anaerobic and Aerobic Processes. The proposed UASB-AS control strategy, including fault detection and recovery, and its successful implementation in real time is presented. This novel control strategy was developed to keep the final effluent suspended solids concentration in the range specified by the State environmental agency, in spite of incoming load disturbances. The control strategy is based on two cascaded PI (Proportional + Integral) controllers, which manipulates the recycling rate into the AS-reactor to control the effluent suspended solids concentration. A 2-dimensional nonlinear mapping (an empirical look-up table), which gives the sludge waste rate as a function of the influent flowrate and AS-reactor biomass concentration, is used to keep the AS-reactor biomass concentration in a range that guarantees a good substrate removal without inconveniences to the AS-settler operation (and consequently to the solids removal). Experimental results are provided to demonstrate the system performance.
Asunto(s)
Aguas del Alcantarillado/química , Aguas del Alcantarillado/microbiología , Purificación del Agua/instrumentación , Purificación del Agua/métodos , Bacterias Anaerobias/metabolismo , Biomasa , Reactores Biológicos , Simulación por Computador , Sistemas de Computación , Factores de Tiempo , Microbiología del AguaAsunto(s)
Hemoproteínas/biosíntesis , Hemoproteínas/química , Schistosoma mansoni/metabolismo , Animales , Cristalización , Femenino , Hemo/análisis , Hemo/metabolismo , Hemoproteínas/análisis , Concentración de Iones de Hidrógeno , Masculino , Pigmentos Biológicos/análisis , Pigmentos Biológicos/biosíntesis , Pigmentos Biológicos/química , Schistosoma mansoni/química , Caracteres Sexuales , Solubilidad , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Malaria parasites digest haemoglobin and detoxify the free haem by its sequestration into an insoluble dark-brown pigment known as haemozoin (Hz). Until recently, this pigment could be found only in Plasmodium parasites. However, we have shown that Hz is also present in the midgut of the blood-sucking insect Rhodnius prolixus [Oliveira et al. (1999) Nature 400, 517-518]. Here we show that Hz synthesis in the midgut of this insect is promoted by a particulate fraction from intestine lumen. Haem aggregation activity is heat-labile and is inhibited in vitro by chloroquine (CLQ). Inhibition of Hz formation in vivo by feeding insects with CLQ leads to increased levels of haem in the haemolymph of the insect, which resulted in increased lipid peroxidation. Taken together, these results indicate that a factor capable of promoting Hz crystallisation is present in R. prolixus midgut and that this activity represents an important physiological defence of this insect against haem toxicity.
