Influência da relação entre a área e a profundidade sobre o desempenho de reatores anaeróbios de fluxo ascendente com manta de lodo (UASB).

Abstract

The results of an experimental investigation to establish the influence of the surface/depth ratio of an upflow anaerobic sludge blanket (UASB) reactor treating raw sewage are discussed in this thesis. Three reactors were operated under steady state conditions in the range of 1,5 to 10 h which includes the values applied in regions with a tropical climate, normally between 4 and 8 h. For each detention time the three reactors with equal volumes but with different surface areas and depths received the same raw sewage flow, corresponding to the retention time until steady state was reached, whereupon during a certain period the operational variables to characterise the performance of the reactors were determined concerning the removal efficiency of organic material and suspended solids as well as the sludge mass in the reactors. The experimental work was carried out in five phases each with a different retention time. The three reactors were operated simultaneously and fed with raw sewage of the city of Campina Grande, state of Paraiba. - Brazil. The data show mat in the range of investigated depths mere is little influence of mis parameter on the performance of the UASB reactor for sewage treatment, though there is an indication of slight improvement when the depth increases. It was noted that for a long retention time (10 h) and small depth (1,8 m), mere was an accumulation of inorganic solids (silt) at the bottom section of the reactor, which resulted in a very high concentration (more than 200 g/1) of predominantly inert sludge. The main conclusion of the investigation is that the depth of a UASB reactor has little influence on its performance and the therefore the considerations that determine the depth will be related only to construction costs and the characteristics of the available site.