The effect of organic loading on the performance of a mechanically stirred anaerobic sequencing biofilm batch reactor (ASBBR) has been investigated, by varying influent concentration and cycle period. For microbial immobilization 1-cm polyurethane foam cubes were used. An agitation rate of 500 rpm and temperature of 30+/-2 degrees C were employed. Organic loading rates (OLR) of 1.5-6.0gCODl(-1)d(-1) were applied to the 6.3-l reactor treating 2.0 l synthetic wastewater in 8 and 12-h batches and at concentrations of 500-2000mgCODl(-1), making it possible to analyze the effect of these two operation variables for the same organic loading range. Microbial immobilization on inert support maintained approximately 60 gTVS in the reactor. Filtered sample organic COD removal efficiencies ranged from 73 to 88% for organic loading up to 5.4gCODl(-1)d(-1). For higher organic loading (influent concentration of 2000mgCODl(-1) and 8-h cycle) the system presented total volatile acids accumulation, which reduced organics removal efficiency down to 55%. In this way, ASBBR with immobilized biomass was shown to be efficient for organic removal at organic loading rates of up to 5.4gCODl(-1)d(-1) and to be more stable to organic loading variations for 12-h cycles. This reactor might be an alternative to intermittent systems as it possesses greater operational flexibility. It might also be an alternative to batch systems suspended with microorganisms since it eliminates both the uncertainties regarding granulation and the time necessary for biomass sedimentation, hence reducing the total cycle period. 相似文献
When performed without technical criteria, the rapid expansion of irrigated agricultural frontiers can result in overexploitation of water, causing worrying impacts on the balance of agroecosystems. This study proposes a model applied to the state of Bahia, to estimate the water demand of areas irrigated by a central pivot, in order to contribute to information that will subsidize the inspection and planning of water resources in the promotion of sustainable agriculture. The irrigated areas were identified and measured by photointerpretation using orbital images from the Landsat-8 satellite. With a historical series of data, the reference evapotranspiration was calculated and monthly water balance was elaborated. The data obtained were spatialized by kriging, and with punctual values of water deficit (mm), the water demand of the irrigated perimeter of the equipment was estimated. The results were described considering strategic planning units, proposed from municipalities, hydrographic basins and biomes. A total of 4075 pivots were quantified, covering an irrigated area of 265,896.30 ha and with an average annual consumption of 1,333,473,208.02 m3 of water. Areas of high demand were identified, especially in the western region of Bahia, which includes the hydrographic basin of the São Francisco River and the Cerrado biome, concentrating 80.85% and 75.47% of the state water demand for pivots, respectively. Considering possible points of water vulnerability and continuity of this expansion, the results provide the primary information needed to encourage the adoption of public policies aimed at the management of water resources. The study method proposes guidelines that condition the application in any region of interest in the world.